Bioactive fractions of Eucalyptus camaldulensis inhibit important foodborne pathogens, reduce listeriolysin O-induced haemolysis, and ameliorate hydrogen peroxide-induced oxidative stress on human embryonic colon cells

Abstract

Extract of E. camaldulensis was partitioned into aqueous and ethanol fractions by a precipitation and sedimentation-based technique and profiled for phytochemical components. Antimicrobial evaluation yielded inhibitory concentrations of 16–64 and 158–316 µg/mL, and bactericidal concentrations of 32–64 and 316–>2528 µg/mL for ethanol and aqueous fractions, respectively. Antioxidant activities evaluated using 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic) acid assays showed IC50 values of 7.07 and 65.67 µg/mL, and 17.96 and 201.3 µg/mL for aqueous and ethanol fractions. Total phenolic content of 9.04 ± 0.26 and 3.58 ± 0.04 GAE/mg fraction, and flavonoid content of 2.07 ± 0.02 and 3.37 ± 0.05 QE/mg fraction were recorded for aqueous and ethanol fractions. At subinhibitory concentrations fractions significantly reduced listeriolysin O–induced haemolysis (p < 0.05), and ameliorated H2O2–induced toxicity by 8–23 and 15–83%. Nitrite production reduced by 4–17 and 3–14 µM following fractions treatment. The fractions showed bioactive properties, with oxidative stress amelioratory effects, and could be a potentials source of preservatives and functional food additives.