Eucommia ulmoides Oliv.: ethnopharmacology, phytochemistry and pharmacology of an important traditional Chinese medicine.

Journal of Ethnopharmacology 151 (2014) 78–92

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Journal of Ethnopharmacology journal homepage: www.elsevier.com/locate/jep

Review

Eucommia ulmoides Oliv.: Ethnopharmacology, phytochemistry and pharmacology of an important traditional Chinese medicine Xirui He a,1, Jinhui Wang b,1, Maoxing Li b,c,n,1, Dingjun Hao a, Yan Yang d, Chunling Zhang a, Rui He a, Rui Tao c a

Hong-Hui Hospital, Xi'an Jiaotong University Medical College, Xi'an 710054, PR China University Hospital of Gansu Traditional Medicine, Lanzhou 730020, PR China c Department of Pharmacy, Lanzhou General Hospital of PLA, Lanzhou 730050, PR China d Xi'an Hospital, Aviation Industry Corporation of China, Xi'an 710077, PR China b

art ic l e i nf o

a b s t r a c t

Article history: Received 10 May 2013 Received in revised form 8 November 2013 Accepted 13 November 2013 Available online 1 December 2013

Ethnopharmacological relevance: Eucommia ulmoides Oliv. (Family Eucommiaceae), also known as Dù), Tuchong (in Japanese), is the sole species of the genus Eucommia. The leaf, stem, zhòng (Chinese: and bark as well as staminate flower of Eucommia ulmoides have been traditionally used to cure many diseases in China, Japan, Korea, among others. The aim of this review is to comprehensively outline the botanical description, ethnopharmacology, phytochemistry, biological activities, and toxicology of Eucommia ulmoides and to discuss possible trends for further study of Eucommia ulmoides. Materials and methods: Information on Eucommia ulmoides was gathered via the internet (using Pub Med, Elsevier, Baidu Scholar, Google Scholar, Medline Plus, ACS, CNKI, and Web of Science) and from books in local libraries. Results: One-hundred twelve compounds of Eucommia ulmoides, including the main active constituents, lignans and iridoids, have been isolated and identified. In vitro and in vivo studies indicated that monomer compounds and extracts from Eucommia ulmoides possess wide-ranging pharmacological actions, especially in treating hypertension, hyperlipemia, diabetes, obesity, sexual dysfunction, osteoporosis, Alzheimer's disease, aging, lupus-like syndrome, and immunoregulation. Conclusions: Eucommia ulmoides has been used as a source of traditional medicine and as a beneficial health food. Phytochemical and pharmacological studies of Eucommia ulmoides have received much interest, and extracts and active compounds continue to be isolated and proven to exert various effects. Further toxicity and clinical studies are warranted to establish more detailed data on crude extracts and pure compounds, enabling more convenient preparations for patients. Therefore, this review on the ethnopharmacology, phytochemistry, biological activities, and toxicity of Eucommia ulmoides will provide helpful data for further studies as well as the commercial exploitation of this traditional medicine. & 2013 Elsevier Ireland Ltd. All rights reserved.

Keywords: Eucommia ulmoides Ethnopharmacology Lignans Anti-hypertensive activity Hypolipidemic activity

Abbreviations: AChE, acetylcholinesterase; AD, Alzheimer's disease; AIDS, acquired immunodeficiency syndrome; Ang II, angiotensin II; AST, aspartate transaminase; BAT-SNA, Brown adipose tissue sympathetic nerve activity; cAMP, cyclic adenosine monophosphate; CJ-S (131), Campylobacter jejuni enteritis 131; CNKI, China National Knowledge Infrastructure; COX-2, cyclooxygenase-2; DPPH, 1, 1-diphenyl-2-picrylhydrazyl; EC50, concentration for 50% of maximal effect; EDTA, ethylenediaminetetraacetic acid; ELE, extracts of leaves from Eucommia ulmoides Oliv.; ELISA, enzyme-linked immunosorbent assay; FFA, free fatty acids; GRd, glucocorticoid receptor; GSH, glutathione; GST, glutathione S-transferase; GVNA, gastric vagal nerve activity; HDL, high density lipoprotein; HIV, human immunodeficiency virus infection; HL-60, human promyelocytic leukemia cells; HMG-CoA, hydroxy methylglutaryl coenzyme A; IC50, 50% inhibition concentration; ID, intraduodenal; IL, interleukin; LDL, low density lipoprotein; LPS, lipopolysaccharide; MeOH, methyl alcohol; MMC, mitomycin C; NO, nitric oxide; nNOS, neuronal nitric oxide synthase; OVX, ovariectomy; PAGE, polyacrylamide gel electrophoresis; PDE, phosphodiesterase; ROS, reactive oxygen species; SD, Sprague-Dawley; SHRs, spontaneously hypertensive rats; SOD, superoxide dismutase; STZ, streptozotocin; TAG, tumor-associated glycoprotein; TCM, traditional Chinese Medicine; TFAs, total fatty acids; THP-1 cells, human acute monocytic leukemia cell line; Tk gene, thymidine kinase gene; TNF-α, tumor necrosis factor-α; UPLC, ultra performance liquid chromatography; UPLC-ESI-MS, ultra performance liquid chromatography with electrospray ionization-tandem mass spectrometry; WAT-SNA, white adipose tissue sympathetic nerve activity n Corresponding author at: Department of Pharmacy, Lanzhou General Hospital of PLA, Lanzhou 730050, PR China. Tel.: þ 86 931 2115262. E-mail address: [email protected] (M. Li). 1 These authors contributed equally to this work. 0378-8741/$ - see front matter & 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jep.2013.11.023

X. He et al. / Journal of Ethnopharmacology 151 (2014) 78–92

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Contents 1. 2. 3.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Botanical description and ethnopharmacology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phytochemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Lignans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Iridoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. Phenolics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4. Steroid and terpenoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5. Flavonoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6. Other compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7. Variance of major components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Biological activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Anti-hypertensive activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Hypolipidemic activity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. Anti-obesity activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Anti-diabetic activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5. Effect on bone metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6. Anti-inflammatory, anti-viral and anti-bacterial activities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7. Neuroprotective activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8. Antioxidative activity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9. Improving erectile function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10. Anti-fatigue activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11. Anti-aging activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.12. Anti-tumor activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13. Hepatoprotective activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.14. Enhancing immune-function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Toxicity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Future perspectives and conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

79 79 80 80 80 80 80 80 80 82 84 84 85 85 86 87 88 88 88 89 89 89 89 89 89 89 90 90 90

1. Introduction

2. Botanical description and ethnopharmacology

In the monotypic genus Eucommia, Eucommia ulmoides Oliv. is ), Tuchong (in Japanese), Guttaknown as Dù-zhòng (Chinese: percha tree, Chinese rubber tree, Sixian, Sizhong, and Yusipi (Cronquist, 1981). The leaves, stem, bark, and even the staminate flower are used as medicinal remedies. People believe it can “nourish the kidney and reinforce the Yang.” In China, extracts of the aerial parts of this plant have been widely used in famous botanical tonics and antirheumatic supplements for more than 2000 years. It can be used alone or mixed with other compounds in the prescription of traditional Chinese medicine (TCM) to treat impotence, spermatorrhoea, prospermia, forgetfulness, osteoporosis, menopause syndrome, hypertension, rheumatoid arthritis, lumbago, ischialgia, aching knees, kidney deficiency pain, weak bones, bone fractures and joint diseases, and lower back pain. In modern pharmacological studies, the in vivo and in vitro activities of Eucommia ulmoides against hypertension, hyperglycemia, diabetes, obesity, osteoporosis, Alzheimer's disease, aging, and sexual dysfunction have garnered much attention (Zhou et al., 2009). At the same time, extensive studies of the chemical components of Eucommia ulmoides have led the identification of compounds 1–112, which include lignans, iridoids, phenolics, steroids, terpenoids, and flavonoids. Among these compounds, lignans and iridoids are the two major constituents and are important chemotaxonomic markers. The main components of lignans, liriodendrin, (þ)-pinoresinol di-O-β-Dglucopyranoside, and (þ)-syringaresinol were shown to have antihypertensive effects; aucubin, genipin, and geniposidic acid, which are the main components of iridoids, exhibit anti-hypertensive and antiaging properties. In this review, we present and assess recent studies concerning the ethnopharmacology, phytochemistry, pharmacological activities and toxicity of Eucommia ulmoides.

