In recent years, enzymatic activity of tyrosinase has been the focus of investigation due to its potential applications in medicine, agriculture and cosmetics. Tyrosinase, entitled poly-phenol oxidase, is a key enzyme that catalyzes synthesis of melanin in plants, microorganisms and mammalian cells. Presence of some antioxidants can delay or inhibit the activity of this enzyme as well. In this survey, molecular docking calculation method using Autodock 4.0 software for prediction of binding energy of the protein with some antioxidant ligands was executed. The pose with the lowest energy of binding or inhibition constant was extracted at 298.15 K for kojic acid. Number of conformations in the cluster of rank was 13. The first and second boxes free energy and the inhibition constant were as follows: -5.60 kcalmol-1, 78.99 mM and -3.32 kcalmol-1, 3.66 mM, respectively. Since the first box presented a lower value of free energy, it was considered as the best mode of structure of kojic acid and the protein docking for further analysis. Thus, our present study could contribute to development and discernment of tyrosinase inhibitors in order to prevent hyper pigmentation.

Nano silica sulfuric acid as a solid acid, was described to be an effective catalyst for one-pot three-component reaction of kojic acid, aryl aldehydes and indoles for the preparation of 2-substituted aryl (indolyl) kojic acid derivatives. High yields, simple operation, easy-work procedure, mild reaction conditions are some advantages of this protocol. The present method does not involve any hazardous organic solvent. Therefore, this procedure could be classified as green chemistry.

Background and Aim: Malaria is a life-threatening infection in the world. The emergence of strains of Plasmodium species that are resistant to anti-parasitic drugs, and the lack of licensed high-performance malaria vaccines have raised serious concerns worldwide. In recent years, new treatment strategies such as nanoformulations have been suggested as effective drug delivery systems to enhance the therapeutic efficiency of various drugs. Materials and Methods: In this study, kojic acid-solid lipid nanoparticles (KA-SLNs) and kojic acidnanostructured lipid carriers (KA-NLCs) were synthesized using high-speed homogenization and ultra-probe sonication methods to improve their antiplasmodial activities. The obtained nanoformulations were evaluated against the Plasmodium berghei malaria parasite in mice. Anti-plasmodium activities and cytotoxicity of the nanoparticles were assed. Fifty percent effective dose (ED50) was calculated as well. Moreover, ex vivo human red blood cells (RBCs) hemolysis was assessed. Results: Kojic acid solution was significantly effective in all concentrations on the seventh day (D7) and the tenth day (D10) (P. value <0. 05). The toxicity test revealed no toxic impact on the subjects. ED50 was obtained at 150 mg/kg concentration for KA-NLCs and 400 mg/kg concentration for KA-SLNs on D10. The results of the evaluation of KA nanoformulations and KA solution on RBCs indicated that KA nanoformulations could reduce the lysis of RBCs. These results also showed that the lysis of RBCs increased with raising drug concentration in KA nanoformulations, and KA-NLCs (100 mg/kg) gave the least lysis. KA nanoformulations (especially KANLCs) and KA solution significantly reduced parasite growth. Conclusion: These results revealed that the KA solution was safe and had no side effects on the subjects in the range of evaluated concentrations. Moreover, the results of this study showed that KA nanoformulations had a better therapeutic effect on Plasmodium berghei in Balb/c mice compared with KA solution.

Tyrosinase is a multifunctional oxidase that is widely distributed in nature. It is a key enzyme in melanin biosynthesis and is involved in determining the color of mammalian skin and hair. In addition it is responsible for the undesirable enzymatic browning that occurs in plant-derived foods, limiting the shelf -life of fresh-cut products with the resultant economic loss. In recent years there has been considerable interest to study the inhibitory activity of tyrosinase and a number of inhibitory compounds derived from natural sources or partly/fully synthetic have been described. However, the current conventional methods to control tyrosinase action are inadequate. Considering the significant industrial and economic impact of the inhibitors of tyrosinase, this study was set to seek new potent inhibitors of this enzyme. A series of 3-hydroxypyridine-4-one derivatives were prepared in high yield and evaluated for their inhibitory activity on tyrosinase enzyme using dopachrome method. Our results show that all synthesized compounds have inhibitory effect on tyrosinase activity for the oxidation of L-DOPA. Among compounds studied those containing two free hydroxyl group (ie Va and V’a) were more potent than their analogues with one hydroxyl group (ie Vb and V’b). Also substitution of a methyl group on position N1 of the hydroxypyridinone ring seems to confer more inhibitory potency.

An electrochemical amplified sensor based on carbon paste electrode modified with reduced graphene oxide/NiO nanocomposite (CPE/rGO/NiO-NC) was suggested for kojic acid determination in food samples. rGO/NiO-NC were characterized by SEM and EDAX methods. The CPE/rGO/NiO-NC showed highly catalytic activity to kojic acid electro-oxidation in aqueous solution. The oxidation currents of kojic acid increased linearly with kojic acid concentration by differential pulse voltammetric (DPV) method in the ranges of 0. 3– 700 μ M with limit of detection ~0. 09 μ M. The ability of CPE/rGO/NiO-NC was check for the analysis of kojic acid in foodstuff.