Antioxidant Activity and Tyrosinase Inhibition of Avocado (Persea americana Mill.) Leaves and Seeds Extracts

Background: Ultraviolet radiation (UVR) can stimulate melanin production in the skin, leading to hyperpigmentation. One way to reduce melanin formation is by inhibiting the enzyme tyrosinase. Often discarded as waste, avocado leaves and seeds are rich in flavonoids with potential tyrosinase-inhibiting properties. Objectives: This study aimed to perform phytochemical screening, measure antioxidant and tyrosinase inhibitor activities, and explore the correlation between free radical scavenging and tyrosinase inhibition in ethanol extracts of young avocado leaves (EAL(O)) and old avocado leaves (EAL(Y)), as well as the ethyl acetate extract of avocado seeds (EAS). Methods: Antioxidant activity was assessed using the 2,2-Diphennyl-1-picrylhydrazyl (DPPH) method, while tyrosinase inhibition was evaluated in vitro with mushroom tyrosinase and L-DOPA as a substrate. Results: The results of the antioxidant activity test using the DPPH method yielded IC₅₀ values for EAL(Y), EAL(O), and EAS of 17.9±0.15 μg/mL, 15.33±0.02 μg/ mL, and 745.66±6.08 μg/mL, respectively. Tyrosinase inhibition tests indicated that EAL(Y), EAL(O), and EAS could significantly inhibit tyrosinase activity (P <0.01), with IC₅₀ values of 10133.26±140.12 μg/mL, 8496.20±155.06 μg/mL, and 48375.8±553.06 μg/mL, respectively. The correlation coefficients between tyrosinase inhibition and antioxidant activity for EAL(Y), EAL(O), and EAS were r = 0.955, r = 0.947, and r = 0.991, respectively. Conclusion: These findings suggest that EAL(Y), EAL(O), and EAS may be potential natural skin-whitening agents due to their flavonoid content and antioxidant and anti-tyrosinase properties.