CHEMICAL DEFENSE BY WITHANOLIDES DURING FRUIT-DEVELOPMENT IN PHYSALIS-PERUVIANA

The concentrations of withanolide E and 4beta-hydroxywithanolide E were followed in the berry as well as in the surrounding calyx during fruit development in Physalis peruviana. On a fresh weight basis, they all decreased with the exception that 4beta-hydroxywithanolide E in the calyx remained almost unchanged. However, if related to the tissue water to obtain a measure for chemical defence, there was a decrease in the berry but a strong increase in the calyx during maturation for both withanolides. When compared with concentrations from the literature on the antifeedant effect of the isolated compounds on insects, we see clearly that the ripe berry is chemically well protected by high levels of withanolides in the calyx. Obviously, chemical defence is supported by mechanical and topographical features of the fruit. Additionally, evidence is presented that the two withanolides may exist in vivo as glycosides.