Antioxidant and Anti-Diabetic Properties of Olive (Olea europaea) Leaf Extracts: In Vitro and In Vivo Evaluation

Abstract

(1) Objective: The main objective of the current study was to evaluate in vitro and in vivo an antioxidant property of three genotypes of olive leaf extract (OLE) (picual, tofahi and shemlali), and furthermore to assess potential activity in the treatment and/or prevention of diabetes mellitus type II and related implications. (2) Methodology: Antioxidant activity was determined by using three different methods (DDPH assay, reducing power and nitric acid scavenging activity). In vitro α-glucosidase inhibitory activity and hemolytic protective activity were assessed for the OLE. Five groups of male rats were used in in vivo experiment for evaluating the antidiabetic potential of OLE. (3) Results: The genotypes of the extracts of the three olive leaves exhibited meaningful phenolic and flavonoids content with superiority for picual extract (114.79 ± 4.19 µg GAE/g and 58.69 ± 1.03 µg CE/g, respectively). All three genotypes of olive leaves demonstrated significant antioxidant activity when using DPPH, reducing power and nitric oxide scavenging activity with IC50 ranging from 55.82 ± 0.13 to 19.03 ± 0.13 μg/mL. OLE showed a significant α-glucosidase inhibition activity and dose-dependent protection from hemolysis. In vivo experimentation revealed that the administration of OLE alone and the combination of OLE+ metformin clearly restored the blood glucose and glycated hemoglobin, lipid parameters and liver enzymes to the normal level. The histological examination revealed that the OLE and its combination with metformin successfully repaired the liver, kidneys and pancreatic tissues to bring them close to the normal status and maintain their functionality. (4) Conclusion: Finally, it can be concluded that the OLE and its combination with metformin is a promising treatment for diabetes mellitus type 2 due to their antioxidant activity, which emphasizes the potential use of OLE alone or as an adjuvant agent in the treatment protocol of diabetes mellitus type II.

Comparative analysis of silver-nanoparticles and whey-encapsulated particles from olive leaf water extracts: Characteristics and biological activity

“…Tiny amounts of the OLE revealed a high scavenging activity against DPPH • and ABTS • radicals: Tofahy and Shemlali’ OLE extracts effectively scavenged 50% of DPPH • (IC 50 = 35.44 ± 0.45 and 30.39 ± 0.22 μg/mL, respectively) and ABTS • (IC 50 = 13.91 ± 0.63 and 11.99 ± 0.22 μg/mL, respectively). The high scavenging activity could be due to the high concentrations of oleuropein, rutin, benzoic acid, salicylic acid, p-hydroxybenzoic acid, and ellagic acid [ 63 ]. We obtained a higher scavenging activity in the present study than Urzúa et al [ 25 ], who reported that 0.15 mg/mL scavenged 50% of DPPH • .…”

Redox State Modulatory Activity and Cytotoxicity of Olea europaea L. (Oleaceae) Leaves Extract Enriched in Polyphenols Using Macroporous Resin

“…Despite different results for the antioxidant activity of olive leaf extracts, the comparison with these is difficult due to the various experimental conditions, methods, and plant matrix used. Mansour et al [40] found an IC50 of approximately 50 μg/mL in aqueous olive leaf non-enriched extracts. This higher antioxidant activity is probably related to the different phytochemical profiles.…”

The Bioactivity of a Hydroxytyrosol-Enriched Extract Originated after Direct Hydrolysis of Olive Leaves from Greek Cultivars

“…Despite the fact that there are many studies concerning the in vitro antioxidant activity of OLs extracts [ 52 , 53 , 54 , 55 , 56 ], less is known about hydrolyzed extracts. In the first case, the bioactivity of the extracts is mainly exerted due to OLE, as the main phenol in OLs, while after hydrolysis, the main drastic component is HT.…”