Table 2.
Selected polyphenol compounds with antioxidant properties and their influence on the skin [21,23,35,36,40,41,42].
| Compounds | Role as Antioxidants | Beneficial Effects on the Skin | |
|---|---|---|---|
| Flavonoids | flavonols (e.g., quercetin, kaempferol, isorhamnetin) | interruption of free radical chain reactions; reducing properties (by donating an electron or a hydrogen atom); stabilization or delocalization of an unpaired electron leading to the formation of a stable phenoxyl radical; ability to chelate metal ions; ideal scavengers of superoxide radicals and inhibitors of lipid peroxidation | - can act as cofactors of enzymes - influence angiogenic and inflammatory processes - protect against radiation, moisturize and soften the skin - are used in anti-ageing, anti-cellulite, anti-couperose, and skin-lightening products |
| flavones (e.g., apigenin, luteolin, rutin) | |||
| flavanols (e.g., catechin, epicatechin, procyanidins) | |||
| flavanones (e.g., naringenin, hesperetin) | |||
| anthocyanidins (e.g., cyanidin, peonidin, delphinidin) | |||
| isoflavonoids (e.g., genistin, daidzein) | |||
| Phenolic acids | hydroxybenzoic acid derivatives (e.g., p-hydroxybenzoic, vanillic acid, protocatechuic acid) | predominantly radical scavenging via hydrogen atom donation; also electron donation and singlet oxygen quenching | - exhibit depigmenting properties by controlling the activity of tyrosinase - moisturize the skin and stimulate the synthesis of collagen and elastin fibres - anti-allergic, anti-cancer, anti-inflammatory, antimicrobial, anti-ageing properties - act as photoprotectors, prevent UV-induced erythema formation in the skin |
| hydroxycinnamic acid derivatives (e.g., caffeic, p-coumaric, ferulic acids) | |||
| Tannins | hydrolysable tannins | inhibition of lipid peroxidation and lipoxygenases in vitro, ability to scavenge radicals (e.g., hydroxyl, superoxide, and peroxyl) | - promote tropoelastin synthesis and reduce elastase activity - protect the skin from inflammation caused by external irritation - anti-inflammatory and wound healing properties - antimicrobial, cytotoxic, anti-cancer, antiulcer activity |
| condensed tannins (proanthocyanidins) | |||
| Stilbenes | trans-resveratrol and its glucoside |
effective antioxidant in various in vitro assays, including total antioxidant activity, reducing power, DPPH•, ABTS•+, O2•−, H2O2 scavenging, and metal chelating; upregulate endogenous antioxidant pathways via activation of the Nrf2 pathway | - protect skin cells against oxidative damage caused by free radicals - anti-inflammatory effect - reduce hyperpigmentation (inhibit tyrosinase activity via suicide substrate type (Kcat) inhibition; affect post- transcriptional regulation of melanogenic genes; inhibit mRNA expression of TYR, TYR- related proteins 1 and 2, MITF and DCT in human melanocytes) |
Nrf2, nuclear factor erythroid 2-related factor 2; TYR, tyrosinase; MITF, microphthalmia transcription factor; DCT, dopachrome tautomerase.