The ESR properties, DNA nicking, and DNA association of aged solutions of catechol versus aqueous extracts of tar from cigarette smoke.

Previous studies in our laboratories have shown that extracts from mainstream or sidestream tobacco smoke nick DNA. These solutions contain the tar semiquinone free radical, and the tar radical becomes associated with cellular DNA. Aged solutions of catechol contain a semiquinone species that has ESR properties similar to those of the radical in cigarette tar extracts, and we have used these catechol solutions as a model for the tar radical. Both the radical in aged catechol solutions and the cigarette tar radical become associated with the DNA in mammalian cells and also nick DNA. The nicking of DNA caused by both tar and aged catechol solutions follows saturation kinetics. Aged catechol solutions thus allow the study of a model for the radical present in cigarette tar, without interference from the other toxic constituents in tar extracts.