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Natural Product Research: Formerly Natural Product Letters Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gnpl20
Scillapersicene: a new homoisoflavonoid with cytotoxic activity from the bulbs of Scilla persica HAUSSKN a
b
c
Salar Hafez Ghoran , Soodabeh Saeidnia , Esmaeil Babaei , d
e
Fumiyuki Kiuchi & Hidayat Hussain a
Faculty of Basic Sciences, Department of Chemistry, Golestan University, Gorgan 4913815739, Iran b
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Faculty of Pharmacy, Medicinal Plants Research Center, Tehran University of Medical Sciences, Tehran 1417614411, Iran c
Department of Animal Biology, School of Natural Sciences, University of Tabriz, Tabriz, Iran d
Faculty of Pharmacy, Department of Pharmaceutical Sciences, Keio University, Tokyo, Japan e
UoN Chair of Oman’s Medicinal Plants and Marine Natural Products, University of Nizwa, Nizwa, Sultanate of Oman Published online: 03 Jul 2015.
To cite this article: Salar Hafez Ghoran, Soodabeh Saeidnia, Esmaeil Babaei, Fumiyuki Kiuchi & Hidayat Hussain (2015): Scillapersicene: a new homoisoflavonoid with cytotoxic activity from the bulbs of Scilla persica HAUSSKN, Natural Product Research: Formerly Natural Product Letters, DOI: 10.1080/14786419.2015.1054286 To link to this article: http://dx.doi.org/10.1080/14786419.2015.1054286
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NATURAL PRODUCT RESEARCH, 2015 http://dx.doi.org/10.1080/14786419.2015.1054286
SHORT COMMUNICATION
Scillapersicene: a new homoisoflavonoid with cytotoxic activity from the bulbs of Scilla persica HAUSSKN Salar Hafez Ghorana, Soodabeh Saeidniab, Esmaeil Babaeic, Fumiyuki Kiuchid and Hidayat Hussaine Faculty of Basic Sciences, Department of Chemistry, Golestan University, Gorgan 4913815739, Iran; bFaculty of Pharmacy, Medicinal Plants Research Center, Tehran University of Medical Sciences, Tehran 1417614411, Iran; cDepartment of Animal Biology, School of Natural Sciences, University of Tabriz, Tabriz, Iran; dFaculty of Pharmacy, Department of Pharmaceutical Sciences, Keio University, Tokyo, Japan; eUoN Chair of Oman’s Medicinal Plants and Marine Natural Products, University of Nizwa, Nizwa, Sultanate of Oman
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a
ARTICLE HISTORY
ABSTRACT
The phytochemical investigation of Scilla persica HAUSSKN bulbs led to the isolation of a novel homoisoflavonoid that named Scillapersicene (1) and identified as 3-(3′,4′-dihydroxybenzylidene)8-hydroxy-5,7-dimethoxychroman-4-one along with five known homoisoflavonoids 2–6, whose structures were elucidated using HRFAB-MS, 1D and 2D NMR spectroscopic data. The known compounds were identified as 3-(3′,4′-dihydroxybenzyl)-5,8dihydroxy-7-methoxychroman-4-one (2), 3,9-dihydro-autumnalin (3), autumnalin (4), 3-(3′,4′-dihydroxybenzylidene)-5,8-dihydroxy-7methoxychroman-4-one (5) and scillapersicone (6). All compounds obtained, expect 2 and 4, showed strong cytotoxic activity against AGS cell line. The toxicity on AGS cell line was measured by 1, 3, 5 and 6 with IC50 values of 8.4, 30.5, 10.7 and 24.2 μM, respectively. In addition, the physico-chemical properties of these natural compounds were optimised using density functional method (B3LYP) with standard 6-311+G* basis set. These natural products have low-energy gaps between the first ionisation potentials and highest occupied molecular orbital. In conclusion, the low-energy gap could cause reason for cytotoxic activity of homoisoflavonoids.
GRAPHICAL ABSTRACT
OH MeO
Scillapersicene O
OH OH
OMe O
Inhibitory activity of Homoisoflavonoids on AGS concerous cell lines
CONTACT Salar Hafez Ghoran © 2015 Taylor & Francis
[email protected], [email protected]
Received 14 March 2015 Accepted 17 May 2015 KEYWORDS
AGS; B3LYP; cytotoxic activity; Scillapersicene; homoisoflavonoid; Liliaceae; Scilla persica
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1. Introduction The genus Scilla is believed to globally represent 81 taxa, and most of which are widespread in Iran. Scilla persica HAUSSKN is a perennial herb belonging to the Liliaceae family. In Iran, the habitat of this plant is West Azerbaijan (Sardasht), Khorramabad, Alvand, Hamedan, Qasr Shirin, Sanandaj and mountains Razaab (Mozaffarian 1997). According to previous studies on Scilla species, they contain alkaloids (Kato et al. 2007), cardiac glycosides (Kamano & Petit 1974), triterpenoids (Mimaki et al. 1993; Nishida et al. 2008), triterpenoid glycosides (Arjune & Klar 2011; Ono et al. 2011), nortriterpenoid glycosides (Ono et al. 2011, 2013), eucosterol oligoglycosides (Lee et al. 2002), stilbenoids (Bangani et al. 1999; Nishida et al. 2008), xanthone, lignin and phenylpropanoid glycoside (Nishida et al. 2008), as well as homoisoflavanones (Heller & Tamm 1981; Bangani et al. 1999; Silayo et al. 1999; Mutanyatta et al. 2003; Shim et al. 2004; Nishida et al. 2008; Hafez Ghoran et al. 2014). These compounds possess antibacterial and antiangiogenic activities, and inhibit in vitro the growth of several microorganisms (Heller & Tamm 1981; Srinivas et al. 2003; Shim et al. 2004). Homoisoflavonoids exclusively represent a modification of the flavonoidal skeleton. Feeding laboratory experiments show that the biosynthesis of 3-benzylchroman-4-ones is a modification of the C6–C3–C6 chalcone–flavonoid pathway by incorporation of an additional carbon atom (Dewick 1975). These compounds were mainly discovered from plants belonging to the Liliaceae family and a few other plant species (Sievänen et al. 2010). Homoisoflavonoids have been reported to display multiple biological properties such as antioxidant activity (Siddaiah et al. 2006; Zhou et al. 2008), cytotoxic activity (Nguyen et al. 2006; Yan et al. 2012; Hafez Ghoran et al. 2014), inhibition of platelet aggregation (Kou et al. 2006), cough sedative (Ishibashi et al. 2001), hyperglycemia (Choi et al. 2004), anti-angiogenic (Shim et al. 2004), anti-fungal (Srinivas et al. 2003), anti-inflammatory, antiallergic, antihistaminic, angioprotective activities, and have been detected as potent phosphodiesterase inhibitors (Della Loggia et al. 1989; Amschler et al. 1996; Shim et al. 2004). Many natural products have traditionally played a prominent role in drug discovery and were the basis of most early medicines (Grabley & Thiericke 1999; Buss et al. 2003). In this study, we report a phytochemical study on fresh bulbs of S. persica that resulted in isolation of new homoisoflavonoid (1), together with five known compounds (2–6, see Figure 1). Moreover, we also used the B3LYP/6-311+G* method implemented in Gaussian 98 package to determine the relative geometric structures, molecular orbital energy, and other physico-chemical properties of 1–6 (Frisch et al. 1998).
