Three new Diels-Alder adducts, macrourins E - G (1: -3: ), one new 2-arylbenzofuran, macrourin H (4: ), and eight known Diels-Alder adducts (5: -12: ) were isolated from Morus macroura. Their structures were elucidated through extensive analysis of spectroscopic data. The 1H NMR and ECD trends in the determination of the configurations of these Diels-Alder adducts were summarized. The tyrosinas...

Melanin biosynthesis in insects involves the following three key steps: oxidation of tyrosine to dopa by monophenoloxidase (tyrosinase), conversion of dopa to dopachrome by diphenoloxidase and formation of melanin by polymerization of dopachrome.1] Whenthe larval haemolymphof Bombyxmori is exposed to air, it changes from pale yellow to black. This color change is based on melanin formation, by ...

There is a continual need to develop novel and effective melanogenesis inhibitors for the prevention of hyperpigmentation disorders. The plant Artemisia capillaris Thunberg (Oriental Wormwood) was screened for antipigmentation activity using murine cultured cells (B16-F10 malignant melanocytes). Activity-based fractionation using HPLC and NMR analyses identified the compound 4,5-O-dicaffeoylqui...

Tyrosinase exists in three forms in the catalytic cycle depending on the oxidation state of the copper: met- (Em), oxy- (E(ox)), and deoxy- (Ed). When O-quinones, products of the enzymatic reaction, evolve chemically to generate an O-diphenol in the reaction medium, the enzyme acts on a monophenol with O-diphenol as reductant, converting Em to Ed. The binding of Ed to molecular oxygen gives E(o...

This research has been an effort to develop synthetic resveratrol analogs in order to improve the depigmenting potential of natural resveratrol. Six resveratrol analogs were synthesized and tested for tyrosinase inhibitory activity in vitro, by qualitative and quantitative steps. The results showed the analog C as being the most powerful tyrosinase inhibitor (IA50=65.67±0.60 μg/mL), followed by...

background tyrosinase, as a copper-containing enzyme, is widely distributed in different levels of life span. it is also a key enzyme in melanin biosynthesis, which plays a crucial role in determining the color of mammalian skin and hair. objectives the current study aimed to determine the effect of a palladium complex on cresolase and catecholase reactions of mushroom tyrosinase (mt). material...

needed to bring about 60% saturation must be accurately calculated. The serum protein fraction salted out at 50 to 60% saturation with the salt was dissolved in deionized water and diluted with large volume of 1 m@phosphate buffer (monobasic and dibasic sodium phosphates; Mallinckrodt Chemical Works, St. Louis, Mo.) pH 6.8; desalted against the same phosphate buffer to remove ammonium sulfate; ...

Phenylthiourea (PTU) is commonly used for inhibiting melanization of zebrafish embryos. In this study, the standard treatment with 0.2 mM PTU was demonstrated to specifically reduce eye size in larval fish starting at three days post-fertilization. This effect is likely the result of a reduction in retinal and lens size of PTU-treated eyes and is not related to melanization inhibition. This is ...

Preparation and characterization of cross linked amine-functionalized magnetic nanoparticles as an appropriate support for covalent immobilization on tyrosinase was presented in the study "Covalent immobilization of tyrosinase onto cyanuric chloride crosslinked amine-functionalized superparamagnetic nanoparticles: synthesis and characterization of the recyclable nanobiocatalyst" (Abdollahi et a...

Melanogenesis inhibitors, OH-3984 K1 and K2 were isolated from fermentation broth of Streptomyces sp. OH-3984. OH-3984 K1 and K2 inhibited the melanogenesis of B16 melanoma cells at concentrations of 7.5 and 3.8 micrograms/ml, respectively, whereas inhibition of tyrosinase activity has not been observed. The microbial metabolites showed no antimicrobiological activities against Gram-positive an...