In this study, to assess the feasibility of phlorotannins isolated from Ecklonia cava as an inhibitor of
melanin formation, we evaluated its inhibitory effects on mushroom
tyrosinase and
3-isobutyl-1-methylxanthine (
IBMX)-induced
melanin formation inhibitory effects in B16F10
melanoma cell. The ethanolic (EtOH) extract and
ethyl acetate (EtOAc) soluble fraction obtained from E. cava evidenced a marked inhibitory effect on mushroom
tyrosinase at a concentration of 50 μg/mL. Repeated column chromatography of the active EtOAc fraction resulted in the isolation of three phlorotannins. Their structures were elucidated on the basis of spectroscopic techniques [1D and 2D nuclear magnetic resonance (NMR)] and characterized as
phloroglucinol (1),
dioxinodehydroeckol (2), and
7-phloroeckol (3), respectively. Among the compounds,
7-phloroeckol (3) evidenced more potent
tyrosinase inhibitory effect with an IC(50) value of 0.85 μM than
arbutin (IC(50) = 243.16 μM) and
kojic acid (IC(50) = 40.28 μM), which were used as positive controls. Lineweaver-Burk plots suggest that
7-phloroeckol plays as a noncompetitive inhibitor against
tyrosinase. Furthermore, these compounds were evaluated for their inhibitory effects on
IBMX-induced
melanin formation in B16F10
melanoma cells. Treatment with
7-phloroeckol (6.25-100 μM) resulted in a significant inhibition of
melanin production in the
melanoma cells. In this study, we suggest that
7-phloroeckol might prove useful as a novel inhibitor of
melanin formation in cosmetic applications.