This article was downloaded by: [Deakin University Library] On: 13 September 2014, At: 09:29 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Asian Natural Products Research Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ganp20
Two new coumarins from the seeds of Solanum indicum ac
b
c
c
c
c
Hai-Long Yin , Jie-Hui Li , Bin Li , Li Chen , Jian Li , Ying Tian , c
c
c
ac
Shi-Jun Liu , Yong-Kun Zhao , Yan-Hua Xiao & Jun-Xing Dong a
Beijing University of Technology, Beijing, 100124, China
b
Anhui Medical University, Hefei, 230032, China
c
Beijing Institute of Radiation Medicine, Beijng, 100850, China Published online: 24 Oct 2013.
To cite this article: Hai-Long Yin, Jie-Hui Li, Bin Li, Li Chen, Jian Li, Ying Tian, Shi-Jun Liu, Yong-Kun Zhao, Yan-Hua Xiao & Jun-Xing Dong (2014) Two new coumarins from the seeds of Solanum indicum, Journal of Asian Natural Products Research, 16:2, 153-157, DOI: 10.1080/10286020.2013.841142 To link to this article: http://dx.doi.org/10.1080/10286020.2013.841142
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. 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 &
Downloaded by [Deakin University Library] at 09:29 13 September 2014
Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Journal of Asian Natural Products Research, 2014 Vol. 16, No. 2, 153–157, http://dx.doi.org/10.1080/10286020.2013.841142
Two new coumarins from the seeds of Solanum indicum Hai-Long Yinac, Jie-Hui Lib, Bin Lic, Li Chenc, Jian Lic, Ying Tianc, Shi-Jun Liuc, Yong-Kun Zhaoc, Yan-Hua Xiaoc and Jun-Xing Dongac* a
Beijing University of Technology, Beijing 100124, China; bAnhui Medical University, Hefei 230032, China; cBeijing Institute of Radiation Medicine, Beijng 100850, China
Downloaded by [Deakin University Library] at 09:29 13 September 2014
(Received 15 May 2013; final version received 1 September 2013) Two new coumarins, (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-methoxy-2H-[1,4] dioxino[2,3-h ]chromene-3,9-dione (indicumin E, 1) and 7-hydroxy-6,8-dimethoxy-3(40 -hydroxy-30 -methoxyphenyl)-coumarin (2), together with two known coumarins isofraxidin (3) and fraxetin (4), were isolated from the Solanum indicum seeds. Their structures were established on the basis of 1D and 2D spectroscopic data. Compound 1 was the rarest coumarinolignoid known to date. Keywords: Solanum indicum; coumarins; coumarinolignoid; indicumin E; NMR
1.
Introduction
Solanum indicum L. (Solanaceae), widely distributed in the south of China, has been used as anti-inflammatory and woundhealing agents, and as an analgesic for rhinitis, toothache, and breast cancer [1]. Previous investigations on S. indicum have revealed that it contained steroids (indiosides A – F, isoanguivine, protodioscin), steroidal alkaloids (solamargine, solasonine), coumarins (scopoletin, 4,40 -biisofraxidin, arteminorin A, cleosandrin), amide [N-( p-trans-coumaroyl)-tyramine], sesquiterpenes (solavetivone, solafuranone) and coumarinolignoids (indicumines A – D) [1 – 4]. As a part of our continuing study on the constituents of the seeds of S. indicum, we have isolated another two new coumarins, indicumine E and 7-hydroxy-6,8dimethoxy-3-(40 -hydroxy-30 -methoxyphenyl)-coumarin, together with two known coumarins, isofraxidin (3) and fraxetin (4) (Figure 1) [5]. In this paper, we report the isolation and structure elucidation of these compounds on the basis of extensive spectroscopic analysis, including 2D NMR
data. To the best of our knowledge, 1 was a rare coumarinolignoid.
2.