1. R1 = R3 = OMe, R2 = H, R4 = R5 = OH 4. R1 = R3 = OH, R2 = OMe, R4 = R5 = H 5. R1 = R4 = R5 = OH, R2 = H, R3 = OMe
Figure 1. Chemical structures of compounds 1–6.
2. R1 = R4 = R5 = OH, R2 = H, R3 = OMe 3. R1 = R3 = OH, R4 = R5 = H 6. R1 = R3 = OMe, R2 = H, R4 = R5 = OH
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2. Results and discussion The Et2O extract of S. persica bulbs was fractionated by normal phase chromatography using a Column Chromatography system, and six homoisoflavonoids were isolated. The six isolated compounds include one new homoisoflavonoid (1), together with five known compounds (2–6, Figure 1). The homoisoflavonoids showed the spots with orange, dark orange and red-orange colours on TLC by spraying anisaldehyde-H2SO4 reagent followed by heating. The known compounds (2–6) were identified as 3-(3′,4′-dihydroxybenzyl)-5,8-dihydroxy-7-methoxychroman-4-one (2) (Adinolfi et al. 1986), 3-(4′-hydroxybenzyl)-5,7-dihydroxy-6-methoxy- chroman4-one or 3,9-dihydro-autumnalin (3) (Silayo et al. 1999; Mutanyatta et al. 2003; Nishida et al. 2008), 3-(4′-hydroxybenzylidene)-5,7-dihydroxy-6-methoxychroman-4-one or autumnalin (4) (Silayo et al. 1999), 3-(3′,4′-dihydroxybenzylidene)-5,8-dihydroxy-7-methoxychroman-4-one (5) (Mašterov et al. 1991) and scillapersicone (6) (Hafez Ghoran et al. 2014) based on the comparison of their spectroscopic data with those described in the literature. The known compounds (2–6) had previously been reported from Muscari armeniacum (2), S. nervosa and S. socialis (3 and 4), Muscari Racemosum (5) and S. persica (6). Compound 1 was obtained as a yellowish amorphous powder. The mass spectra of 1 indicated an [M]+ ion peak at 345.0952, and the molecular formula of 1 was defined as C18H16O7 by HRFAB-MS. In the IR spectrum, absorption bands at 1613 and 3458 cm−1 were in accordance with the presence of carbonyl and hydroxyl functions, respectively. The 1H, 13 C-NMR and 1H-13C-correlation (HSQC and HMBC) spectra showed that this natural product has a homoisoflavonoidal skeleton (Agrawal et al. 1989) (see Supplementary Table S1). In its 1 H-NMR spectrum, signals for two methoxy groups at δH 3.77 (S, 3H) and 3.88 (S, 3H) were clearly exhibited. The aromatic A-ring proton resonated at δH 6.38 (1H, s, H-6) and the aromatic B-ring protons resonated at δH 6.80 (1H, d = 2.0 Hz, H-2′), 6.73 (1H, dd = 2.1, 8.3 Hz, H-6′), and 6.82 (1H, d = 8.1 Hz, H-5′). The 13C-NMR spectrum displayed 18 signals. In the HMBC of 1, characteristic correlation signals of δH 5.2 (2H-2) with C-3 (δC 130.0), C-4 (δC 179.1), C-8a (δC 150.4) and C-9 (δC 135.5), of δH 7.44 (H-9) with C-4, C-1′ (δC 126.1), C-5′ (δC 116.3) and C-6′ (δC 123.3), of proton of aromatic A-ring δH 6.38 (H-6) with C-4a (δC 107.5), C-5 (δC 154.7), C-7 (δC 154.0) and C-8 (δC 128.4), of proton of aromatic B-ring δH 6.8 (H-2′) with C-9, C-4′ (δC 147.7) and C-6′, of δH 6.73 (H-6′) with C-9, C-2′ (δC 117.8) and C-4′, of δH 6.82 (H-5′) with C-1′ and C-3′. Therefore, the structure of this compound suggestion was confirmed by correlations in the HMBC (Supplementary Figure S1). As a result, all spectroscopic data led to the structure 3-(3′, 4′-dihydroxybenzylidene)-8-hydroxy-5,7-dimethoxychroman-4-one that trivially named Scillapersicene (1). As shown in Supplementary Table S2, the results of cytotoxic evaluations in this study revealed that the compounds 1–6, expect 2 and 4, were able to affect the viability of cancerous AGS cells significantly. This anti-cancer effect at 0–200 μM concentrations was detected in a time- and dose-dependent manner. Compounds 2 and 4 could not be considered as an anti-tumour compounds as they affect normal cells like cancerous ones. And also compounds 1, 3, 5 and 6 showed cytotoxic activity with IC50 values of 8.4, 30.5, 15.0 and 24.2 μM, respectively. Molecular structure of 1, obtained by theoretical calculations, is shown in Supplementary Figure S2. The electronic densities in the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for compounds 1–6 at the B3LYP/6-311+G* level were studied. Our calculation exhibits that the energy levels of HOMO and LUMO are −5.60 and −2.02 eV for Scillapersicene (1), respectively. As shown in Supplementary Figure S2, the HOMO in Scillapersicene molecule is primarily situated on the carbonyl group atoms,
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oxygen and the carbon atoms of the A ring, while LUMO is located on the carbon atoms of the A, B and C rings. The HOMO–LUMO energy separation has been applied as an indicator of kinetic stability of the system. The energy gap (Δε = εHOMO − εLUMO) of these natural compounds are calculated with the values of 3.58, 3.86, 4.26, 3.60, 3.26 and 4.29 eV at the B3LYP method, respectively. This small HOMO–LUMO gap reveals a low kinetic stability and high chemical reactivity; because it is energetically unfavourable to append electrons to a high-lying LUMO or to draw out electrons from a low-lying HOMO. Therefore, the low-energy gap can cause reason for cytotoxic activity of homoisoflavonoids. The MEP, plotted in Supplementary Figure S2, show that oxygen atoms are negatively charged (red colour) while the hydrogen atoms of hydroxyl groups are positively charged (blue colour) in the molecule. In Supplementary Table S3, the quantum molecular descriptors for 1–6 such as amount of HOMO, LUMO, the energy gaps, Fermi energy level (EF), global softness (S), hardness (η), electrophilicity index (ω), electronegativity (χ) and the maximum amount of electronic charge (∆Nmax) were determined (Hafez Ghoran et al. 2014).
