L-Tartaric acid ((2R,3R)-(+)-Tartaric acid) occurs naturally in many plants, particularly grapes and tamarinds, and is one of the main acids found in wine. It is used as an antioxidant. Salts of tartaric acid are known as tartrates. L-Tartaric acid is a muscle toxin, which works by inhibiting the production of malic acid, and in high doses causes paralysis and death.