Bioatividade da Quassia amara L. e estabilidade oxidativa sobre o óleo de soja

Abstract

The increasing demand for natural products by consumers leads to an intensified search for natural antioxidants, aimed at replacing the synthetic antioxidants used by the food industry. Such substitution is necessary because of the harmful effects these substances cause to health. Quassia amara is a plant native to northern Brazil, belonging to the family Simaroubaceae and used to combat malaria and gastrointestinal problems. The objective of this work was to optimize the extraction of compounds with antioxidant activity in the leaves of Quassia amara by means of a factorial design, to evaluate antioxidant and antibacterial activity, to identify and isolate their active substances. It was also the objective to apply the extract in soybean oil and evaluate the effects on oxidative inhibition and sensorial characteristics. The optimal condition found for extracting compounds with antioxidant activity from Quassia amara leaves was with solvent methanol at 70 °C for 60 minutes of extraction. Chromatographic analysis revealed the presence of gallic acid (58.12 μg.g-1) and catechin (42.4 μg.g-1). By means of 1H and 13C NMR spectroscopic analysis, it was possible to identify the alkane octadecane, which was isolated for the first time in the leaves of Quassia amara. The methanolic extract of Quassia amara showed high antioxidant activity by the sequestration method of the DPPH radical (1898.02 μmol Trolox.g-1), and presented an inhibitory action against Staphylococcus aureus and Salmonella bongori microorganisms, with minimum inhibitory concentration (MIC) of 0.625 mg.mL-1 and 0.312 mg.mL-1, respectively. Finally, the methanolic extract of Quassia amara was able to retard the oxidation of soybean oil. Such ability could be confirmed by both chemical analyzes and by the sensory analysis with panel of judges trained as to the rancid flavor. In view of this, the plant has potential for substitution to synthetic antioxidants widely used in the food industry.