2.1. Spectroscopic data of new compound (Scillapersicene 1) Yellowish amorphous powder; mp 209–211 °C; UV (MeOH): λmax, nm (log ε): 232 (4.15), 365; IR (KBr) = 3458 (OH), 3128, 1613 (C=O), 1401 (Aromatic C=C), 1132 cm−1 (etheric C–O); EIMS m/z (rel. int.): 344.1 [M]+, 328 (12), 307.2 (65), 289.1 (31), 176.1 (8), 154.1 (97), 137.1 (57), 107.1 (33), 89.0 (30), 69.1 (9); HRFAB-MS m/z 345.0952 [M+H]+ (calcd for C18H16O7, 345.0974); 1H and 13 C-NMR assignments are shown in Supplementary Table S1.
3. Conclusion Previous investigations have illustrated that homoisoflavonoids are efficient cytotoxic agents (Nguyen et al. 2006; Yen et al. 2010; Hafez Ghoran et al. 2014). The cellular mutability control by natural antimutagens can provide ways for preventing mutations that conceivably result in cancer as well as diseases caused by genotoxic agents. An intensive research in the area of antimutagenesis and anticarcinogenesis has led to the identification of a broad range of natural inhibitors acting through different mechanisms (Birt et al. 2001). In this study, one homoisoflavonoid, Scillapersicene along with five known homoisoflavonoids (2–6) were isolated by column chromatography method and identified from the medicinal plant S. persica. A bibliography demonstrated that Scillapersicene are also the first homoisoflavonoids that identified from plants of the Liliaceae family so far. In addition, this is the first report of HRFAB-MS, IR, UV, 1H and 13C-NMR assignments for compound 1. On the basis of cytotoxic assay, the natural compounds 1, 2, 3, 5 and 6 exhibited cytotoxicity towards one human cancer cell line, especially compounds 1 and 5 which showed in vitro cytotoxic activity against AGS cell line more potent than that of the normal cells. Through the calculations of the first ionisation potentials, HOMO, LUMO and energy gaps, it was found that these natural products have low-energy gaps between the first ionisation potentials and the HOMO. Accurate theoretical calculations can help identify and provide ways to obtain important chemical and physical information that cannot be easily obtained by experimental approaches.
Acknowledgements The authors wish to thank Mr Abbas Biglari (Zanjan Institute of Chemistry) for NMR spectroscopic measurements and MPRC colleagues (Medicinal Plants Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences) for their support during the purification process. The authors are also grateful to Tabriz University research councils for partial support of this work.
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Disclosure statement No potential conflict of interest was reported by the authors.
Supplemental data and research materials Supplementary material relating to this study is available online http://dx.doi.org/10.1080 /14786419.2015.1054286, alongside Tables S1–S3, Figures S1, S2 and the original spectra of compound 1.