Eucommia ulmoides Oliv., indigenous to China and growing to 15– 20 m in height, is widely distributed in Shanxi, Gansu, Zhejiang, Henan, Hubei, Sichuan, Guizhou, and Yunnan. The tree bark is beige and rough. The leaves are arranged alternately, are simple and ovate with an acuminate tip, are 6–16 cm long and 3.5–6.5 cm wide, and have a serrated margin. If a leaf is torn across, strands of latex that exude from the leaf veins solidify into rubber and hold the two parts of the leaf together. Strands of latex can also be found after the bark is broken and can be used to identify the material in Chinese Traditional Medicine. The flower of Eucommia ulmoides is monotropic, inconspicuous, small, and greenish and displays heterothallism, stamen of up to 1 cm, and female flower of up to 8 mm. The male flowers, consisting of 5–12 linear stamen without perianth, are crowded by the bract in young shoots. The flower blossoms simultaneously or before the appearance of the leaf during April, with a blooming period of approximately 20 days. The fruit, which ripens between June and November, is a thin and flat samara with one seed (Fig. 1) (Call and Dilcher, 1997; Dong et al., 2011; http://en.wikipedia. org/wiki/Eucommia, 2013). Two thousand years ago, the bark of Eucommia ulmoides was listed in the Chinese medical classic Shen Nong Ben Cao Jing and was considered a “Middle grade” drug. In 1590, it was reported to enhance kidney, bones, and tendons in the most famous Chinese medical document, Ben Cao Gang Mu. In East Asia, especially in China, Korea, and Japan, Eucommia ulmoides is widely used as traditional medicine with a long history of safety for its kidney-tonifying function. It is used to cure lumbago associated with kidney deficiency and to promote human longevity. In China, the stem and bark of Eucommia ulmoides have been recorded in the Pharmacopoeia of PR China for the treatment of hypertension, impotence, lumbago, and

80


Fig. 1. Eucommia ulmoides Oliver. (A) Whole Eucommia ulmoides Oliver plants, (B) leaves, and (C) the bark and the strand of latex in it.

ischialgia (Chien, 1957; Li, 1994; Committee for the Pharmacopoeia of P.R. China, 2010; Zhang et al., 2012). At the same time, the leaf of this tree is a functional food with anti-obesity properties. In Korea, the leaves of Eucommia ulmoides have been used as a folk remedy for the treatment of diabetes (Kim et al., 2004), and the aqueous extract of Eucommia ulmoides leaves has been used commonly as a popular beverage and/or health food (Nakasa et al., 1995) in Japan. More recently, even the staminate flower has been widely used to prepare tea and/or nutraceuticals. Almost all aerial parts of this plant can be used for health care.

3. Phytochemistry From Eucommia ulmoides, 112 compounds have been isolated, including 28 lignans, 24 iridoids, 27 phenolics, 6 steroids, 5 terpenoids, 13 flavonoids and 9 other compounds (Table 1). Some of these compounds exhibit a variety of bioactivities in vivo or in vitro (Table 2). In Chinese Pharmacopoeia 2010 edition, pinoresinol di-O-β-Dglucopyranoside was used as quality control marker for Eucommia ulmoides bark by HPLC, and chlorogenic acid was used as quality control marker for Eucommia ulmoides leaves. According to this source, the pinoresinol diglucoside content in the bark of Eucommia ulmoides should be more than 0.1%, and chlorogenic acid should be more than 0.1% of the content in the leaves of Eucommia ulmoides (Committee for the Pharmacopoeia of PR China, 2010). 3.1. Lignans Lignans represent a class of secondary metabolites consisting of two phenyl-propanoid molecules connected by 8-8′ carbon atoms. Lignans and their derivatives are the main components of Eucommia ulmoides (Fig. 2). To date, 28 lignans, including bisepoxylignans (1–15), monoepoxylignans (16–20), neolignans (21–26) and sesquilignans (27–28), have been isolated from the bark, seeds and leaves of Eucommia ulmoides. 3.2. Iridoids The other main component of Eucommia ulmoides is iridoid glycoside, a typical monoterpenoid with a glucose moiety attached to C1 in the pyran ring. Twenty-four iridoids (29–52) have been isolated and identified from Eucommia ulmoides. Among these compounds, geniposidic acid, aucubin and asperuloside have been

confirmed to possess various pharmacological activities in vivo and in vitro (Li et al., 1998; Bermejo, 2000; Takeshi et al., 2001; Ho et al., 2005a, 2005b; Zhou et al., 2009; Hirata et al., 2011). 3.3. Phenolics Phenolics are a major group of nonessential dietary components that possess antioxidant, antimutagenic, anti-inflammatory, and anticancer activities. To date, 27 phenolics (53–79) have been isolated and identified from Eucommia ulmoides. Among them, chlorogenic acid, with neuroprotective effects (Zhou et al., 2009), has been frequently used as the quality control marker for Eucommia ulmoides and its medicinal extracts and preparations. 3.4. Steroid and terpenoids Only six steroids (80–85) and five terpenoids (86–90) have been purified and characterized from Eucommia ulmoides. β-Sitosterol, daucosterol, ulmoprenol, betalin, betulic acid, ursolic acid, eucommidiol, rehmaglutin C and 1, 4α, 5, 7α-tetrahydro-7-hydroxymethylcyclopenta [c] pyran-4-carboxylic methyl ester have been isolated from the bark of Eucommia ulmoides (Hua et al., 2003). Loliolide has been isolated from the leaves (Okada et al., 1994). 3.5. Flavonoids Flavonoids are very common and important secondary metabolites in nature. To date, 13 flavonoids (91–103) with various substitutions have been obtained and identified from the barks, leaves and seeds of Eucommia ulmoides, including kaempferol, kaempferol 3-O-6″-acetyl-glucoside, kaempferol 3-O-rutinoside, astragalin, quercetin, quercetin 3-O-sambubioside, quercetin 3-Ogalactoside (hyperin), quercetin 3-O-α-L-arabinopyranosyl-(1-2)β-D-glucopyranoside, isoquercetin, rutin, hirsutin and wogonside. 3.6. Other compounds Fatty acids, polysaccharides, amino acids, microelements, vitamins, and Cutta-percha have been studied from Eucommia ulmoides. In 1990, two new polysaccharides, eucomman A and eucomman B, were isolated (Tomoda et al., 1990). Ethylglucopyranoside, noetaeosanoic acid, and tetraeosanoie-2, 3-dihydroxypropylester were also isolated from Eucommia ulmoides in the following few years (Cheng et al, 2000; Sun et al., 2004). In 2010, compounds


81

Table 1 The compounds isolated from Eucommia ulmoides. Resource

References

Lignans Bisepoxylignans 1 ( þ )-Medioresinol di-O-β-D-glucopyranoside 2 Eucommin A [(þ )-medioresinol 4′-β-D-glucopyranoside] 3 ( þ )-Medioresinol 4 ( þ )-Pinoresinol-4-O-β-D-glucopyranosyl (1-6)-β-D-glucopyranoside 5 ( þ )-Pinoresinol di-O-β-D-glucopyranoside 6 ( þ )-Pinoresinol 4′-O-β-D-glucopyranoside 7 ( þ )-Pinoresinol 8 ( þ )-Syringaresinol O-β-D-glucopyranoside 9 Liriodendrin [( þ)-syringaresinol di-O-β-D- glucopyranoside] 10 ( þ )-Syringaresinol 11 ( þ )-1-Hydroxypinoresinol 4′,4″ di-O-β-D-glucopyranoside 12 ( þ )-1-Hydroxypinoresinol 4″-O-β-D-glucopyranoside 13 ( þ )-1-Hydroxypinoresinol 4′-O-β-D-glucopyranoside 14 ( þ )-l-Hydroxypinoresinol 15 ( þ )-Epipinoresinol

