Resveratrol is a naturally occurring phytoalexin produced by certain plants to protect themselves from attacks by pathogens such as bacteria or fungi. Grapes, peanuts and other plants that are constantly under attack by fungus produce Resveratrol to prevent the fungus from damaging and infecting the plant. The concentration of Resveratrol is highly dependent on its geographic origin and its exposure to fungal infection--the higher the probability of fungal infection the higher the concentration of Resveratrol.