Antioxidants from Plants Protect against Skin Photoaging

Table 1

Defence levels and mechanism of action of antioxidants.

The first line of defence		The second line of defence		The third line of defence
Antioxidant	Mechanism of action	Antioxidant	Mechanism of action	De novo enzymes	Mechanism of action
Superoxide dismutase	O2^•− → H2O2	Ascorbic acid	Chain breaking: donate an electron to the free radical	Polymerases	DNA repair
Catalase	2H2O2 → O2 + H2O	Uric acid		Glycosylases
Glutathione peroxidase	H2O2 + GSH → GSSG + H2O	Glutathione		Nucleases
Transferrin	Metal chelators or sequesters	α-Tocopherol
Caeruloplasmin		Ubiquinol		Proteinases	Protein proteolysis
		β-Carotene	Incorporation of free radical	Proteases
		Lycopene		Peptidases