Compound 1 was obtained as a yellow amorphous powder. The positive ion HRESI-MS of 1 showed a quasimolecular ion peak at m/z 383.0773 [M þ H]þ, indicating the molecular formula to be C20H14O8. The 1 H NMR spectrum of 1 showed typical protons of coumarin core at dH 6.43 (1H, d, J ¼ 9.6 Hz, H-3) and 7.95 (1H, d, J ¼ 9.6 Hz, H-4) and dH 7.12 (1H, s, H-5), and the HMBC cross peaks from H-5 to C-4 (dC 144.0), C-7 (dC 131.6), C-10 (dC 114.6), and C-9 (dC 135.8) were observed. These signals suggested the presence of a 6,7,8trisubstituted coumarin moiety [6]. In addition, four aromatic protons at dH 7.92 (1H, d, J ¼ 2.0 Hz, H-20 ), 7.18 (1H, dd, J ¼ 8.0, 2.0 Hz, H-6 0 ), 6.82 (1H, d, J ¼ 8.0 Hz, H-50 ), and 6.98 (1H, s, H-70 ) were observed in the 1H NMR spectrum. The HMBC spectrum showed cross peaks from 40 -OH at dH 9.69 (1H, s) to C-50 (dC 115.3), C-40 (dC 148.7), and C-30 (dC 147.7);
*Corresponding author. Email: [email protected] q 2013 Taylor & Francis
Results and discussion
Downloaded by [Deakin University Library] at 09:29 13 September 2014
154
H.-L. Yin et al.
Figure 1. Structures of compounds 1 –4.
from H-70 to C-20 (dC 112.6), C-60 (dC 126.0), C-80 (dC 132.3), and C-90 (dC 154.5); and from H-20 to C-10 (dC 123.7), C-40 , C-60 , and C-70 (dC 119.2) (Figure 2). The NOESY experiment showed correlations of H-70 with H-20 and H-60 . These signals were suggestive of the existence of 80 -substituted feruloyl group [7]. The ESI-MS/MS of m/z 383 [M þ H]þ showed two predominant daughter ion peaks at m/z 207 and 177 deriving from the fission of the C-80 ZO and C-90 ZO bond, together with the ion peaks at m/z 193 and 175 formed from the fission of the C-7ZO and C-8ZO bond [6]. Furthermore, the key HBMC correlations of H-4, H-5, and H-70 with C-8 (dC 127.7) indicated the connections of the two moieties through C(7)
ZOZC(90 ) and C(8)ZOZC(80 ) by two ether bonds. The E stereochemistry of the double bond C-70 /C-80 was established on the basis of strong deshielding experienced by H-20 (dH 7.92) due to the proximity of the carbonyl group, similar to other componds with that double bond (Figure 3) [7 – 9]. Therefore, the structure of 1 was determined as (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-methoxy-2H-[1,4] dioxino[2,3-h ]chromene-3,9-dione and was named indicumin E. Compound 2 was obtained as a yellow amorphous powder. The negative ion HRESI-MS of 2 showed a quasimolecular ion peak at m/z 343.0816 [M 2 H]2, indicating a molecular formula of C18H16O7. 1H NMR spectrum of 2 was well dispersed
Figure 2. Key HMBC correlations for compounds 1 and 2.
Journal of Asian Natural Products Research
155
Downloaded by [Deakin University Library] at 09:29 13 September 2014
Figure 3. Key NOESY correlations for compounds 1 and 2.
and contained distinctive resonances, similar to that of diagnostic of the tetrasubstituted coumarin and trisubstituted aromatic ring group. The 1H NMR spectrum of 2 showed protons of coumarin core at dH 7.12 (1H, s, H-5) and 8.12 (1H, s, H-4), and the NOESY cross peaks from H-5 to H-4 and 6-OCH3 at dH 3.89 (3H, s) were observed. In addition, the HMBC experiment showed long-range correlations of H-5 with C-7 (dC 143.3) and C-4 (dC 139.7), of 7-OH at dH 9.60 (1H, s) with C-6 (dC 145.7) and C-8 (dC 134.3), and between 8-OCH3 at dH 3.93 (3H, s) and C-8. Thus, the structure of this moiety was deduced as 3,6,7,8-tetrasubstituted coumarin. Furthermore, these resonances were sharp singlets at dH 7.34 (1H, d, J ¼ 2.0 Hz, H-20 ), 6.88 (1H, d, J ¼ 8.0 Hz, H-50 ), and 7.24 (1H, dd, J ¼ 8.0, 2.0 Hz, H-60 ), indicating this part of the structure was the 10 ,30 ,40 -trisubstituted aromatic ring group (Figures 2 and 3). Finally, a key HMBC correlation between H-4 and C-10 (dC 126.1) was observed, which indicated that 40 -hydroxy30 -methoxyphenyl was connected to C-3. Therefore, the planar structure of compound 2 was established as 7-hydroxy-6,8dimethoxy-3-(40 -hydroxy-30 -methoxyphenyl) coumarin. The two known compounds were identified as isofraxidin (3) and fraxetin (4) [5], by comparing their UV, ESI-MS, and 1H, 13C NMR data with those reported.
