The antimutagenicity of 9 kinds of chemical compounds (osthol, Bergaten, Isopimpinellin, Imperatorin, Xanthotoxol, Xnthotoxin, Thymine, Uracil and unknown one that need authenticating) was studied with the Ames test and the micronucleus and chromosomal aberretion assays in mice in vivo. These compounds were isolated from the water extract of Cnidium monnieri (L.) Cuss in Chinese traditional medicine. The results showed that osthol., bergapten, isopimpinellin, imperatorin, xanthotoxol and xanthotoxin had inh...