Avaliação da atividade antioxidante e inibitória da tirosinase das folhas de Dipteryx alata Vogel (Baru)

Abstract

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), the chelation capability of copper ions, and the inhibition capability of tyrosinase from leaf extract of the species Dipteryx alata Vogel. Results for total phenols showed concentration of 112.3 mg GAE.g-1 in ethanol extract and 45 mg GAE.g-1 in hexane extract. The antioxidant capacity of extracts indicates that ethanol extract, compared to hexane extract and BHT, has higher content of antioxidant compounds, showing the respective values of the necessary amount of extract to decrease the initial DPPH concentration by 50%: 52.9 ± 1.3 ppm, 169.1 ± 2.3 ppm and 181 ± 6 ppm. On the other hand, the chelation capacity of copper ions showed that the ethanol extract has insignificant chelation capacity. In the tyrosinase inhibition test, the ethanol extract had 42% enzyme inhibition after one hour.