13 ツルレイシ(Momordica charantia L.)果実の苦味成分およびその関連化合物

抄録

An extensive survey for the triterpenoid constituents of Momordica charantia L. has been carried out in this laboratory, and so far, five glycosides (momordicosides A-E) of cucurbit-5-ene derivatives were isolated from the seeds, and their structures were determined. They are unique cucurbitacins being highly oxygenated only in the side chain and having no oxygen function at C_<11>. This study concerns the structure elucidation of two bitter glycosides, momordicosides K and L, and four non-bitter glycosides, momordicosides F_1, F_2, G and I isolated from the fruits. The structure of F_1 was proposed as 3-O-β-D-glucopyranoside of 5,19-epoxy-25-methoxy-5β-cucurbita-6,23-dien-3β-ol on the basis of PMR, CMR and CD spectral data and chemical conversion into a cucurbit-5-ene derivative. G is the corresponding β-D-allopyranoside. F_2 and I are the C_<25>-OH derivatives corresponding to G and F_1, respectively. K and L were determined as 7-O-β-D-glucopyranosides of 19-oxo-25-methoxy-cucurbita-5,23-diene-3β, 7β-diol and its C_<25>-OH derivative, respectively, on the basis of spectral data and chemical correlation with F_1-aglycone. F_1, F_2, G and I are the first cucurbitacins having 5β-cucurbitane nucleus found in nature, and K and L are noted as the new cucurbitacins having C_9-aldehyde and 7-O-β-D-glucopyranosyl groups. Among momordicosides, G and F_2 are the first triterpenoid glycosides having D-allose as a component sugar.