Updated: Aug 31, 2021
Extra Virgin Olive Oil and Olive Leaf Extract ally for your health.
Anti-proliferative and apoptotic effects of oleuropein and hydroxytyrosol on human breast cancer MCF-7 cells.
Olive oil intake has been shown to induce significant levels of apoptosis in various cancer cells. These anti-cancer properties are thought to be mediated by phenolic compounds present in olive. These beneficial health effects of olive have been attributed, at least in part, to the presence of oleuropein and hydroxytyrosol. In this study, oleuropein and hydroxytyrosol, major phenolic compound of olive oil, was studied for its effects on growth in MCF-7 human breast cancer cells using assays for proliferation (MTT assay), cell viability (Guava ViaCount assay), cell apoptosis, cellcycle (flow cytometry). Oleuropein or hydroxytyrosol decreased cell viability, inhibited cell proliferation, and induced cell apoptosis in MCF-7 cells. Result of MTT assay showed that 200 μg/mL of oleuropein or 50 μg/mL of hydroxytyrosol remarkably reduced cell viability of MCF-7 cells. Oleuropein or hydroxytyrosol decrease of the number of MCF-7 cells by inhibiting the rate of cell proliferation and inducing cell apoptosis. Also hydroxytyrosol and oleuropein exhibited statistically significant block of G1 to S phase transition manifested by the increase of cell number in G0/G1 phase.
Evidence to Support the Anti-Cancer Effect of Olive Leaf Extract and Future Directions
EVOO is primarily a monounsaturated fatty acid (MUFA) in the form of oleic acid, with minor components including various phenolics . It has been recognised that the polyphenol content plays an important role in health benefits. The European Food Safety Authority (EFSA) have approved the use of the general claim “olive oil polyphenols contribute to the protection of blood lipids from oxidative stress” when oil contains no less than 5 mg of hydroxytyrosol (HT) and its derivatives (such as tyrosol and oleuropein) per 20 mL OO  (Figure 1). There are several studies that have shown that EVOO with higher phenolic content provides stronger anti-inflammatory and antioxidant effects than OO with a lower phenolic content [17,18]. This suggests the phenolic component, rather than the fat in the oil, is the effector.
Olive tree leaves (Olea europaea) are widely used in traditional medicine in the Mediterranean region . In the Bible, the olive plant is referenced numerous times for its medicinal use . The bioactive properties of the leaf have created a foundation for use as an antioxidant, anti-hypertensive, anti-atherogenic, anti-inflammatory, hypoglycemic, and hypocholesterolemic treatment . Olive tree leaves contain similar polyphenols to those found in EVOO or the fruit itself, albeit at a much higher concentration [20,22]. Consequently, olive leaf extract (OLE) may hold an even greater potential than EVOO for improving health outcomes. During EVOO processing leaves can unintentionally be left in the mixture if the separation methods are inadequate, alternately leaves can also be added to EVOO mixtures to provide health benefits and improve flavor . The addition of leaves increase the phenolic and chlorophyll content of the oil but also the organoleptic traits as measured in volunteer taste tests . Components of OLE that are not detected in the oil from the fruit include several flavonoids, namely luteolin and apigenin, which have demonstrated anti-cancer properties [25,26,27,28,29]. In addition, the structure of phenolics differs between the olive fruit and leaf, with OLE containing a higher proportion with a glycoside moiety (Figure 2 and Table 1) . The presence of a glucose molecule could play an important role in respect to both bioavailability and bioactive potential of the polyphenols, thereby impacting the health benefits for humans.
Hydroxytyrosol and Potential Uses in Cardiovascular Diseases, Cancer, and AIDS
Hydroxytyrosol is one of the main phenolic components of olive oil. It is present in the fruit and leaf of the olive (Olea europaea L.). During the past decades, it has been well documented that this phenolic compound has health benefits and a protective action has been found in preclinical studies against several diseases. Here, we review its bioavailability in human beings and several assays showing significant results related with cardiovascular diseases, cancer, and acquired immunodeficiency syndrome (AIDS).