MUTAGENICITY OF TOXIC WEED SEEDS IN THE AMES TEST - JIMSON WEED (DATURA-STRAMONIUM), VELVETLEAF (ABUTILON-THEOPHRASTI), MORNING GLORY (IPOMOEA SPP.), AND SICKLEPOD (CASSIA-OBTUSIFOLIA)

Commercial grain, such as soybean and wheat, may be contaminated with nongrain impurities such as toxic weed seeds that coexist with harvested crops. The present study investigated the genotoxic potential of seeds from four nongrain sources: jimson weed (Datura stramonium), velvetleaf (Abutilon theophrasti), sicklepod (Cassia obtusifolia), and morning glory (Ipomoea spp.). Mutagenic responses of methanolic extracts of these seeds were determined by using four bacterial strains (TA98, TA100, TA102, and TA2637) with and without microsomal activation. Relative potencies were compared by using the following parameters derived from dose-response curves: (a) mutagenic potency or revertants per milligram equivalent seeds (R/MES), which is defined as the maximal mutagenic response produced by 1 mg of seeds, and (b) mutagenic potential, which relates minimal effective dose (MED) with the estimated number of seeds required to produce a significant mutagenic response. Although the seed extracts elicited responses in all four bacterial strains, TA102 was the most sensitive. The following numbers of toxic weed seeds per 15 g of grain are estimated to constitute a minimal effective dose with TA102 and microsomal activation: morning glory, 1; sicklepod, 6; velvetleaf, 50; jimson weed, 566. These results show that morning glory and sicklepod seeds contain high levels of mutagens. Possible sources of mutagens and possible reasons for the observed variation of relative mutagenic potency are discussed. These observations provide a rational basis for relating seed composition to genotoxic effects and for assessing the possible safety of low levels of weed seeds in the diets of food-producing animals and in human diets.