Ethanolic extract from olive leaves may help fight cancer and infections


A study recently published in the journal Antioxidants The therapeutic potential of ethanolic extracts obtained from olive leaves from Spain and Greece was investigated. The results show that both extracts, especially the extract obtained from Greece, exhibit high antioxidant capacity and significant antimicrobial and anticancer properties, suggesting potential applications in healthcare as antimicrobial agents and in the treatment of melanoma.

Ethanolic extract from olive leaves may help fight cancer and infectionsStudy: Antioxidant extracts from Greek and Spanish olive leaves: antimicrobial, anticancer and antiangiogenic effects. Image credit: Artmim / Shutterstock

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In previous studies, phytochemicals derived from medicinal plants have shown promising results in the development of new medicines, especially chemotherapeutics for various cancers including melanoma, which is known for its aggressiveness and metastasis. However, while extensive research has established the antioxidant and antimicrobial properties of olive leaf extracts and their potential in treating several cancers, there is a gap in understanding the phytochemical profile of olive leaves from different regions and their specific anti-melanoma effects, especially when applied topically.

About the study

This study addressed existing research gaps by characterizing ethanolic extracts of olive leaves from Spain and Greece, focusing on their chemical, micronutrient and inorganic content, and assessing their therapeutic potential as antimicrobial, anti-melanoma and angiogenesis-modulating agents. Researchers harvested olive leaves from Seville, Spain (OFS) and Lefkada, Greece (OFG). These leaves were dried, ground and mixed with a solvent to prepare for analysis. The mixture was then extracted, filtered, concentrated and stored.

Laboratory procedures were used to identify and quantify the compounds and chemicals in the extracts. The inorganic elements were analyzed after combining them with nitric acid and then using graphite furnace-atomic absorption spectrometry (GF-AAS). Other important aspects of the analysis were the assays the researchers used to evaluate antioxidant activity, while they examined antimicrobial activity by looking at how the chemicals in the extracts worked against various microorganisms. They also tested whether the substances in the extracts were toxic to target cells (cytotoxicity) using human melanoma cells and directed the movement of cells (cell migration) using a scratch assay. The extracts were also evaluated for potential inflammation and angiogenesis, or blood vessel growth, effects using an assay on chick embryos. Statistical analyses were performed using one-way variance analysis (ANOVA), which took into account multiple comparisons.

Findings

The study investigated the beneficial compounds present in olive leaf extracts from Spain (OFS) and Greece (OFG). The extraction yield, the percentage of dry extract obtained from the total dry plant matter, was 11.34% for OFS and 9.46% for OFG. OFG had a higher total phenolic content (99.228 µg/mg) than OFS (56.733 µg/mg). Phenolics are important plant compounds with health benefits, and luteolin 6-C-glucoside and luteolin 7-O-glucoside were the main phenolics in OFG, while oleuropein was the most abundant in OFS.

Triterpenes, another group of beneficial compounds, were higher in OFG (111.747 µg/mg) than OFS (57.085 µg/mg), with oleanolic acid being the most significant component. Elemental analysis showed that OFS had almost twice the metal content than OFG.

Antioxidant activity, which measures how well an extract can neutralize harmful free radicals, was slightly higher in OFG (91.89% at 1000 µg/mL) than OFS (89.97%). Antimicrobial tests showed that OFS was more effective against a wider range of bacteria, especially at higher concentrations, than OFG. Cytotoxicity assays, which assess the ability to kill cancer cells, revealed that OFG was more effective against melanoma cells, reducing cell viability by 38.5% at 200 µg/mL after 72 hours, while OFS reduced it by 60.8%. Scratch assays, which measure cell migration, indicated that OFG reduced the movement of melanoma cells more significantly. Both extracts were safe for cells and affected blood vessel formation, with OFG having the stronger effect.

Stereomicroscopic images of OFS and OFG effects on the CAM assay. Images were taken at 0, 24, and 48 h after treatment.Stereomicroscopic images of OFS and OFG effects on the CAM assay. Images were taken at 0, 24, and 48 h after treatment.

conclusion

The study emphasises the health benefits of olive leaves, particularly their rich antioxidant composition. Greek and Spanish olive leaf extracts were analysed and found to contain significant concentrations of phenolic compounds and triterpenes, with the Greek extracts showing higher amounts. The study states that the variation in compound concentrations from previous research is likely due to differences in climate and cultivation regions. The strengths of the study include detailed phytochemical characterisation and comparative analysis of the Greek and Spanish extracts. The study also highlights the antioxidant and antimicrobial properties of these extracts, with the Greek extract showing higher activity. However, limitations of the study include a limited geographical focus, which may not represent global variations, and the inability to identify all potential metal-polyphenol complexes.

Future research should explore wider geographical variations, investigate the mechanisms behind metal chelation by polyphenols in depth, and investigate the long-term health effects of these extracts. Additionally, further studies can investigate the potential synergistic effects of the various compounds present in the extracts, thereby enhancing their therapeutic applications.

Journal Reference:

  • Antioxidant extracts from Greek and Spanish olive leaves: antimicrobial, anticancer and antiangiogenic effects. Magyari-Pavel, I.Z., Moaca, E., Avram, S., Diaconesa, Z., Haidu, D., Stefanut, M.N., Rostas, A.M., Muntean, D., Bora, L., Badescu, B., Iouhas, C., Dehlean, C.A., Danciu, C. Antioxidants (2024). DOI: 10.3390/antiox13070774, https://www.mdpi.com/2076-3921/13/7/774

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