3. 3.1
Experimental General experimental procedures
Optical rotations were measured using a PerkinElmer 343 polarimeter (PerkinElmer, Waltham, MA, USA). IR spectra were recorded on the Bio-Rad FTS-65A spectrometer (Bio-Rad, Richmond, VA, USA). UV spectra were recorded using the UA-2501PC spectrometer (Shimadzu, Kyoto, Japan). 1 H and 13 C NMR spectra were obtained on Bruker ECA-400 MHz (JEOL, Tokyo, Japan) and Varian UNITYINOVA 600 (Varian, Palo Alto, CA, USA), and the chemical shifts were given on d (ppm) scale using tetramethylsilane as an internal standard. The HR-ESI-MS were measured on a 9.4 T Q-FT-MS Apex Qe (Bruker Co., Billerica, MA, USA). ESI-MS and ESIMS/MS were measured on a Finnigan LCQDECA spectrometer (Thermo Electron, Pittsburgh, PA, USA). Silica gel (60 – 120 mesh, 200 – 300 mesh, Qingdao Marine Chemical Group Co., Qingdao, China) and Sephadex LH-20 (Pharmacia, Uppsala, Sweden) were used for column chromatography (CC). TLC was carried out using silica gel 60 (. 230 mesh, Qingdao Marine Chemical Group Co., Qingdao, China) and GF254 plates precoated using silica gel 60. Spots on TLC were visually observed under UV light and/or by spraying with anisaldehyde – H2SO4 reagent followed by heating.
156
H.-L. Yin et al.
Table 1.
1
H and 13C NMR spectral data for compounds 1 and 2.
Downloaded by [Deakin University Library] at 09:29 13 September 2014
Compound 1a Position
dC
2 3 4 5 6 7 8 9 10 10 20 30 40 50 60 70 80 90 6-OCH3 7-OH 8-OCH3 30 -OCH3 40 -OH
159.0 115.4 144.0 103.6 143.5 131.6 127.7 135.8 114.6 123.7 112.6 147.6 148.7 115.3 126.0 119.2 132.3 154.5 55.8 56.3
Compound 2b
dH mult. (J in Hz)
dC
6.43 (1H, d, J ¼ 9.6) 7.95 (1H, d, J ¼ 9.6) 7.12 (1H, s)
7.92 (1H, d, J ¼ 2.0) 6.82 (1H, d, J ¼ 8.0) 7.18 (1H, dd, J ¼ 8.0, 2.0) 6.98 (1H, s, H-70 ) 3.86 (3H, s) 3.95 (3H, s) 9.69 (1H, s)
160.0 122.2 139.7 104.2 145.7 143.3 134.3 142.0 111.1 126.1 112.3 147.2 146.8 115.1 121.2
56.1 60.8 55.6
dH mult. (J in Hz)
8.12 (1H, s) 7.12 (1H, s)
7.34 (1H, d, J ¼ 2.0) 6.88 (1H, d, J ¼ 8.0) 7.24 (1H, dd, J ¼ 8.0, 2.0)
3.89 (3H, s) 9.60 (1H, s) 3.93 (3H, s) 3.87 (3H, s) 9.32 (1H, s)
a
Spectra were recorded in DMSO-d6, 600 MHz for 1H, 150 MHz for 13C, TMS, d in ppm, J in Hz.b Spectra were recorded in DMSO-d6, 400 MHz for 1H, 100 MHz for 13C, TMS, d in ppm, J in Hz.
