83(P09) 日本産カバノキ属植物の成分研究(ポスター発表の部)

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In Japan, II species of genus Betula are known. They are recognized as medicinal plants in foreign countries but their constituents have not been investigated well. In this study, we examined the constituents of 6 Betula species in Japan, B. platyphylla var. japonica, B. ermanii Cham., B. maximowicziana Regel, B. davurica Pall, B. schmidtii Regel and B. corylifolia Regel. The outer bark of B. platyphylla var. japonica contains a considerable amount of betulin as a component of suberin wax. Suberin is very resistant to biodegradation by fungi, but over many years of decay, extracellar enzymes of fungi gradually degrade it. On the basis of these facts, we investigated the constituents of decayed outer bark of B. platyphylla var. japonica and found the biodegradation product of betulin. Fresh leaves Sixteen dammarane-type triterpenes including six new ones were isolated together with several known flavonoids and the following remarkable feature was revealed. The dammarane-type triterpenes of leaves of B. platyphylla var. japonica have 3α, 12β-hydroxyl groups, while those of B. ermanii Cham. have 3β, 11α, 20-hydroxyl groups and of B. maximowicziana Regel have 3α, 12β, 20-hydroxyl groups and of B. davurica Pall. Have 3α, 17α, 20-hydroxyl groups. The secodammarane-type triterpene, 17 was isolated from B. schmidtii Regel. Its structure was established by measurement of the ^1H-^1H, long-range ^<13>C-^1H COSY and the NOESY to be methyl (12R,20S)-20-hydroxy-12-O-β-D-xylopyranosyl-3,4-secodammar-4(28),24-diene-3-oate. Compounds 1, 7 and 9 exhibited cytotoxicity against HeLa cells (IC_<50>: 1, 27μg/ml; 7, 11μg/ml; 9, 15μg/ml). Outer bark Eight lupane- and four oleanane-type triterpenes were isolated. It is noteworthy that B. platyphylla var. japonica contains 10% betulin. The content of betulin is proportional to whiteness of the bark. Inner bark Ten diarylheptanoids including six new ones were isolated together with fourteen known compounds. Cyclic-type diarylheptanoids, 31 and 32, exhibited cytotoxicity against HeLa cells (IC_<50>: 31, 25μg/ml; 32, 15μg/ml). Decayed outer bark of B. platyphylla var. japonica The biodegradation product of betulin, 61,was isolated from decayed outer bark of B. platyphylla var. japonica. The structure of 61 was elucidated by 2D-NMR and other spectroscopic studies.
天然有機化合物討論会の論文
1997-07-20

83(P09) 日本産カバノキ属植物の成分研究(ポスター発表の部)

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