Oleuropein

Oleuroppein is one of the bioactive secoiridoids found in the leaves of Olea europaea and possesses health-promoting properties, thus requiring practical purification guidelines. This study reports a two-step chromatographic strategy for isolating and purifying oleuropein. First, an optimised high-speed counter-current chromatography (HSCCC) protocol by means of a novel three-phase solvent system (water/acetonitrile/n-hexane/dichloromethane, 5:5:5:1, v/v) was developed to fractionate olive leaf extracts. The HSCCC step enriched oleuropein but did not achieve analytical-grade purity, likely due to HSCCC's lower chromatographic resolution (fewer theoretical plates) compared to HPLC. Therefore, the HSCCC fraction containing oleuropein was further purified by preparative high-performance liquid chromatography (HPLC). The HSCCC-prep-HPLC system yielded an oleuropein fraction that was 94.7 % pure by analytical HPLC. Mass spectrometric analysis and co-chromatography with established standards were used to support the compound's structural identity and purity. This combined approach, by taking advantage of the ability of HSCCC to handle crude extract mixtures in combination with the high resolution of HPLC, avoided the limitations that were inherent with HSCCC itself. As a result, a high-purity oleuropein isolate suitable for quality-control tests or bioactivity studies could be obtained, thus demonstrating the effectiveness of the combination of HSCCC and preparative HPLC in isolating near-pure oleuropein and related natural products from complex botanical samples.

Noise and toluene are environmental stressors that induce oxidative stress and inflammation, contributing to renal dysfunction. This study evaluated the protective effects of Olea europaea leaf extract (OeLE; 40 mg/kg/day) against combined noise‐ and toluene‐induced nephrotoxicity in Wistar rats. Forty‐eight male rats were divided into eight groups and exposed for 6 weeks (6 h/day, 5 days/week) to noise, toluene, or their combination, with or without OeLE supplementation. Renal function biomarkers (urea and creatinine), oxidative stress indices (malondialdehyde, catalase [CAT], and superoxide dismutase [SOD]), histopathology, and in silico docking targeting key redox and inflammatory mediators (CAT, SOD, IL‐1β, TNF‐α, and NF‐κB) were assessed. Co‐exposure caused significant renal dysfunction, elevated lipid peroxidation, impaired antioxidant defenses, glomerular collapse, tubular necrosis, vascular congestion, and interstitial inflammation, with the combined exposure group showing the most severe lesions. OeLE supplementation markedly mitigated these effects by restoring renal biomarkers, reducing oxidative injury, enhancing enzymatic antioxidant activity, and preserving renal architecture. Molecular docking confirmed strong interactions between OeLE bioactive compounds (oleuropein and luteolin‐7‐O‐glucoside) and antioxidant/inflammatory mediators. OeLE exerts antioxidant and anti‐inflammatory effects, protecting the kidneys from combined noise‐ and toluene‐induced damage, highlighting its potential as a natural therapeutic agent.