Alternative Medicine Review
olive leaf properties
Below is an article from the Alternative Medicine Review Volume 14, Number 1, published in 2009, explaining the benefits of Oleuropein, a compound found in olive leaf extract.
Introduction
Olive leaf from Olea europaea, the olive tree, is native to the Mediterranean and has been known for its medicinal properties since ancient times. It is the first botanical noted in the Bible, where it is described in Ezekiel 47:12, “The fruit thereof shall be for meat, and the leaf thereof for medicine.” Ancient Egyptians used it in the process of mummifying royalty, and other cultures including the Greeks employed it as a folk remedy for fever. The leaves of Olea europaea are narrow and elongated, dusty-green on top and silvery-white underneath.1
The first mention of olive leaf properties as medicinal use in modern times was in 1843 when Daniel Hanbury of England reported a bitter substance from olive leaf tea was the agent responsible for healing malaria and associated fevers. These findings were reported in 1854 in the Pharmaceutical Journal, along with dosing instructions and a recipe for making the curative tea.2 In 1898, a strong decoction of olive leaves was cited in King’s American Dispensatory as helpful in regulating body temperature.3 In the last century, extracts of olive leaf have been studied in both animals and humans and have been found to exhibit strong antimicrobial properties against viruses, bacteria, yeast, and parasites. Olive leaf properties also have numerous cardiovascular benefits, some hypoglycemic activity, and possess antioxidant activity.
olive leaf properties
Active Constituents
The primary olive leaf constituents are secoiridoids (oleuropein and its derivatives), hydroxytyrosol,4 polyphenols (verbascoside, apigenin-7-glucoside, and luteolin-7-glucoside),5 triterpenes including oleanolic acid,6 and flavonoids (rutin and diosmin).7 These constituents afford the tree and its fruits and leaves resistance to damage from pathogens and insects.8 The primary constituent, oleuropein, first isolated in 1908, is believed to be responsible for many of the therapeutic properties of olive leaf extracts.9 Although oleuropein is present in the olive fruit and oil, content in the leaf is significantly higher than in other parts of the tree.
olive leaf properties
Hypotensive/Vasodilatory
The hypotensive property of olive leaf extract (OLE) was first reported in 195110 and confirmed by Italian researchers a decade later.11 These results spurred numerous in vitro and animal studies on its hypotensive properties. In 1991 researchers at the University of Grenada’s School of Pharmacy demonstrated that oleuropein exhibited the vasodilatory properties likely responsible for OLE’s reported hypotensive action.12 More recently, two studies demonstrate olive leaf extract suppresses the L-type calcium channel both directly and indirectly, resulting in vasodilation.13,14
olive leaf properties
Antimicrobial
In 1969 researchers demonstrated olive leaf constituents are powerful in vitro inhibitors of numerous viruses, including parainfluenza, herpes, pseudorabies, and some forms of polio. Nearly every virus studied, including several cold and influenza viruses, was inactivated when exposed to a constituent of OLE, calcium elenolate.15 More recently, olive leaf extract was shown to be effective against human immunodeficiency virus (HIV), inhibiting its replication via neutralization of reverse transcriptase and protease.15,16 Olive leaf also prevents viral infectivity by inhibiting assembly at the cell membrane, interfering with critical amino acid production, and stopping viral shedding.15,17
Olive leaf extract also inhibits many gram-negative and -positive bacteria, yeast, and parasites, including the malaria-causing Plasmodium falciparum.18,19 Its antibacterial activity is thought to be via either inactivation of cellular enzymes crucial for bacterial replication or direct attack on the cell membrane resulting in leakage of intracellular components, such as glutamate, potassium, and phosphorus.20
olive leaf properties
Antioxidant/Anti-inflammatory
In 2007, researchers in Australia studying the antioxidant capacity of 55 medicinal herbs found olive leaf properties had the highest radical-scavenging activity of all herbs studied – more than twice that of Camellia sinensis (green tea) and Silybum marianum (milk thistle).21 Oleuropein has been shown to decrease the oxidation of low-density lipoprotein (LDL), both in vitro and in rabbits.22,23 Olive leaf extract also possesses anti-inflammatory properties (likely attributable to anti-complement activity) and inhibition of platelet aggregation and thromboxane A2 production.24,25
olive leaf properties
Hypoglycemic
The University of Grenada researchers who demonstrated olive leaf’s vasodilatory properties also report it has a beneficial effect on blood sugar levels in animals. In rats with alloxan-induced diabetes, doses of 16 and 32 mg/kg decreased blood glucose values significantly and increased peripheral glucose uptake in a dose-dependent manner.26 Its luteolin and oleanolic acid constituents have also been shown to have an inhibitory effect on postprandial glucose increase in diabetic rats.27
olive leaf properties
Cardiovascular Disease
Olive leaf extract has a beneficial effect on several aspects of cardiovascular disease via its vasodilatory, anti-platelet aggregation, anti-inflammatory, and antioxidant properties.
