Flavonoid, iridoid, and lignan glycosides from Putoria calabrica

From the aerial parts of Putoria calabrica, two new flavonol triglycosides were isolated and their structures were elucidated as quercetin-3-O-[alpha -L-rhamnopyranosyl-(1 -->2)-alpha -L-arabinopyranosidel-7-O-beta -D-glucopyranoside (1, calabricoside A) and quercetin-3-O-[4"'-O-caffeoyl-alpha -L-rhamnopyranosyl-(1 -->2)-alpha -L-arabinopyranosidel-7-0-,8-D-glucopyranoside (2, calabricoside B). Additionally, seven iridoid and three lignan glycosides were isolated and characterized. Radical scavenging activities of all compounds were determined by quantifying their effects on luminol-enhanced chemiluminescence in formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated human polymorphonuclear neutrophils (PMNs). Calabricoside A and B showed strong radical scavenging activity with IC50 values of 0.25 and 0.3 muM, respectively.