Prenylated Flavonoids from Roots of Glycyrrhiza uralensis Induce Differentiation of B16-F10 Melanoma Cells

Roots of Glycyrrhiza uralensis have been used as herbal medicine and natural sweetener. By activity-guided phytochemical investigation of the extracts from G.uralensis root, ten flavonoids, namely GF-1⁻GF-10, of which five were prenylated flavonoids, were found to show antiproliferative effects in melanoma B16-F10 cells. Three of the prenylated flavonoids, namely GF-1, GF-4 and GF-9, significantly induced the differentiation of B16-F10 cells; the inductions included increase of tyrosinase activity, tyrosinase protein, and melanin content. In GF-1 and GF-9 induced melanoma differentiation, the phosphorylation of p38 MAPK (mitogen activated potein kinase) was identified; while GF-4 could trigger the phosphorylation of PI3K/AKT (phosphatidylinositol 3-kinase/Protein Kinase B) signaling. However, application of GF-6 to the melanoma cells did not induce differentiation; but which promoted cell apoptotic signaling, i.e., increase levels of cleaved-PRAP, cleaved-caspase 3, and cleaved-caspase 9. These results suggested that different types of prenylated flavonoids from might have potential anticancer effects against melanoma cells by acting through different signaling pathways.