Identification and characterization of organic and glycosidic acids in the crude resin glycoside fraction of Ipomoea alba seeds

Resin glycosides act as laxatives in crude drugs derived from plants of the Convolvulaceae family. These compounds have exhibited antibacterial, ionophoric, anti-inflammatory, antiviral, and multidrug resistance-modulating properties, as well as cytotoxicity against cancer cells. This study investigated the organic acid, hydroxyl fatty acid, monosaccharide, and glycosidic acid components of the crude resin glycoside fraction obtained from the methanol extract of Ipomoea alba L. (Convolvulaceae) seeds, which was subjected to alkaline and acidic hydrolysis. The alkaline hydrolysis yielded acetic, isobutyric, (E)-2-methylbut-2-enoic, and 2S-methyl-3S-hydroxybutyric acids as organic acid components, along with a glycosidic acid fraction. The acidic hydrolysis of the glycosidic acid fraction resulted in the isolation of 11S-hydroxytetradecanoic and 11S-hydroxyhexadecanoic acids as hydroxyl fatty acid components, as well as d-glucose, d-quinovose, d-fucose, d-xylose, and l-rhamnose as monosaccharide components. In addition, 10 new glycosidic acid methyl esters were isolated from the glycosidic acid fraction treated with trimethylsilyldiazomethane-hexane, along with one known glycosidic acid methyl ester. Of these, eight compounds contained new glycans. Four of these compounds were unusual natural glycosides with four glycosidic linkages to one monosaccharide. Their structures were determined using MS and NMR spectral analyses, which provided valuable insights into the unique glycosidic composition of I. alba seeds.