Antioxidant and Tyrosinase Inhibitory Potential of Urtica urens : a source for skin whitening agents

Objectives: Oxidative stress contributes to skin damage and hyperpigmentation through excessive melanin production.Tyrosinase plays a central role in melanogenesis by catalyzing the oxidation of tyrosine to melanin precursors.Although several tyrosinase inhibitors are available, their clinical use is limited due to adverse effects.Therefore, identifying safer inhibitors with concomitant antioxidant properties remains of considerable interest.In ethnomedicine, Urtica urens L. (Urticaceae) is traditionally used to treat inflammatory conditions.This study aims to evaluate the antioxidant, tyrosinase inhibitory, and photoprotective activities of its ethanolic extract.Methods: Here, 80% ethanolic extract of U. urens aerial parts (E) was chemically characterized and standardized based on total polyphenol, flavonoid, and chlorogenic acid contents.Antioxidant activity was assessed by inhibiting UV-induced lipid peroxidation in egg yolk.Tyrosinase inhibitory activity was evaluated using mushroom tyrosinase, and kinetic analysis was conducted to determine the inhibition mechanism.The in vitro sun protection factor was also determined.Results: E inhibited UV-induced lipid peroxidation (EC 50 = 44.4µg/mL) and exhibited tyrosinase inhibitory activity (EC 50 = 1,016 µg/mL, relative to the maximal observed effect), with a mixed-type inhibition pattern.The extract also showed in vitro photoprotective capacity.Chlorogenic acid was identified as the major polyphenolic constituent; although it exhibited antioxidant and anti-tyrosinase activities, its concentration in the extract did not fully account for the overall inhibitory effect observed. Conclusion:The findings indicate that the biological activities of E likely result from the combined action of multiple phytochemical constituents.These findings support its potential as a source of bioactive compounds for cosmetic and dermatological applications targeting oxidative and pigmentation-related skin alterations.