[Effects of nordihydroguairetic acid and ethanol on the growth of Entamoeba invadens].

The effects of the alcoholic extract (resin) obtained from Larrea tridentata, of nordihydroguiaretic acid (NDGA) and of ethanol over axenic cultures of Entamoeba invadens PZ strain were studied. The activity of these substances was demonstrated in growht curves. Inocula of 1-3 x 10(5) trophozites by milliliter in culture tubes containing 11 ml of TP-S-1 medium were done, and incubated at 25 degree C. In each experiment the follwoing was done: a) tipical growth curve as a control, b) curve with the medium plus 0.2 ml of a mixture of ethanol and water v/v (solvent used for resin and NDGA), and c) curves with different concentrations of the test compounds. The trophozoite number was counted each 24 hours by means of an hemocitometer. The results obtained indicate that the resin has inhibitory activity at a concentration of 0.0001 per cent. The NDGA activity was observed at 10(-6) to 10(-8) M concentrations. The ethanol had, "per se", inhibitory effect over the cultures, and was annulated by the presence of NDGA. At higher contentrations of the acid acid the temporal curse of the graphas was similar to that observed for the control.