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References Adinolfi M, Corsaro MM, Lanzetta R, Laonigro G, Mangoni L, Parrilli M. 1986. Ten homoisoflavanones from two Muscari species. Phytochemistry. 26:285–290. Agrawal PK, Thakur RS, Bansal MC. 1989. Carbon-13 NMR of flavonoids. New York (NY): Elsevier Science. Amschler G, Frahm AW, Hatzelmann A, Kilian U, Müller-Doblies D, Müller-Doblies U. 1996. Constituents from Veltheimia viridifolia; I. Homoisoflavones of the bulbs. Planta Med. 62:534–539. Arjune S, Klar F. 2011. Characterization of glycosidic triterpenoids of Scilla litardierei and investigation of its potential cytotoxic effects. Planta Med. 77:PM187. Bangani V, Crouch NR, Mulholland DA. 1999. Homoisoflavanones and stilbenoids from Scilla nervosa. Phytochemistry. 51:947–951. Birt DF, Hendrich S, Wang W. 2001. Dietary agents in cancer prevention: flavonoids and isoflavonoids. Pharmacol Ther. 90:157–177. Buss AD, Buss BC, Waigh RD. 2003. Burger’s medicinal chemistry and drug discovery. 6th ed. Hoboken (NJ): Wiley; p. 847–900. Choi SB, Wha JD, Park SM. 2004. The insulin sensitizing effect of homoisoflavone enriched fraction in Liriope platyphylla Wang et Tang via PI3-kinase pathway. Life Sci. 75:2653–2664. Della Loggia R, Del Negro P, Tubaro A, Barone G, Parrilli M. 1989. Homoisoflavanones as anti-inflammatory principles of Muscari comosum. Planta Med. 55:587–588. Dewick PM. 1975. Biosynthesis of the 3-benzylchroman-4-one eucomin in Eucomis bicolor. Phytochemistry. 14:983–988. Frisch MJ, Trucks GW, Schegel HB, Scuseria GE, Robb MA, Cheeseman JR, Montgomery JA Jr, Vreven T, Kudin KN, Burant JC, et al. 1998. Gaussian 98, Revision D01. Wallingford (CT): Gaussian Inc. Grabley S, Thiericke R. 1999. Drug discovery from nature. Berlin: Springer; p. 3–37. Hafez Ghoran S, Saeidnia S, Babaei E, Kiuchi F, Dusek M, Eigner V, Dehno Khalaji A, Soltani A, Ebrahimi P, Mighani H. 2014. Biochemical and biophysical properties of a novel homoisoflavonoid extracted from Scilla persica HAUSSKN. Bioorg Chem. 57:51–56. Heller W, Tamm C. 1981. Homoisoflavanones and biogenetically related compounds. Prog Chem Org Nat Prod. 4:105–152. Ishibashi H, Mochidome T, Okai J, Ichiki H, Shimada H, Takahama K. 2001. Activation of potassium conductance by ophiopogonin-D in acutely dissociated rat paratracheal neurones. Br J Pharmacol. 132:461–466. Kamano Y, Pettit GR. 1974. Bufadienolides. 26. Synthesis of scillarenin. J Org Chem. 39:2629–2631. Kato A, Kato N, Adachi I, Hollinshead J, Fleet GW, Kuriyama C, Ikeda K, Asano N, Nash RJ. 2007. Isolation of glycosidase-inhibiting hyacinthacines and related alkaloids from Scilla socialis. J Nat Prod. 70:993– 997. Kou JP, Tian YQ, Tang YK, Yan J, Yu BY. 2006. Antithrombotic activities of aqueous extract from Radix Ophiopogon japonicus and its two constituents. Biol Pharm Bull. 29:1267–1270. Lee SM, Chun HK, Lee CH, Min BS, Lee ES, Kho YH. 2002. Eucosterol oligoglycosides isolated from Scilla scilloides and their anti-tumor activity. Chem Pharm Bull. 50:1245–1245. Mašterov I, Suchý V, Uhrín D, Ubik K, Grančaiová Z, Bobovnický B. 1991. Homoisoflavanones and other constituents from Muscari Racemosum. Phytochemistry. 30:713–714. Mimaki Y, Ori K, Sashida Y, Nikaido T, Song L, Ohmoto T. 1993. Peruvianosides A and B, novel triterpene glycosides from the bulbs of Scilla peruviana. Bull Chem Soc Jpn. 66:1182–1186. Mozaffarian V. 1997. Dictionary of the names of Iranian Plants. Tehran: Farhang Moaser; p. 489–490.
Downloaded by [FU Berlin] at 22:37 06 July 2015
6
S. HAFEZ GHORAN ET AL.
Mutanyatta J, Matapa BG, Shushu DD, Abegaz BM. 2003. Homoisoflavonoids and xanthones from the tubers of wild and in vitro regenerated Ledebouria graminifolia and cytotoxic activities of some of the homoisoflavonoids. Phytochemistry. 62:797–804. Nishida Y, Eto M, Miyashita H, Ikeda T, Yamaguchi K, Yoshimitsu H, Nohara T, Ono M. 2008. A new homostilbene and two new homoisoflavones from the bulbs of Scilla scilloides. Chem Pharm Bull. 56:1022–1025. Nguyen AT, Fontaine J, Malonne H, Duez P. 2006. Homoisoflavanone from Disporopsis aspera. Phytochemistry. 67:2159–2163. Ono M, Ochiai T, Yasuda S, Nishida Y, Tanaka T, Okawa M, Kinjo J, Yoshimitsu H, Nohara T. 2013. Five new nortriterpenoid glycosides from the bulbs of Scilla scilloides. Chem Pharm Bull. 61:592–598. Ono M, Toyohisa D, Morishita T, Horita H, Yasuda S, Nishida Y, Tanaka T, Okawa M, Kinjo J, Yoshimitsu H, Nohara T. 2011. Three new nortriterpene glycosides and two new triterpene glycosides from the bulbs of Scilla scilloides. Chem Pharm Bull. 59:1348–1354. Shim JS, Kim JH, Lee J, Kim SN, Kwon HJ. 2004. Anti-angiogenic activity of a homoisoflavanone from Cremastra appendiculata. Planta Med. 70:171–173. Siddaiah V, Rao CV, Venkateswarlu S, Krishnaraju AV, Subbaraju GV. 2006. Synthesis, stereochemical assignments, and biological activities of homoisoflavonoids. Bioorg Med Chem. 14:2545–2551. Sievänen E, Toušek J, Lunerová K, Marek J, Jankovská D, Dvorská M, Marek R. 2010. Structural studies of homoisoflavonoids: NMR spectroscopy, X-ray diffraction, and theoretical calculations. J Mol Struct. 979:172–179. Silayo A, Ngadjui BT, Abegaz BM. 1999. Homoisoflavonoids and stilbenes from the bulbs of Scilla nervosa subsp. rigidifolia. Phytochemistry. 52:947–955. Srinivas KVNS, Rao YK, Mahender I, Das B, Rama Krishna KVS, Hara Kishore K, Murty USN. 2003. Flavonoids from Caesalpinia pulcherrima. Phytochemistry. 63:789–793. Yan J, Sun LR, Zhou ZY, Chen YC, Zhang WM, Dai HF, Tan JW. 2012. Homoisoflavonoids from the medicinal plant Portulaca oleracea. Phytochemistry. 80:37–41. Yen CT, Nakagawa GK, Hwang TL, Wu PC, Morris NSL, Lai WC, Bastow KF, Chang FR, Wu YC, Lee KH. 2010. Antitumor agents. 271: total synthesis and evaluation of brazilein and analogs as anti-inflammatory and cytotoxic agents. Bioorg Med Chem Lett. 20:1037–1039. Zhou YF, Qi J, Zhu DN, Yu BY. 2008. Homoisoflavonoids from Ophiopogon japonicas and its oxygen free radicals (OFRs) scavenging effects. Chin J Nat Med. 6:201–204.
