On the Weak Intrinsic Luminescence from Paclitaxel Dissolved in Nonelectrolyte Solvents

Paclitaxel, a diterpene natural product from the Pacific Yew tree, Taxus brevifolia, has emerged as a promising chemotherapeutic agent for treating solid tumors. We report here on the electronic absorbance and fluorescence spectra, fluorescence quantum yield, and excited-state fluorescence intensity decay kinetics of paclitaxel dissolved in several nonelectrolyte solvents. The results of these experiments show that the paclitaxel absorbance spectra are a function of paclitaxel concentration, consistent with concentration-dependent paclitaxel association. The paclitaxel molar absorptivity, fluorescence quantum yield, and radiative and nonradiative decay rates are all consistent with the excited state being of an (n, π*) type. We propose that this observation arises from one or both of the phenyl–C = O moieties in paclitaxel. To the best of our knowledge, this paper represents the first comprehensive report on the intrinsic fluorescence from any member of the taxane family.