Triterpenoid saponins from Polaskia chichipe Backbg. and their inhibitory or promotional effects on the melanogenesis of B16 melanoma cells

Five new oleanane-type saponins 1-5 together with a known saponin 6 and a steroidal glycoside 7 were isolated from Polaskia chichipe Backbg., and their structures were determined from their 1D and 2D NMR and HRFABMS spectral data. The six isolated saponins 1-6 were tested for their effects on the melanogenesis of B16 melanoma 4A5 cells. Compound 1 exerted an inhibitory effect at 100 mu M whereas compound 3 promoted melanogenesis at the same concentration, even though these two compounds contain the same aglycon structure. The dose-dependent activities of compounds 1 and 3 on melanin synthesis were investigated.