A new 3-Acetoxy-urs-23,28,30-trioic acid from the leaves of Acanthopanax trifoliatus

121 Journal of Chemistry, Vol. 42 (1), P. 121 - 124, 2004 A new 3
-acetoxy-urs-23,28,30-trioic acid from the leaves of Acanthopanax trifoliatus Received 7-7-2003 Phan Van Kiem1, Nguyen Tien Dat3, Chau Van Minh1, Jung Joon Lee2, Young Ho Kim3 1Institute of Natural Products Chemistry, Vietnamese Academy of Science and Technology 2Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea 3College of Pharmacy, Chungnam National University, Daejeon, Korea ABSTRACT A new 3
-acetoxy-urs-23,28,30-trioic acid, named acantrifoic acid B (1), has been isolated from the leaves of Acanthopanax trifoliatus. Its chemical structure has been characterized on the basis of spectral and chemical evidence. I - INTRODUCTION Acanthopanax trifoliatus (L.) Merr., (Araliaceae) is distributed in North Vietnam and used in the folk medicines of south–east Asia (Chi, 1997; Loi, 2001) as a drug with ginseng- like activity. Lupane-triterpene carboxylic acids and a lupane-triterpene glycoside have been reported from the leaves of A. trifoliatus (Ty et al., 1984; Lischewski et al., 1985; Yook et al., 1998). As a part of our continuing studies on Acanthopanax species, we report here the isolation and the structure determination of a new compound from A. trifoliatus. Based on spectroscopic data, the chemical structure of constituent was determined as 3
-acetoxy-urs- 23,28,30-trioic acid (1). II - RESULTS AND DISCUSSION Repeated column chromatography on silica gel of the dichloromethane extract of the dried leaves of A. trifoliatus yielded a new carboxylic acid 1. Compound 1 was formed as white crystals, and produced a due to carbonyl IR absorption peaks at 1748 - 1750 cm-1, acid IR absorption peaks at 3400 cm-1. The FAB-MS spectrum of 1 showed an [M+H]+ ion peak at m/z 561, correspond to a molecular formula of C32H48O8. The 1H-NMR spectrum of 1 (Table 1) showed signals due to five tertiary methyl groups [ 0.96 (3H, s, H3-25), 1.01 (3H, s, H3-26), CH3-C-O O COOH COOH COOH 3 4 810 13 14 17 19 20 22 23 24 25 26 27 28 29 30 32 Fig. 1: Structure of compound 1 1.04 (3H, d, J = 7.2 Hz, H3-29), 1.08 (3H, s, H3-27) and 1.24 (3H, s, H3-24)], one oxygen bearing a proton ( 4.92, H-3) and one acetoxy proton [ 1.95 (3H, s)]. The 13C-NMR and DEPT spectrums revealed 32 carbon signals, 122 including three carboxyl groups at  177.0, 178.0 and 178.1, one ester carbonyl group at 170.0, one oxygen bearing methine carbon at  76.0, and six methyl carbons at  9.8, 15.2, 16.7, 16.9, 17.5 and 21.3. A 1H-1H COSY experiment allowed analysis of their spin systems and assignments of their proton resonances. The assignment of their correspon- ding carbons, made by a HMQC spectrum. The C-H long-range correlations between proton H-3 (H 4.92) and carbons C-31 (C 170.0) / C-32 (C 21.3), between protons H-3 (H 4.92) / H-24 (H 1.24) and carbon C-23 (C 177.0), between protons H-29 (H 1.04) / H19 (H 2.70) and carbon C-30 (C 178.0), and between protons H-18 (H 1.45) / H-22 (H 1.35) and carbon C-28 (C 178.1) were observed in the HMBC spectrum. This evidence confirmed that an acetoxy group was connected to C-3, three carboxyl groups (C 177.0, 178.1, 178.0) were connected to C-23, C-28 and C-30, respectively. Further more, NOESY correlations were observed between H-3 [4.92 (1H, br s)] and H3-24 [1.24 (3H, s)]. This evidence confirmed the location of C-23 carboxyl group. The chemical shift at C 76.0 (C-3) is typical for the location of 3
-acetoxy of pentacyclic triterpenoids (Shashi B. M. et al., 1994). Based on the 1H-1H COSY, NOESY, HMQC, HMBC spectral data, compound 1 was determined to be 3
