Allelochemicals in foliage of unfavored tree hosts of the gypsy moth,Lymantria dispar L. : 2. Seasonal variation of saponins inilex opaca and identification of saponin aglycones.

A greater variety of qualitative chemical defenses has been reported in eastern forest trees than might be expected from current interpretation of the plant apparency theory. For the gypsy moth there is an association between the occurrence of alkaloids and unfavorability of certain tree species, as well as the presence of saponins. The latter association, however, is not statistically significant. Species in the genusIlex have been reported to contain both alkaloids and saponins (Barbosa and Krischick, 1987). In this study, determinations were made of the occurrence of alkaloids and saponins inI. opaca and their changes in concentration over time. No alkaloids were detected. Saponins were isolated, and the aglycone siaresinolic acid was identified. Saponin concentration changes seasonally, being highest in early May and lowest in early June leaves.