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The aim of this study was to enhance the refined olive oil (ROO) quality stabilization during storage with phenolic compound fractions obtained from C18 silica gel fractionation of olive mill waste (OMW) ethyl acetate extract. HPLC–DAD–ESI/MS analysis was used to identify the main phenolic compounds present in the obtained fractions. 16 compounds were identified belonged to four classes: simple phenols, secoiridoids, flavonoids, and lignans. In this study, Diosmetin was identified for the first time in OMW and the major compound was hydroxytyrsol. On the other hand OMW extract and its related fractions conserved their antioxidant activity until 110 min heating at 185 °C. In addition, physicochemical characteristics such as peroxide value as well as conjugated dienes (CD) and conjugated trienes (CT) were determined to evaluate the oxidation of OMW polyphenols-enriched ROO during storage. Results demonstrated that OMW monomeric fraction and hydroxytyrosol improved the quality of ROO by decreasing peroxide value and absorptions at specified wave lengths at 232 and 270 nm related to conjugated dienes and trienes formation, respectively. This study suggests that the enrichment of ROO with phenolic compounds from OMW mainly hydroxytyrosol makes the oil more functional with a higher stability. Phenolic compounds from OMW with antioxidant activity improve the stability of ROO during storage and hence would be used as a natural alternative for chemical additives.

Methanol and methanol/water extracts of olive stones and seeds from Olea europaea var. meski were analyzed by reversed-phase high-performance liquid chromatography (HPLC) with diode array detection and mass spectrometry (LC-MS/MS). A total of 28 metabolites were identified; among them are hydroxycinnamic acid derivatives, phenolic alcohols, flavonoids and flavonoid glucosides, secoiridoids, and terpenes. All the extracts were screened for the inhibitory effect of key enzymes related to diabetes and obesity, such as α-amylase and lipase. An in vitro study revealed that Olea meski stone ethanol (MSE) and methanol (MSM) extracts and Olea meski seed ethanol (MSE1) and methanol (MSM1) extracts exert an inhibitory action against lipase and α-amylase. The most potent activity was observed in the StM extract with IC50 equal to 0.19 mg/ml against DPPH oxidation, 1.04 mg/ml against α-amylase, and 2.13 mg/ml against lipase. In HFFD rats, the findings indicated that the increase of body weight, LDL, TC, and glucose levels and then the decrease in HDL-C were significantly suppressed in the MSM-treated group than those in HFFD rats. Moreover, the MSM extract exhibited a prominent selective inhibitory effect against intestinal lipase and α-amylase activities. The MSM extract was also able to protect the liver-kidney functions efficiently, which was evidenced by biochemicals and histological studies.