Melantheraside A–E, five original triterpenes with natural chloride or oxime group from the aerial parts of Melanthera elliptica O. Hoffm.
Abstract
Five new pentacyclic triterpenoids, Melantheraside A–E (1–5) together with eleven known compounds (6-16) were isolated from the methanol extract of the aerial parts of Melanthera elliptica O. Hoffm. Their structures were established by extensive analysis of 1D- (1H, 13C), 2D- (COSY, ROESY, HSQC and HMBC) NMR data experiments in conjunction with mass spectrometry (TOFESIMS and HR-TOFESIMS) and by comparison with data reported in the literature. The structures of the new compounds were established as: 12α-chloro-3β-hydroxyoleanan-28,13β-olide (1), 3β-acetoxy-12α-hydroxytaraxer-14-en-28-oic acid (2), 3β-hydroxy-12-oximetaraxeran-28,14β-olide (3), 3β-acetoxy-12-oximetaraxeran-28,14β-olide (4) and 2β-carboxyamino-12α-chloro-3-oxo-1-nor-oleanan-28,13β-olide (5). The 3β-acetoxy-12α-chloro-oleanan-28,13β-olide (6) was isolated for the first time as natural product.
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