TWO COUMARINS FROM THE ROOT BARK OF CLAUSENA EXCAVATA
SHIOW-CHYNHUANG,*PEI-LIN Wul" and TIAN-SHUNGWo't$
*Department of Pharmacy, Chia Nan College of Pharmacy and Science, Tainan Hsien, Taiwan, R.O.C. tDepartment of Chemistry, National Cheng Kung University,Talnan, Taiwan, R.O.C.
(Received in revised form 1 July 1996)
Key Word I n d e x - - C l a u s e n a claucavatin-B.
INTRODUCTION
Clausena excavata has been used as a folk medicine in
at 6 2.73 and a gem-dimethyl singlet at 6 1.62 indicated a 2'-2'-dimethyl-4-pyranone ring linearly attached to the coumarin ring. Unlike the two cis-vinyl protons found in 4, in 1 only one downfield singlet proton was seen (6 7.89). This suggests that there is a substituent attached to C-3. The remaining peaks disclosed pairs of 1,1-dimethylallyl groups at 8 1.46 and 1.47 (each 6H, s, each 2×CH3), 4.88 and 5.09 (each 1H, rid, each J = 10.4, 0.8 Hz), 4.92 and 5.10 (each 1H, dd, J = 17.8, 0.8, and 17.0, 0.8 Hz), 6.15 and 6.22 (each rid, 1H, J = 17.8, 10.4 and 17.0, 10.4 Hz) which would substitute on C-3 and C-8. On the basis of the above results, the structure of claucavatin-A was deduced as 1. Claucavatin-B (2) was obtained as granules. Its molecular formula, containing two more hydrogen atoms than 1, was established as C24H3oO5. However, the spectral data were very closely related to those of 5 (Table 1). The major difference was the presence of three mutually coupled aliphatic protons at 6 2.08, 2.41 (each 1H, br d, J = 15.0 Hz)) and 4.22 (1H, br s) which were attributed to two H-4' and one H-3', respectively. The downfield signal of the latter (6 4.22) indicated that the H-3' proton is connected to an oxygen functionality, the fact that this signal is a broad singlet (actually a doublet of doublet w ., small coupling constant to two H-4') suggests that H-3' is oriented in toward the equatorial direction. Examining the molecular formula, a hydroxyl group (8 5.05) must be attached to C-3' and orientated in the axial direction. Thus, the double bond between C-3' and C-4' in 5 is hydrated to an alcohol in 2. Hence, structure 2 was established for claucavatin-B.
the treatment of snake-bite and as a detoxification agent [1]. We have reported the isolation of a strong antibacterial compound, nordentatin (6), along with some coumarins and carbazole alkaloids from the root bark of C. excavata [2]. After reinvestigating the acetone extract, two new coumarins, claucavatin-A ( 1 ) a n d - B (2), together with eight known coumarins, kinocoumarin (3) [3], clausenidin (4) [2], clausarin (5) [2, 4], nordentatin (6) [2, 4], xanthoxyletin (7) [2, 4], xanthyletin (8) [2, 4], osthol (9) [5] and cedrelopsin (10) [6], two known flavonoids, isoliquiritigenin (11) [7, 8] and liquiritigenin (12) [8], and several carbazole alkaloids were obtained. Here we report the structural elucidation of the two new coumarins by spectroscopic analyses,
RESULTSAND DISCUSSION Comparison of the UV, IR and ~H NMR spectra of I and 2 with the previously recorded spectra 3, 4, 5 and 6 suggested that a 5,7-dioxycoumarin ring system is involved in the structures of 1 and 2 [9, 10]. A dimethylpyranyl ring fused to a coumarin skeleton was also found and the junction of these two units was found to be between C-6 and C-7, rather than C-5 and C-6. Claucavatin-A (1) has the molecular formula C24H2805 as determined by high resolution mass spectrometry. The 1H NMR spectrum of 1 showed similar absorptions to those of 4 or 5 (Table 1). The broad IR band at 3450 cm -1 and the low-feld tH NMR peak at 8 13.00 indicated a strongly intramolecular hydrogen bonded phenolic proton (5-OH) located at the peri position of a carbonyl group. A methylene singlet :~Author to whom correspondence should be addressed,
EXPERIMENTAL General. Mps: uncorr. UV: in MeOH. IR: in KBr. ~H and 13C NMR: in CDC13 and TMS as internal reference. MS: a direct inlet system.
