Study of the changes of trans-resveratrol caused by ultraviolet light and determination of trans- and cis-resveratrol in Spanish white wines

Trans-resveratrol is a polyphenolic compound found in several foods items like wines, legumes, berries, peanuts and pistachios and lately it has attracted great attention due to its beneficial health effects such as anti-cancer, neuroprotective, anti-aging and anti-inflammatory. Therefore, it is important to identify all isomers and derivatives of this compound in order to avoid any errors in their quantification. This paper focus on the study of the transformation of trans-resveratrol into the cis form after subjecting the trans form to UV light. Several conditions were tested and results show the transformation should be made in perfectly controlled conditions (UV light wavelength; distance between the UV lamp and the solution and exposure surface) otherwise the formation of a third compound is observed whose concentration increases as does the light exposure time. This new compound is derived from cis-resveratrol and it appears in a higher concentration when the initial concentration of the trans-resveratrol solution is low. Trans- and cis-resveratrol were determined in white wines from the northwestern of Spain.