Barks Barks Barks Barks Barks Barks Barks Barks Barks Barks Barks Barks Barks Barks Barks

Deyama (1983) Deyama et al. (1985) Deyama et al. (1987a) Shi et al. (2013) Sih et al. (1976) Deyama (1983) Deyama et al. (1987a) Deyama et al. (1985) Deyama (1983) Deyama et al. (1987a) Deyama et al. (1985) Deyama et al. (1986a) Deyama et al. (1986a) Deyama et al. (1987a) Deyama et al. (1987a)

Monoepoxylignans 16 ( þ )-Olivil 17 ( þ )-Cyclo-olivil 18 ( þ )-Olivil- 4′-O-β-D-glucopyranoside 19 ( þ )-Olivil- 4″-O-β-D-glucopyranoside 20 (-)-Olivil 4′,4″ di-O-β-D-glucopyranoside

Barks Barks Barks, leaves Barks Barks

Deyama Deyama Deyama Deyama Deyama

et et et et et

al. al. al. al. al.

(1986a) (1986a) (1986b), Shimoyamo et al. (1993) (1986b) (1985)

Neolignans 21 Citrusin B 22 Dihydroxydehy-drodiconiferyl alcohol 24 Threo-dihydroxydehy-drodiconiferyl alcohol 25 Erythro-dihydroxydehy-drodiconiferyl alcohol 26 Dehydrodiconiferyl alcohol 4, γ′- di-O-β-D-glucopyranoside

Barks Barks Barks Barks Barks

Deyama Deyama Deyama Deyama Deyama

et et et et et

al. al. al. al. al.

(1987b) (1987a) (1987a) (1987a) (1987b)

Sesquilignans 27 (-)-Hedyotol C 4′,4″′-di-O-β-D-glucopyranoside 28 Syringylgylycerol-β-syringaresinol ether 4″ -4″′-O-β-D-glucopyranoside

Barks Barks

Deyama et al. (1986b) Deyama et al. (1987b)

Iridoids 29 Geniposide 30 Geniposidic acid 31 Genipin 32 Aueubin or aueuboside 33 Ulmoside 34 Scandoside 10-O-acetate 35 Ajugoside 36 Harpagide acetate 37 Asperulosidic acid 38 Deacetyl asperulosidic acid 39 Reptoside 40 Eucommiol 41 Eucommioside 42 Eucommiside I 43 Eucommiol-II 44 1-Deoxyeucommiol 45 Ulmoidoside A 46 Ulmoidoside B 47 Ulmoidoside C 48 Ulmoidoside D 49 Asperuloside 50 Eucomoside A 51 Eucomoside B 52 Eucomoside C

Barks Barks, leaves Barks Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Leaves Barks Barks Barks Seeds Seeds Seeds Seeds Leaves Leaves Leaves Leaves

Deyama et al. (1986b) Deyama et al. (1986b), Takamura et al. (2007) Deyama et al. (1987a) Bianeo et al. (1974) Bianeo et al. (1982), Hattori et al. (1988) Takamura et al. (2007) Bianeo et al. (1974) Bianeo et al. (1974) Nakamura et al. (1997) Nakamura et al. (1997) Bianeo et al. (1974) Bianeo et al. (1974) Bianeo et al. (1982) Deyama et al. (1986b) Deyama et al. (1986b) Deyama et al. (1986b) Yahara et al. (1990) Yahara et al. (1990) Yahara et al. (1990) Yahara et al. (1990) Takamura et al. (2007) Takamura et al. (2007) Takamura et al. (2007) Takamura et al. (2007)

Phenolics 53 Eatechol 54 Vanillic acid 55 Koaburaside 56 Caffeic acid 57 Dihydro-caffeic acid 58 Methyl chlorogenate 59 Chlorogenic acid 60 Chlorgenic acid methyl ester 61 Isochlorogenic acid A 62 Isochlorogenic acid C 63 Erythro-guaiacylglycerol-β-coniferyl aldehyde ether 64 Threo-guaiacylglycerol-β-coniferyl aldehyde ether 65 Syringin 66 Coniferin

Leaves Barks Stems Barks, leaves Seeds Barks Leaves, barks Leaves Leaves Leaves Barks Barks Stems Stems

Hattori et al. (1988) Li et al. (1986) Gewali et al. (1988) Deyama et al. (1987a); Zhang et al. (2012) Yahara et al. (1990) Deyama et al. (1987a) Takamura et al. (2007), Sun et al. (2004) Peng et al. (2013) Si et al. (2008) Si et al. (2008) Deyama et al. (1987a) Deyama et al. (1987a) Gewali et al. (1988) Gewali et al. (1988)

No.

Compounds

82


Table 1 (continued ) No.

Compounds

Resource

References

67 68 69 70 71 72 73 74 75 76 77 78 79

Coniferol 3-(3-Hydroxy phenyl-propionic acid) 3, 4-Dihydrobenzonic acid 3-(3, 4-Dihy-droxyphenyl) propionic acid Eucophenoside ( 7 )-Erythro-guaiacylglycerol ( 7 )-Threo-guaiacylglycerol Catechin (-)Epieateehin Protocatechuic acid methyl ester Protocatechuic acid Pyrogallol p-trans-Coumaric acid

Barks Leaves Leaves Leaves Barks Barks Barks Barks Barks Barks Leaves Leaves Leaves

Deyama et al. (1987a) Hattori et al. (1988) Cheng et al. (2000) Hattori et al. (1988) Yao (2010) Deyama et al. (1986a) Deyama et al. (1986a) Sun et al. (2004) Sun et al. (2004) Chen et al. (2012) Nakamura et al. (1997) Nakamura et al. (1997) Nakamura et al. (1997)

Steroid and terpenoid 80 β-Sitosterol 81 Daucosterol 82 Ulmoprenol 83 Betalin 84 Betulic acid 85 Ursolic acid 86 Loliolide 87 1, 4α, 5, 7α-Tetrahydro-7-hydroxymethyl-cyclopenta [c]pyran-4-carboxylic methyl ester 88 Rehmaglutin C 89 Eucommidiol 90 Ulmoidol

Barks Barks Barks Barks Barks Barks Leaves Barks Barks Barks Leaves

Li et al. (1986) Xu et al. (1989) Horri et al. (1978) Li et al. (1986) Li et al. (1986) Li et al. (1986) Okada et al. (1994) Hua et al. (2003) Hua et al. (2003) Hua et al. (2003) Chie et al. (1997)

Flavonoids 91 Kaempferol 92 Kaempferol 3-O-6″-acetyl-glucoside 93 Kaempherol 3-O-rutinoside 94 Astragalin 95 Quercetin 96 Isoquercetin 97 Quercetin 3-O-sambubioside 98 Quercetin 3-O-galactoside(hyperin) 99 Quercetin 3-O-α-L-arabinopyranosyl- (1–2)-β-D-glucopyranoside 100 Quercetin 3-O-xyloglucoside 101 Rutin 102 Hirsutin 103 Wogonside

Leaves Leaves Leaves Leaves, barks Barks Leaves, barks Leaves Barks Barks, leaves Bark Leaves, barks Leaves Barks

Cheng et al. (2000) Wei et al. (2001) Takamura et al. (2007) Takamura et al. (2007); Wang et al. (1996) Wang et al. (1996) Takamura et al. (2007); Si et al. (2008) Takamura et al. (2007) Wang et al. (1996) Sun et al. (2009); Kim et al. (2009); Kim et al. (2004) Si et al. (2008) Takamura et al. (2007); Sun et al. (2004) Cheng et al. (2000) Yao (2010)

