Tyrosinase Inhibitory Activity of Extracts and Bioactive Compounds from Elephantopus mollis Kunth.

Elephantopus mollis Kunth is a medicinal plant known for its diverse phytochemical constituents and potential pharmacological properties. This study aimed to evaluate the tyrosinase inhibitory activity, antioxidant capacity, and total phenolic and flavonoid contents of various extracts from E. mollis Kunth, and to isolate and characterize the bioactive compounds responsible for these effects. The leaves, bark, and roots were extracted using n-hexane, ethyl acetate, and methanol through Soxhlet extraction, while whole-plant extracts were prepared separately via maceration with the same solvents. All extracts were analyzed for total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity using the DPPH assay, and tyrosinase inhibitory activity through in vitro enzymatic assays. Bioactive compounds were isolated using chromatographic techniques and structurally characterized by UV-Vis, FTIR, MS, and 1D/2D NMR spectroscopy. Among the whole-plant extracts, the ethyl acetate fraction showed the highest TPC (21.39 ± 0.70 mg GAE/g) and TFC (4.06 ± 0.60 mg QE/g), as well as the strongest antioxidant (IC₅₀: 54.17 ± 2.48 µg/mL) and tyrosinase inhibitory activities (IC₅₀: 91.98 ± 3.90 µg/mL), followed by n-hexane and methanol extracts, although all were less potent than kojic acid (IC₅₀ = 29.58 ± 0.53 µg/mL). Six compounds were isolated: epifriedelanol, stigmasterol, deoxyelephantopin, molephantinin, tricin, and 3,4-di-O-caffeoylquinic acid. Among these, stigmasterol and molephantinin exhibited notable tyrosinase inhibitory activity, with IC₅₀ values of 57.96 and 62.00 µg/mL, respectively. These findings highlight E. mollis Kunth as a promising natural source of antioxidant and tyrosinase inhibitors for potential application in cosmeceutical and pharmaceutical products targeting hyperpigmentation.