Tyrosinase Inhibition, Antioxidant Activity, and Bioactive Compound Profiling in Acetone Extracts of Erythrophleum suaveolens Stem Bark

Abstract

This study investigates the inhibitory activity of Erythrophleum suaveolens bark extracts on mushroom tyrosinase, a key enzyme in melanin synthesis, as well as ascertaining the antioxidant properties and elucidating the phyto-constituents in the most potent extract. Extracts were obtained using five solvents: n-hexane, dichloromethane, acetone, methanol, and distilled water. Among these, the acetone extract demonstrated the best tyrosinase inhibitory activity compared to the enzyme standard inhibitor, kojic acid, at the highest concentration (400 µg/ml). Specifically, the acetone extract demonstrated an inhibitory activity value at 50% inhibition (IA50) of 39.2 ± 0.20 µg/ml for mushroom tyrosinase diphenolase activity, surpassing other extracts, including hexane (65.8 ± 1.06 µg/ml) and kojic acid (45.1 ± 0.10 µg/ml). Furthermore, the acetone extract showed dose-dependent antioxidant properties, with ferric reducing antioxidant power of 57.16 ± 0.11 mg vitamin C/g extract, DPPH radical scavenging activity of 118.7 ± 0.16%, and iron chelating activity of 26.4 ± 0.07% at the highest concentration (100 µg/ml), suggesting potential de-pigmenting effects. High-performance liquid Chromatography (HPLC) analysis, which separates, identifies and quantifies extract components via an acetonitrile/water (80:20, v/v) mobile phase and a Phenyl stationary phase, revealed a rich flavonoid content in the acetone extract, with rutin (1.418 ppm) and quercetin (4.758 ppm) being the most prominent compounds. This bioactive compound profile reveals the inhibitory properties of the E. suaveolens acetone extract and underscores its potential as a natural tyrosinase inhibitor with promising implications for improving skin appearance and health.