Tyrosinase inhibition activity assay and identification of chemical compounds of the most active extract and fraction of johar (Cassia siamea Lam.) leaves and stem bark

Tyrosinase inhibitors are compounds regulating the metabolism of melanin. It is often used as an agent for preventing hyperpigmentation and whiten the skin in cosmetic products. An extract from Trengguli (Cassia fistula L.) had been known to have inhibitory activity against tyrosinase. This study aims to determine the percent inhibition of extracts and fractions of leaves and stem bark of johar (Cassia siamea Lam.). Three extracts of johar, n-hexane, ethyl acetate, and methanol extract on final concentration 250 ppm were tested. An extract with the highest inhibition activity was fractionated by vacuum column chromatography. Fractions were obtained tested on final concentration 250 ppm. The result showed that the methanol extract gave the highest inhibitory activity for both part of the plant, for leaves extract with IC₅₀ values 170.27 μg/mLand the most active fraction with IC₅₀ value 482,36 μg/mL. Whereas the stem bark extract with inhibitory percentage 22,57% and the most active fractions with inhibitory percentage 19,19%.