Antioxidant and antibacterial activity of extracts, fractions and isolated substances from the flowers of Acacia podalyriifolia A. Cunn. ex G. Don

Abstract

The extracts and fractions from the flowers of A. podalyriifolia were analyzed previously for antibacterial activity using diffusion in disk, Antioxidant properties were evaluated by determining radical scavenging power (DPPH test) and total phenol content was measured (Folin method). The present study describes the in vitro antibacterial (determining minimum inhibitory concentration) and antioxidant activities (by thiobarbituric acid reactive species - TBARS method) for the ethanol extract, dichloromethane and ethyl acetate fractions and two flavanones (naringenin and 5-β-D-glycosyl-naringenin) isolated from the flowers of Acacia podalyriifolia A. Cunn. ex G. Don. The flavanones naringenin and 5-β-D-glycosyl-naringenin had not previously been obtained from this species. The most effective antibacterial activity was observed in the ethyl acetate fraction (MIC=0.25 mg mL-1 against Staphylococcus aureus ATCC 6538, MIC = 0.125 mg mL-1 against Staphylococcus epidermidis ATCC 12229, MIC=0.5 mg mL-1 against Streptococcus pyogenes ATCC 19615, Klebsiella pneumoniae ATCC 13883 and Proteus mirabilis ATCC 43071). The evaluated samples showed antioxidant activity on the TBARS test, especially for ethanol extract (1000 ppm), which was the most active (29.43% ± 0.65) followed by ethyl acetate fraction (1000 ppm, 24.84% ± 1,28), both demonstrating higher activity than that presented by ascorbic acid (1000 ppm, 21.73% ± 1.77), although lower than the BHT (1000 ppm 35.15% ± 3.42), both reference compounds. Naringenin and 5-β-D-glycosyl-naringenin demonstrated antioxidant action, but only naringenin inhibited the growth of gram-positive and gram-negative bacteria.