QUERCETIN AND QUERCITRIN FROM PLUCHEA-LANCEOLATA AND THEIR EFFECT ON GROWTH OF ASPARAGUS BEAN

Two flavonols, quercetin and quercitrin (quercetin 3-O-rhamnoside), were isolated from the leaves of the rapidly spreading noxious perennial weed, Pluchea lanceolata. Quercitrin was also detected from the natural soils associated with the weed, while quercetin was not detected from the weed-associated soils. High performance liquid chromatography established that quercitrin concentration was higher in weed-infested soils with cultivation than in weed-infested, uncultivated soils. Aqueous extracts of 1x10(-4) M, 5x10(-4) M and 1x10(-3) M concentrations of quercetin and quercitrin affected the seedling growth of the legume, asparagus bean (Vigna unguiculata var. sesquipedalis). Mixture of the two flavonols also were effective inhibitors. These data indicate that quercetin and quercitrin produced by P. lanceolata may cause allelopathic interference of crops associated with this weed.