Seasonal and population variation in flavonoid and alliarinoside content of Alliaria petiolata

Pieris napi oleracea, an indigenous butterfly in North America, lays eggs o n Alliaria petiolata, an invasive weed that was introduced from Europe. How ever, larval development on plants from different sources varies considerab ly. A. petiolata is a compulsive biennial, and its foliage is rich in apige nin flavonoids. We compared the chemistry of different vegetative forms fro m different populations in the vicinity of Ithaca, NY throughout the year. Significant differences occurred in the number of apigenin derivatives in d ifferent populations and vegetative forms, and seasonal variations in the a mounts of these compounds were found. We have previously isolated two major compounds, alliarinoside [(2Z)-4-(beta -D-glucopyranosyloxy)-2-butenenitri le] (1) and isovitexin-6-O"-beta -D-glucoside (3), which negatively affect development of P. napi oleracea larvae. Comparative analyses of these compo unds in two populations throughout the year showed that their concentration s reached maxima twice annually. Foliage is almost devoid of flavonoids in June-July. Thus, variation in the chemistry of the plant may account for ob served variation in development rates and survival of the larvae. Several a pigenin compounds were isolated and identified by spectral studies.