IDENTITY AND OCCURRENCE OF CERTAIN FLAVONOL GLYCOSIDES IN 4 VARIETIES OF PEARS

The principal flavonol glycosides of Packingham pears were isolated and identified. Mass spectrometry and nuclear magnetic resonance were used to confirm the identities of the aglycones. GLC and TLC were used to compare the aglycone and sugar moieties of hydrolyzed glycosides with known compounds.All compounds were characterized by UV spectrophotometry. Previously reported identities of quercetin 3-glucoside isolated from Bartlett and Bon Chretien pears and isorhamnetin 3-glucoside isolated from Bon Chretien pears were confirmed. Isorhamnetin 3-rutinoside, isorhamnetin 3-galactoside, and quercetin 7-xyloside were isolated from Packingham pears and identified. A compound of isorhamnetin substituted with another disaccharide of glucose and rhamnose at position three was also isolated. Two other glycosides of quercetin were observed; one contained substituents at the 3′ and 7 positions. Three other varieties of pears—Bartlett, Bose, and D’Anjou— were compared. © 1969, American Chemical Society. All rights reserved.