Xanthoxyline (1-(2-hydroxy-4,6-dimethoxyphenyl) ethanone) has been isolated from the crude ethyl acetate extractfrom Zanthoxylum limonella fruit.In a previous study, using vial test, the results found that at concentrations greater than 250 ppm, the germination of Chinese amaranth seeds was inhibited by xanthoxyline.To determine the mode of action on the inhibition which xanthoxyline exerts its toxicity, the α-amylase assay was performed.Seeds of Chinese amaranth were treated with a series of concentrations, ranging from 250 to 2000 ppm.The results found that xanthoxyline also inhibited the induction of α-amylase activity in the Chinese amaranth seeds at concentrations greater than 250 ppm.The inhibition of α-amylase by xanthoxyline occurred within 24 h after seed incubation.These results suggest that xanthoxyline may inhibit the germination of Chinese amaranth seeds by inhibiting the induction of α-amylase activity.