Preventive effects of tamarind seed coat extract on UVA-induced alterations in human skin fibroblasts

One of the most damaging actions on skin is from solar radiation, particularly from its ultraviolet (UV) component, through the formation of oxidative species. Thus, an antioxidant strategy that prevents the formation of these oxidants could form the basis of an efficacious cutaneous protectant. Many herbal materials contain antioxidant polyphenols, and this study assessed the possibility that tamarind seed coat extract could fulfill this role. An alcoholic extract of the tamarind (Tamarindus indica L.) seed coat showed stronger antioxidant activity (2,2-diphenyl-1-picrylhydrazyl inhibition, EC(50) = 12.9 μg/ml) than L-ascorbic acid (EC(50) = 22.9 μg/ml) and α-tocopherol (EC(50) = 29.3 μg/ml). In cultured fibroblasts taken from human skin, hydrogen peroxide (100-1000 μM) damaged 62-92% of the cells compared to only 35-47% when the cells were preincubated in extract (200 μg/ml) for 24 h. UVA (40 J/cm2) irradiation of human fibroblasts damaged 25% of the cells but the death rate was reduced to 10% with extract. UV irradiation increased the proportion of cells arrest in G(0)/G(1) phase (from 59% to 78%) but this was largely prevented by the extract (64%), according to flow cytometry. Intracellular total glutathione of UVA-irradiated cells pretreated with the extract increased to 10-25% compared to the non-pretreated group at 24-72 h after irradiation. Fibroblasts typically increased matrix metalloproteinase-1 secretion after photodamage, and this is prevented by the extract. This is the first report showing that tamarind seed coat extract is an antioxidant and can protect human skin fibroblasts from cellular damage produced by UVA and thus may form the foundation for an antiaging cosmetic.