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.