Antiallergic agent from natural sources. Structures and inhibitory effect of histamine release of naphthopyrone glycosides from seeds of Cassia obtusifolia L

Two new naphthopyrones, cassiasides B2 (1) and C2 (2), were isolated from the seeds (Cassiae Semen) of Cassia obtusifolia L. The structures of the two new compounds 1 and 2 were established as rubrofusarin 6-O-beta-D- glucopyranosyl-(1-->6)-O-beta-D-glucopyranosyl-(1-->3)-O-beta-D- glucopyranosyl-(1-->6)-O-beta-D-glucopyranoside and toralactone 9-O-beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranosyl- (1-->3)-O-beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranoside, respectively, on the basis of spectral and chemical evidence. Compound 2 was found to inhibit the histamine release from rat peritoneal exudate mast cells induced by antigen-antibody reaction.