Structures of antimutagenic constituents in the peels of Citrus limon.

The methanolic extracts from the peels of Citrus limon were found to show antimutagenic effects against 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the Ames test. From the methanolic extracts, four new coumarins (wakayamalimonol A-D) and a new furanocoumarin (wakayamalimonol E) were isolated together with fifteen known compounds. The absolute stereostructures of the new compounds were determined by chemical synthesis and the modified Mosher's method. Among the isolated constituents, coumarins, furanocoumarins, and limonoids showed antimutagenic effects in the Ames test. One of the major constituent, limonin, showed significant antimutagenic effects against mitomycinC and PhIP in the micronucleus test in vivo.