Identification and characterization of organic and glycosidic acids in the crude resin glycoside fraction from the leaves and stems of Calystegia japonica

AbstractThe alkaline hydrolysis of the crude resin glycoside fraction from the leaves and stems of the plantCalystegia japonica Choisy (Convolvulaceae) yielded organic acid and glycosidic acid fractions. The organic acid fraction was esterified withp-bromophenacyl bromide to obtainp-bromophenacyl 2R-methyl-3R-hydroxybutyrate (1) andp-bromophenacyl (E)-2-methylbut-2-enoate (2).  By treating the glycosidic acid fraction with trimethylsilyldiazomethane–hexane, seven new methyl esters of glycosidic acids, namely calyjaponic acid A methyl ester (3) calyjaponic acid B methyl ester (5), calyjaponic acid C methyl ester (6), calyjaponic acid D methyl ester (7), calyjaponic acid E methyl ester (8), calyjaponic acid F methyl ester (9), and calyjaponic acid G methyl ester (10), were isolated along with one known ester (4). Their structures were characterized based on spectroscopic and chemical analyses. Compounds3–8 had the same sugar moiety, α-L-rhamnopyranosyl-(1 → 2)-O- β-D-glucopyranosyl-(1 → 2)-[O- α-L-rhamnopyranosyl-(1 → 6)]-O- β-D-glucopyranose, and the aglycones of3–8 were methyl 3S,11S-dihydroxyhexadecanoate, methyl 3S,12S-dihydroxyhexadecanoate, methyl 11S-hydroxyhexadecanoate, methyl 11S-hydroxypentadecanoate, methyl 3S,11S-dihydroxypentadecanoate, and methyl 3S,12S-dihydroxypentadecanoate, respectively. Compounds9 and10 were derivatives of3 and4, respectively, in which the C-6 of the second glucosyl residue was methylated. Compounds6–8 containe...
Source: Journal of Natural Medicines - Category: Drugs & Pharmacology Source Type: research