Tyrosinase Inhibitory Impact of Morus alba L. Root Bark: In Vitro and In Silico Studies

Background and objectives: The demand for skin care is a major concern, not only for women but also for men. Mulberry (Morus alba L.) is a medicinal plant widely used in traditional medicine, as well as for beauty and skin whitening.In this study, we investigated the inhibitory effect of Morus alba L. root bark extract on the enzyme tyrosinase. Methods: Mulberry root bark was extracted with ethanol (70%) at room temperature for 24 hours (repeated three times). The total ethanol extract was then suspended in water and successively partitioned with n-hexane, ethyl acetate and n-butanol. Tyrosinase enzyme inhibitory activity was determined spectrophotometrically at 475 nm. Additionally, we conducted virtual screening of 60 compounds from mulberry roots to evaluate their inhibitory effects on tyrosinase enzyme. Results: Our results showed that the ethyl acetate fraction exhibited the highest tyrosinase enzyme inhibitory effect, with an IC50 value of 12.68 ± 1.64 µg/mL, compared to kojic acid, the positive control (IC50 13.94 ± 0.30 µg/mL). Virtual screening identified 11 compounds with lower binding energies than twopositive control compounds (kojic acid and arbutin). These compounds were evaluated for drug-like properties and predicted pharmacokinetic-toxicological properties. Finally, two compounds, alfafuran and mulberroside C, which demonstrated the ability to inhibit the tyrosinase enzyme, were introduced. Conclusion:Our results indicated that the ethyl acetate fraction of Morus alba root bark extract has strong inhibitory effects on the tyrosinase enzyme.