Alpha-tocopherol is the most biologically active and predominant form of vitamin E, functioning as a potent lipid-soluble antioxidant. It protects cell membranes and lipoproteins from oxidative damage by scavenging free radicals and inhibiting lipid peroxidation. Naturally occurring in vegetable oils, nuts, seeds, and green leafy vegetables, it is widely used as a dietary supplement, food preservative, and in cosmetic formulations. Its chromanol ring and phytyl tail enable membrane integration and radical quenching.