| Summary: | Euphorbia retusa is an endemic medicinal plant of Sahara. This study aimed to determine the total phenolic and flavonoid contents of Euphorbia retusa seed, capsule and leaves aqueous extracts as well as to evaluate the antioxidant and photoprotective activities. The correlations between these activities and the different contents were also performed. The antioxidant activity was estimated by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis-3-ethyl benzthiazoline-6-sulfonic (ABTS) scavenging, β-carotene bleaching, cupric-reducing activity (CUPRAC) and reducing power essays. In addition, the sun protection factor (SPF) was reported for the first time and measured according to the Mansur equation. Results showed that, seeds exhibit a higher total phenolics and flavonoids contents. This organ showed the highest capacity in DPPH (IC50 = 50.79 ± 1.87 µg ml-1), ABTS (IC50 < 6.25 µg ml-1), β-carotene bleaching (IC50 < 6.25 µg ml-1), reducing power (A0.50 = 6.97 ± 0.75µg ml-1) and CUPRAC (A0.50 = 7.64 ± 0.30µg ml-1) essays. Accordingly, seed extracts characterized by a high sun protection factor (SPF = 38.26 ± 0.07). Nevertheless, the Pearson correlation coefficients calculated show the highest positive correlation between total phenolic and flavonoids contents and photoprotective activity, while no correlations were found between SPF and other antioxidant activity. This plant could be used as alternative adjuncts in sunscreen product preparation.
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