Others 104 n-Oetaeosanoic acid 105 Tetraeosanoie-2,3-dihydroxypropylester 106 (αR)-α-O-β-D-glucopyranosyl-4,2′,4′-trihydroxydihydrochalcone 107 4,2′,4′-Trihydroxychalcone 108 (αR)-α,4,2′,4′-Tetrahydroxydihydrochalcone 109 Ethylglucopyranoside 110 Eucomman A 111 Eucomman B 112 Ulmoidol A

Barks Barks Barks Barks Barks Leaves Barks Barks Leaves

Sun et al. (2004) Sun et al. (2004) Yao (2010) Yao (2010) Yao (2010) Cheng et al. (2000) Gonda et al. (1990) Tomoda et al. (1990) Li et al. (2012, 2013)

(αR)-α-O-β-D-glucopyranosyl-4,2′,4′-trihydroxy-dihydrochalcone, 4, 2′, 4′-trihy-droxychalcone, and (αR)-α,4,2′,4′-tetrahydroxy-dihydrochalcone were obtained from the bark of Eucommia ulmoides for the first time (Yao, 2010). In the same year, the composition of fatty acids in the seed oil of Eucommia ulmoides was analyzed by fraction chain length and mass spectrometry. The results showed that main polyunsaturated fatty acids are a-linolenic acid (56.51 % of total fatty acids, TFAs) and linolelaidic acid (12.66 % of TFAs). Meanwhile, the main monounsaturated fatty acid is oleic acid (15.80 % of TFAs). Palmitic acid and stearic acid are the dominant saturated fatty acids, representing 9.82 % and 2.59 % of TFAs, respectively (Zhang et al., 2010). 3.7. Variance of major components In the history of Chinese Traditional Medicine, there have been many records describing the effects of environment and procedure on the quality of medicinal material, even detailing the effects on clinical efficacy. Variations in harvest time (Zhang et al., 2013a), medicinal

parts, habitat, processing, and extraction methods may contribute to alterations in active component contents in Eucommia ulmoides. Leaves harvested from April to June have higher than average contents of aucubin, geniposidic acid, geniposide, and chlorogenic acid compared to those collected in autumn (Du et al., 2011; Li et al., 2011a; Tang et al., 2004). Although all parts of the Eucommia ulmoides plant contain the same compounds and therefore can be used as medicine, the abundance of compounds differs among plant tissue. Briefly, the leaf has the highest chlorogenic acid content, whereas the bark, especially the bast, has the highest concentration of iridoids (Wang and Yang, 2009; Wang et al., 2009; Chai et al., 2012). The increased consumption of materials from Eucommia ulmoides has led to the widespread distribution of the plant in China. Eucommia ulmoides is found in more than 17 provenances over a very large area of China, from Guizhou in southern China to Gansu in northwestern China. An analysis of syringaresnol diglucoside and geniposidic acid content in autumn leaves (collected in October) revealed that areas in central China with moderate temperature and rainfall are optimal for the growth of Eucommia ulmoides (Tang et al.,


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Table 2 The activities of some compounds from Eucommia ulmoides. Effects

Compounds

Anti-hypertensive activity

( þ )-Pinoresinol di-O-β-Dglucopyranoside

In vivo

Liriodendrin

( þ )-Syringaresinol

Syringin

Asperuloside

Geniposidic acid Genipin

Asperuloside

Anti-diabetic activity

Quercetin 3-O-α-Larabinopyranosyl-(1-2)-β-Dglucopyranoside Astragalin Isoquercitrin

Anti-inflammatory

Aucubin

Antibacterial activity

Aucubin

Anticomplement

( þ )-Syringaresinol O-β-Dglucopyranoside Liriodendrin

Immunosuppressive activity Neuroprotective effects

Deyama et al. (1988) Okada et al. (1993) Okada et al. (1993) Takeshi et al. (2001) Takeshi et al. (2001) Taubert et al. (2002)

Exhibited glycation inhibitory activity comparable to that of aminoguanidine Exhibited glycation inhibitory activity comparable to that of aminoguanidine

Kim et al. (2004)

Kim et al. (2004)

Kim et al. (2004) Inhibited the arachidonic acid pathway Obviously inhibit the growth of Escherichia coli and Staphylococcus aureus with the MIC of 9.664 mg/ml and 4.832 mg/ml, respectively. Anticomplement activty was shown to be 27.7% Anticomplement activty was shown to be 18.3% Anticomplement activty was shown to be 15.0% Anticomplement activty was shown to be 13.7% Anticomplement activty was shown to be 27.7% Anticomplement activty was shown to be 12.0% Anticomplement activty was shown to be 18.7% Anticomplement activty was shown to be 18.0%

Showed the growth inhibitory activity on human nasopharyngeal carcinoma and mouse lymphocytic leukemia P388

Geniposidic acid

Caffeic acid

Quercetin-3-O-sambubioside Isoquercitrin Rutin Pinoresinol 4′-O-β-Dglucopyranoside

Okada et al. (1993)

Hirata et al. (2011)

Chlorogenic acid

Estrogenic properties

Sih et al. (1976)

Suppressed increases in model mouse body weight, white adipose tissue weight, plasma triglyceride levels and free fatty acids levels Exhibited glycation inhibitory activity comparable to that of aminoguanidine

Chlorogenic acid Antioxidative activity

Inhibited the cAMP activity and calcium ion internal flow, relaxed vessel and raise coronary flow Inhibited the cAMP activity and calcium ion internal flow, relaxed vessel and raise coronary flow Inhibited the cAMP activity and calcium ion internal flow, relaxed vessel and raise coronary flow Inhibited the cAMP activity and calcium ion internal flow, relaxed vessel and raise coronary flow Inhibited the cAMP activity and calcium ion internal flow, relaxed vessel and raise coronary flow

Induced the nitric-oxide synthase in endotheliocyte, thus promoted NO synthesis and relaxed vessel

( þ )-1-Hydroxypinoresinol 4′,4″ di-O-β-D-glucopyranoside Eucommin A ( þ )-Medioresinol di-O-β-Dglucopyranoside ( þ )-Pinoresinol di-O-β-Dglucopyranoside ( þ )-Olivil- 4″-O-β-Dglucopyranoside ( þ )-Olivil- 4′-O-β-Dglucopyranoside Loliolide

References

30 mg/kg reduce the blood pressures of hypertensive rats with 20–40 mmHg 30 mg/kg reduce the blood pressures of hypertensive rats with 5–10 mmHg

Caffeic acid

Anti-obesity activity

In vitro

10 7, 10 6, 10 5, 10 4 M, respectively caused a significant increase of luciferase activity in ERβ and ERα

Efficiently protect PC-12 cells against the cytotoxicity of Aβ(25–35) Efficiently protect PC-12 cells against the cytotoxicity of Aβ(25–35) Exhibited strong DPPH radical activities with IC50 values 0.8 mg/ml Exhibited strong DPPH radical activities with IC50 values 2.3 mg/ml Exhibited strong DPPH radical activities with IC50 values 5.7 mg/ml Exhibited strong DPPH radical activities with IC50 values 7.2 mg/ml Exhibited strong DPPH radical activities with IC50 values 19.8 mg/ml

Bermejo (2000) Zheng et al. (2012)

Oshima et al. (1988) Oshima et al. (1988) Oshima et al. (1988) Oshima et al. (1988) Oshima et al. (1988) Oshima et al. (1988) Oshima et al. (1988) Oshima et al. (1988) Okada et al. (1994) Zhou et al. (2009) Zhou et al. (2009) Dai et al. (2013) Dai et al. (2013) Dai et al. (2013) Dai et al. (2013) Dai et al. (2013) Wang et al. (2011)

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Table 2 (continued ) Effects