3.2
Plant material
The plant was collected in Lufeng, Yunnan Province, China, and verified by Prof. Bin Lin (Beijing Institute of Radiation Medicine). A voucher specimen (No. 2011-0701) was deposited in the Herbarium of Beijing Institute of Radiation Medicine, Beijing. 3.3 Extraction and isolation The air-dried seeds of S. indicum (50 kg) were exhaustively extracted using 60% EtOH three times under reflux. The concentrated extract (2.4 kg) was suspended in water and then partitioned using petroleum ether, EtOAc, and nBuOH successively. The EtOAc soluble part (210 g) was subjected to silica gel CC eluted with CHCl 3:MeOH gradient (from10:1 to 0:1) to yield 10 fractions A – J. Fraction A (21.3 g) was chromatographed on silica gel with petroleum ether:
acetone (from 10:1 to 3:1) to yield 20 fractions A1 – A20. Fractions A5 – A8 (3.5 g) were combined and filtered to yield compound 1 (112 mg). Fraction B (12.5 g) was filtered, and the mother liquid was purified by Sephadex LH-20 (with CHCl3:MeOH, 1:1) to give 10 fractions B1 – B10. Fractions B6 – B9 (900 mg) were combined and chromatographed by Sephadex LH-20 (with MeOH) to obtain compound 2 (7 mg) and fraxetin (4, 17 mg). Fraction D (18.5 g) was subjected to silica gel CC eluted with CHCl3:MeOH (from 10:0 to 5:1) to give 10 fractions D1 – D10. Fraction D2 (560 mg) was filtered to obtain isofraxidin (3, 78 mg). 3.3.1 Indicumin E (1) Yellow amorphous powder; ½a20 D þ 14.3 (c 0.11, C5H5N); UV (MeOH) lmax (log 1) 327 (4.12) nm; IR (KBr) nmax 3423, 1749,
Journal of Asian Natural Products Research
Downloaded by [Deakin University Library] at 09:29 13 September 2014
1727, 1593, 1518, 1465, 1346, 1270, 1152 cm21. For 1H and 13C NMR (DMSOd6) spectroscopic data, see Table 1. ESI-MS: m/z 383 [M þ H]þ, 415 [M þ Na]þ. ESIMS/MS m/z 365 [M þ H 2 H2O]þ, 337 [M þ H 2 H2O 2 CO]þ, 193 [M þ H 2 C10H6O4]þ, 177 [M þ H 2 C10H6O5]þ, 207 [M 2 C10H7O3]þ, 191 [M 2 C10H7O4]þ. HR-ESI-MS m/z 383.0773 [M þ H]þ (calcd for C20H15O8, 383.0761). 3.3.2 7-Hydroxy-6,8-dimethoxy-3-(4 0 hydroxy-3 0 -methoxyphenyl)coumarin (2) Yellow amorphous powder; ½a20 D þ 2.5 (c 0.12, MeOH); UV (MeOH) lmax (log 1) 366 (3.85), 255 (3.84) nm; IR (KBr) nmax 3396, 3334, 1723, 1588, 1503, 1467, 1230 cm21. For 1H and 13C NMR (DMSO-d6) spectroscopic data, see Table 1. ESI-MS: m/z 345 [M þ H]þ, 343 [M 2 H]2. HR-ESI-MS m/z 343.0816 [M 2 H]2 (calcd for C18H15O7, 343.0823). Acknowledgments We are grateful to Mrs Yan Xue, Mrs Mei-feng Xu, and Mrs Yu-mei Zhao of the National
157
Center of Biomedical Analysis for the measurements of the MS and NMR spectra.
References [1] W.J. Syu, M.J. Don, G.H. Lee, and C.M. Sun, J. Nat. Prod. 64, 1232 (2001). [2] S. Yahara, T. Nakamura, Y. Someya, T. Matsumoto, T. Yamashita, and T. Nohara, Phytochemistry 43, 1319 (1996). [3] M. El-Aasr, H. Miyashita, T. Ikeda, J.H. Lee, H. Yoshimitsu, T. Nohara, and K. Murakmi, Chem. Pharm. Bull. 57, 747 (2009). [4] H.L. Yin, J.H. Li, J. Li, B. Li, L. Chen, Y. Tian, S.J. Liu, T. Zhang, and J.X. Dong, Fitoterpia 84, 360 (2013). [5] X.D. Xu, X.R. Hu, J.Q. Yuan, and J.S. Yang, China J. Chin. Mater. Med. 33, 900 (2008). [6] Z.Z. He, J.F. Yan, Z.J. Song, F. Ye, X. Liao, S.L. Peng, and L.S. Ding, J. Nat. Prod. 72, 1198 (2009). [7] A.G. Gonzaˆlez, R. Este´vez-Reyes, C. Mateo, and A.M. Este´vez-Braun, Phytochemistry 29, 675 (1990). [8] A.F. Barrero, M.M. Herrador, M. Akssira, P. Arteaga, and J.L. Romera, J. Nat. Prod. 62, 946 (1999). [9] V.F. Traven, D.V. Kravtchenko, and T.A. Chibisova, Mendeleev Commun. 7, 249 (1997).
