In vitro study of potential prebiotic properties of extra virgin olive oils from Marche region

The current definition describes prebiotic as “a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host wellbeing and health“ [1, 2]. Fermentation by the intestinal microbiota and the selective stimulation of the growth and/or activity of specific intestinal bacteria associated with health and wellbeing are concepts that are pursued by prebiotic compounds and prebiotic food ingredients [2]. Recent works on olive oil phenolic compounds and other bioactive molecules showed their ability to influence gut microbial populations and metabolic output [3]. The aim of the study was to investigate whether extra virgin olive oil (EVOO), with its compounds, may show prebiotic properties and so benefits, and positive changes on human microbiota. The study was focused on twenty EVOOs from Marche region of five cultivars: Piantone di Mogliano, Raggia, Mignola, Coroncina and Ascolana tenera. To evaluate potential prebiotic properties of EVOO samples, selected intestinal bacteria groups were monitored, using an in vitro anaerobic culture system simulating physiological processes, first digestion and then colonic fermentation. Each EVOO performed a 24h fermentation cycle in a semi-continuous culture system, to analyse the biodiversity of gut microbiota, in terms of selected bacterial groups and production of Short Chain Fatty Acids (SCFAs). After DNA extraction, based on a modified benzyl chloride method [4], the detection and quantification of bacterial levels were performed through Real‐Time PCR [5]. The study evaluated the concentration of Bifidobacterium spp., Lactobacillus spp. and Clostridium coccoides – Eubacterium rectale group, using specific primers from reference strains [5]. SCFAs, as metabolites of intestinal fermentation, were analysed in each fermented sample and quantified by gas-chromatography coupled to flame ionization detection [6]. Inulin, naturally occurring polysaccharides well known as prebiotic compound [1], was used as control. The results obtained from Real-Time PCR and GC analysis of EVOO samples were compared with those obtained from inulin assay and showed similar behaviour during time, with statistically significant growth stimulation and activity of Lactobacillus spp. and Bifidobacterium spp. (p<0.05). Any significant changes of cell count of Clostridium coccoides-Eubacterium rectal group were detected. Quantification of fermentation end products showed significant production of specific SCFAs during fermentation time, in particular acetic, propionic and butyric acids. Among all EVOO samples, Raggia and Piantone di Mogliano cultivars showed the best prebiotic trend. In conclusion, all twenty EVOO samples under study have satisfied the concepts for classification as prebiotic [1, 2]. Extra virgin olive oil can be defined prebiotic and natural functional food. Further investigations will be done to better understand the role of compounds that may be involved in this activity.