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.

Based upon diachronic-cognitive linguists, language structure is the product of our interaction with the world around us. The way we build discourse and develop linguistic categories can immediately be derived from the way we experience our environment and use that experience in specific communication. Thanks to recent works on the evolution of grammatical categories e. g auxiliaries, we now have a sizable knowledge of the main patterns of grammaticalization which allows for fairly reliable linguistic reconstructions and hypotheses on genetic evolution through main cognitive processes e. g semantic bleeching. Following the doctorines of cognitive semantics, the present proposal bears an attempt to discover and define which aspects of meaning of a lexical source are lost and which are preserved through grammaticalization. Analyzing a specific grammaticalized product, namely the auxiliary verb xâ, stan, the future marker, through the lexical xâ, stan ‘, to want’,in Persian, we will suggest that the evolution of the target grammatical meaning, the future, through grammaticalization process occurs applying semantic bleaching by way of which the entire idiosyncratic semantic features are vanished but the image-schematic structure. This must mean that an image-schema is abstracted from the earlier lexical sense since it would be potentially much more immanent and pervasive than the fully fleshed-out lexical meaning.