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-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranoside and toralactone 9-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl-(1→3)-O-β-D-glucopyranosyl-(1→6)-O-β-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.