Journal of Asian Natural Products Research Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ganp20
Two new coumarins from the seeds of Solanum indicum ac
b
c
c
c
c
Hai-Long Yin , Jie-Hui Li , Bin Li , Li Chen , Jian Li , Ying Tian , c
c
c
ac
Shi-Jun Liu , Yong-Kun Zhao , Yan-Hua Xiao & Jun-Xing Dong a
Beijing University of Technology, Beijing, 100124, China
b
Anhui Medical University, Hefei, 230032, China
c
Beijing Institute of Radiation Medicine, Beijng, 100850, China Published online: 24 Oct 2013.
To cite this article: Hai-Long Yin, Jie-Hui Li, Bin Li, Li Chen, Jian Li, Ying Tian, Shi-Jun Liu, Yong-Kun Zhao, Yan-Hua Xiao & Jun-Xing Dong (2014) Two new coumarins from the seeds of Solanum indicum, Journal of Asian Natural Products Research, 16:2, 153-157, DOI: 10.1080/10286020.2013.841142 To link to this article: http://dx.doi.org/10.1080/10286020.2013.841142
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. 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 &
Downloaded by [Deakin University Library] at 09:29 13 September 2014
Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Journal of Asian Natural Products Research, 2014 Vol. 16, No. 2, 153–157, http://dx.doi.org/10.1080/10286020.2013.841142
Two new coumarins from the seeds of Solanum indicum Hai-Long Yinac, Jie-Hui Lib, Bin Lic, Li Chenc, Jian Lic, Ying Tianc, Shi-Jun Liuc, Yong-Kun Zhaoc, Yan-Hua Xiaoc and Jun-Xing Dongac* a
Beijing University of Technology, Beijing 100124, China; bAnhui Medical University, Hefei 230032, China; cBeijing Institute of Radiation Medicine, Beijng 100850, China
Downloaded by [Deakin University Library] at 09:29 13 September 2014
(Received 15 May 2013; final version received 1 September 2013) Two new coumarins, (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-methoxy-2H-[1,4] dioxino[2,3-h ]chromene-3,9-dione (indicumin E, 1) and 7-hydroxy-6,8-dimethoxy-3(40 -hydroxy-30 -methoxyphenyl)-coumarin (2), together with two known coumarins isofraxidin (3) and fraxetin (4), were isolated from the Solanum indicum seeds. Their structures were established on the basis of 1D and 2D spectroscopic data. Compound 1 was the rarest coumarinolignoid known to date. Keywords: Solanum indicum; coumarins; coumarinolignoid; indicumin E; NMR
1.
Introduction
Solanum indicum L. (Solanaceae), widely distributed in the south of China, has been used as anti-inflammatory and woundhealing agents, and as an analgesic for rhinitis, toothache, and breast cancer [1]. Previous investigations on S. indicum have revealed that it contained steroids (indiosides A – F, isoanguivine, protodioscin), steroidal alkaloids (solamargine, solasonine), coumarins (scopoletin, 4,40 -biisofraxidin, arteminorin A, cleosandrin), amide [N-( p-trans-coumaroyl)-tyramine], sesquiterpenes (solavetivone, solafuranone) and coumarinolignoids (indicumines A – D) [1 – 4]. As a part of our continuing study on the constituents of the seeds of S. indicum, we have isolated another two new coumarins, indicumine E and 7-hydroxy-6,8dimethoxy-3-(40 -hydroxy-30 -methoxyphenyl)-coumarin, together with two known coumarins, isofraxidin (3) and fraxetin (4) (Figure 1) [5]. In this paper, we report the isolation and structure elucidation of these compounds on the basis of extensive spectroscopic analysis, including 2D NMR
data. To the best of our knowledge, 1 was a rare coumarinolignoid.
2.