Natural Product Research: Formerly Natural Product Letters Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gnpl20
Scillapersicene: a new homoisoflavonoid with cytotoxic activity from the bulbs of Scilla persica HAUSSKN a
b
c
Salar Hafez Ghoran , Soodabeh Saeidnia , Esmaeil Babaei , d
e
Fumiyuki Kiuchi & Hidayat Hussain a
Faculty of Basic Sciences, Department of Chemistry, Golestan University, Gorgan 4913815739, Iran b
Click for updates
Faculty of Pharmacy, Medicinal Plants Research Center, Tehran University of Medical Sciences, Tehran 1417614411, Iran c
Department of Animal Biology, School of Natural Sciences, University of Tabriz, Tabriz, Iran d
Faculty of Pharmacy, Department of Pharmaceutical Sciences, Keio University, Tokyo, Japan e
UoN Chair of Oman’s Medicinal Plants and Marine Natural Products, University of Nizwa, Nizwa, Sultanate of Oman Published online: 03 Jul 2015.
To cite this article: Salar Hafez Ghoran, Soodabeh Saeidnia, Esmaeil Babaei, Fumiyuki Kiuchi & Hidayat Hussain (2015): Scillapersicene: a new homoisoflavonoid with cytotoxic activity from the bulbs of Scilla persica HAUSSKN, Natural Product Research: Formerly Natural Product Letters, DOI: 10.1080/14786419.2015.1054286 To link to this article: http://dx.doi.org/10.1080/14786419.2015.1054286
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
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This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
NATURAL PRODUCT RESEARCH, 2015 http://dx.doi.org/10.1080/14786419.2015.1054286
SHORT COMMUNICATION
Scillapersicene: a new homoisoflavonoid with cytotoxic activity from the bulbs of Scilla persica HAUSSKN Salar Hafez Ghorana, Soodabeh Saeidniab, Esmaeil Babaeic, Fumiyuki Kiuchid and Hidayat Hussaine Faculty of Basic Sciences, Department of Chemistry, Golestan University, Gorgan 4913815739, Iran; bFaculty of Pharmacy, Medicinal Plants Research Center, Tehran University of Medical Sciences, Tehran 1417614411, Iran; cDepartment of Animal Biology, School of Natural Sciences, University of Tabriz, Tabriz, Iran; dFaculty of Pharmacy, Department of Pharmaceutical Sciences, Keio University, Tokyo, Japan; eUoN Chair of Oman’s Medicinal Plants and Marine Natural Products, University of Nizwa, Nizwa, Sultanate of Oman
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a
ARTICLE HISTORY
ABSTRACT
The phytochemical investigation of Scilla persica HAUSSKN bulbs led to the isolation of a novel homoisoflavonoid that named Scillapersicene (1) and identified as 3-(3′,4′-dihydroxybenzylidene)8-hydroxy-5,7-dimethoxychroman-4-one along with five known homoisoflavonoids 2–6, whose structures were elucidated using HRFAB-MS, 1D and 2D NMR spectroscopic data. The known compounds were identified as 3-(3′,4′-dihydroxybenzyl)-5,8dihydroxy-7-methoxychroman-4-one (2), 3,9-dihydro-autumnalin (3), autumnalin (4), 3-(3′,4′-dihydroxybenzylidene)-5,8-dihydroxy-7methoxychroman-4-one (5) and scillapersicone (6). All compounds obtained, expect 2 and 4, showed strong cytotoxic activity against AGS cell line. The toxicity on AGS cell line was measured by 1, 3, 5 and 6 with IC50 values of 8.4, 30.5, 10.7 and 24.2 μM, respectively. In addition, the physico-chemical properties of these natural compounds were optimised using density functional method (B3LYP) with standard 6-311+G* basis set. These natural products have low-energy gaps between the first ionisation potentials and highest occupied molecular orbital. In conclusion, the low-energy gap could cause reason for cytotoxic activity of homoisoflavonoids.
GRAPHICAL ABSTRACT
OH MeO
Scillapersicene O
OH OH
OMe O
Inhibitory activity of Homoisoflavonoids on AGS concerous cell lines
CONTACT Salar Hafez Ghoran © 2015 Taylor & Francis
[email protected], [email protected]
Received 14 March 2015 Accepted 17 May 2015 KEYWORDS
AGS; B3LYP; cytotoxic activity; Scillapersicene; homoisoflavonoid; Liliaceae; Scilla persica
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1. Introduction The genus Scilla is believed to globally represent 81 taxa, and most of which are widespread in Iran. Scilla persica HAUSSKN is a perennial herb belonging to the Liliaceae family. In Iran, the habitat of this plant is West Azerbaijan (Sardasht), Khorramabad, Alvand, Hamedan, Qasr Shirin, Sanandaj and mountains Razaab (Mozaffarian 1997). According to previous studies on Scilla species, they contain alkaloids (Kato et al. 2007), cardiac glycosides (Kamano & Petit 1974), triterpenoids (Mimaki et al. 1993; Nishida et al. 2008), triterpenoid glycosides (Arjune & Klar 2011; Ono et al. 2011), nortriterpenoid glycosides (Ono et al. 2011, 2013), eucosterol oligoglycosides (Lee et al. 2002), stilbenoids (Bangani et al. 1999; Nishida et al. 2008), xanthone, lignin and phenylpropanoid glycoside (Nishida et al. 2008), as well as homoisoflavanones (Heller & Tamm 1981; Bangani et al. 1999; Silayo et al. 1999; Mutanyatta et al. 2003; Shim et al. 2004; Nishida et al. 2008; Hafez Ghoran et al. 2014). These compounds possess antibacterial and antiangiogenic activities, and inhibit in vitro the growth of several microorganisms (Heller & Tamm 1981; Srinivas et al. 2003; Shim et al. 2004). Homoisoflavonoids exclusively represent a modification of the flavonoidal skeleton. Feeding laboratory experiments show that the biosynthesis of 3-benzylchroman-4-ones is a modification of the C6–C3–C6 chalcone–flavonoid pathway by incorporation of an additional carbon atom (Dewick 1975). These compounds were mainly discovered from plants belonging to the Liliaceae family and a few other plant species (Sievänen et al. 2010). Homoisoflavonoids have been reported to display multiple biological properties such as antioxidant activity (Siddaiah et al. 2006; Zhou et al. 2008), cytotoxic activity (Nguyen et al. 2006; Yan et al. 2012; Hafez Ghoran et al. 2014), inhibition of platelet aggregation (Kou et al. 2006), cough sedative (Ishibashi et al. 2001), hyperglycemia (Choi et al. 2004), anti-angiogenic (Shim et al. 2004), anti-fungal (Srinivas et al. 2003), anti-inflammatory, antiallergic, antihistaminic, angioprotective activities, and have been detected as potent phosphodiesterase inhibitors (Della Loggia et al. 1989; Amschler et al. 1996; Shim et al. 2004). Many natural products have traditionally played a prominent role in drug discovery and were the basis of most early medicines (Grabley & Thiericke 1999; Buss et al. 2003). In this study, we report a phytochemical study on fresh bulbs of S. persica that resulted in isolation of new homoisoflavonoid (1), together with five known compounds (2–6, see Figure 1). Moreover, we also used the B3LYP/6-311+G* method implemented in Gaussian 98 package to determine the relative geometric structures, molecular orbital energy, and other physico-chemical properties of 1–6 (Frisch et al. 1998).
