Abstract:

Trans-resveratrol (C₁₄H₁₂O₃, 5-(4-hydroxystyryl)benzene-1, 3-diol), with a variety of physiological activities and abundant sources, shows instability to light irradiation. The control solution was balanced by photo-isomerization and high performance liquid chromatography (HPLC) method was developed for the simultaneous determination of trans-resveratrol and cis-resveratrol. The methodology study showed good linear correlations (R²=0.999) in the range of 1.5-60 μ mol/L of trans-resveratrol and 1.5-55 μ mol/L of cis-resveratrol which conforms to the request of content determination. The method was used to study the kinetics and equilibrium constant of photo-isomerization. The results showed that trans-resveratrol protected from light was stable in neutral, weak acid and ethanol media at room temperature. The photo-isomerization equilibrium constant was 11.7±0.3 at 25 ℃ in dilute ethanol solution. The method of making the standard curve by photo-isomerization equilibrium solution is simple, convenient and practicable. The stability of trans-resveratrol is related to the medium. When pH value is less than 7, the photo-isomerization is a first order reaction.

Key words: equilibrium constant, high performance liquid chromatography (HPLC), kinetics, photo-isomerization, resveratrol