Showing papers by "Tojiro Tsushida published in 2005"

Procyanidin Trimers to Pentamers Fractionated from Apple Inhibit Melanogenesis in B16 Mouse Melanoma Cells

Abstract: The effects of apple polyphenols on melanogenesis in B16 mouse melanoma cells were investigated. The inhibitory effect of apple polyphenols was stronger than that of arbutin or kojic acid. Three polyphenol fractions (phenolic acid derivatives, procyanidins and other flavonoids) were isolated, and the procyanidins were fractionated according to the degree of polymerization using normal-phase chromatography. The procyanidin trimer-to-pentamer fractions were found to have the most pronounced effect on melanogenesis. Furthermore, each procyanidin fraction inhibited mushroom tyrosinase. No correlation between the degree of procyanidin polymerization and tyrosinase inhibitory activity was observed. Nevertheless, these observations suggest that procyanidins are effective inhibitors of tyrosinase.

Coumarin and Flavone Derivatives from Estragon and Thyme as Inhibitors of Chemical Mediator Release from RBL-2H3 Cells

Abstract: Estragon and thyme extracts showed potent inhibitory activities against chemical mediator release from rat basophilic leukemia RBL-2H3 cells. 7-Methoxycoumarin was isolated from estragon, and 5,4′-dihydroxy-6,7,3′-trimethoxyflavone, 5,4′-dihydroxy-6,7,8,3′-tetramethoxyflavone, 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavone and luteolin were isolated from thyme as active components. Structure-activity relationship studies among the active isolates and their related compounds indicated that the oxygen-containing functional group at the 7-position of the coumarin structure was advantageous for the inhibitory activity and that methylation of the hydroxyl group at the 4′-position of the flavone structure was disadvantageous. It was also found that coumarin derivatives inhibited an earlier step than intracellular calcium release and proteinkinase C activation, while flavones inhibited a later step or both earlier and later steps.