Compounds

In vivo

Pinoresinol di-O-β- Dglucopyranoside

10 5, 10 4 M, respectively caused a significant increase of luciferase activity in ERβ and ERα 10 6, 10 5, 10 4 M, respectively, were shown to increase luciferase expression in ERβ and ERα in a dose-dependent manner 10 5, 10 4 M could increase luciferase activity in both ERβ and ERα., and 10 5 M exhibited a clear ERβ-selectivity 10 5, 10 4 M could increase luciferase activity in both ERβ and ERα., and 10 5 M exhibited a clear ERβ-selectivity 10 6, 10 5, 10 4 M exhibited a clear increasing luciferase expression in ERβ and ERα Stimulated collagen synthesis in false aged model rats Stimulated collagen synthesis in false aged model rats Stimulated collagen synthesis in false aged model rats

Aucubin

Wogonin

Baicalein

α-O-β-D-glucopyranosyl-4,2′,4′trihydroxy-dihydrochalcone Anti-aging

Geniposidic acid Aucubin Eucommiol

Preventing photoaging

Aucubin

Anti-tumor

Liriodendrin

Sedative and hypnotic effects

Eucommiol

PDE inhibitory activities

( þ )-Medioresinol di-O-β-Dglucopyranoside

In vitro

Wang et al. (2011)

Wang et al. (2011)

Wang et al. (2011)

Wang et al. (2011)

Wang et al. (2011)

Li et al. (1998) Li et al. (1998) Li et al. (1998) Significantly suppressed the production of matrix metalloproteinase-1 by nearly 57%, and against reactive oxygen species in ultraviolet B-irradiated human fibroblasts

12.5 mg/kg showed an effect on lymphocytic leukemia p388 system Reduced spontaneous activity, and increased the sleep ratio or lengthened the sleep time with a subthreshold or superthreshold dose of pentobarbital sodium, respectively. Besides, it shorten effectively sleep latency, reduce convulsion rate and prolong convulsion latency.

( þ )-Pinoresinol di-O-β-Dglucopyranoside ( þ )-Pinoresinol-4-O-β-Dglucopyranosyl (1-6)-β-Dglucopyranoside Liriodendrin

( þ )-Pinoresinol 4′-O-β-Dglucopyranoside

2004). Moreover, the leaves or bark collected from Eucommia ulmoides planted in elfin forests exhibit higher concentrations of geniposidic acid, aucubin and chlorogenic acid than those growing in timber forests (Lv et al, 2012b). Following collection, plant material from Eucommia ulmoides should be dried as quickly as possible. Different drying processes impact the quality of Eucommia ulmoides (Dong et al., 2011; Lv et al., 2012a; He et al., 2013). Recently, it has been shown that microwaving deactivates glucosidases in fresh leaves, bark, and male flowers. Compared to sun-drying, microwave-based drying has been shown to be effective in protecting geniposidic acid, aucubin, and other functional constituents (Dong et al., 2011; Lv et al., 2012a).

4. Biological activities Pharmacological actions of Eucommia ulmoides have gained much attention. Orally, Eucommia ulmoides has traditionally been

References

Ho et al. (2005a, 2005b)

Xin et al. (2007b) Li et al. (2013)

Exhibited effective PDE inhibitory activities with IC50 values of 42.1 μmol/l Exhibited effective PDE inhibitory activities with IC50 values of 63.5 μmol/l Exhibited effective PDE inhibitory activities with IC50 values of 89.4 μmol/l Exhibited effective PDE inhibitory activities with IC50 values of 110.6 μmol/l Exhibited effective PDE inhibitory activities with IC50 values of 123.8 μmol/l

Shi et al. (2013)

Shi et al. (2013)

Shi et al. (2013)

Shi et al. (2013)

Shi et al. (2013)

used to treat impotence, hypertension, hyperlipemia, diabetes, obesity, osteoporosis, Alzheimer's disease (AD), aging, and lupuslike syndrome. In clinics, anti-hypertensive effects of Eucommia ulmoides leaves have been well documented. Modern pharmacological evaluations, combined with phytochemistry technology, have revealed an increasing number of active compounds in Eucommia ulmoides (Table 2 and Fig. 3). 4.1. Anti-hypertensive activity Recently, in vivo and in vitro experiments have shown that different extracts and lignans of Eucommia ulmoides exert antihypertensive activities by inhibiting cAMP activity and calcium ion internal flow, regulating NO and the renin–angiotensin system, relaxing blood vessels, and increasing coronary flow. In 2004, Kwan et al. evaluated the anti-hypertensive activity of aqueous extracts of Eucommia ulmoides leaf and bark. At doses of 0.4–1.6 mg/ml, these extracts caused endothelium-dependent


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lowered blood pressure in both SD rats and SHR in a dosedependent manner, but iridoids of Eucommia ulmoides failed to affect blood pressure with either type of administration. Moreover, treatment of SHR with lignans of Eucommia ulmoides (oral dose of 300 mg/kg twice a day) markedly increased plasma NO levels but decreased renin activity and Ang II levels over the long-term. In perfusion experiments, lignan fractions from Eucommia ulmoides rapidly relaxed mesenteric arteries in a dose-dependent fashion. Lignans of Eucommia ulmoides may be the effective fraction for lowering blood pressure, and this antihypertensive effect is most likely associated with regulation of NO and the renin–angiotensin system, and directly relaxing arteries (Luo et al., 2010). Intragastric administration of lignan extracted from Eucommia ulmoides to SHR (at a dose of 300 mg/kg/d for 16 weeks) significantly decreased the mean arterial blood pressure and improved vascular remodeling. Interestingly, aldose reductase plays a vital role in the pathology of hypertensive vascular remodeling and may be a new target for the treatment of cardiovascular diseases. Lignans of Eucommia ulmoides may serve as a new therapeutic agent for the treatment of hypertension by improving vascular remodeling (Gu et al., 2011). 4.2. Hypolipidemic activity

Fig. 2. The parent nucleus structure of the lignans from Eucommia ulmoides.

relaxation in a dose-dependent manner in isolated rat aortic and dog carotid rings (precontracted with 1 mmol/l phenylephrine). This relaxation effect was either abolished or substantially inhibited by NG-nitro-L-arginine methyl ester and methylene blue, indicating the involvement of the nitric oxide synthase pathway in vaso-relaxant action (Kwan et al., 2004a). Additional studies showed that aqueous extracts isolated from Eucommia ulmoides bark (0.2–1.6 mg/ml) had relaxant effects on the aorta, the proximal, and distal ends of the superior mesenteric arteries, and the smaller muscular arteries in rats. These findings offer a plausible mechanism for the antihypertensive effects and vasorelaxing actions of Eucommia ulmoides (Kwan et al., 2004b). In 2010, the anti-hypertensive fractions of Eucommia ulmoides and the underlying mechanisms in spontaneously hypertensive rats were investigated in vivo and in vitro. In an in vivo study, lignans and iridoids of Eucommia ulmoides were administered to Sprague-Dawley rats and spontaneously hypertensive rats (SHRs), and their blood pressure plasma levels of nitric oxide, renin activity and plasma concentrations of angiotensin II (Ang II) were observed and measured. In an in vitro study, rat mesenteric arteries were treated with lignans of Eucommia ulmoides and vessel relaxation responses were determined. Intravenous or intragastric administration of the lignan fraction at Eucommia ulmoides, at doses of 15, 30 and 60 mg/kg for 8 weeks, strongly

