Simple spectrophotometric assessment of the trans-/cis-resveratrol ratio in aqueous solutions.

The solubility and molar absorptivity of trans- and cis-resveratrol isomers in aqueous solvents are poorly described. This study aimed to develop and describe a new simple method for the determination of trans- and cis-resveratrol concentrations in aqueous solutions. Up to 300 microM trans-resveratrol was dissolved in water by sonication for 2h. Cis-resveratrol was obtained by exposing a 100-muM trans-resveratrol aqueous solution to sunlight for 8h, followed by HPLC separation and analysis by mass spectrometry (resveratrol oxidation products were absent). Accurate values for UV absorbance in water were [see text], epsilon(286 nm)=23400 M(-1)cm(-1) for trans-resveratrol and [see text], epsilon(304nm)=9515 M(-1)cm(-1) for cis-resveratrol. These values allowed us to propose formulae to assess the trans-/cis-resveratrol ratio in water, using a simple and reliable UV-vis spectrophotometric method. Statistical analysis revealed no significant difference between our UV method and the commonly used HPLC method. All these data are transferable to 150 mM NaCl and 10 mM phosphate buffer solutions, which could be particularly useful for cell culture, ex vivo and in vivo studies.