Raw red sour grape Resvital is the top source of grape antioxidants, including resveratrol and proanthocyanidins (OPCs). It is the only grape product made from the entire red sour grape including the vine, skin, and seeds. It is handpicked from remote mountain sources and is free of solvents and fungicides. Resvital is more natural and powerful than mere grape seed extracts. It is also rich in natural-source chromium.