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.

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 IC 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 HO-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.