Olive oil possesses a predominant role in the diet of countries around the Mediterranean basin, whereas it is a known constituent of several sectors of human culture. The polyphenolic composition of olive oil seems to be a key factor in its beneficial biological properties. Based on the above, the aim of this study was to correlate the polyphenolic composition of five extracts derived from a Greek olive oil variety with their antioxidant potency and antimutagenic activities in vitro with chemical-based techniques and cell culture-based assays. According to the results obtained, the polyphenol samples with higher concentration of hydroxytyrosol (HT) were more potent in antioxidant and antimutagenic activity in vitro, as indicated by their ability to scavenge ABTS⋅+ radical and to protect the strand of plasmid DNA from free radical-induced breaking compared to the corresponding samples with higher levels of tyrosol (T) and its derivatives. However, this observation was not evident in the cell culture model (i.e., the HeLa cervical cancer cell line) to which the tested extracts were administered. Specifically, the T-rich extracts more effectively increased endogenous GSH levels measured by flow cytometry than did the HT-rich compounds. Also, olive oil compounds contributed variously to the expression of genes implicated in the cell antioxidant machinery, as indicated by quantitative PCR. Therefore, the relationship between structure and function in redox regulation is complex and merits the combination of tests. Given that factors like the production and storage regimen of the plants are major determinants of the composition of the generated extracts, we propose that specific conditions should be adopted in order to achieve their maximum biological activity. These results followed by others in the same direction could provide a solid basis for the production of functional foods enriched in olive oil extracts with potential antioxidant action in vivo.

Oleocanthal and oleacein are known for a wide range of beneficial activities in human health and the prevention of diseases. The inability to isolate significant and pure amounts of these natural compounds and their demanding synthesis lead to the development of an efficient, five-step, three-pot procedure. The synthesis is performed by a convenient biomimetic approach, starting from oleuropein, an abundant raw material in olive leaves, through the mixed anhydride of oleoside. The method is stereocontrolled and provides an efficient approach to the synthesis of various oleocanthal analogues; thus, a small library of four compounds was prepared with 35–45% overall yield.

The physiological characteristics of liquid digestate retrieved from various biogas plants based in northern Greece are presented. Preliminary photocatalysis experiments on inoculated liquid di-gestate sampled showed that disinfection is possible when pre-treated digestate with a combination of centrifuge-flocculation-μFiltration after 5.5 hours of 0.7g/L suspended TiO2 under UVA illumination for the experimental conditions is used. A novel design photocatalytic nanofiltration reactor was implemented for disinfection experiments on pre-treated liquid digestate, giving promising results. This work sets the basis for the efficient operation and engineering application of technology collaboration with photocatalysis as the final step for liquid digestate sanitation and reusable water recovery.

The disinfection properties of photocatalysis on liquid digestate derived from biogas plants have been investigated for the first time. The study presents the physiological characteristics of liquid digestate retrieved from various biogas plants based in northern Greece, revealing the heterogeneity of this matrix. Preliminary photocatalysis experiments conducted on inoculated liquid digestate samples showed that disinfection was possible when a pre-treated digestate underwent a combination of centrifuge–flocculation–μfiltration after 5.5 h with 0.7 g/L suspended TiO2 under UVA illumination. To explore the feasibility of an industrial application based on this concept, a novel design photocatalytic nanofiltration reactor was implemented for disinfection experiments on pre-treated liquid digestate. The synergistic action of photocatalysis during nanofiltration alleviated the leakage phenomena, and both the retentate and permeate effluents had lower concentrations of pathogens by approximately 1–2 log10 cfu/mL. This work sets out the basis for the efficient operation and engineering application of collaborative technology, with photocatalysis as the final step for liquid digestate sanitation and reusable water recovery.

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