Antioxidant Activity and Tyrosinase Inhibition of Extracts and Flavonoids Isolated from the Leaves of Gymnosporia chevalieri: In Vitro and In Silico Studies

Gymnosporia chevalieri is a recently explored medicinal plant known for its phytochemical and activity properties; however, its antioxidant and tyrosinase inhibitory activities remain uninvestigated. Extracts and flavonoids ( 1 – 9 ) isolated from G. chevalieri leaves were assessed for their in vitro antioxidant capacity (TPC, TFC, FRAP, RP, ABTS and DPPH), in vitro, and in silico tyrosinase inhibition. Among the extracts, the aqueous and EtOAc extracts exhibited higher antioxidant activity compared to the others. These extracts exhibited comparable antioxidant activities in the FRAP and RP assays, whereas in the ABTS and DPPH radical scavenging assays, the aqueous extract showed significantly superior activity ( p < 0.05). Compounds 1 – 5 , 6 and 9 neutralized ABTS and DPPH radicals with IC 50 values of 5.28–38.95 µM. Four extracts and nine flavonoids inhibited the tyrosinase enzyme at 250 and 500 µg/mL, with inhibition percentages of 3.01%–86.03%. The in silico docking study of flavonoids with the tyrosinase enzyme (PDB ID: 2Y9X) revealed binding energies ranging from −7.6 to −9.7 kcal/mol, compared to vitamin C, which exhibited a binding energy of −5.5 kcal/mol. Compounds 2 , 3 and 5 demonstrated significant tyrosinase inhibitory activity in vitro, findings that were consistent with and further supported by molecular dynamics (MD) simulation.