Interaction of gossypol with amino acids and peptides as a model of enzyme inhibition.

In order to clarify the interaction of gossypol with proteins, the pure diastereoisomeric Schiff bases from L-tryptophan methyl ester and both gossypol enantiomers were prepared. Their c.d. and n.m.r. spectra demonstrate that the interaction between gossypol and tryptophan, previously reported to involve a weakly associated complex, consists in Schiff base formation. Recent studies on enzyme inhibition by gossypol are discussed; it is suggested that nonspecific covalent binding of gossypol to proteins may be responsible for a significant proportion of the in vitro effects of gossypol.