Development of competitive direct ELISA for gossypol analysis.

Anti-gossypol monoclonal antibody was purified from cell culturing supernatant by ammonium sulfate precipitation and Protein A AffinityPak. The antigen (i.e., gossypol) was labeled with horseradish peroxidase through Schiff-base formation. Both the purified antibody and the enzyme-labeled gossypol were employed to develop a competitive direct enzyme-linked immunosorbent assay (cdELISA) for gossypol analysis. I50 value, the concentration of gossypol causing 50% inhibition of the maximum ELISA signal in the competitive standard curve, was 0.067 microg/mL, whereas the detection limit for gossypol was 0.005 microg/mL. We also observed a good correlation (R2= 0.96, P < 0.05) between the cdELISA method and the AOCS official method for "free" gossypol (extractable gossypol and gossypol derivatives by 70% acetone) analysis of cottonseed meals. This indicates that the newly developed cdELISA could be a valuable and feasible alternative for determination of "free" gossypol, especially when the available sample is limited with relatively low gossypol concentration.