Resveratrol - also referred to as trans-3,5,4′-trihydroxystilbene - is an organic compound that occurs naturally in various plants. The compound belongs to the Stilbene derivatives and is a polyphenol - a secondary plant substance. The compound is synthesized as a white solid that forms crystals. At 254°C (melting point of resveratrol) decomposition occurs. Natural sources of resveratrol are grapes, raspberries, mulberries, plums, peanuts, and the Japanese knotweed. Above all, however, the red grape seems to have an increased proportion of this active ingredient. In numerous test series a connection between UV radiation and the concentration of resveratrol has been established, especially in the skin of the grape.