Extraction yield optimization of Oleaster (Olea europaea var. sylvestris) fruits using response surface methodology, LC/MS profiling and evaluation of its effects on antioxidant activity and autophagy in HFF cells
2021
Ghorbel, Amal | Wedel, Sophia | Kallel, Imen | Cavinato, Maria | Sakavitsi, Maria Eleni | Fakhfakh, Jawhar | Halabalaki, Maria | Jansen-Dürr, Pidder | Allouche, Noureddine
Oleaster (Olea europaea var. sylvestris) is a wild olive tree distributed in the Mediterranean area. It is known to possess several biological activities due to their richness in polyphenols. However, enhanced autophagic activity in human cells by using this plant has not been studied before. The objective of the present study was to determine the phytochemical composition of the fruits paste from Tunisian Oleaster, and evaluate its antioxidant activity using the DPPH• and ABTS•⁺ methods as well as the evaluation of its effect on autophagy activity. The extraction conditions were optimized using response surface methodology (RSM) leading to the best phenolic extract yield. It was noted that ethyl acetate extract presented the highest amount of total phenols and the best solvent for extraction of phenolic compounds. After optimization, the ethyl acetate extract was fractionated into 15 fractions by silica gel column chromatography. The most phenolic components in the fifth and sixth fractions (F5 and F6) were identified using UPLC-ESI(-)-HRMS analysis. Accordingly, F6 was the richer fraction in polyphenols. In vitro antioxidant activity evaluation showed that F6 exhibited a strong ability to scavenge DPPH and ABTS radicals. Furthermore, this fraction was also the most effective to induce autophagic activity in Human foreskin fibroblasts (HFF) cells. These results could be presumably due to the presence of oleuropein aglycon in this fraction which is absent in fraction F5. Oleaster fruits paste would be used as a natural source of bioactive compounds useful in various pharmaceutical drugs.
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