Whitening activity of luteolin related to the inhibition of cAMP pathway in alpha-MSH-stimulated B16 melanoma cells

Abstract

To examine the possibility of luteolin as a whitening agent, we measured antioxidant activity using DPPH assay, NBT/XO assay and intracellular ROS scavenging assay and depigmenting activity using tyrosinase assay, alpha-MSH-induced melanin production in B-16 cells. Luteolin showed dose-dependent anti-oxidant activity in DPPH, NBT/XO and intracellular ROS assay. Also, luteolin directly inhibited xanthine oxidase activity in a dose-dependent manner. Although luteolin did not directly inhibit tyrosinase activity, it dose-dependently inhibited both tyrosinase activity and melanin production in B16 melanoma cells stimulated by 1 mu M alpha-MSH. Luteolin dose-dependently inhibited cAMP levels in B16 melanoma cells stimulated by 1 mu M alpha-MSH and 1 mu M forskolin, which suggest that luteolin directly inhibits adenyl cyclase in B16 melanoma cells. Therefore, these results suggest that whitening activity of luteolin may be due to the inhibition of adenyl cyclase involved in the signal pathway of alpha-MSH in B16 melanoma cells.