Antihyperlipidemic and antioxidant potential of Olea europaea L. leaves: An experimental study in vivo, in vitro and in silico

Abstract

Hyperlipidemia is an enduring metabolic ailment that affects glucose and lipid processing.
 The research objective was to measure the total phenolic, flavonoid, and tannin contents in Olea europaea L. leaves and to to identify their antioxidant and antihyperlipidemic potential. The study included an in silico model of interaction for hydroxytyrosol, oleuropein, and xanthine dehydrogenase. The in vivo experiment involved rabbits that received olive leaves (150 mg/kg) and 10 mL of egg yolk as a high-fat diet. At the end of the experimental period, blood samples were tested for lipid profile, and tissue specimens were used for liver histology. 
 The total phenolic content was 119.84 ± 3.86 mg GAE/g, the total flavonoid content was 2.22 ± 0.07 mg CE/g, and the total tannin content was 21.25 ± 1.24 mg REQ/g dry weight. According to DPPH and FRAP analyses, the antioxidant capacities were 0.34 ± 0.06 μg/mL and 6.35 ± 0.52 μmol Fe(II)/g dry weight, respectively. In the experimental animals, O. europaea leaves reduced such parameters as total cholesterol, low-density lipoprotein, total triglycerides, total cholesterol vs. high-density lipoprotein, and low-density lipoprotein vs. high-density lipoprotein. The histopathological liver assay showed no signs of tissue damage while the samples obtained from the control group demonstrated steatosis deposits and cellular necrosis. Based on the energy and RMSD results, hydroxytyrosol proved an effective xanthine dehydrogenase inhibition.
 These findings constitute a good scientific basis for the complementary future research on the potential of O. europaea leaves as ingredients of functional foods or medical drugs.