Antioxidant and Anti-Tyrosinase Potentials of Extracts of Nigella sativa and Senna alexandrina from Sudan

Exposure to sunlight causes melanin accretion, oxidative stress, and generations of free oxygen radicals. Therefore, using sun creams rich in natural antioxidants is common to protect the skin from direct sunlight contact. Nigella sativa (NS) and Senna alexandrina (SA) are medicinal plants with numerous health benefits and therapeutic effects due to their antioxidant and anti-inflammatory properties. This experiment was conducted to examine the antioxidant and whitening (antityrosinase) effects of NS and SA from Sudan in vitro. Hydro-methanol extracts (methanol: distilled water, 4:1 v/v) of NS and SA were made and partitioned into five fractions (n-hexane, chloroform, ethyl acetate, n-butanol, and water) to investigate the antioxidant effects, diphenylpicrylhydrazyl (DPPH) free radical scavenging assay and to explore the whitening effects, tyrosinase inhibition activity. The most potent antioxidant potential was shown by ethyl-acetate fractions of both plant extracts, which reduced the scavenging activity by 79.3 and 53.0%, respectively. In addition, the best whitening effect was revealed by chloroform and n-hexane fractions of SA and NS extracts, with 86.0 and 93.0% inhibitory activity of tyrosinase, respectively. The outcome is comparable to the existing theory that antioxidants of natural origin can reduce free radicals and potentiate the whitening effects. Nonetheless, more studies are recommended to confirm its efficacy using animal models and elucidate any side effects.