-acetoxy-urs-23,28,30-trioic acid, which we named acantrifoic acid B. Table 1: 1H-, 13C- NMR spectral data of compound 1 (in acetone-d6) Pos. C (150 MHz) H (600 MHz) 1 33.7 (t) 1.49 (2H, m) 2 25.2 (t) 1.55 (2H, m) 3 76.0 (d) 4.92 (1H, br s) 4 50.4 (s) - 5 46.1 (d) 1.96 (1H, m) 6 21.6 (t) 1.67 (2H, m) 7 34.9 (t) 1.35 (2H, m) 8 42.2 (s) - 9 51.3 (d) 1.58 (1H, m) 10 37.7 (s) - 11 21.9 (t) 1.52 (2H, m) 12 27.4 (t) 1.82 (2H, m) 13 39.0 (d) 2.45 (1H, dt, J = 12.6, 3.6 Hz) 14 43.6 (s) - 15 30.4 (t) 1.29 (2H, m) 16 23.0 (t) 1.66 (2H, m) 17 57.1 (s) - 18 49.1 (d) 1.45 (1H, m) 19 41.7 (d) 2.7 (1H, dd, J = 10.2, 3.0 Hz) 20 40.8 (d) 2.94 (1H, ddd, J = 7.8, 3.0 Hz) 21 32.8 (t) 2.28 (2H, ddd, J = 7.8, 2.4 Hz) 22 38.1 (t) 1.35 (1H, m); 1.86 (1H, m) 23 177.0 (s) - 24 17.5 (q) 1.24 (3H, s) 25 16.7 (q) 0.96 (3H, s) 123 26 16.9 (q) 1.01 (3H, s) 27 15.2 (q) 1.08 (3H, s) 28 178.1 (s) - 29 9.8 (q) 1.04 (3H, d, J = 7.2 Hz) 30 178.0 (s) - 31 170.0 (s) - 32 21.3 (q) 1.95 (3H, s) CH3-C-O O COOH COOH COOH 1H-1H COSY HMBC Fig. 2: Important H-C correlations in HMBC and H-H correlations in 1H-1H COSY spectrums of 1 iii - MATERIALS AND METHODS General experimental procedures Melting points were determined using a Yanagimoto micro hot-stage melting point apparatus. IR spectra was obtained on a JASCO DIP-370 Digital polarimeter. Optical rotations were determined on a JASCO DIP-1000 KUY polarimeter. FAB-MS and HR FAB-MS were obtained using a JEOL JMS-DX 300 spectro- meter. 1H-NMR (600 MHz) and 13C-NMR (150 MHz) spectra were recorded on a Bruker- AM600 FT-NMR unit and chemical shifts are expressed as  values using TMS as an internal standard. Column chromatography (CC) was performed on silica gel 60. Plant material A. trifoliatus was collected in Langson province, Vietnam in January 2001 and identified by Prof. Dr. Tran Minh Hoi, Institute of Ecology, Biological Resourses, Vietnamese Academy of Science and Technology (VAST). Voucher specimens (No 2539) are deposited at the herbarium of the Institute of Natural Product Chemistry, VAST, and at the herbarium of the College of Pharmacy, Chungnam National University, Korea. Extraction and isolation Dried and powdered leaves (3.7 kg) were extracted repeatedly with hot MeOH three times. The combined solutions were evaporated under reduced pressure to give MeOH extract (250.0 g), which was suspended in water and then partitio- ned with dichloromethane. The dichloro-methane fraction (56.0 g) was then subjected to repeated chromatography on a silica gel column, using hexane-acetone (4 : 1) as eluent and repeatedly recrystallized from hexane-acetone (8 : 1) to yield 1 (10.0 mg) as white crystals. 3.4 3
-acetoxy-urs-23,28,30-trioic acid (1) White crystals, m.p. 225 - 228oC, [
]25D -35.7o (c 0.51, MeOH); IR KBrmax cm-1: 3400 (br, -COOH), 124 2890 - 2950 (C-H), 1748 - 1750 (>C=O); FAB-MS (positive) m/z: 561 [M+H]+; 1H- and 13C-NMR: see Table 1. Acknowledgements: This study was suppor- ted by a grant from the Vietnam - Korea inter- national cooperation project. We are grateful to KBSI for measuring NMR and MS spectra and we thank to Prof. Dr. Tran Minh Hoi, Institute of Ecology, Biological Resources, VAST for the plant identification. REFERENCES 1. V. V. Chi. Vietnamese Medical Plant Dictionary. Hanoi Medicine Pub. (1997). 2. D. T., Loi. Glossary of Vietnamese Medical Plants. Hanoi S&T Pub (2001). 3. M. Lischewski, P. D. Ty, L. Kutschabsky, D. Pfeiffer, H. V. Phiet, A. Preiss, T. V. Sung, and G. Adam. Phytochemistry, Vol. 24, P. 2355 - 2357. 4. B. M. Shashi B. M. and P.K. Asish. Phytochemistry, Vol. 37, P. 1517 - 1575 (1994). 5. S. Siddiqui, B. S. Siddiqui, F. Hafeez, and S. Begum. Planta Medica, Vol. 54, P. 232 (1988). 6. S. Siddiqui, S. Begum, B. S. Siddiqui, and F. Hafeez. J. Nat. Prod., Vol. 52, P. 57 (1989). 7. Ph. D. Ty, M. Lischewski, H. V. Phiet, A. Preiss, T. V. Sung, J. Schmidt, and G. Adam. Phytochemistry, Vol. 23, P. 2889 - 2891 (1984). 8. C. S. Yook, I. L. Kim, D. Y. Hahn, T. Nohara, and S. Y. Chang. Phytochemistry, Vol. 49, P. 839 - 843 (1998).