After being fed with Eucommia ulmoides leaf extracts (0.175 g/100 g diet) for 10 weeks, hyperlipidemic hamsters exhibited smaller epididymal adipocytes compared to the control group, which was fed a high-fat diet (10% coconut oil/0.2% cholesterol, wt/wt). Supplementation with Eucommia ulmoides leaf extract significantly lowered plasma levels of triglyceride, total cholesterol, LDL-cholesterol, non-HDL cholesterol, and free fatty acid, whereas it elevated HDL-cholesterol/ total cholesterol ratio and apolipoprotein A-I levels. Hepatic cholesterol concentrations were lower in hamsters fed Eucommia ulmoides compared to control animals. Plasma concentrations of total cholesterol positively correlated with hepatic HMG-CoA reductase activity (r¼0.547, po0.05) and hepatic cholesterol concentration (r¼0.769, po0.001). In high fat-fed hamsters, hepatic fatty acid synthase and HMG-CoA reductase activities were significantly reduced by supplementation with Eucommia ulmoides leaf extract. Plasma fatty acid concentrations, which positively correlate with hepatic fatty acid synthase activity, were lower in animals given Eucommia ulmoides leaf extract. These results demonstrate that in high fat-fed hamsters, Eucommia ulmoides leaf extract exerts anti-hyperlipidemic effects by suppressing hepatic fatty acid and cholesterol biosynthesis while simultaneously reducing plasma and hepatic lipids (Choi et al., 2008). At the same time, intraduodenal (ID) injection of 1 or 5 mg of Eucommia ulmoides leaf extracts (ELE) elevated epididymal white adipose tissue sympathetic nerve activity (WAT-SNA) and interscapular brown adipose tissue sympathetic nerve activity (BAT-SNA) in urethane-anesthetized rats. Moreover, ELE injection increased plasma concentrations of free fatty acids (FFA, a marker of lipolysis) and body temperature (BT, a marker of thermogenesis) in conscious rats. Furthermore, ID administration of ELE decreased gastric vagal nerve activity (GVNA) in urethane-anesthetized rats. At the same time, including ELE in the diet reduced food intake, body and abdominal adipose tissue weight and plasma triglyceride levels (Horii et al., 2010). Based on observations of ELE's effects on lipid metabolism, the underlying mechanisms may include the following three points: (1) suppressing hepatic fatty acid and cholesterol biosynthesis; (2) stimulating lipolysis and thermogenesis; and (3) suppressing appetite. 4.3. Anti-obesity activity In a metabolic syndrome-like rat model (produced by feeding a 35% high fat diet), Eucommia ulmoides leaf minimized the weight gain and accumulation of visceral fat in a dose-dependent fashion and curtailed increases in plasma levels of tumor-associated

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glycoprotein (TAG) and non-esterified fatty acid. Concomitantly, Eucommia ulmoides leaf increased adiponectin levels while suppressing resistin and tumor necrosis factor-α levels in plasma. Treatment with the Eucommia ulmoides leaf also enhanced metabolic function in several organs, including diminishing ATP production in white adipose tissue, accelerating β-oxidation in liver, and increasing the use of ketone bodies/glucose in skeletal muscle (Fujikawa et al., 2010). At the same time, the 30% MeOH fraction of Eucommia ulmoides leaves, which contains more asperuloside, significantly inhibited body weight, white adipose tissue weight, plasma triglyceride levels and total cholesterol levels, indicating strong anti-obesity properties in vivo (Hirata et al., 2011). 4.4. Anti-diabetic activity Eucommia ulmoides leaves exhibit anti-diabetic activity in several diabetic models. In fructose-drinking rats, daily oral administration of

ELE at doses of 500 and 1000 mg/kg over 4 weeks significantly decreased plasma levels of insulin and the homeostasis model assessment ratio without affecting blood glucose levels and significantly lowered systolic blood pressure. At the same time, ELE treatment of fructose-drinking rats decreased tyrosine hydroxylaselike immunoreactivity never fiber density and increased calcitonin gene-related peptide-like immunoreactivity never fiber density in mesenteric arteries (Jin et al., 2010). In an intraperitoneal glucose tolerance test, the aqueous extract of Eucommia ulmoides leaves significantly lowered blood glucose levels, enhanced glucose disposal, and increased plasma insulin and C-peptide levels. Meanwhile, aqueous ELE also lowered the glucose-6-phosphatase, phosphoenolpyruvate carboxykinase, hepatic fatty acid synthase, HMG-CoA reductase and acyl coenzyme A-cholesterol activities of diabetic rats. The aqueous extract of Eucommia ulmoides leaves may partly ameliorate hyperglycemia and hyperlipidemia associated with type 2 diabetes (Park et al., 2006a). At the same time, it improved

Fig. 3. The chemical structure of some activities compounds from Eucommia ulmoides.


87

O Fig. 3. (continued)

hyperglycemia and seemingly enhanced the function of pancreatic beta-cells in streptozotocin (STZ, 70 mg/kg B.W., i.p.)-induced diabetic rats (Lee et al., 2005). In conclusion, long-term administration of ELE may ameliorate pre-diabetic insulin resistance and abnormal perivascular innervation, increase glycolysis, and suppress gluconeogenesis and biosynthesis of fatty acid and cholesterol. 4.5. Effect on bone metabolism Eucommia ulmoides is one of the most important tonic herbs in traditional Chinese medicine for the treatment of bone fractures and other bone diseases. Modern pharmacological and molecular biology studies have supported these traditional uses and suggest that crude extracts and total glycosides of Eucommia ulmoides may yield safe and mild anti-osteoporosis agents. Daily oral administration of an Eucommia ulmoides cortex extract [100, 300, and 500 mg/kg/d started on week 4 after ovariectomy (OVX) for 16 weeks] significantly inhibited OVX-induced decreases in biomechanical quality of the femur and improved bone microarchitecture. Meanwhile, an Eucommia ulmoides cortex extract dosedependently inhibited total bone mineral density decreases in the femur caused by OVX and decreased levels of the bone turnover markers osteocalcin, alkaline phosphatase, deoxypyridinoline, and urinary Ca and P excretions. In particular, Eucommia ulmoides cortex

extract at a dose of 500 mg/kg significantly mitigated the decreases in bone volume/tissue volume, connect density, trabecula number, and trabecula thickness associated with OVX in rats and increased trabecular separation and structure model indices (Zhang et al., 2009). In 2011, Li et al. (2011b) found that total glycosides from Eucommia ulmoides seeds enhanced bone density and bone strength in rat femurs. Oral administration of total glycosides isolated from Eucommia ulmoides seeds (400 mg/kg for 1 month) to rats led to a significant increase in biomechanical quality of the femur; dramatically increased bone volume/tissue volume, connectivity density, trabecular number, trabecular thickness and bone density; decreased trabecular separation and structure model indices; and altered bone histomorphology (Li et al., 2011a, 2011b). These results indicate that Eucommia ulmoides exhibits preventive effects on estrogen deficiency-induced osteoporosis, and may be a potential alternative medicine for treatment of postmenopausal osteoporosis. In vitro studies showed that crude water extract of Eucommia ulmoides enhanced proliferation of osteoblast-like cells by 45% when used at a concentration of 0.4 mg/ml in 48 h co-cultures UMR106 cells (Wang et al., 2000). Calcium phosphate cement and Eucommia ulmoides extract also had effects on the proliferation and adhesion of MC3T3E1 osteoblasts in vitro. This extract, at concentrations of 0.152 and 0.304 mg/ml, enhanced MC3T3E1 osteoblast growth, proliferation and adhesion (Lin et al., 2008).

