Alkaline hydrolysis of the ether-insoluble resin glycoside ("convolvulin") fraction, pharbitin, of the seeds of Pharbitis nil (Convolvulaceae) provided three organic acids, S-2-methylbutyric acid, (2R, 3R)-nilic acid and tiglic acid, and a new glycosidic acid named pharbitic acid B along with the known compounds pharbitic acids C and D. Pharbitic acid B was characterized as (3S, 11S)-3, 11-dihydroxyhexadecanoic acid 11-O-α-L-rhamnopyranosyl-(1→3)-O-β-D-quinovopyranosyl-(1→4)-O-α-L-rhamnopyranosyl-(1→2)-O-β-D-glucopyranosyl-(1→2)-[O-α-L-rhamnopyranosyl-(1→6)]-β-D-glucopyranoside. The structures of the sugar moieties of pharbitic acids C and D were revised.