Antioxidant activity was also determined using eukaryotic cells of the S. cerevisiae XV 185–14C (MATα, ade 2-1, arg 4-17, his 1-7, lys 1-1, trp 1-1, trp 5-48, hom 3-10) yeast, provided by Dr. R.C. Von Borstel (Genetics Department, University of Alberta, Edmonton, AB, Canada) ( Lopes et al., 2004). A stock of this strain was maintained on YPD solid media

containing yeast extract (1% w/v), glucose (2% w/v), peptone (2% w/v) and agar (2%, w/v) (Merck KGaA, Darmstadt, Germany). Natural Product Library mw Cells were then transferred into a liquid medium (same composition of solid media without agar) and placed on an orbital shaker at 28 °C and 160 rpm. Cellular suspensions containing 2 × 106 yeast cells/mL were then treated with AR27 and AR9 extracts diluted 1:4 (extract:water) and incubated for 1 h at 28 °C under constant stirring in the dark; this dilution was the highest non-cytotoxic SCH727965 concentration determined in preliminary assays. Cells were then centrifuged (2,000g at 28 °C for 5 min) and washed with a 0.9% (w/v) sodium chloride

solution (twice). Finally cells were stressed with 50 mM hydrogen peroxide solution for 1 h at 28 °C. Samples were then diluted with a sodium chloride solution (0.9% w/v), seeded into a complete YPD culture medium and incubated at 28 °C for 48 h. After incubation, colonies were counted and the total number of colonies observed on the control Cytidine deaminase plate (untreated cells) was defined as 100% cell survival. Antimicrobial activity of the extracts was tested against S. enteritidis (ATCC 13076) by the disk diffusion method and by determining the minimal inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards (2003). S. enteritidis was kept at 5 °C in trypticase soy agar media (Acumedia, Neogen, Lansing, MI, USA) and cell suspensions (107 CFU mL−1; obtained by the turbidity standard

McFarland N 0.5) were standardised adjusting the optical density to 0.1 when measuring absorbance at 625 nm. The antibiotic ciprofloxacin (Oxoid, Hampshire, England) (166 mg mL−1) was utilised as positive control, and pure water as negative control. A S. enteritidis suspension was spread on Mueller–Hinton agar (Acumedia) in 15 cm diameter plates. Filter paper disks (6 mm diameter) were soaked in the extracts for 5 h. The disks were then dried at room temperature (20 ± 3 °C) and placed on the surface of the inoculated plates and incubated at 37 °C for 24 h. The diameter of the inhibition zones was measured in millimetre. Inhibition zones were compared to those of control disks. Minimal inhibitory concentration was defined as the lowest concentration that inhibited the growth of the microorganism detected visually and the extract concentrations were tested at 100%, 40%, 16%, 10% and 5%.