Compound 1 was obtained as a yellow amorphous powder. The positive ion HRESI-MS of 1 showed a quasimolecular ion peak at m/z 383.0773 [M þ H]þ, indicating the molecular formula to be C20H14O8. The 1 H NMR spectrum of 1 showed typical protons of coumarin core at dH 6.43 (1H, d, J ¼ 9.6 Hz, H-3) and 7.95 (1H, d, J ¼ 9.6 Hz, H-4) and dH 7.12 (1H, s, H-5), and the HMBC cross peaks from H-5 to C-4 (dC 144.0), C-7 (dC 131.6), C-10 (dC 114.6), and C-9 (dC 135.8) were observed. These signals suggested the presence of a 6,7,8trisubstituted coumarin moiety [6]. In addition, four aromatic protons at dH 7.92 (1H, d, J ¼ 2.0 Hz, H-20 ), 7.18 (1H, dd, J ¼ 8.0, 2.0 Hz, H-6 0 ), 6.82 (1H, d, J ¼ 8.0 Hz, H-50 ), and 6.98 (1H, s, H-70 ) were observed in the 1H NMR spectrum. The HMBC spectrum showed cross peaks from 40 -OH at dH 9.69 (1H, s) to C-50 (dC 115.3), C-40 (dC 148.7), and C-30 (dC 147.7);
*Corresponding author. Email: [email protected] q 2013 Taylor & Francis
Results and discussion
Downloaded by [Deakin University Library] at 09:29 13 September 2014
154
H.-L. Yin et al.
Figure 1. Structures of compounds 1 –4.
from H-70 to C-20 (dC 112.6), C-60 (dC 126.0), C-80 (dC 132.3), and C-90 (dC 154.5); and from H-20 to C-10 (dC 123.7), C-40 , C-60 , and C-70 (dC 119.2) (Figure 2). The NOESY experiment showed correlations of H-70 with H-20 and H-60 . These signals were suggestive of the existence of 80 -substituted feruloyl group [7]. The ESI-MS/MS of m/z 383 [M þ H]þ showed two predominant daughter ion peaks at m/z 207 and 177 deriving from the fission of the C-80 ZO and C-90 ZO bond, together with the ion peaks at m/z 193 and 175 formed from the fission of the C-7ZO and C-8ZO bond [6]. Furthermore, the key HBMC correlations of H-4, H-5, and H-70 with C-8 (dC 127.7) indicated the connections of the two moieties through C(7)
ZOZC(90 ) and C(8)ZOZC(80 ) by two ether bonds. The E stereochemistry of the double bond C-70 /C-80 was established on the basis of strong deshielding experienced by H-20 (dH 7.92) due to the proximity of the carbonyl group, similar to other componds with that double bond (Figure 3) [7 – 9]. Therefore, the structure of 1 was determined as (E)-2-(4-hydroxy-3-methoxybenzylidene)-5-methoxy-2H-[1,4] dioxino[2,3-h ]chromene-3,9-dione and was named indicumin E. Compound 2 was obtained as a yellow amorphous powder. The negative ion HRESI-MS of 2 showed a quasimolecular ion peak at m/z 343.0816 [M 2 H]2, indicating a molecular formula of C18H16O7. 1H NMR spectrum of 2 was well dispersed
Figure 2. Key HMBC correlations for compounds 1 and 2.
Journal of Asian Natural Products Research
155
Downloaded by [Deakin University Library] at 09:29 13 September 2014
Figure 3. Key NOESY correlations for compounds 1 and 2.
and contained distinctive resonances, similar to that of diagnostic of the tetrasubstituted coumarin and trisubstituted aromatic ring group. The 1H NMR spectrum of 2 showed protons of coumarin core at dH 7.12 (1H, s, H-5) and 8.12 (1H, s, H-4), and the NOESY cross peaks from H-5 to H-4 and 6-OCH3 at dH 3.89 (3H, s) were observed. In addition, the HMBC experiment showed long-range correlations of H-5 with C-7 (dC 143.3) and C-4 (dC 139.7), of 7-OH at dH 9.60 (1H, s) with C-6 (dC 145.7) and C-8 (dC 134.3), and between 8-OCH3 at dH 3.93 (3H, s) and C-8. Thus, the structure of this moiety was deduced as 3,6,7,8-tetrasubstituted coumarin. Furthermore, these resonances were sharp singlets at dH 7.34 (1H, d, J ¼ 2.0 Hz, H-20 ), 6.88 (1H, d, J ¼ 8.0 Hz, H-50 ), and 7.24 (1H, dd, J ¼ 8.0, 2.0 Hz, H-60 ), indicating this part of the structure was the 10 ,30 ,40 -trisubstituted aromatic ring group (Figures 2 and 3). Finally, a key HMBC correlation between H-4 and C-10 (dC 126.1) was observed, which indicated that 40 -hydroxy30 -methoxyphenyl was connected to C-3. Therefore, the planar structure of compound 2 was established as 7-hydroxy-6,8dimethoxy-3-(40 -hydroxy-30 -methoxyphenyl) coumarin. The two known compounds were identified as isofraxidin (3) and fraxetin (4) [5], by comparing their UV, ESI-MS, and 1H, 13C NMR data with those reported.
