Bioassay-directed fractionation of clove terpenes from the plant Eugenia caryophyllata has led to the isolation of the following five active known compounds: beta-caryophyllene , beta-caryophyllene oxide , alpha-humulene , alpha-humulene epoxide I , and eugenol . Their structures were determined on the basis of spectral analysis (hreims, 1H and 13C nmr). These compounds showed significant activity as inducers of the detoxifying enzyme glutathione S-transferase in the mouse liver and small intestine. The ability of natural anticarcinogens to induce detoxifying enzymes has been found to correlate with their activity in the inhibition of chemical carcinogenesis. Thus, these sesquiterpenes show promise as potential anticarcinogenic agents.