Caracterização química e avaliação da atividade antioxidante do extrato seco de Miconia albicans (Sw.) Triana (Melastomataceae)

Abstract

Miconia albicans (Sw) Triana (Melastomataceae) is popularly known as "canela-de-velho" and is used in folk medicine for the treatment of arthrosis, pain in general and as anti-inflammatory. Some pharmacological properties of this species have already been scientifically proven, including antitumor, antimicrobial and analgesic activities. However, further studies are needed in order to better understand the biological potential of this plant species. Thus, the objective of the present study was to characterize chemically as well as to evaluate the antioxidant activity, in vitro, of the dry extract of M. albicans (DEMA). In the chemical characterization, a preliminary phytochemical screening was carried out in addition to determination of the phenols and flavonoids total content. In order to evaluate the antioxidant effect, tests were performed on 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals, as well as inhibition of lipid peroxidation (TBARS) and iron reduction potential (FRAP). The antioxidant results were expressed as mean±SEM and analyzed by analysis of variance (ANOVA) followed by the Tukey's test (p<0.05). Phytochemical prospecting indicated the presence of tannins, flavonoids, saponins, leucoantocyanidins, steroids and terpenes in M. albicans species DEMA had a total phenols content of 551.300±3.72 mg of gallic acid equivalent/ g of extract, whereas for total flavonoid content was obtained a result of 367.193±10.52 mg of catechin equivalent/g of extract. The DEMA presented antioxidant activity against all the methods used. In the assay against the DPPH radical, the DEMA presented an IC50 = 33.8651 μg/mL, a result superior to the Trolox (positive control). In the ABTS radical assay, DEMA was able to reduce the radical by 80% at the lowest concentration tested (1 μg/mL). In inhibition of lipid peroxidation, DEMA showed an IC 50 of 1338.34 μg/mL. Finally, in the iron reduction potential test, DEMA showed a significant reduction potential at the concentration of 10 μg/mL. These results show that the species studied has antioxidant activity and this effect can be attributed, at least in part, to the phenolic content present in its composition, especially the flavonoids.