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4.6. Anti-inflammatory, anti-viral and anti-bacterial activities Crude extracts of Eucommia ulmoides bark exhibit antiinflammatory effects and thus may serve as a potential treatment for inflammatory diseases. Aqueous extracts of Eucommia ulmoides significantly suppressed COX-2 enzyme with IC50 ¼9.92 mg/ml, although this effect was less potent than common synthetic nonsteroidal anti-inflammatory drugs (Kim et al., 2009). In lipopolysaccharide (LPS, 1 μg/ml)-induced responses of mouse peritoneal macrophages, the Eucommiae cortex (0.1 and 0.5 mg/ml) inhibited production of tumor necrosis factor-α, interleukin-6, cyclooxigenase-2, prostaglandin E and nitric oxide (Kim et al., 2012). Crude polysaccharides isolated from the stem bark of Eucommia ulmoides have also been shown to exert beneficial effects on lupuslike syndrome induced by CJ-S (131) in mice. In BALB/c mice immunized with CJ-S (131) in Freund's complete adjuvant, intragastric administration of crude polysaccharides from the stem bark of Eucommia ulmoides (15 and 30 mg/kg/d for 5 weeks) protected against glomerular injury by reducing immunoglobulin deposition, lowering proteinuria and inhibiting the production of serum autoantibodies and total immunoglobulin G (Jiang et al., 2011). Daily intake of alkaline extracts of Eucommia ulmoides tea and/ or Eucommia ulmoides extracts may suppress HIV infection. Eucommia ulmoides may be a new efficacious drug for AIDS. The alkaline extracts of Eucommia ulmoides tea leaves, an acid polysaccharide with 27% reducing sugar, 46% neutral sugars and 22% uronic acid, suppressed HIV-induced cytopathicity in HIV (HTLVIII) infected MT-4 cells with an extremely low cytotoxicity (EC50 ¼12–67 mg/ml, CC50 41.0 mg/ml) (Nakano et al., 1997). In addition, samples of Eucommia ulmoides had potent inhibitory effects on the HIV gp41 six-helix bundle formation, as determined by a modified sandwich ELISA and PAGE, indicating that Eucommia ulmoides may be the source of a new efficacious drug for treatment of AIDS (Lv et al., 2008). Extracts of Eucommia ulmoides were found to inhibit the growth of Propionibacterium acnes with minimum inhibitory concentrations of 0.5 mg/ml. An Eucommia ulmoides extract (0.1 mg/ ml) also reduced the secretion of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin-8, and IL-1β, by human monocytic THP-1 cells pretreated with heat-killed Propionibacterium acnes (Tsai et al., 2010). The 95% (v/v) ethanol extract of Eucommia ulmoides (at 0.1 and 1.0 mg/ml) exhibited activity against bacteria (Acinetobacter baumannii and Staphylococcus aureus) and fungi (Aspergillus fumigatus) (Zhang et al., 2013b). 4.7. Neuroprotective activity The aqueous extract of Eucommia ulmoides exhibits significant neuroprotective effects in several experimental models and thus may be a potential therapeutic in neurodegenerative diseases, such as Alzheimer's disease (AD). In mice, the aqueous extract of Eucommia ulmoides bark (5 and 10 mg/kg, p.o.) exerted a neuroprotective effect on amyloid beta (25–35) [Aβ (25–35)]-induced (6 nm, i.c.v.) learning and memory impairment. In in vivo studies, the aqueous extract of Eucommia ulmoides significantly improved Aβ (25–35)-induced memory deficits in the Y-maze test and increased step-through latency time with Aβ (25–35)-induced learning and memory deficits in the passive avoidance test. In addition, treatment with the Eucommia ulmoides aqueous extract decreased escape latencies in Aβ (25–35)-induced cognitive impairments in the Morris water maze test. The aqueous extract of Eucommia ulmoides also strongly inhibited acetylcholinesterase (AChE) activity in the hippocampus and frontal cortex at 20 mg/kg concentrations and suppressed AChE activity in a dose-dependent manner; the degrees of inhibition were 27.3% and 25.3% (Kwon et al., 2011).

In an in vitro study, the aqueous extract of Eucommia ulmoides (at 10, 50, 100, 200, and 400 μg/ml concentrations) were found to inhibit AChE activity in a dose-dependent manner (IC50 ¼172 μg/ ml). The extract also protected human SH-SY5Y neuroblastoma cells against hydrogen peroxide-induced neuronal cell death (Kwon et al., 2012). 4.8. Antioxidative activity Eucommia ulmoides has a strong anti-oxidation capacity and can scavenge free radicals in vivo and in vitro. It can also decrease oxidative damage to biomolecules. An ethanol extract of Eucommia ulmoides remarkably reduced oxidative damage to cells and increased cell survival rate in a dose-dependent manner, with a half-effective concentration of 25 mg/ml. Moreover, the extract significantly decreased H2O2–induced expression of caspases 3, 6, 7, and 9 by MC3T3E1 cells, with a half-effective concentration ranging from 12.5 to 25 mg/ml. The results indicate that Eucommia ulmoides is a potent antioxidant and may contribute to its many cellular protective functions (Lin et al., 2011). In type 2 diabetic mice, an Eucommia ulmoides extract significantly enhanced the activities of erythrocyte superoxide dismutase, catalase, and glutathione peroxidase but lowered the levels of hydrogen peroxide and lipid peroxide in erythrocytes, liver, and kidney, revealing powerful antioxidant activity (Park et al., 2006b). The aqueous extracts of Eucommia ulmoides leaves, raw cortex, and roasted cortex inhibited oxidation of deoxyribose by Fe3 þ – EDTA/H2O2/ascorbic acid in a concentration dependent manner. At a concentration of 1.14 mg/ml, the inhibitory effects of the extracts of leaves, roasted cortex, and raw cortex were 85.2%, 68.0%, and 49.3%, respectively. Meanwhile, the extract of leaves inhibited the strand- breaking of DNA induced by the Fenton reaction at concentrations of 5 and 10 mg/ml, which was similar to mannitol. The leaf extract also inhibited the oxidation of 2′-dG to 8-OH-2′dG induced by Fe3 þ –EDTA/H2O2/ascorbic acid. The leaf extract had the most pronounced inhibitory effect on Fenton reaction-induced oxidative damage to biomolecules, followed by roasted cortex extract and raw cortex extract. Therefore, drinking Eucommia ulmoides tea (leaf extract) over a long period may have anticancer potential (Hsieh and Yen, 2000). In 2010, the antioxidant activities of extracts from the leaves, roasted cortexes, and seeds of Eucommia ulmoides were compared by measuring the radical scavenging activity of 2, 2-diphenyl-1picrylhydrazyl, ferric reducing antioxidant power, and lipid peroxidation inhibition capacity in a β-carotene/linoleic acid system. The results showed that leaf extract exhibited the highest DPPH radical scavenging activity, with an inhibition rate of 81.40%, followed by BHT (76.60%) and the roasted cortex extract (16.72%), whereas the seed extract had the lowest activity, at 7.65%. In ferric reducing antioxidant power assays, the order of ferric reducing activities of three Eucommia ulmoides extracts compared with positive control was leaf 4roasted cortex 4seed. In the β-carotene/linoleic acid emulsion system, the leaf extract also possessed better antioxidant capacity (43.58%) than the roasted cortex extract (26.71%) or seed extract (25.10%) (Xu et al., 2010). In addition, the hot water extract of Eucommia ulmoides leaves exhibited marked activity as a reactive oxygen species (ROS) scavenger and was able to scavenge hydroxyl radicals, superoxide anions and hydrogen peroxides; the scavenging effect was concentration dependent. The extract of roasted cortex exhibited a modest scavenging effect on ROS, while the extract of raw cortex had the weakest scavenging effect. The results presented herein indicate that extract of Eucommia ulmoides could act as a prophylactic agent to prevent free radical-related diseases (Yen and Hsieh, 2000). The above three studies showed that extracts from the leaf of Eucommia ulmoides have a stronger antioxidant activity than


