Arvensic acids A-D, novel heptasaccharide glycosidic acids as the alkaline hydrolysis products of crude resin glycosides from Convolvulus arvensis

Abstract

In this study, a resin glycoside fraction with cytotoxic activity was isolated from the alcoholic extract of C. arvensis whole plants. To describe the chemical feature of the resin glycosides, the fraction was alkaline hydrolyzed and four novel glycosidic acids, named arvensic acids A-D (1–4), were isolated. Their structures were thoroughly elucidated on the basis of spectroscopic data and chemical evidences. They all possess a same heptasacharride core, consisting of one D-fucose, two L-rhamnose and four d-glucose units. The difference among these glycosidic acids was placed on the aglycone, which is 12S-hydroxypentadecanoic acid for 1, 12S-hydroxyhexadecanoic acid for 2, 3S,12S-dihydroxypentadecanoic acid for 3, and 3S,12S- dihydroxyhexadecanoic acid for 4. These aglycones are rarely found in the structures of resin glycosides and are firstly identified in the genus Convolvulus.