Estudo da atividade antioxidante do extrato e do óleo essencial obtidos das folhas de alfavaca (Ocimum gratissimum L.)
The isolation and identification of natural antioxidants from plants contribute to the discovery of new sources of chemical compounds. Wild basil (Ocimum gratissimum L.) is used as a herbal medicine and also as a culinary spice. The antioxidant activity of wild basil leaf crude extract and essential oil was confirmed by the ferric thiocyanate method. The crude extract showed 96.89% inhibition of lipid oxidation, while the essential oil showed 92.44% inhibition, both in a 0.02% concentration. The crude extract was purified by column chromatography using silica gel and different proportions of hexane:ethyl acetate as an eluant. The plants chemical compounds were identified by spectral analyses using NMR (hydrogen and 13C) and infrared spectroscopy. The isolated substance was eugenol, which presented antioxidant activity of 86.56%. Some of the constituents of the essential oil were characterized by gas chromatography, which showed eugenol as the main component (53.90%). It was concluded that wild basil is a new source of eugenol and, hence, of natural antioxidant.