Plantas do cerrado: obtenção e caracterização espectroscópica de extratos e avaliação do potencial de inibição da tirosinase

Abstract

The enzyme tyrosinase is crucial on the biosynthesis of the melanin. Consequently, its inhibition stops the synthesis and even can minimize some of its consequences. For instance, it is well known that lotions and creams containing those inhibitors are employed to reduce or eliminated some skins blemishes, originated by the excessive formation or accumulation of the melanin. The first step of the present work was the collection of 13 different species, native or not, of the Cerrado (brazilian savannah). It was followed by obtention and characterization of 18 extracts. That characterization was achieved employing various chromatographic and spectrometric methods and, when possible, by comparison with commercial or isolated standards. The inhibition proprieties themselves were evaluated in vitro (through the effect of the extracts on the formation of the dopachrome, an intermediary of the melaninas biosynthesis process, via UV-Vis spectroscopy) or their ability to curb or stop the spontaneous darkening in discs of potato, a natural and rich source of tyrosinase. Those results were compared with those achieved by the use of the kojic acid, a widely studied and known inhibitor of the melanins formation. In general, both methods indicated that the most actives extracts were, in decrescent order, those obtained from Brosimum gaudichaudii, Schinus terebinthifolius, Stryphnodendron adstringens, Kalanchoe pinnata and Rosa alba. Finally, it was evaluated the inhibition activity of some lotions, made from those three most active extracts, and the results were remarkable coincident with those recorded for the crude extracts, which indicated their anti-tyrosinase power and their potential use on products utilized on the healing of some skins blemishes