Olive oil is known to have health benefits, but what about the olive leaf? The researchers harvested olive leaves from Seville, Spain, and Lefkada, Greece, dried and ground them, and then mixed them with a solvent to prepare them for analysis. The extracts were tested for toxicity to human melanoma cells and evaluated for their effect on blood vessel growth. When a tumor develops, more blood vessels typically begin to grow to supply the tumor with nutrients.
The olive leaf extracts from Greece contained more polyphenols, such as lutein, which improves eye health, and oleuropein, which has antioxidant, lipid-lowering, anti-atherosclerosis, and anti-inflammatory properties. Additionally, Spanish olive leaf extracts contained nearly double the metal content of extracts from Greece. Spanish olive leaf extracts had higher levels of nickel, zinc, copper, chromium, and iron—all necessary nutrients.
However, they also contained higher levels of cadmium and aluminum, which can be toxic in high doses. The researchers did not determine the levels to be toxic. Olive leaf extracts from Greece had greater antioxidant activity, making them more effective at combatting free radicals.
They were also more effective at killing melanoma cells and better at preventing the formation of blood vessels, another anti-cancer property. However, olive leaf extracts from Spain were more effective against a broader range of bacteria, indicating they contain more antimicrobial properties. Spanish extracts.