1. R1 = R3 = OMe, R2 = H, R4 = R5 = OH 4. R1 = R3 = OH, R2 = OMe, R4 = R5 = H 5. R1 = R4 = R5 = OH, R2 = H, R3 = OMe
Figure 1. Chemical structures of compounds 1–6.
2. R1 = R4 = R5 = OH, R2 = H, R3 = OMe 3. R1 = R3 = OH, R4 = R5 = H 6. R1 = R3 = OMe, R2 = H, R4 = R5 = OH
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2. Results and discussion The Et2O extract of S. persica bulbs was fractionated by normal phase chromatography using a Column Chromatography system, and six homoisoflavonoids were isolated. The six isolated compounds include one new homoisoflavonoid (1), together with five known compounds (2–6, Figure 1). The homoisoflavonoids showed the spots with orange, dark orange and red-orange colours on TLC by spraying anisaldehyde-H2SO4 reagent followed by heating. The known compounds (2–6) were identified as 3-(3′,4′-dihydroxybenzyl)-5,8-dihydroxy-7-methoxychroman-4-one (2) (Adinolfi et al. 1986), 3-(4′-hydroxybenzyl)-5,7-dihydroxy-6-methoxy- chroman4-one or 3,9-dihydro-autumnalin (3) (Silayo et al. 1999; Mutanyatta et al. 2003; Nishida et al. 2008), 3-(4′-hydroxybenzylidene)-5,7-dihydroxy-6-methoxychroman-4-one or autumnalin (4) (Silayo et al. 1999), 3-(3′,4′-dihydroxybenzylidene)-5,8-dihydroxy-7-methoxychroman-4-one (5) (Mašterov et al. 1991) and scillapersicone (6) (Hafez Ghoran et al. 2014) based on the comparison of their spectroscopic data with those described in the literature. The known compounds (2–6) had previously been reported from Muscari armeniacum (2), S. nervosa and S. socialis (3 and 4), Muscari Racemosum (5) and S. persica (6). Compound 1 was obtained as a yellowish amorphous powder. The mass spectra of 1 indicated an [M]+ ion peak at 345.0952, and the molecular formula of 1 was defined as C18H16O7 by HRFAB-MS. In the IR spectrum, absorption bands at 1613 and 3458 cm−1 were in accordance with the presence of carbonyl and hydroxyl functions, respectively. The 1H, 13 C-NMR and 1H-13C-correlation (HSQC and HMBC) spectra showed that this natural product has a homoisoflavonoidal skeleton (Agrawal et al. 1989) (see Supplementary Table S1). In its 1 H-NMR spectrum, signals for two methoxy groups at δH 3.77 (S, 3H) and 3.88 (S, 3H) were clearly exhibited. The aromatic A-ring proton resonated at δH 6.38 (1H, s, H-6) and the aromatic B-ring protons resonated at δH 6.80 (1H, d = 2.0 Hz, H-2′), 6.73 (1H, dd = 2.1, 8.3 Hz, H-6′), and 6.82 (1H, d = 8.1 Hz, H-5′). The 13C-NMR spectrum displayed 18 signals. In the HMBC of 1, characteristic correlation signals of δH 5.2 (2H-2) with C-3 (δC 130.0), C-4 (δC 179.1), C-8a (δC 150.4) and C-9 (δC 135.5), of δH 7.44 (H-9) with C-4, C-1′ (δC 126.1), C-5′ (δC 116.3) and C-6′ (δC 123.3), of proton of aromatic A-ring δH 6.38 (H-6) with C-4a (δC 107.5), C-5 (δC 154.7), C-7 (δC 154.0) and C-8 (δC 128.4), of proton of aromatic B-ring δH 6.8 (H-2′) with C-9, C-4′ (δC 147.7) and C-6′, of δH 6.73 (H-6′) with C-9, C-2′ (δC 117.8) and C-4′, of δH 6.82 (H-5′) with C-1′ and C-3′. Therefore, the structure of this compound suggestion was confirmed by correlations in the HMBC (Supplementary Figure S1). As a result, all spectroscopic data led to the structure 3-(3′, 4′-dihydroxybenzylidene)-8-hydroxy-5,7-dimethoxychroman-4-one that trivially named Scillapersicene (1). As shown in Supplementary Table S2, the results of cytotoxic evaluations in this study revealed that the compounds 1–6, expect 2 and 4, were able to affect the viability of cancerous AGS cells significantly. This anti-cancer effect at 0–200 μM concentrations was detected in a time- and dose-dependent manner. Compounds 2 and 4 could not be considered as an anti-tumour compounds as they affect normal cells like cancerous ones. And also compounds 1, 3, 5 and 6 showed cytotoxic activity with IC50 values of 8.4, 30.5, 15.0 and 24.2 μM, respectively. Molecular structure of 1, obtained by theoretical calculations, is shown in Supplementary Figure S2. The electronic densities in the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for compounds 1–6 at the B3LYP/6-311+G* level were studied. Our calculation exhibits that the energy levels of HOMO and LUMO are −5.60 and −2.02 eV for Scillapersicene (1), respectively. As shown in Supplementary Figure S2, the HOMO in Scillapersicene molecule is primarily situated on the carbonyl group atoms,
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oxygen and the carbon atoms of the A ring, while LUMO is located on the carbon atoms of the A, B and C rings. The HOMO–LUMO energy separation has been applied as an indicator of kinetic stability of the system. The energy gap (Δε = εHOMO − εLUMO) of these natural compounds are calculated with the values of 3.58, 3.86, 4.26, 3.60, 3.26 and 4.29 eV at the B3LYP method, respectively. This small HOMO–LUMO gap reveals a low kinetic stability and high chemical reactivity; because it is energetically unfavourable to append electrons to a high-lying LUMO or to draw out electrons from a low-lying HOMO. Therefore, the low-energy gap can cause reason for cytotoxic activity of homoisoflavonoids. The MEP, plotted in Supplementary Figure S2, show that oxygen atoms are negatively charged (red colour) while the hydrogen atoms of hydroxyl groups are positively charged (blue colour) in the molecule. In Supplementary Table S3, the quantum molecular descriptors for 1–6 such as amount of HOMO, LUMO, the energy gaps, Fermi energy level (EF), global softness (S), hardness (η), electrophilicity index (ω), electronegativity (χ) and the maximum amount of electronic charge (∆Nmax) were determined (Hafez Ghoran et al. 2014).
