Quantitative tritium exchange of [3H] aflatoxin B1 during penetration through isolated human skin

Tritium labelled aflatoxin B1 ([G-3H]AFB1) underwent an almost total tritium exchange with water during penetration through isolated human skin. The process was not enzymatic and the site of exchange appeared to be within the epidermis. The mechanism which mediated this extensive exchange was not determined. However, the tritium in [G-3H]AFB1 was found to be very susceptible to chemical conditions which favored carbanion formation at the alpha-carbon of the cyclopentenone ring. The relative effectiveness of the various solvents in mediating the loss of the tritium label was 1 N3NaOH much greater than methanol greater than 1 N HCl greater than water. This work serves as a warning that [G-3H]AFB1 can easily undergo significant changes in specific activity in biological tissues and under relatively mild experimental conditions. It is possible that conditions within the skin favor carbanion formation.