BIOCHEMICAL AND MECHANISTIC EVALUATION OF OLIVE LEAF EXTRACT-MEDIATED GREEN SYNTHESIZED ZNO NANOPARTICLES: ANTIDIABETIC POTENTIAL IN STZ-INDUCED RATS

Abstract

Olive leaves are a rich source of phytochemicals, particularly phenolic compounds and flavonoids with various biological activities. HPLC analysis confirmed that oleuropein was the predominant phenolic constituent in the extract. In this study, olive leaf extract (OLE) was utilized as a natural bio-reductant for the green synthesis of ZnO nanoparticles (OLE/ZnO-NPs). The antidiabetic potential of OLE and OLE/ZnO nanoparticles was evaluated using streptozotocin-induced diabetic rats, in addition to physicochemical characterization of the synthesized nanoparticles. UV–visible spectroscopy showed a new absorption peak at 350 nm, while FT-IR analysis indicated the involvement of the extract's functional groups in nanoparticle reduction and stabilization. TEM revealed spherical nanoparticles with an average size of 15–40 nm. Zeta potential analysis confirmed negatively charged particles (−15.58 ± 4.49 mV). In vivo, treatment with OLE/ZnO-NPs significantly reduced fasting blood glucose levels compared to diabetic controls. Improvements were also observed in HbA1c, insulin levels, adiponectin, leptin, and lipid profile, along with a reduction in the leptin/adiponectin ratio and insulin resistance index. In vitro, erythrocyte glucose uptake was significantly increased following treatment with the extract or its nano-formulation. These findings suggest that the antidiabetic effect of OLE and OLE/ZnO-NPs may be mediated through enhanced glucose uptake, improved antioxidant values, and modulation of adipokines.