Avaliação do teor de compostos fenólicos e da atividade antioxidante das folhas de Banisteriopsis argyrophylla (A.Juss.) B. Gates (Malphigiaceae)

Abstract

Studies have reported that synthetic antioxidants, such as 2,6-di-tert-butyl-4-methylphenol (BHT) and tert-butylhydroquinone (t-BHQ) are harmful to human health and are capable of promoting DNA damage. Therefore, the search for new bioactive molecules is a trend and the natural products have been a great source of new ones. Brazil is a country with a rich biodiversity, which enhances the importance of studies on natural products. Among the biomes, Cerrado stands out for its fauna, flora and folk knowledge. The species Banisteriopsis argyrophylla (Malpighiaceae) is Cerrado´s native plant, known as “cipó-prata”, and is used in folk medicine to treat kidney problems, inflammations and hemorrhages. Until the moment, there are no studies about the antioxidant activity of this plant. However, species of the genus Banisteriopsis and family Malpighiaceae presented antioxidant potential. The objective of this work was to measure the levels of total phenolics, flavonoids and proanthocyanidins and to evaluate the antioxidant activity by the scavenging free radical method of 2,2-diphenyl-1picrylhydrazyl (DPPH) from the ethanolic extract of leaves of B. argyrophylla and its fractions, obtained by liquid-liquid extraction. The levels of total phenolics, flavonoids and proanthocyanidins were quantified by the Folin-Ciocalteau reagent, the aluminum chloride reagent and by sulfuric vanillin technique, respectively. Results for the levels of total phenolic, flavonoids and proanthocyanidins were expressed in gallic acid equivalent (EAG), quercetin (EQ) and catechin (EC), respectively. The ethanolic extract showed higher amount of total phenolics (337.13±1.44 mg EAG/gextract). Among the fractions, the ethyl acetate fraction (FAE) had the higher content of phenolics (405.46 ±3.20 mg EAG/gextract) and flavonoids (211.85±2.89 mg EQ/gextract), and n-butanol fraction (FB) presented higher proanthocyanidins content (226.59±2.86 mg EC/ gextract). The result of antioxidant activity was expressed in effective concentration (EC50). The FAE (CE50=4.10± 0.1 μg/mL) and the FB (CE50=4.80 ± 0.1μg/mL) had higher antioxidant activities with values lower than the positive control BHT (EC50=4.90 μg/mL). Thus, B. argyrophylla is an important species with compounds with high antioxidant potential.