Category: biosynthesis
Vitamins A, C, E + carotenoids serve as the body's "non-enzymatic" antioxidant system, complementing the enzymatic antioxidants (SOD, catalase, GPx — covered in ros_oxidative_stress). Vitamin E is a lipid-soluble chain-breaking antioxidant for polyunsaturated membrane lipids — α-tocopherol is the major preserved form (selective hepatic α-TTP). Tocotrienols (rarer in diet) have unique lipid-membrane mobility. Vitamin C is water-soluble — regenerates oxidized α-tocopheryl radical back to active α-tocopherol, plus is collagen-synthesis cofactor (proline + lysine hydroxylase). Carotenoids (lycopene, β-carotene, lutein, zeaxanthin, astaxanthin) are conjugated-polyene singlet-oxygen quenchers; lutein + zeaxanthin specifically accumulate in macular pigment (AREDS2 trial supplementation for AMD).