Tetrahydropentagamavunon-O (THPGV-O) is assumed to be main metabolite product of biotransformation process of PGV-O. THPGV-O was synthesized by converting PGV-O to the compound by hydrogenation with PdjC as a catalyst. PGV-O potently inhibited the histamine release from ~at mast cells in vitro and in vivo, however, ironically only traces amount of compound was found in the blood. THPGV-O is ass…