Antiallergic activity of tylogenin, a novel steroidal compound from Tylophora sylvatica.

Tylogenin, a steroidal aglycone generated by acid hydrolysis from two seasonal glycosides occurring in Tylophora sylvatica, inhibits IgE-induced basophil mediator release for allergic reactions. In the rabbit basophil-dependent serotonin release (BDSR) assay system, the inhibitory activity of tylogenin (geom mean IC50 = 39 microM) was significantly (P < 0.05) greater than that of its parent glycosides, tylophoroside (geom mean IC50 263 microM) and acetyltylophoroside (geom mean IC50 331 microM), and that of dexamethasone (geom mean IC50 = 912 microM). The activity of tylogenin was found to increase with the incubation time. In the human leukocyte-dependent histamine release (LDHR) test model, the glycosides had only a minimal activity. In contrast, tylogenin, with a geom mean IC50 = 49 microM, exerted a significantly (P < 0.05) greater potency than dexamethasone (IC50 = 257 microM). These results suggest that tylogenin could represent a new class of antiallergic agents.