Table 4.

Antioxidant activity of dominant carotenoids present in human skin [58,59,60,61,62].

Compound	Main Effects
β-Carotene	- directly scavenges ROS - ↑ GPx, CAT, GST and vit C - protects liquid crystal lipid structures from UVR - inhibits UVR-induced proline oxidation in collagen - protects lipids in the intercellular matrix from oxidation - inhibits oxidant-induced NF-kB activation and IL-6 and TNF-α production - protects the immune system from damage by UVA - suppresses UVA induction of MMP-1, MMP-3, and MMP-10 involved in photoageing - blocks 1O2-mediated induction of MMP-1 and MMP-10
Lycopene	- ↓ production of ROS and protects cells against OxS - antioxidant activity based on hydrogen transfer reactions - quenches radicals in the hydrophobic part of the membrane - can eliminate ROO•, thereby inhibiting LPO - more effective than β-carotene in protecting cells against H2O2 - stabilizes other antioxidants, such as vit C and vit E
Lutein	- protects cell membranes against oxidative damage - effective as an antioxidant in the polar region - may reduce LPO and quench 1O2 - prevents the decrease in CAT and SOD - protects the fibroblasts from UVA-induced oxidative action - protects against UVB-induced skin damage, photoageing and photocarcinogenesis

↑, enhances; ↓, reduces; ROS, reactive oxygen species; GPx, glutathione peroxidase; CAT, catalase; GST, glutathione transferase; UVR, ultraviolet radiation; NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells; IL-6, interleukin 6; TNF-α, tumour necrosis factor α; MMP, metalloproteinase; OxS, oxidative stress; ¹O_2, singlet oxygen; ROO^•, peroxyl radicals; LPO, lipid peroxidation; H₂O_2, hydrogen peroxide; SOD, superoxide dismutase.