Synthesis and recovery of high bioactive phenolics from table-olive brine process wastewater

Abstract

The generated wastewater of table-olive brine processing contains a high amount of polyphenols which are endowed with interesting biological activities. The ethyl acetate extract (EAE) of such wastewater shows high hydroxytyrosol (HT) and tyrosol concentrations of 690 and 98 mg g −1 dry weight extract, respectively. Phenolic compounds analysis was performed by gas chromatography–mass spectrometry (GC–MS). The antioxidant activity was evaluated by the scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-Azinobis[3-ethylbenzothiazoline-6-sulfonate] radicals. Total polyphenol content was estimated with the Folin–Ciocalteu assay. Hydroxytyrosol has DPPH and ABTS radicals scavenging activities higher than 2,6-di- tert-butyl-hydroxytoluene (BHT), while triacetylated hydroxytyrosol (triAcHT) was devoid of any antioxidant activity. The assessment of these antioxidant compounds in biological systems was carried out by the determination of their in vitro cytotoxicity against two different human cancer cell lines (HeLa and DG75) and normal peripheral blood lymphocytes (PBL) using the MTT assay. The 50% cytotoxic concentrations were ranged between 27 and 210 μg mL −1 for Hela and DG75. At the same concentration range, the EAE and the pure HT and triAcHT exhibited an insignificant cytotoxicity against PBL. Incubation of HeLa and DG75 cells with non-cytotoxic concentrations of EAE, HT or triAcHT resulted in a remarkable protection from the oxidative stress induced by Fe 2+. The antimicrobial activity evaluated by the broth dilution NCCL method using Gram-positive ( Staphylococcus aureus, Bacillus subtilis) and Gram-negative ( Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica) bacteria and ( Candida albicans, Aspergillus niger) fungi showed a broad spectrum bactericidal and fungicidal effect of table-olives-EAE, HT and triAcHT. The MICs vary from 125 to 500 μg mL −1 for bacteria and from 500 to 2000 μg mL −1 for fungi.