Evaluation of the chemical composition and antioxidant activity of extracts and fractions of Ocotea notata (Ness) Mez (Lauraceae)

Abstract

The specie Ocotea notata (Nees & Mart). Mez is a tree with 5 meters high, that can be found in restinga regions in the Brazilian coast. This study describes a phytochemical investigation, total phenolic content and the antioxidant activity of extracts and fractions by DPPH and ORAC. Phenolic content revealed equivalent concentration between evaluated samples, similar to found in the leave extract (66.4 mEq GA/g). By DPPH, extracts and fractions showed effective concentration (EC₅₀) lower than the standards Ginkgo biloba 761^® (23.60 ± 0.64 µg/ml) and quercetin (6.06 ± 0, 92 µg/mL); for the ORAC method, ethyl acetate partition showed a value of 2.06 mmol Trolox equivalent g^-1 better than obtained in Ginkgo biloba (1.03 ± 0.25 mmol.Trolox equivalent g^-1. The butanol partition (0.52 mmol.Trolox equivalent g^-1) and the aqueous residue (0.74 mmol Trolox equivalent g^-1) have a lesser ORAC potential than ethyl acetate partition. The butanolic partition, investigated by LC-DAD-MS/MS and QTOF-MS, revealed six major compounds: miquelianin (1), isoquercitrin (2), quercitrin (3), kaempferol-3-O-pentose (4), afzelin (5) and isorhamnetin-glucuronide (6).

Keywords: Antioxidant activity; Ocotea notata; afzelin; glycosylated flavonoids; isoquercitrin; isorhamnetin-glucuronide; kaempferol-3-O-pentose; miquelianin; quercitrin.