Tyrosinase is known to be a key enzyme in melanin biosynthesis, involved in determining the color of mammalian skin and hair.Various dermatological disorders,such as melasma, age spots and sites of actinic damage, arise from the accumulation of an excessive level of epidermal pigmentation. Plants and their extracts are inexpensive and rich resources of active compounds that can be utilized to inhibit tyrosinase and the treatment of dermatological disorders associated with melanin hyperpigmentation. In searching for effective tyrosinase inhibitors from natural products, seventy native and naturalized plants collected from the central region of Kurdistan province. Inhibitory effect of hexane extracts from aerial parts of them was tested on tyrosinase activity. All extracts were screened for their tyrosinase inhibitory activity at 1, 0.1, 0.01, 0.001 µg/ml concentrations. Assay method was based on Microplate spectrophotometric study of absorption in 492 nm and arbutin was used as positive control. From the hexane extracts evaluated, only 9 plant extracts showed more than 50% Tyrosinase inhibitory activities, including Gundelia Tourneforti ( L.( , Astragalus vegetus Bunge,ViciahyrcanicaFisch.& C. A. Mey, Campanula involucrata Auch.ex DC. , Isatis cappadocica Desv., Sanguisorba minor Scop.subsp.lasiocarpa(Boiss&Hausskn)Nordborg, Eremostachys laevigata Bunge, Ballota nigra L. subsp. Kurdica P.H.Davis, Aristolochia bottae Jaub.& Spach.at 1 µg/ml extract concentration. Gundelia Tourneforti ( L.( showed a considerable inhibition value, 75.92 (1 µg/ml) and its IC50 was 173 µg/ml. These results suggest that the most effective plant extracts, especially that of Gundelia Tourneforti ( L.( deserve further investigation with the aim of obtaining new Tyrosinase inhibitors with a broad range of applications for suppressing unwanted hyperpigmentation in human skin.
