Hyaluronidase-Inhibitory and Anti-allergic Activities of the Photo-Irradiated Products of Tranilast

We found that N-(trans-3, 4-dimethoxycinnamoyl) anthranilic acid (tranilast) is readily transformed by photo-irradiation to N-(cis-3, 4-dimethoxycinnamoyl) anthranilic acid (cis-isomer) and a cyclobutane derivative (dimer). Of these photo-irradiated products of tranilast, the cis-isomer was found to inhibit hyaluronidase more effectively than tranilast. From these results, it wsa expected that the cis-isomer might have more effective anti-allergic activity than tranilast ; indeed, the cis-isomer was found to show more effective prevention than tranilast of (1) histamine release from sensitized rat peritoneal mast cells induced by antigen (egg white albumin), (2) histamine release from rat peritoneal mast cells induced by concanavalin A and calcium ionophore A-23187, and (3) the 48 h homologous passive cutaneous anaphylaxis (PCA) in rats.