Dalia Sekmokiene is a Full Professor in Lithuanian University of Health Sciences, Department of Food Safety and Quality. During her career she was involved in different scientific projects regarding functional food investigations and EU funded projects milk production and processing at small dairy farms.
Producers are looking for a possibility to create products not only acceptable by sensory properties, but also rich in biological active substances. Cyclopia intermedia (honeybush) extracts have been used as an alternative to the use of synthetic antioxidants in order to preserve oils from oxidative degradation. Additionally, these extracts add special flavors and aromas to the food. Thus, the objective of this study was to evaluate the effect of ethanol, methanol and aqueous extracts of honeybush in the oxidative stability of olive oil. Total phenolic content (TPC), trolox equivalent antioxidant capacity (TEAC) in scavenging 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and oxygen radical absorbance capacity (ORAC) activities of extracts and solid plant materials were determined. Consecutive extractions with increasing polarity solvents enabled to isolate different amounts of antioxidants. Generally, in case of extracts higher antioxidant capacity values were obtained with acetone. The antioxidant activity showed that highest amount of phenolic compounds (48.50 mg/g) was found in ethanol extract, while the concentration of these compounds in aqueous and methanol extracts was lower (11.32 and 43.8 mg/g respectively). The extracts inhibited oxidation of rape seed oil and its emulsion at 120°C as measured by the oxipres methods. The application of the extracts in the oil showed that all extracts can reduce the formation of oxidation products, but acetone extract was better. The major phytochemicals, namely hesperetin, hesperidin and mangiferin were quantified in Cyclopia intermedia extracts by ultra-performance liquid chromatography coupled to electrospray ionization quadropole time of fight mass spectrometry (UPLC-ESI-Q-TOF-MS). The results obtained that extracts are therefore potential sources of natural antioxidants and they would be well accepted by consumers if applied by the food industry to replace synthetic antioxidants.
Eva Skrivanova is a Microbiologist and Nutritionist at the Institute of Animal Science in Prague and Czech University of Life Sciences in Prague, Czech Republic. Her expertise is evaluation of antibacterial effect of various plant extracts, their combinations with antibiotics, both in vitro and in vivo, using animal models. Furthermore, her projects aim to study nutritional impact of antioxidants and enzymes as the feed additives in food animals and their effect of oxidative stability of animal products.
Statement of the Problem: Combining antibiotics with other antibacterial have currently been one of the solutions tested for decreasing the antibiotic resistance in many emerging bacteria, including foodborne pathogens. The example of intense antibacterial resistance is methicillin-resistant Staphylococcus aureus (MRSA), being considered a high priority pathogen. Aim: The aim of our study was to evaluate the effect of vegetable oils rich in lauric acid (C12:0) with oxacillin towards various strains of S. aureus. Methodology & Theoretical Orientation: Analysis of possible interactions of lauric acid and oxacillin was performed on ten strains of (multi)drug resistant or sensitive S. aureus. Combinatory effect of A. aculeatum, C. nucifera and E. guineensis oils (natural source of lauric acid) with oxacillin was tested against two strains of S. aureus. At first, single-drug minimum inhibitory concentrations were determined by microdilution method (minimum inhibitory concentration, MIC). Following combinatory effect was tested by the by the checkerboard method (fractional inhibitory concentration, FIC). The determination of distinctive MIC of oxacillin, palm oils and lauric acid, as well as their combinatory effect evaluation by FICs, was performed in 96-well microtiter plates in three independent experiments, each performed in triplicate. Findings: Lauric acid was active against all tested strains of S. aureus (MIC = 256 µg/mL); the MICs of oxacillin were 0.5 – 682 µg/mL, depending on the strain and its resistance. Very interesting finding was done in the combinatory effect testing, where the combination of lauric acid with oxacillin caused antagonism (FIC≥4). This effect was observed in all tested bacterial strains. Conclusion & Significance: To our knowledge, this is the first observed antagonistic effect of lauric acid with oxacillin in S. aureus. From our perspective, consumption of C12:0 rich oils, such as coconut or palm oil, can lead to the complications in staphylococcal infection treatment with oxacillin.