Further studies on the in vitro activity of gossypol as antiamebic agent.

Gossypol has an in vitro antiamebic effect, which is 11,39, and 980 times more potent than emetime, metronidazole and diiodohydroxyquinolein, respectively, on five Entamoeba histolytica axenic strains. The trophozoite NADP-dependent malic enzyme and alcohol dehydrogenase are inhibited by (+/-)-gossypol, in a noncompetitive manner with respect to the substrate. From the (-)- and (+)- enantiomers, which integrate the natural gossypol mixture, the first one is three and four times more active in inhibiting both the amebic culture growth and the mentioned oxidoreductases, respectively. The above results justify the analysis of gossypol as an antiamebic drug in experimentally infected animals.