Topical isoflavones provide effective photoprotection to skin.

BACKGROUND/PURPOSE: Isoflavones, one main group of phytoestrogens, have antioxidative and photoprotective effects in cellular and mouse studies. The aim of this study is to obtain a more comprehensive understanding of the isoflavone-mediated photoprotection with the pig skin model, a more human-resembling model.

METHODS

The pig skin was treated with five well-known isoflavone compounds (genistein, equol, daidzein, biochanin A, and formononetin) and one antioxidant combination solution of 15% vitamin C and 1% vitamin E and 0.5% ferulic acid (CEF) daily for 4 days. Skin was irradiated with solar-simulated UV irradiation, 1 to 5 minimal erythema dose (MED) at 1-MED intervals. Evaluation was carried out 24 h later by colorimeter-measured erythema and sunburn cell numbers.

RESULTS

Topical application of 0.5% solutions of three individual phytoestrogens - genistein, daidzein, biochanin A - are better than similar solutions of equol or formononetin in protecting pig skin from solar-simulated ultraviolet (SSUV)-induced photodamage, as measured by sunburn cell formation and/or erythema. However, the protection was less than that provided by a topical combination antioxidant standard containing 15% L-ascorbic acid, 1%alpha-tocopherol, and 0.5% ferulic acid.

CONCLUSION

Isoflavones provide effective photoprotection and are good candidate ingredients for protection against ultraviolet (UV) photodamage.