Studies on the Mode of Action of Tomatine as a Fungitoxic Agent

Abstract

Removal of 1 or more sugar residues from the α-tomatine molecule markedly decreased its fungitoxicity. While partial hydrolysis of α-tomatine did not greatly affect its surfactant properties, it did destroy the ability of this alkaloid to form a complex with cholesterol. Only unprotonated α-tomatine was capable of binding cholesterol; the protonated form did not. Since α-tomatine was far more toxic at a high pH than at a low pH, this suggests that the unprotonated alkaloid is the active form and that it acts by complexing with fungal sterols.