Complexes involving gossypol, DNA and Cu(II).

Gossypol, a polyphenolic binaphthyl dialdehyde found in cotton seeds, is a dietary mutagen and a potential male contraceptive. We have earlier shown that in the presence of Cu(II) gossypol causes strand breakage in double stranded DNA and that active oxygen species are involved in this reaction. In this paper we present experiments to suggest that gossypol may be oxidised by Cu(II) to a gossypol radical that may directly react with DNA. Changes in absorption spectrum and fluorescence emission spectrum of gossypol indicated that it binds to both double stranded and single stranded DNA. Gossypol and Cu(II) were shown to form a charge transfer complex that decayed in an oxygen independent reaction. The rate of DNA degradation by gossypol-Cu(II) complex was found to be the same both in the presence and absence of molecular oxygen.