Substances in grapes can reduce the amount of cell damage caused in skin exposed to the sun''s ultraviolet radiation, researchers in University of Barcelona, Spain say. Marta Cascante, a biochemist at the University of Barcelona, and colleagues at the Spanish National Research Council say UV rays act on the skin by activating "reactive oxygen species," and these compounds in turn oxidize macromolecules such as lipids and DNA, stimulating certain reactions and enzymes -- JNK and p38MAPK -- that cause cell death. The researchers showed some polyphenolic substances extracted from grapes, flavonoids, can reduce the formation of reactive oxygen species in human epidermis cells that have been exposed to long-wave ultraviolet A and medium-wave ultraviolet B radiation. "These polyphenolic fractions inhibit the generation of the reactive oxygen species and, as a result, the subsequent activation of the JNK and p38 enzymes, meaning they have a protective effect against ultraviolet radiation emitted by the sun," Cascante says in a statement. The study is published in the Journal of Agricultural and Food Chemistry.