3. 3.1
Experimental General experimental procedures
Optical rotations were measured using a PerkinElmer 343 polarimeter (PerkinElmer, Waltham, MA, USA). IR spectra were recorded on the Bio-Rad FTS-65A spectrometer (Bio-Rad, Richmond, VA, USA). UV spectra were recorded using the UA-2501PC spectrometer (Shimadzu, Kyoto, Japan). 1 H and 13 C NMR spectra were obtained on Bruker ECA-400 MHz (JEOL, Tokyo, Japan) and Varian UNITYINOVA 600 (Varian, Palo Alto, CA, USA), and the chemical shifts were given on d (ppm) scale using tetramethylsilane as an internal standard. The HR-ESI-MS were measured on a 9.4 T Q-FT-MS Apex Qe (Bruker Co., Billerica, MA, USA). ESI-MS and ESIMS/MS were measured on a Finnigan LCQDECA spectrometer (Thermo Electron, Pittsburgh, PA, USA). Silica gel (60 – 120 mesh, 200 – 300 mesh, Qingdao Marine Chemical Group Co., Qingdao, China) and Sephadex LH-20 (Pharmacia, Uppsala, Sweden) were used for column chromatography (CC). TLC was carried out using silica gel 60 (. 230 mesh, Qingdao Marine Chemical Group Co., Qingdao, China) and GF254 plates precoated using silica gel 60. Spots on TLC were visually observed under UV light and/or by spraying with anisaldehyde – H2SO4 reagent followed by heating.
156
H.-L. Yin et al.
Table 1.
1
H and 13C NMR spectral data for compounds 1 and 2.
Downloaded by [Deakin University Library] at 09:29 13 September 2014
Compound 1a Position
dC
2 3 4 5 6 7 8 9 10 10 20 30 40 50 60 70 80 90 6-OCH3 7-OH 8-OCH3 30 -OCH3 40 -OH
159.0 115.4 144.0 103.6 143.5 131.6 127.7 135.8 114.6 123.7 112.6 147.6 148.7 115.3 126.0 119.2 132.3 154.5 55.8 56.3
Compound 2b
dH mult. (J in Hz)
dC
6.43 (1H, d, J ¼ 9.6) 7.95 (1H, d, J ¼ 9.6) 7.12 (1H, s)
7.92 (1H, d, J ¼ 2.0) 6.82 (1H, d, J ¼ 8.0) 7.18 (1H, dd, J ¼ 8.0, 2.0) 6.98 (1H, s, H-70 ) 3.86 (3H, s) 3.95 (3H, s) 9.69 (1H, s)
160.0 122.2 139.7 104.2 145.7 143.3 134.3 142.0 111.1 126.1 112.3 147.2 146.8 115.1 121.2
56.1 60.8 55.6
dH mult. (J in Hz)
8.12 (1H, s) 7.12 (1H, s)
7.34 (1H, d, J ¼ 2.0) 6.88 (1H, d, J ¼ 8.0) 7.24 (1H, dd, J ¼ 8.0, 2.0)
3.89 (3H, s) 9.60 (1H, s) 3.93 (3H, s) 3.87 (3H, s) 9.32 (1H, s)
a
Spectra were recorded in DMSO-d6, 600 MHz for 1H, 150 MHz for 13C, TMS, d in ppm, J in Hz.b Spectra were recorded in DMSO-d6, 400 MHz for 1H, 100 MHz for 13C, TMS, d in ppm, J in Hz.
