Contribuição ao estudo químico de Acacia Polyphylla e avaliação da atividade antioxidante

Abstract

Acacia polyphylla (Leguminosea - Mimosoideae) occurs in the Amazon, Caatinga, Cerrado, Atlantic Forest and Pantanal biomes, being popularly known as monjoleiro. It is used in folk medicine to treat cough, as a source of tanning substances and in the recovery of degraded areas. This work describes the chemical study and evaluation of the antioxidant activity of Acacia polyphylla leaves. The presence of triterpenes, steroids, saponins and flavonoids was assessed by phytochemical prospecting methods. The chemical study, by classical chromatographic techniques, led to the isolation of four flavonoids (luteolin, isovitexin, isoquercitrin and hyperoside), three triterpenes (α-amirin, β-amirin and lupeol), four steroids (stigmastenol, spinasterol, sitostanol and β-sitosterol) and an alkane (n-nonacosane). Its structures were elucidated by analyzes of the ¹H and ¹³C NMR spectra, including 2D, and GC-MS. This is the first report of all these compounds in this specie. Antioxidant activity, the total phenol content (Folin-Denis), the total flavonoid content (AlCl3) and the sequestering activity against free radical DPPH were also evaluated. Based on its EC50 (less than 500 μg/mL), all samples were considered active. In front of the partition with organic solvents the ethyl acetate fraction presented the best result among those obtained with EC50 value of 7.78±0.17 μg/mL and total phenol and total flavonoid contents with values of 563.28±1.13 EAG/g and 217±0.17 EQ/g, respectively, suggesting the potential of A. polyphylla as a source of antioxidants.