RESUMO:Nos últimos anos, uma quantidade substancial de evidências tem indicado o papel chave dos radicais livres e outros oxidantes como grandes responsáveis pelo envelhecimento e pelas doenças degenerativas associadas ao mesmo. Por outro lado, substâncias fenólicas são reconhecidamente detentoras de pronunciada atividade antioxidante, muitas vezes envolvidas em tratamentos de pigmentação que resultam em hiperpigmentação ou hipopigmentação cutânea. Para o tratamento desses problemas de pigmentação vários produtos cosméticos e farmacêuticos são utilizados, porém, não são totalmente eficazes ou seguros, o que justifica a intensa pesquisa na busca de novos agentes ativos, principalmente àqueles envolvidos na melanogênese, como a tirosinase. Considerando que algumas substâncias obtidas de plantas apresentam essa atividade, a flora brasileira constitui-se uma importante fonte de pesquisa de novas substâncias. Assim, este trabalho foi realizado para avaliar os fenóis (método de FolinCiocalteau), a atividade antioxidante (CE50) (método de seqüestro do radical livre DPPH), a capacidade de quelação dos íons cobre, e a capacidade de inibição da tirosinase do extrato das folhas da espécie Dipteryx alata Vogel. Os resultados de fenóis totais mostraram uma concentração de 112,3 mg EAG.g -1 no extrato etanólico e 45 mg EAG.g -1 no extrato hexânico. A capacidade antioxidante dos extratos indica que o extrato etanólico, em comparação ao hexânico e ao BHT, possui maior teor de compostos antioxidantes, apresentando os respectivos valores sobre a quantidade de extrato necessária para decrescer a concentração inicial de DPPH em 50%: 52,9 ± 1,3 ppm, 169,1 ± 2,3 ppm, e 181± 6 ppm. Já a capacidade de quelação dos íons cobre mostrou que o extrato etanólico possui capacidade de quelação insignificante. No ensaio de inibição da tirosinase o extrato etanólico demonstrou um percentual de inibição da enzima de 42% após uma hora. Palavras-chave:Dipteryx alata Vogel, DPPH, hiperpigmentação, tirosinase.ABSTRACT: Antioxidant and inhibitory action on tyrosinase from Dipteryx alata Vogel (Baru) leaves. In recent years, a substantial amount of evidence has shown the key role of free radicals and other oxidants as largely responsible for aging and associated degenerative diseases. On the other hand, phenolic substances are known to hold pronounced antioxidant activity, often involved in pigmentation treatments, which result in skin hyperpigmentation or hypopigmentation. For the treatment of these pigmentation problems several cosmetic and pharmaceutical products have been used; however, they are not fully effective or safe, which justifies intense research to find new active agents, especially those involved in melanogenesis such as tyrosinase. Considering that some substances obtained from plants have this activity, the Brazilian flora constitutes an important source of research for new substances. Thus, this study was conducted to evaluate the phenols (Folin-Ciocalteau assay), the antioxidant activity (EC50) (DPPH free radical scavenging assay), ...
Determination of total phenol, antioxidant activity and inhibition by tyrosinase extract of jatobá (Hymenaea stigonocarpa Mart. ex Hayne) leaves. The jatobá species, also known as Brazilian cherry, are traditionally used for the treatment of various diseases. Chemotaxonomic studies have described the Hymenaea genus as a potential source of phenolic compounds, tannins and flavonoids, which have antioxidant activity, thus being potential inhibitors of tyrosinase, which is the enzyme responsible for skin pigmentation defects. There are approximately 15 species in the genus Hymenaea of which 13 are found in Brazil. This study was conducted to evaluate the phenols, the antioxidant activity, the ability to chelate copper ions and the ability to inhibit tyrosinase of the extract of the H. Stigonocarpa leaves. The plant material (leaves) was harvested from trees in the savannah (Brazilian Cerrado) area of environmental preservation of the FESURV campus -University of Rio Verde -state of Goiás, dried in a forced circulation oven at 42° C for 2 days and subjected to extraction with hexane (hexane crude extract) and extraction with absolute ethanol (ethanol crude extract). When determining the phenolic content performed with the Folin-Ciocalteu reagent, we found that the crude ethanol extract (CEE) presented the highest concentration (235.7 mg gallic acid equivalent per gram of CEE). In the evaluation of radical scavenging activity, using the DPPH free radical, the ethanol extract again showed higher antioxidant activity (IC50 = 19 ± 0.1 ppm). For the procedure for chelation of copper ions, the crude ethanol extract tested showed no such ability. For the process of inhibiting the tyrosinase enzyme, the crude ethanol extract tested after 30 and 60 minutes presented inhibition of 38 and 48%, respectively.
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