Tyrosinase is a key enzyme for melanin biosynthesis, catalyzing the oxidation of L-tyrosine to L-dopaquinone. The tyrosinase inhibition is an effective approach to control hyperpigmentation in human skin and enzymatic browning in fruits and vegetables. Kojic acid is a naturally-occurring tyrosinase inhibitor which has been clinically used to treat the hyperpigmentation of skin. However, kojic a...

silica-bonded n-propyldiethylenetriamine sulfamic acid (sbpdsa) was found as an efficient solid acid for the synthesis of coumarins. coumarin derivatives were obtained via the pechmann condensation reaction of phenols and β-keto-esters at 80 oc under solvent-free conditions. also, biscoumarins were obtained via the condensation of aldehydes and 4-hydroxycoumarin in water at reflux conditions. t...

A water soluble, Bronsted acid, 5-sulfosalicylic acid as an efficient organocatalyst was used for the synthesis of physiologically active 2-substituted benzimidazole derivatives from o-phenylenediamine and aromatic aldehydes in ethanol at reflux condition. Cost-effectiveness, use of non-hazardous solvents, metal free and commercially available catalyst, single-step, environmentally fri...

Melanin is one of the most important pigments which exist ubiquitously from microorganisms to plants and animals. It is secreted by melanocyte cells and determines the color of skin and hair in mammalians. It protects the skin from photocarcinogenesis by absorbing UV sunlight and removing reactive oxygen species (ROS) (Gupta, 2006; Kim, 2005; Sapkota, 2011). It is formed by enzymatically cataly...

The presence of glucuronic acid in the complex molecules of specific bacterial polysaccharides (1) has stimulated a study of certain derivatives of this important substance and its lactone, glucuron. These investigations have entailed the necessity of elaborating a satisfactory method for preparing both the acid and its lactone, and at the same time they have embraced a study of the comparative...

A novel method for oxazine derivatives formation is established using the reaction of ammonium thiocyanate and acid chlorides with 1-naphthol in the presence of Nanoparticle of ZnO to afford [1,3]oxazine-4-thione derivatives under solvent-free conditions at room temperature in excellent yields. 

Silica Vanadic Acid, SVA, (oxo-vanadium has been supported on silica) as a dual Lewis and Bronsted acid ability was prepared and efficiently catalyzed one-pot multi-component condensation of enolizable ketones or alkyl acetoacetates with aromatic aldehydes, acetonitrile and acetyl chloride. The described reaction was produced β-acetamido ketone or ester derivatives in high to excellent yields i...

Our research to discover potential new multitarget agents led to the synthesis of 10 novel derivatives of cinnamic acids and propranolol, atenolol, 1-adamantanol, naphth-1-ol, and (benzylamino) ethan-1-ol. The synthesized molecules were evaluated as trypsin, lipoxygenase and lipid peroxidation inhibitors and for their cytotoxicity. Compound 2b derived from phenoxyphenyl cinnamic acid and propra...

Reaction of 2-hydrazinocarbonyl-3-chloro-5-phenoxy-benzo[b] thiophene with different substituted phenyl isothiocyanate gave N-substituted arylthiosemi-carbazide derivatives (1a-h). 1,3,4-Thiadiazole derivatives (2a-h) were prepared by the cyclization of arylthiosemicarbazides (1a-h) with concentrated sulphuric acid. All the compounds were screened for their antitubercular activity against Mycob...

A water soluble, Bronsted acid, 5-sulfosalicylic acid as an efficient organocatalyst was used for the synthesis of physiologically active 2-substituted benzimidazole derivatives from o-phenylenediamine and aromatic aldehydes in ethanol at reflux condition. Cost-effectiveness, use of non-hazardous solvents, metal free and commercially available catalyst, single-step, environmentally fri...