2.1. Spectroscopic data of new compound (Scillapersicene 1) Yellowish amorphous powder; mp 209–211 °C; UV (MeOH): λmax, nm (log ε): 232 (4.15), 365; IR (KBr) = 3458 (OH), 3128, 1613 (C=O), 1401 (Aromatic C=C), 1132 cm−1 (etheric C–O); EIMS m/z (rel. int.): 344.1 [M]+, 328 (12), 307.2 (65), 289.1 (31), 176.1 (8), 154.1 (97), 137.1 (57), 107.1 (33), 89.0 (30), 69.1 (9); HRFAB-MS m/z 345.0952 [M+H]+ (calcd for C18H16O7, 345.0974); 1H and 13 C-NMR assignments are shown in Supplementary Table S1.
3. Conclusion Previous investigations have illustrated that homoisoflavonoids are efficient cytotoxic agents (Nguyen et al. 2006; Yen et al. 2010; Hafez Ghoran et al. 2014). The cellular mutability control by natural antimutagens can provide ways for preventing mutations that conceivably result in cancer as well as diseases caused by genotoxic agents. An intensive research in the area of antimutagenesis and anticarcinogenesis has led to the identification of a broad range of natural inhibitors acting through different mechanisms (Birt et al. 2001). In this study, one homoisoflavonoid, Scillapersicene along with five known homoisoflavonoids (2–6) were isolated by column chromatography method and identified from the medicinal plant S. persica. A bibliography demonstrated that Scillapersicene are also the first homoisoflavonoids that identified from plants of the Liliaceae family so far. In addition, this is the first report of HRFAB-MS, IR, UV, 1H and 13C-NMR assignments for compound 1. On the basis of cytotoxic assay, the natural compounds 1, 2, 3, 5 and 6 exhibited cytotoxicity towards one human cancer cell line, especially compounds 1 and 5 which showed in vitro cytotoxic activity against AGS cell line more potent than that of the normal cells. Through the calculations of the first ionisation potentials, HOMO, LUMO and energy gaps, it was found that these natural products have low-energy gaps between the first ionisation potentials and the HOMO. Accurate theoretical calculations can help identify and provide ways to obtain important chemical and physical information that cannot be easily obtained by experimental approaches.
Acknowledgements The authors wish to thank Mr Abbas Biglari (Zanjan Institute of Chemistry) for NMR spectroscopic measurements and MPRC colleagues (Medicinal Plants Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences) for their support during the purification process. The authors are also grateful to Tabriz University research councils for partial support of this work.
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Disclosure statement No potential conflict of interest was reported by the authors.
Supplemental data and research materials Supplementary material relating to this study is available online http://dx.doi.org/10.1080 /14786419.2015.1054286, alongside Tables S1–S3, Figures S1, S2 and the original spectra of compound 1.
