The in vivo function of vitamin E is to scavenge peroxyl radicals via its phenolic (chromanol) hydroxyl group, thus protecting lipids against free radical-catalyzed peroxidation. The tocopheryl radical formed can then be reduced by reductants such as L-ascorbate. Other major products of α-tocopherol oxidation include α-tocopherylquinone and epoxy-α-tocopherols. The metabolites α-tocopheronic acid and its lactone, known as the Simon metabolites, are generally believed to be artefacts. In addition to these oxidation products, the other major class of tocopherol metabolites is the carboxyethyl-hydroxychromans (this pathway). These metabolites are produced in significant amounts in response to excess vitamin E ingestion.