Concentration of Bioactive Phenolic Compounds in Olive Mill Wastewater by Direct Contact Membrane Distillation

Abstract

Olive mill wastewater (OMW), generated as a by-product of olive oil production, is considered one of the most polluting effluents produced by the agro-food industry, due to its high concentration of organic matter and nutrients. However, OMW is rich in several polyphenols, representing compounds with remarkable biological properties. This study aimed to analyze the chemical profile as well as the antioxidant and anti-obesity properties of concentrated fractions obtained from microfiltered OMW treated by direct contact membrane distillation (DCMD). Ultra-high performance liquid chromatography (UHPLC) analyses were applied to quantify some phenols selected as phytochemical markers. Moreover, a-Amylase, a-glucosidase, and lipase inhibitory activity were investigated together with the antioxidant activity by means of assays, namely b-carotene bleaching, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic) acid (ABTS) diammonium salts, 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and Ferric Reducing Activity Power (FRAP) tests. MD retentate—which has content of about five times greater of hydroxytyrosol and verbascoside and about 7 times greater of oleuropein than the feed—was more active as an antioxidant in all applied assays. Of interest is the result obtained in the DPPH test (an inhibitory concentration 50% (IC50) of 9.8 mg/mL in comparison to the feed (IC50 of 97.2 mg/mL)) and in the ABTS assay (an IC50 of 0.4 mg/mL in comparison to the feed (IC50 of 1.2 mg/mL)).

Recovery of Hydroxytyrosol from Olive Mill Wastewater Using the Promiscuous Hydrolase/Acyltransferase PestE

“…[4][5][6][7][8] Several methods have been developed to facilitate the degradation or extraction of phenolic compounds, such as chemical oxidation, solvent extraction, membrane systems or adsorbents. [9][10][11][12][13][14][15][16][17][18][19][20] However, all these systems require several laborious steps. In the case of solvent extraction, several extraction steps are required due to the hydrophilic nature of the contained phenols, e. g., the major phenolic compound 3hydroxytyrosol (HT).…”

“…The phenols of olives have several health‐promoting properties, e. g., neuroprotective, which are associated with their antioxidant and anti‐inflammatory benefits [4–8] . Several methods have been developed to facilitate the degradation or extraction of phenolic compounds, such as chemical oxidation, solvent extraction, membrane systems or adsorbents [9–20] . However, all these systems require several laborious steps.…”

Therapeutic Properties and Use of Extra Virgin Olive Oil in Clinical Nutrition: A Narrative Review and Literature Update

“…In a prospective study in people with hydrocarbon intolerance, plasma β-sitosterol level acted as a protective factor against the development of DM2 [ 269 ]. Ex vivo studies in humans have indicated that oleuropein and hydroxytyrosol can inhibit α-amylase, α-glucosidase, sucrase, lipase, and glucose transporter 2 (GLUT-2) [ 112 , 270 , 271 , 272 ]. In animal models, oleanolic acid and luteolin have shown a superior ability to olive leaf extract in reducing postprandial blood glucose, all being significantly superior to placebo [ 266 ].…”

Potential of Olive Oil Mill Wastewater as a Source of Polyphenols for the Treatment of Skin Disorders: A Review

“…Some of the most abundant bioactive phenolic compounds in OMW, presented in Figure , are derivatives of phenolic acids, containing from a single to several hydroxyl moieties on their phenol groups, and are derived from hydroxylation by benzoic acid (C 6 –C 1 ) or cinnamic acid (C 6 –C 3 ) (phenylpropanoid family). The phenolic compounds most commonly found are primarily HT and tyrosol. ,,, Other phenolic compounds are frequently found in OMW, albeit in lower concentrations, for example, caffeic and ferulic acids. , More complex recurrent phenolic compounds have been identified in OMWs, such as verbascoside , or oleuropein , and isomers/derivatives. , The concentration of oleuropein and its derivatives in OMWs is highly variable between samples and studies, , principally as a result of the degradation of oleuropein during malaxation in the production of olive oil. − …”

“…10,11,13,14 Other phenolic compounds are frequently found in OMW, albeit in lower concentrations, for example, caffeic and ferulic acids. 11,12 More complex recurrent phenolic compounds have been identified in OMWs, such as verbascoside 10,12 or oleuropein 13,15 and isomers/derivatives. 16,17 The concentration of oleuropein and its derivatives in OMWs is highly variable between samples and studies, 18,19 oleuropein during malaxation in the production of olive oil.…”