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References Adinolfi M, Corsaro MM, Lanzetta R, Laonigro G, Mangoni L, Parrilli M. 1986. Ten homoisoflavanones from two Muscari species. Phytochemistry. 26:285–290. Agrawal PK, Thakur RS, Bansal MC. 1989. Carbon-13 NMR of flavonoids. New York (NY): Elsevier Science. Amschler G, Frahm AW, Hatzelmann A, Kilian U, Müller-Doblies D, Müller-Doblies U. 1996. Constituents from Veltheimia viridifolia; I. Homoisoflavones of the bulbs. Planta Med. 62:534–539. Arjune S, Klar F. 2011. Characterization of glycosidic triterpenoids of Scilla litardierei and investigation of its potential cytotoxic effects. Planta Med. 77:PM187. Bangani V, Crouch NR, Mulholland DA. 1999. Homoisoflavanones and stilbenoids from Scilla nervosa. Phytochemistry. 51:947–951. Birt DF, Hendrich S, Wang W. 2001. Dietary agents in cancer prevention: flavonoids and isoflavonoids. Pharmacol Ther. 90:157–177. Buss AD, Buss BC, Waigh RD. 2003. Burger’s medicinal chemistry and drug discovery. 6th ed. Hoboken (NJ): Wiley; p. 847–900. Choi SB, Wha JD, Park SM. 2004. The insulin sensitizing effect of homoisoflavone enriched fraction in Liriope platyphylla Wang et Tang via PI3-kinase pathway. Life Sci. 75:2653–2664. Della Loggia R, Del Negro P, Tubaro A, Barone G, Parrilli M. 1989. Homoisoflavanones as anti-inflammatory principles of Muscari comosum. Planta Med. 55:587–588. Dewick PM. 1975. Biosynthesis of the 3-benzylchroman-4-one eucomin in Eucomis bicolor. Phytochemistry. 14:983–988. Frisch MJ, Trucks GW, Schegel HB, Scuseria GE, Robb MA, Cheeseman JR, Montgomery JA Jr, Vreven T, Kudin KN, Burant JC, et al. 1998. Gaussian 98, Revision D01. Wallingford (CT): Gaussian Inc. Grabley S, Thiericke R. 1999. Drug discovery from nature. Berlin: Springer; p. 3–37. Hafez Ghoran S, Saeidnia S, Babaei E, Kiuchi F, Dusek M, Eigner V, Dehno Khalaji A, Soltani A, Ebrahimi P, Mighani H. 2014. Biochemical and biophysical properties of a novel homoisoflavonoid extracted from Scilla persica HAUSSKN. Bioorg Chem. 57:51–56. Heller W, Tamm C. 1981. Homoisoflavanones and biogenetically related compounds. Prog Chem Org Nat Prod. 4:105–152. Ishibashi H, Mochidome T, Okai J, Ichiki H, Shimada H, Takahama K. 2001. Activation of potassium conductance by ophiopogonin-D in acutely dissociated rat paratracheal neurones. Br J Pharmacol. 132:461–466. Kamano Y, Pettit GR. 1974. Bufadienolides. 26. Synthesis of scillarenin. J Org Chem. 39:2629–2631. Kato A, Kato N, Adachi I, Hollinshead J, Fleet GW, Kuriyama C, Ikeda K, Asano N, Nash RJ. 2007. Isolation of glycosidase-inhibiting hyacinthacines and related alkaloids from Scilla socialis. J Nat Prod. 70:993– 997. Kou JP, Tian YQ, Tang YK, Yan J, Yu BY. 2006. Antithrombotic activities of aqueous extract from Radix Ophiopogon japonicus and its two constituents. Biol Pharm Bull. 29:1267–1270. Lee SM, Chun HK, Lee CH, Min BS, Lee ES, Kho YH. 2002. Eucosterol oligoglycosides isolated from Scilla scilloides and their anti-tumor activity. Chem Pharm Bull. 50:1245–1245. Mašterov I, Suchý V, Uhrín D, Ubik K, Grančaiová Z, Bobovnický B. 1991. Homoisoflavanones and other constituents from Muscari Racemosum. Phytochemistry. 30:713–714. Mimaki Y, Ori K, Sashida Y, Nikaido T, Song L, Ohmoto T. 1993. Peruvianosides A and B, novel triterpene glycosides from the bulbs of Scilla peruviana. Bull Chem Soc Jpn. 66:1182–1186. Mozaffarian V. 1997. Dictionary of the names of Iranian Plants. Tehran: Farhang Moaser; p. 489–490.
Downloaded by [FU Berlin] at 22:37 06 July 2015
6
S. HAFEZ GHORAN ET AL.
Mutanyatta J, Matapa BG, Shushu DD, Abegaz BM. 2003. Homoisoflavonoids and xanthones from the tubers of wild and in vitro regenerated Ledebouria graminifolia and cytotoxic activities of some of the homoisoflavonoids. Phytochemistry. 62:797–804. Nishida Y, Eto M, Miyashita H, Ikeda T, Yamaguchi K, Yoshimitsu H, Nohara T, Ono M. 2008. A new homostilbene and two new homoisoflavones from the bulbs of Scilla scilloides. Chem Pharm Bull. 56:1022–1025. Nguyen AT, Fontaine J, Malonne H, Duez P. 2006. Homoisoflavanone from Disporopsis aspera. Phytochemistry. 67:2159–2163. Ono M, Ochiai T, Yasuda S, Nishida Y, Tanaka T, Okawa M, Kinjo J, Yoshimitsu H, Nohara T. 2013. Five new nortriterpenoid glycosides from the bulbs of Scilla scilloides. Chem Pharm Bull. 61:592–598. Ono M, Toyohisa D, Morishita T, Horita H, Yasuda S, Nishida Y, Tanaka T, Okawa M, Kinjo J, Yoshimitsu H, Nohara T. 2011. Three new nortriterpene glycosides and two new triterpene glycosides from the bulbs of Scilla scilloides. Chem Pharm Bull. 59:1348–1354. Shim JS, Kim JH, Lee J, Kim SN, Kwon HJ. 2004. Anti-angiogenic activity of a homoisoflavanone from Cremastra appendiculata. Planta Med. 70:171–173. Siddaiah V, Rao CV, Venkateswarlu S, Krishnaraju AV, Subbaraju GV. 2006. Synthesis, stereochemical assignments, and biological activities of homoisoflavonoids. Bioorg Med Chem. 14:2545–2551. Sievänen E, Toušek J, Lunerová K, Marek J, Jankovská D, Dvorská M, Marek R. 2010. Structural studies of homoisoflavonoids: NMR spectroscopy, X-ray diffraction, and theoretical calculations. J Mol Struct. 979:172–179. Silayo A, Ngadjui BT, Abegaz BM. 1999. Homoisoflavonoids and stilbenes from the bulbs of Scilla nervosa subsp. rigidifolia. Phytochemistry. 52:947–955. Srinivas KVNS, Rao YK, Mahender I, Das B, Rama Krishna KVS, Hara Kishore K, Murty USN. 2003. Flavonoids from Caesalpinia pulcherrima. Phytochemistry. 63:789–793. Yan J, Sun LR, Zhou ZY, Chen YC, Zhang WM, Dai HF, Tan JW. 2012. Homoisoflavonoids from the medicinal plant Portulaca oleracea. Phytochemistry. 80:37–41. Yen CT, Nakagawa GK, Hwang TL, Wu PC, Morris NSL, Lai WC, Bastow KF, Chang FR, Wu YC, Lee KH. 2010. Antitumor agents. 271: total synthesis and evaluation of brazilein and analogs as anti-inflammatory and cytotoxic agents. Bioorg Med Chem Lett. 20:1037–1039. Zhou YF, Qi J, Zhu DN, Yu BY. 2008. Homoisoflavonoids from Ophiopogon japonicas and its oxygen free radicals (OFRs) scavenging effects. Chin J Nat Med. 6:201–204.
