جستجوی مقالات مرتبط با کلیدواژه "تیروزیناز" در نشریات گروه "پزشکی"

Tyrosinase is a multifunctional, glycosylated and copper containing oxidase, and is found in fungi, microorganisms, plants and animals. The most important function of tyrosinase in mammals is melanogenesis. Hyperpigmentation is a serious problem for beauty. It is possible to cure these diseases with inhibition of tyrosinase. There have been attempts to control the metabolism of pigmentations by means of natural chemical agents.

The aim of this study was to find new potent inhibitors for ،tyrosinase among plant extracts.  

The subject of this study was anti-tyrosinase activity of methanolic extracts of 70 plant species, using mushroom tyrosinase inhibition method. All extracts were screened for their tyrosinase inhibitory activity at 400, 100, 25, 6.2 µg/ml final concentrations in reaction mixture. Assay method was based on spectrophotometric study of absorption in 492 nm and kojic acid was used as positive controls.

The results showed that nine plant extracts including Bongardia chrysogonum (L.) Spach, Podophylaceae, Heptaptera anatolica (Boiss.) Tutin, Apiaceae, Hyoscyamus kurdicus Bornm, Solanaceaes, Hypericum scabrum, Marrubium cuneatum, Nonea hypoleia, Salvia suffruticosa, Scrophularia pruinosa Boiss, Scrophulariaceae and Verbascum phoenicum L, Scrophulariaceae, (400 µg/ml) and two plant extracts including Asperugo procumbens L, Boraginaceae and Astragalus siliquosus Boiss. subsp. siliquosus, Papilionaceae (25µg/ml) have inhibitory activity more than 60%. Saliva suffruticosa showed a considerable inhibition value, 92.62% (400 µg/ml) and low IC50 (94.77 µg/ml) and according to kinetic analysis its type of inhibition on tyrosinase is noncompetitive.

Because of its high inhibitory activity and low IC50, Saliva suffruticosa extract would be interesting for further studies.

Given the importance of Stachys genus in Iran and their significant biological activity, we collected three species of this plant: St. aucheri Benth., Stachys benthamiana Boiss and St. inflata Benth. from different regions of Iran. We examined the free radical scavenging potential, total phenol content and tyrosinase inhibitory activity of their methanol, methanol 80% and dichloromethane extracts.

Antioxidant activity and total phenol content of the mentioned extracts were assessed using DPPH and FolinCiocalteu reagent, respectively. The inhibitory activity of the extracts on tyrosinase was also investigated.

Total phenol content of different extracts was high in the extracts as 98.5-139.7 mg eq. gallic acid/g in methanol 80% extract, 36.8-54.7 mg eq. gallic acid/g in methanol extract and 17.9-44.9 mg eq. gallic acid/g  in dichloromethane extract. Furthermore, their antioxidant activity was correlated with total phenol content of the extracts. Methanol 80% extract had the highest total phenol content and antioxidant activity. Evaluation of the tyrosinase inhibitory potential of the extracts revealed that St.inflata exhibited a considerable inhibitory potential (IC50= 5.4 ± 0.6 µM).

It can be concluded that tyrosinase inhibitory activity of Stachys genus might be due to the less polar compounds and these compounds are mostly present in the dichloromethane extract of St. inflatai over St. aucheri and St. benthamiana

The enzyme tyrosinase is a copper-containing polyphenol oxidase, which is involved in melanogenesis. It catalyzes the conversion of tyrosine to melanin pigments in mammals. Tyrosinase plays an important role in enzymatic browning, which causes discoloration and loss economic value of many plant food products. This enzyme is widely distributed in fungi, higher plants and animals. The aim of this study was to determine the tyrosinase inhibitory effect of hexane extracts of different aerial parts of Astragalus vegetus Bungi and Gundelia turnifortii L. Later the kinetics and antioxidant activities of the extracts with the highest inhibitory properties were assessed. Aerial parts of the plants were divided to stems, leaves and flowers and air-dried. Hexane extract of each part has obtained by maceration in n-hexane. Inhibitory effects assayed at four different concentrations, using a microplate reader at 492 nm. Kojic acid used as positive control. DPPH method used to determine the antioxidant activities of the extracts and ascorbic acid (positive control). GC/MS device utilized to determine the composition of the extracts. Main inhibitory activity detected at 1 mg/ml concentration of hexane extract of leaves of Astragalus vegetus Bunge (66.6%), and the leaves and flowers of Gundelia turnifortii L. (71.7 and 68.7 percent respectively). IC50 values for Astragalus vegetus Bungi leaves was 0.5 mg/ml. and for Gundelia turnifortii L. leaves and flowers, were 0.5 and 0.32 mg/ml respectively. Astragalus vegetus Bungi.plant leaves also showed a considerable antioxidant activity. GC/MS analysis of extracts didn't show any reliable result. These results suggest that some of the most effective extracts from analyzed plants in this study, may be worthy for further investigation to obtain some new tyrosinase inhibitors with pharmacological applications.

Tyrosinase is a key enzyme in pigment synthesis.Overproduction of melanin in parts of the skin results in hyperpigmentation diseases. Thus, its inhibitors are highly important in the medical, cosmetic and agricultural fields. The aim of this research is the bioinformatical study of tyrosinase inhibition by a number of hydroxy nitrodiphenyl ether derivatives.
Material & This is a descriptive-analytic study. In order to investigate the mode of interaction of the compounds with tyrosinase active site, the chemical structures of all compounds were designed using ChemDraw program, then transferred into Hyperchem software for energy minimization. Docking study was performed by AutoDock 4.2 program and the resulting docking poses were analyzed in AutoDockTools, DS Visualizer 3.5 and Ligplot software.
Among the all studied compounds, the best docking results were related to 4-Hydroxy- 2'-nitrodiphenyl etherdisplayed. In fact, this compound had the most negative ΔGbind (-12.79 Kcal/mol) that indicated favorable interactions with the key amino acid residues at active site of tyrosinase. Docking results for this compound are in accordance with those of co-crystallized ligand (tropolone). In this compound, the oxygen of nitro group has an efficient metal-ligand interaction with the Cu2 ions in the active site.
Finally, in respect to high effectiveness and docking results, we can conclude that the compound 4-Hydroxy- 2'-nitrodiphenyl ether may be regarded as an effective anti-tyrosinase inhibitor.