Characterization of Phytochemicals and Biological Activities of Olive Pomace By-Products

Since ancient times, olive oil has played a fundamental role in human diet and especially olive oil has covered an indispensable place in Mediterranean diet [1]. Approximately 63% of international olive annual production is conducted in Spain, Italy and Greece [2]. These countries have to deal with the environmental issues related to the supply chains within these products life cycles [3] and, notably, they must address the issue of eco-friendly friendly disposal of their by-products. The greater awareness of the need to better exploit resources still available, led researchers to focus their efforts on getting nutraceuticals from by-products of the food chain. In this context of circular economy, the potential of olive pomace (OP) by-product as a functional ingredient has been investigated in this work. Three methanolic extracts (obtained by Soxhlet apparatus and rotavapor device) of different lot of OP have been characterized for their profile in phenolic compounds (phenolic acids, flavonoids, secoiridoids) through HPLC-DAD, and in vitro antioxidant properties (ABTS∙+ , FRAP and DPPH assays) have been studied. The same evaluations have been performed on OP samples that underwent to an in vitro digestion to simulate the physiological digestive process [4] The OP digested solution was then dialyzed using a membrane with a cut-off of 3.5 kDa against water for 12 h so that two fractions were obtained: the solution left outside the dialysis tube (colon available sample: OUT) and the solution that diffused into the dialysis tube (absorbable fraction: IN). Furthermore, the OUT and IN samples with the higher phenolic content and antioxidant properties were investigated for their potential ability to modulate the inflammatory response in ex vivo horse peripheral blood mononuclear cell (PBMC) cultures by analyzing the expression of interleukin (IL)-1; IL-6 and IL-10 by RT-PCR. OP extracts have shown a quite high level of total phenolic compounds together with relative high antioxidant properties. Phenolic profile showed significant differences among the three samples, and most compounds were still present in both IN and OUT solutions, with a different distribution between them, depending on single molecules. Accordingly, the three OP samples and their digested solutions showed different antioxidant activities with OUT samples having the highest activity. Nevertheless, the evaluation of the anti-inflammatory properties of digested OP samples in an ex vivo cellular model (horse PBMC) revealed a higher efficacy of IN samples in down regulating the expression of inflammatory cytokines (IL-1 and IL-6) compared to OUT samples. These results suggest that OP is a valuable source of nutraceuticals that should be further investigated to both counteract inflammation and reduce olive oil by-products impact on the environment