ABSTRACT
BACKGROUND: Melanogenesis, a process producing the pigment melanin in human skin, eyes and hair, is a major physiological response against various environmental stresses, in particular exposure to ultraviolet radiation, and its pathway is regulated by a key enzyme, tyrosinase. In this study, we evaluated the effects of ephedrannins A and B, which are polyphenols from the roots of Ephedra sinica, commonly used in herbalism in oriental countries, on mushroom tyrosinase and melanogenesis in B16F10 melanoma cells. METHODS: Their effects on mushroom tyrosinase were determined via kinetic studies using a spectrophotometric analysis and those on melanin and tyrosinase production in melanoma cells treated with α-MSH (melanin stimulating hormone) were examined using PCR and ELISA. RESULTS: Both ephedrannins A and B exhibited concentration-dependent inhibitory effects on L-tyrosine oxidation by mushroom tyrosinase, and the inhibition mechanism was competitive and reversible with L-tyrosine as the substrate. In addition, melanin production in melanoma cells was also suppressed in a concentration-dependent manner by ephedrannins A and B without significant effects on cell proliferation at the concentrations tested. Both compounds showed inhibitory effects on melanin production by suppressing the transcription of tyrosinase in the cells. CONCLUSION: Both compounds exhibited significant inhibitory effects, but the inhibition by ephedrannin B was much more effective than that by ephedrannin A. Both ephedrannins A and B may be good candidates for a whitening agent for skin. GENERAL SIGNIFICANCE: This is the first report that describes effective inhibition of melanin production by ephedrannins A and B isolated from Ephedra roots.
Subject(s)
Ephedra sinica/chemistry , Melanins/biosynthesis , Monophenol Monooxygenase/metabolism , Plant Roots/chemistry , Proanthocyanidins/pharmacology , Animals , Biocatalysis/drug effects , Blotting, Western , Cell Line , Cell Line, Tumor , Cell Survival/drug effects , Dose-Response Relationship, Drug , Gene Expression Regulation, Enzymologic/drug effects , Humans , Keratinocytes/cytology , Keratinocytes/drug effects , Kinetics , Mice , Molecular Structure , Monophenol Monooxygenase/genetics , Plant Extracts/pharmacology , Proanthocyanidins/chemistry , Reverse Transcriptase Polymerase Chain Reaction , Substrate Specificity , Tyrosine/metabolismABSTRACT
Objective: To study the flavonoids from the roots of Ephedra sinica in Ephedra Tourn. ex L. Methods: The roots of E. sinica were extracted with 90% ethanol, and isolated and purified by silica gel, Sephadex LH-20, and RP-18 gel column chromatography. All the compounds were identified based on spectral analyses (including MS, 1H-NMR, and 13C-NMR). Results: Thirteen flavonoids were isolated from the roots of E. sinica and were characterized as ephedrannin A (1), mahuannin A (2), mahuannin B (3), mahuannin D (4), apigenin (5), kaempferol (6), quercetin (7), dihydroquercetin (8), 3′, 4′, 5, 7-tetrahydroxy flavanone (9), (+)-catechin (10), (-)-epi-catechin (11), afzelechin (12), and (-)-epi-afzelechin (13), respectively. Conclusion: Compounds 7-13 are obtained from this plant for the first time.