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root bark of C. excavata (0.8 kg) was subjected to chromatography on a silica gel column and successively eluted with CHCI3-MeOH and C6H6-Me2CO. Ten coumarins, 1 (19.0rag), 2 (14.8mg), 3 (14.8 mg), 4 (7.4g), 5 (5.2g), 6 (4.5 g), 7 (8.1 g), 8 (23.7mg), 9 (15.7rag) and 10 (l.lmg), and two flavonoids, 11 (4.2 rag) and 12 (25.8 mg), were found. Several carbazole alkaloids were also found the structures of which have yet to be elucidated. Claucavatin-A (1). Powder, mp 102-104 °. HRMS: calcd for C24H2sOs, m/z 396.1937 [M] +, found 396.1936. UVAmax nm: 201,219 (sh), 237, 287, 328. IR Vma cm-l: 3450, 1730, 1640. EIMS, m/z (rel. int.): ~ 396 (M ÷, 100), 381 (93), 369 (11), 353 (17), 325 (54), 299 (15), 149 (67). Claucavatin-B (2). Granules, mp 148-150 °. HRMS: calcd for C24H3oO5, m/z 398.2079 [M] ÷, found 398.2103. UV Area nm: 203, 217, 286, 326. IR Vma x x cm-l: 3450, 1730, 1640, 1630. EIMS, m/z (rel. int.): 398 (M ÷, 2), 396 (79), 381 (76), 353 (12), 325 (40), 297 (14), 97 (34), 83 (42), 69 (100), 57 (94).
Acknowledgement--We thank the National Science
2 Council, R.O.C. (NSC 81-0420-B-006-10) for support of this research.
REFERENCES
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S., Khoyo Taiwan Minkan Yakyo Shokubutsu Shi, Khobunkan, Taipei, 1924, p. 36. 2. Wu, T. S. and Furukawa, H., Journal of Natural Products, 1982, 45, 718. 1. Sasaki, 3. Ito, C., Matsuoka, M., Mizuno, T., Sato, K., Kimura, Y., Ju-Ichi, M., Inoue, M., Kajiura, I., Omura, M. and Furuka, H., Chemicaland Pharmaceutical Bulletin, 1988, 36, 3805. 4. Wu, T. S., Phytochemistry, 1988, 27, 3717. 5. Wu, T. S., Liou, M. J., Ko, F. N. and Teng, C, M., Chinese Pharmaceutical Journal, 1990, 42, 317. 6. Eshiett, I. T. and Taylor, D. A. H., Journal of the Chemical Society, Part C, 1968, 481. 7. Komatsu, M., Yokoe, I. and Shirataki, Y., Chemical and Pharmaceutical Bulletin, 1978, 26, 1274. 8. Bharadwaj, D. K., Murari, R., Seshadri, T. R. and Singh, R., Phytochemistry, 1976, 15, 352. 9. Steck, W. and Mazurek, M., Lloydia, 1972, 35, 418. 10. Murray, R. D. H., Mendez, J. and Brown, S. A., The Natural Coumarins.Wiley, New York, 1982.
3 : R1 = H, R2 = ---G(CHa)2CH=GH 2 5 : R 1 = ---C(CH3)2CH=CH2, R2 = H 6 : R 1 -- H, R2 = H
Plant material. Clausena excavata was collected from San Dei Men, Pingtung Hsien, Taiwan, in June 1989 and verified by Prof. C. S. Kuoh. The specimen of this plant is deposited in the herbarium of the National Cheng Kung University, Tainan, Taiwan. Extraction and isolation. The acetone extract of the