3.2
Plant material
The plant was collected in Lufeng, Yunnan Province, China, and verified by Prof. Bin Lin (Beijing Institute of Radiation Medicine). A voucher specimen (No. 2011-0701) was deposited in the Herbarium of Beijing Institute of Radiation Medicine, Beijing. 3.3 Extraction and isolation The air-dried seeds of S. indicum (50 kg) were exhaustively extracted using 60% EtOH three times under reflux. The concentrated extract (2.4 kg) was suspended in water and then partitioned using petroleum ether, EtOAc, and nBuOH successively. The EtOAc soluble part (210 g) was subjected to silica gel CC eluted with CHCl 3:MeOH gradient (from10:1 to 0:1) to yield 10 fractions A – J. Fraction A (21.3 g) was chromatographed on silica gel with petroleum ether:
acetone (from 10:1 to 3:1) to yield 20 fractions A1 – A20. Fractions A5 – A8 (3.5 g) were combined and filtered to yield compound 1 (112 mg). Fraction B (12.5 g) was filtered, and the mother liquid was purified by Sephadex LH-20 (with CHCl3:MeOH, 1:1) to give 10 fractions B1 – B10. Fractions B6 – B9 (900 mg) were combined and chromatographed by Sephadex LH-20 (with MeOH) to obtain compound 2 (7 mg) and fraxetin (4, 17 mg). Fraction D (18.5 g) was subjected to silica gel CC eluted with CHCl3:MeOH (from 10:0 to 5:1) to give 10 fractions D1 – D10. Fraction D2 (560 mg) was filtered to obtain isofraxidin (3, 78 mg). 3.3.1 Indicumin E (1) Yellow amorphous powder; ½a20 D þ 14.3 (c 0.11, C5H5N); UV (MeOH) lmax (log 1) 327 (4.12) nm; IR (KBr) nmax 3423, 1749,
Journal of Asian Natural Products Research
Downloaded by [Deakin University Library] at 09:29 13 September 2014
1727, 1593, 1518, 1465, 1346, 1270, 1152 cm21. For 1H and 13C NMR (DMSOd6) spectroscopic data, see Table 1. ESI-MS: m/z 383 [M þ H]þ, 415 [M þ Na]þ. ESIMS/MS m/z 365 [M þ H 2 H2O]þ, 337 [M þ H 2 H2O 2 CO]þ, 193 [M þ H 2 C10H6O4]þ, 177 [M þ H 2 C10H6O5]þ, 207 [M 2 C10H7O3]þ, 191 [M 2 C10H7O4]þ. HR-ESI-MS m/z 383.0773 [M þ H]þ (calcd for C20H15O8, 383.0761). 3.3.2 7-Hydroxy-6,8-dimethoxy-3-(4 0 hydroxy-3 0 -methoxyphenyl)coumarin (2) Yellow amorphous powder; ½a20 D þ 2.5 (c 0.12, MeOH); UV (MeOH) lmax (log 1) 366 (3.85), 255 (3.84) nm; IR (KBr) nmax 3396, 3334, 1723, 1588, 1503, 1467, 1230 cm21. For 1H and 13C NMR (DMSO-d6) spectroscopic data, see Table 1. ESI-MS: m/z 345 [M þ H]þ, 343 [M 2 H]2. HR-ESI-MS m/z 343.0816 [M 2 H]2 (calcd for C18H15O7, 343.0823). Acknowledgments We are grateful to Mrs Yan Xue, Mrs Mei-feng Xu, and Mrs Yu-mei Zhao of the National
157
Center of Biomedical Analysis for the measurements of the MS and NMR spectra.
References [1] W.J. Syu, M.J. Don, G.H. Lee, and C.M. Sun, J. Nat. Prod. 64, 1232 (2001). [2] S. Yahara, T. Nakamura, Y. Someya, T. Matsumoto, T. Yamashita, and T. Nohara, Phytochemistry 43, 1319 (1996). [3] M. El-Aasr, H. Miyashita, T. Ikeda, J.H. Lee, H. Yoshimitsu, T. Nohara, and K. Murakmi, Chem. Pharm. Bull. 57, 747 (2009). [4] H.L. Yin, J.H. Li, J. Li, B. Li, L. Chen, Y. Tian, S.J. Liu, T. Zhang, and J.X. Dong, Fitoterpia 84, 360 (2013). [5] X.D. Xu, X.R. Hu, J.Q. Yuan, and J.S. Yang, China J. Chin. Mater. Med. 33, 900 (2008). [6] Z.Z. He, J.F. Yan, Z.J. Song, F. Ye, X. Liao, S.L. Peng, and L.S. Ding, J. Nat. Prod. 72, 1198 (2009). [7] A.G. Gonzaˆlez, R. Este´vez-Reyes, C. Mateo, and A.M. Este´vez-Braun, Phytochemistry 29, 675 (1990). [8] A.F. Barrero, M.M. Herrador, M. Akssira, P. Arteaga, and J.L. Romera, J. Nat. Prod. 62, 946 (1999). [9] V.F. Traven, D.V. Kravtchenko, and T.A. Chibisova, Mendeleev Commun. 7, 249 (1997).
