Dihydromyricetin from Ampelopsis grossedentata inhibits melanogenesis through down-regulation of MAPK, PKA and PKC signaling pathways.

The inhibitory effects of dihydromyricetin purified from Ampelopsis grossedentata on melanogenesis and its antioxidant characteristics were investigated. Assays of tyrosinase activities and melanin content in B16F10 mouse melanoma cells were carried out spectrophotometrically, and the expression of melanogenesis-related proteins was determined by Western blotting. The possible signaling pathways involved in dihydromyricetin-mediated depigmentation were also examined using specific protein kinase regulators. The results revealed that dihydromyricetin effectively suppresses intracellular tyrosinase activity and decreases melanin amount in cells. Dihydromyricetin also exhibits antioxidant properties and effectively decreases intracellular reactive oxygen species (ROS) and reactive species (RS) levels. Our results indicated that dihydromyricetin inhibits melanogenesis through its antioxidant properties and by downregulating protein kinase A (PKA), protein kinase C (PKC), and mitogen-activated protein kinases (MAPK) signaling pathways. The present study indicates that dihydromyricetin has the potential to be developed into a depigmentation skin care product.

Supercritical Fluid Extract of Spent Coffee Grounds Attenuates Melanogenesis through Downregulation of the PKA, PI3K/Akt, and MAPK Signaling Pathways.

The mode of action of spent coffee grounds supercritical fluid CO2 extract (SFE) in melanogenesis has never been reported. In the study, the spent coffee grounds were extracted by the supercritical fluid CO2 extraction method; the chemical constituents of the SFE were investigated by gas chromatography-mass spectrometry (GC-MS). The effects of the SFE and its major fatty acid components on melanogenesis were evaluated by mushroom tyrosinase activity assay and determination of intracellular tyrosinase activity and melanin content. The expression level of melanogenesis-related proteins was analyzed by western blotting assay. The results revealed that the SFE of spent coffee grounds (1-10 mg/mL) and its major fatty acids such as linoleic acid and oleic acid (6.25-50 µM) effectively suppressed melanogenesis in the B16F10 murine melanoma cells. Furthermore, the SFE decreased the expression of melanocortin 1 receptor (MC1R), microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2 (TRP-2). The SFE also decreased the protein expression levels of p-JNK, p-p38, p-ERK, and p-CREB. Our results revealed that the SFE of spent coffee grounds attenuated melanogenesis in B16F10 cells by downregulation of protein kinase A (PKA), phosphatidylinositol-3-kinase (PI3K/Akt), and mitogen-activated protein kinases (MAPK) signaling pathways, which may be due to linoleic acid and oleic acid.

Properties of the newly isolated extracellular thermo-alkali-stable laccase from thermophilic actinomycetes, Thermobifida fusca and its application in dye intermediates oxidation.

Laccases are diphenol oxidases that have numerous applications to biotechnological processes. In this study, the laccase was produced from the thermophilic actinomycetes, Thermobifida fusca BCRC 19214. After 36 h of fermentation in a 5-liter fermentor, the culture broth accumulated 4.96 U/ml laccase activity. The laccase was purified 4.64-fold as measured by specific activity from crude culture filtrate by ultrafiltration concentration, Q-Sepharose FF and Sephacryl™ S-200 column chromatography. The overall yield of the purified enzyme was 7.49%. The molecular mass of purified enzyme as estimated by SDS-PAGE and by gel filtration on Sephacryl™ S-200 was found to be 73.3 kDa and 24.7 kDa, respectively, indicating that the laccase from T. fusca BCRC 19214 is a trimer. The internal amino acid sequences of the purified laccase, as determined by LC-MS/MS, had high homology with a superoxide dismutase from T. fusca YX. Approximately 95% of the original activity remained after treatment at 50°C for 3 h. and approximately 75% of the original activity remained after treatment at pH 10.0 for 24 h. This laccase could oxidize dye intermediates, especially 2,6-dimethylphenylalanine and p-aminophenol, to produce coloring. This is the first report on laccase properties from thermophilic actinomycetes. These properties suggest that this newly isolated laccase has potential for specific industrial applications.