Abstract
In recent years, there has been a significant rise in consumer demand for food products that offer enhanced health benefits and fortified nutrients. This trend has prompted researchers in the food industry to develop offerings that incorporate healthier ingredients while ensuring safety, sensory appeal, and shelf stability. In this context, natural plant extracts have gained increasing value for their ability to serve as antioxidants and antimicrobials, thereby enhancing the stability and shelf life of food products. Among these, olive leaves stand out due to their richness in bioactive compounds. This study examined the recovery of bioactive compounds from the leaves of olives (Olea europaea) using various extraction techniques: Microwave-Ultrasound-Assisted Extraction (MUAE), Microwave-Assisted Extraction (MAE), Ultrasound-Assisted Extraction (UAE), Conventional Magnetic Stirring Extraction (MASE), and Soxhlet Extraction (SE). To assess extraction efficiency, the yield, the Total Phenolic Content (TPC), and the Trolox Equivalent Antioxidant Capacity (TEAC) were measured using three different solvents: (i) water, (ii) acetone, and (iii) a mixture of acetone and water (70:30 v/v). The results showed that MUAE with the acetone/water mixture produced the highest TPC (105.3 ± 4.2 GAE/g of dry olive leaves) and TEAC values (105.3 ± 4.2 TEAC/g of dry olive leaves), while achieving notable yields of oleuropein, reaching up to 38.4 mg/g of dry leaves. Additionally, this method effectively maximized the extraction of a range of bioactive compounds, including both hydrophilic and lipophilic substances. High-Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD) analysis confirmed that the acetone/water solvent system was superior in extracting a broad spectrum of bioactive compounds. In contrast, the use of water was found to primarily extract hydrophilic phenolics, while acetone was more effective for recovering lipophilic compounds. Notably, optimal results from the MUAE method were achieved at a 15-minuteextraction time; prolonged extraction durations led to the degradation of bioactive compounds. These findings demonstrate that MUAE combined with an acetone/water solvent system (70:30) represents an effective strategy for extracting valuable bioactive compounds from olive leaves. This approach holds significant potential for applications in the pharmaceutical and cosmeceutical industries. Additionally, the acetone/water system is advantageous for scalable applications, given its lack of azeotrope formation, which facilitates solvent recovery in industrial settings. Furthermore, the results of the LCA for all impact categories across all extraction methods, quantified and expressed in Environmental Footprint units (mPt), demonstrated that the MUAE has a less negative environmental impact compared to other methods. Regarding climate change, MUAE was measured at just 0.0047 mPt per gram of olive leaves, whereas the SE method registered an impact of 0.0305 mPt per gram of olive leaves. This indicates that the impact of the SE method is over six times greater than that of MUAE.
| Date of Award | 26 Feb 2026 |
|---|---|
| Original language | English |
| Sponsors | European Union's Horizon 2020 Research & Innovation Programme |
| Supervisor | Athanasios Angelis-Dimakis (Main Supervisor) & Chenyu Du (Co-Supervisor) |