Emission properties of gossypol in solution

Steady-state emission properties of gossypol in acetonitrile at room temperature have been studied using a HPLC system equipped with a specially improved highly sensitive fluorescence detector (ΦF⩾10−7). The fluorescence lifetimes (τ) have been determined using a time-correlated single photon counting system. At room temperature gossypol shows weak fluorescence with the overall quantum yield of ΦF=5×10−5. On the basis of a comparison of the excitation emission spectra with the absorption spectrum and the radiative properties of gossypol, the origin of gossypol fluorescence from two tautomeric forms: aldehyde in S1 (n,π∗) (τ=300 ps) and S2 (π,π∗) (τ=10 ps) and lactol in S1 (n,π∗) (τ=18 ps) state was suggested.