extracts from roasted cortex, raw cortex or seed in all five assay systems. The reason for this finding is most likely due to the leaf's remarkably high phenolic and flavonoid contents, which possess large numbers of aromatic hydroxyl groups. 4.9. Improving erectile function Eucommia ulmoides was traditionally used to reinforce the Kidney Yang and to treat “coldness” and male impotence. Intragastric administration of Eucommia ulmoides at a dosage of 400 mg/kg in a rat for 4 weeks notably increased the catching frequency of the rats, enhanced the expression of nNOS in the penis, and improved the erectile function of diabetic rats (Zhang et al., 2006). These results confirm the traditional use of Eucommia ulmoides, but a wider range of doses should be studied to support the use of Eucommia ulmoides for curing erectile dysfunction and other impotence conditions. Further studies indicate that Eucommia ulmoides is a rich source of new selective estrogen receptor modulators; evaluations of Eucommia ulmoides's health benefits and safety as a food additive should take into account the diverse phytoestrogen activities of the individual components (Wang et al., 2011). 4.10. Anti-fatigue activity Eucommia ulmoides leaves increased the activity of lactate dehydrogenase and 3-hydroxyacetyl-CoA dehydrogenase in skeletal muscles. In addition, mechanical training combined with the use of leaves cooperatively increased the ability to avoid lactate accumulation in skeletal muscle. These results suggest that the administration of Eucommia ulmoides leaves along with light intensity training enhances the ability of a muscle to resist fatigue (Li et al., 1999a). In mouse swimming experiments, administration of the flavonoid glycoside (2 g/kg, i.g., 15 d) from Eucommia ulmoides leaves significantly prolonged swimming time, decreased lactic acid content and serum urea nitrogen, and increased liver glycogen content. This effect was related to increased energy storage, decreased generation of harmful metabolites during exercise, improved the body's tolerance for exercise, and enhanced clearance of free radicals during exercise (Yang et al., 2010). Eucommia ulmoides male flower tea was administered to experimental groups at doses of 130, 260, 520 mg/kg for 30 days, resulting in significantly prolonged swimming time, reduced blood urea nitrogen levels, increased liver glycogen storage and accelerated lactic acid clearance after swimming (Jin et al., 2008). 4.11. Anti-aging activity Administration of a methanol extract from the leaves of Eucommia ulmoides stimulated collagen synthesis and improved the low turnover rate of stratum corneum in false aged model rats. Later studies also showed that the acetone fraction of the methanol extract, which mainly contained iridoid mono-glycosides, was the active anti-aging ingredient (Li et al., 1998; Li et al., 1999b). 4.12. Anti-tumor activity In vitro, the 70% ethanol extract of Eucommia ulmoides (at a concentration of 150 μg/ml) induced the death of the human promyelocytic leukemia cell line HL-60 by increased caspase-3 activity after a 24 h incubation (Nishida et al., 2003). The aqueous extract of Eucommia ulmoides leaves also reduced chromosome aberrations in CHO cells. At the same time, mice receiving 1.0 ml 4% Tochu tea extract by oral gavage 6 h before intraperitoneal injection of Mitomycin C (MMC) exhibited a decrease in the frequency of micronuclei. Notably, of 17 components isolated and identified from Tochu tea, five were iridoids with an α-

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unsaturated carbonyl group (geniposidic acid, geniposide, asperulosidic acid, deacetyl asperulosidic acid, and asperuloside), and three were phenols (pyrogallol, protocatechuic acid, and p-transcoumaric acid) that had significant anti-clastogenic activity (Nakamura et al., 1997). Intragastric administration of Eucommia ulmoides polysaccharide (50, 100, and 200 mg/kg/d) to mice with S-180 tumors for 10 days inhibited tumor growth, increased spleen and thymus indices, elevated leukocyte counts in peripheral blood and bone marrow, and reversed the reduction in leukocyte count induced by cyclophosphamide (Xin et al., 2009). The effect of Tochu tea, which is an aqueous extract of Eucommia ulmoides leaves and a popular beverage in Japan, on urine mutagenicity before and after ingestion of raw fish and cooked beef, was studied using Salmonella typhimurium YG1024. Tochu tea leaves (4 g) (Lot No. 94-21B Youn An Cheng) were boiled with 2000 ml of boiling water for 10 min and stored at 4 1C. Volunteers drank this beverage 7–9 times per day, 150–500 ml per drinking session. Urine was collected from seven healthy, non-smoking Japanese women before and after ingestion of raw fish and cooked beef over 3 days. The mutagenicity of urine collected from the Tochu teadrinking group was much lower. The ingestion of Tochu tea may reduce human exposure to dietary mutagens (Sasaki et al., 1996). Although the ingestion volume was greater than what is normally consumed, the result of this clinical study revealed the potential antimutagenic effect of prolonged, daily ingestion of Tochu tea. 4.13. Hepatoprotective activity The anti-hepatotoxic activity of crude extracts from Eucommia ulmoides in in vivo experimental models was demonstrated by biochemical and pathological analysis. In CCl4-induced (20% CCl4/ olive oil, o.p. twice a week) chronic hepatotoxic rats, intragastric administration of aqueous extract of Eucommia ulmoides leaves, at doses of 0.1, 0.5, and 1.0 g/kg for 4 weeks, decreased the glutamic pyruvic transaminase, l-lactate dehydrogenase, and alkaline phosphatase levels in serum and significantly increased glutathione content and the activities of guaiacol peroxidase, glucocorticoid receptor (GRd) and glutathione S-transferase (GST) in liver. At the same time, liver histopathology showed that the crude extract reduced the incidence of liver lesions including cloudy swelling of hepatic cells, cytoplasmic vacuolization, lymphocyte infiltration, hepatic necrosis and fibrous connective tissue proliferation (Huang et al., 2006). In mice receiving immunological liver-injury by Bacille-Calmette-Guerin and lipopolysaccharide treatment, the alcohol extract from Eucommia ulmoides (at doses of 40.95, 81.90 and 163.80 mg/kg, i.g. once a day for 10 days) significantly decreased the level of ALT and aspartate transaminase (AST) in serum and improved superoxide dismutase (SOD) and GSH activity (Gao et al., 2011). 4.14. Enhancing immune-function Eucommia ulmoides polysaccharides, at oral doses of 50, 100, and 200 mg/kg, mitigated the decrease in body weight, chest gland index, abdominal cavity macrophage swallowing rate and phagocytic count induced by cyclophosphamide. These polysaccharides also elevated the thymus index and increased the abdominal cavity macrophage engulfing rates and engulfing index in an immunosuppressive mouse model (Xin et al., 2007a; Xu et al., 2013). 5. Toxicity Although Eucommia ulmoides has long been used as medicine or food, systematic toxicity and safety evaluations have been rare.

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In 1999, the acute toxicity of Eucommia ulmoides tea was measured by intragastric administration to mice at doses of 88.9 g/kg/d for 7 days. The results of this study revealed no mortality or significant changes in the general behavior or gross appearance of internal organs (Zhang et al., 1999). In a mouse lymphoma assay and mouse bone marrow micronucleus test, Eucommia ulmoides decoction at doses of 2.5, 5, 10, and 20 mg/ml induced the Thymidine kinase (Tk) gene mutation and chromosome damage in L5178Y cells with and without metabolic activation ( 7S9) in a dose-dependent manner. This result suggested potential genotoxicity for human bodies. However, Eucommia ulmoides decoction (12.8, 25.6 and 51.2 g/kg) did not result in chromosome damage in bone marrow cells in ICR mice, and it had no genotoxicity in vivo with metabolic activation (Hu et al., 2009). The subacute toxicity of Eucommia ulmoides extract was studied in a normal Kunming mouse model by intragastric administration of the extract, at doses of 6.17, 2.06 and 0.69 g/kg/d for 7 days. No significant differences were found in treated mice for any parameter analyzed, including serum enzymes and indices of the spleen, liver, heart, lung, kidney and sexual organs (Liu et al., 2006). While these toxicity studies were conducted on cells or small mammals, no safety evaluations have been carried out on dogs, monkeys or humans.

6. Future perspectives and conclusion Eucommia ulmoides, a well-known and the sole species of the genus Eucommia, has been traditionally used in various indigenous systems of medicines. In vitro and in vivo pharmacological studies have increasingly confirmed its traditional use, especially on joint diseases and kidney asthenia. Chlorogenic acid and some iridoids, aucubin, geniposidic acid, and geniposide, have been demonstrated to be the main and active ingredients in this plant. However, there also a number of points that needed to be improved: (1) most pharmacological activities were measured using complex extracts or single isolated compounds in vitro or in vivo with cells or animals. Some data from mice studies were obtained using exorbitant doses, and no relevant components of Eucommia ulmoides were detected in blood. (2) Most of the biological activities of Eucommia ulmoides can be ascribed solely to the activity of lignans and iridoids. However, how the secondary constituents contribute to different activities is not clear. (3) Toxicity and clinical studies are urgently needed to confirm the safety of Eucommia ulmoides or traditional phytotherapy and health care use. (4) Good plant practice should be enforced to meet quantity and quality requirements for Eucommia ulmoides.

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