The electrochemical behaviour, on mercury, of gossypol in the acid pH region in mixed aquo-acetone solvent

Abstract The reduction of gossypol on mercury was investigated in acid (H 2 O + acetone 1 : 1 v:v) and basic (aqueous) solutions. Its stability in both media was studied by UV—Vis spectroscopy and polarography. In acid medium reasonable stability was found while under basic conditions O 2 promoted a fast modification of gossypol. Polarography (d.c. and a.c.), cyclic voltammetry, rotating disc electrode and controlled potential coulometry techniques were used to investigate the electrochemical behaviour of this natural product. D.c. polarography and rotating disc electrode studies revealed only one wave, ill defined owing to its proximity to the discharge of the supporting electrolyte. Therefore, mathematical treatment using the Gauss—Newton algorithm was used to investigate the waves. The cyclovoitammograms only presented a single cathodic peak; no anodic peak was observed at any scan rate investigated. Coulometric measurements indicated a two-electron per aldehyde group transfer at low gossypol concentration (up to 1 × 10 −4 M); at higher concentrations only one electron was transferred. A reduction mechanism for acid conditions is proposed.