correlation between sun protection factor and antioxidant activity, phenol and flavonoid contents of some medicinal plants

long exposure of uv radiation increases risk of skin diseases such as cancer and photoallergic reactions. uv-b (280-320 nm) radiation is mainly responsible for inducing skin problems. skin protection is a suitable method in the fight against ultraviolet radiation induced damage. various synthetic agents have been used as photo protective but because of their potential toxicity in humans, they have limited use. natural substances have been recently considered as potential sunscreen resources because of their absorption in the uv region and their antioxidant activity. in the present study, the uv protective effects of 20 extracts from four common medicinal plants were evaluated. their phenol and flavonoid contents and antioxidant activities were determined and correlation between spf and these contents were evaluated. spfs were between 0.102 and 24.470. the highest value was reached with ultrasonic extract of crataegus pentagyna (spf = 24.47) followed by methanolic extract of feijoa sellowiana (spf = 1.30). good correlation was found between spf and phenolic contents (correlation coefficient = 0.55 and p = 0.01) but no correlations were found between spf and flavonoid contents or antioxidant activity. these extracts can be used alone or as additives in other sun screen formulations to enhance their spf.