EFFECT OF ALKYL SULFIDES ON DIAZOMETHANE-INDUCED METHYLATION OF DNA IN-VITRO

Organosulfur compounds found in Allium species such as garlic and onions inhibit carcinogenesis induced by alkylating agents. One potential mechanism for this activity involves scavenging of ultimate carcinogenic species by the nucleophilic sulfur atom. Carcinogenic methylating agents such as methyl-nitrosourea produce, among others, O6-methylguanine and N7-methylguanine in DNA both in vivo and in vitro. In the present study we have determined the effect of several alkyl sulfides on the formation of O6-methylguanine and N7-methylguanine in DNA reacted with the methylating agent diazomethane in vitro. Dipropyl sulfide and diallyl sulfide affect guanine methylation by increasing the O6/N7 ratio without drastic alterations in the total amount of adduct formed. Three similar compounds - diallyl disulfide, allyl methyl sulfide and diallyl ether - had no appreciable effect on the amount of alkylation at either position. These data suggest that scavenging of diazomethane-like ultimate carcinogens does not play a major role in the inhibition of carcinogenesis by organic sulfides.