Triterpenoid saponins from Cortex Albiziae

概要

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Cortex Albiziae, the dried stem bark of a leguminous plant, Albizia julibrissin Durazz, was specified in Chinese Pharmacopoeia (1995 edit.) as a traditional Chinese medicine to be used to relieve melancholia and uneasiness of body and mind, to invigorate the circulation of blood and subside a swelling. In a course of our quality assessment of traditional Chinese medicines, the n-BuOH soluble part of 95% EtOH extracts from the stem barks of Albizia julibrissin was subjected to a series of solvent treatment and chromatographic separations, including Rp-HPLC methods, giving rise to 28 pentacyclic triterpenoid saponins. Based on chemical methods and spectroscopic evidences, the structures of saponins were identified, which included six pairs of diastereoisomers, five pairs of position isomers, and 26 of them were new compounds. All the saponins are trisdesmosidic saponins, which are composed of an acacic acid moiety, 7-9 monosaccharide moieties, 1-2 monoterpenic acid moieties, and exhibited their molecular ion peaks around m/z 2000. Their carbon-13 signals and most of proton signals were assigned based on 1D and 2D NMR experiments. The proton and carbon signals of several known saponins were revised and reassigned. The spectroscopic properties related to these saponins were analyzed and summarized. The cytotoxic activity and other activities of these saponins and their analogues were discussed also.
2004-03-31