Resveratrol: Isomeric molar absorptivities and stability

Resveratrol has attracted interest as a wine constituent that may reduce heart disease. Published data on the molar absorptivity and chemical stability of cis- and trans-resveratrol have varied greatly. Accurate values for UV absorbance for trans-resveratrol [UV lambda(max) (EtOH) nm (epsilon) 308 (30 000)] and cis-resveratrol [UV lambda(max) (EtOH) nm (epsilon) 288 (12 600)] were determined and are used to improve chromatographic quantitation methods. Trials conducted under a variety of commonly encountered laboratory conditions show that trans-resveratrol is stable for months, except in high-pH buffers, when protected from light. cis-Resveratrol was stable only near pH neutrality when completely protected from light.