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).
Organ Systems
integumentary
cardiovascular
Pathway Steps
lipid-peroxyl-radical → tocopheryl-radical — via α-tocopherol scavenges peroxyl → α-tocopheryl radical. Vitamin E (α-tocopherol) is the principal lipid-phase antioxidant: it donates a hydrogen atom to chain-carrying lipid peroxyl radicals, halting membrane lipid-peroxidation chains and itself becoming a relatively stable tocopheryl radical. This breaks the propagation cycle that would otherwise damage membranes.
tocopheryl-radical → alpha-tocopherol — via vitamin C (or coenzyme Q / glutathione) reduces tocopheryl radical back to active form. The tocopheryl radical is recycled back to active α-tocopherol by other antioxidants — chiefly vitamin C (ascorbate) and the glutathione system. This antioxidant network (not vitamin E alone) sustains protection, illustrating why isolated high-dose vitamin E supplementation has disappointed in trials.
Known Modulators
alpha tocopherol (activator) — lipid peroxyl radical scavenger. preferred vitamin E form (hepatic α-TTP selection); RRR-α-tocopherol natural > synthetic; ATBC + SELECT trial null/harm for cancer prevention
tocotrienols (activator) — lipid peroxyl radical + Ras inhibition. tocotrienol family (α/β/γ/δ-T3); cardiovascular + neuroprotection claims; less hepatic accumulation than tocopherols
mixed tocopherols (activator) — broad-form vitamin E (α/β/γ/δ-tocopherols). full-spectrum vitamin E; γ-tocopherol has unique inflammation-modulating effect; preferred over α-only
gamma tocopherol (activator) — reactive nitrogen species scavenger + α-tocopherol-complementary. specific γ-T form; binds RNS that α-tocopherol misses; competition with α-tocopherol for α-TTP
tocopheryl acetate (activator) — esterified vitamin E (hydrolyzed to free tocopherol). common supplement + topical form; stable to oxidation; esterase activation