Flavokawains B and C, melanogenesis inhibitors, isolated from the root of Piper methysticum and synthesis of analogs

The ethanolic extract of the root of Piper methysticum was found to inhibit melanogenesis in MSH-activated B16 melanoma cells. Flavokawains B and C were isolated from this extract based on their anti-melanogenesis activity and found to inhibit melanogenesis with IC50 values of 7.7 mu M and 6.9 mu M, respectively. Flavokawain analogs were synthesized through a Claisen-Schmidt condensation of their corresponding acetophenones and benzaldehydes and were evaluated in terms of their tyrosinase inhibitory and anti-melanogenesis activities. Compound 1b was the most potent of these with an IC50 value of 2.3 mu M in melanogenesis inhibition assays using MSH-activated B16 melanoma cells. (C) 2015 Elsevier Ltd. All rights reserved.