Animal studies demonstrate OLE given to hypertensive rats at dosages ranging from 100-1,000 mg/kg for 2-6 weeks significantly lowered mean arterial pressure and heart rate.28,29 Another animal study showed OLE given to salt-sensitive, genetically hypertensive rats at 60 mg/kg body weight for six weeks prevented the development of severe hypertension and atherosclerosis and improved insulin resistance.30
The anti-atherosclerotic effect of olive leaf extract was also demonstrated in rabbits on a high-lipid diet. Twenty-four rabbits were assigned to control, high-lipid diet, or high-lipid diet supplemented with hydroxytyrosol-enriched OLE for six weeks. Animals in the high-lipid diet group had higher levels of cholesterol, triglycerides, and LDL cholesterol, as well as a thick layer of lipid disposition in the aortic intima compared to those in the OLE group. These results support olive leaf’s anti-atherosclerotic effect, most likely related to suppression of inflammation.31
In a human clinical trial OLE reduced blood pressure in 40 borderline hypertensive pairs of monozygotic twins. Twins from each pair were assigned to control or two treatment groups receiving either 500 or 1,000 mg OLE daily for eight weeks. Body weight, heart rate, blood pressure, glucose, and lipids were measured at two-week intervals. Blood pressure values decreased within pairs, with an average difference in systolic pressure up to 6 mmHg between the 500-mg OLE group and control group and up to 13 mmHg difference between 500-mg and 1,000-mg groups after six weeks; maximum differences in diastolic blood pressure in the same two groups were 5 mmHg in each. At the end of the study, mean blood pressure remained unchanged for those in the control and 500-mg groups, while those in the 1,000-mg group reported a significant decrease in mean systolic blood pressure (137±10 to 126±6; p<0.01). All subjects reported decreases in cholesterol, with no significant changes in other parameters.32
Another clinical trial (n=30) reported significant decreases in blood pressure in hypertensive patients given 400 mg aqueous OLE four times daily for three months. Full text of the study was unavailable and published in French and actual percentage decrease was not reported in the abstract.33
Olive leaf polyphenols have been shown to inhibit in vitro platelet function in blood obtained from 11 healthy, nonsmoking males. Olive leaf polyphenols (at increasing concentrations of oleuropein) effected a significant dose-dependent suppression of platelet-ATP release and platelet aggregation.34
olive leaf properties
Viral Infections
Researchers have demonstrated olive leaf constituents, particularly elenolic acid and its salt, calcium elenolate, are effective in vitro against many viruses studied, including parainfluenza, Herpes simplex, pseudorabies, polio viruses -1, -2, and -3, rhinoviruses, myxoviruses, coxsackie virus, Varicella zoster, encephalomyocarditis, and two strains of leukemia virus.15 No clinical trials have been conducted on OLE as a therapy for viral infections; given their potent in vitro broad-spectrum antiviral activity and numerous anecdotal reports attesting to OLE’s therapeutic effect, clinical trials are warranted.
olive leaf properties
HIV
Based on the antiviral activity of olive leaf extract15,16 and numerous anecdotal reports from AIDS patients,35 OLE is being widely used to strengthen the immune system, decrease viral load, relieve chronic fatigue, treat Kaposi’s sarcoma and Herpes simplex virus infections, and reduce the side effects of antiretroviral treatment regimens.36 An in vitro study of an olive leaf extract standardized to oleuropein content incubated with HIV-1 infected H9 cells showed a reversal of many HIV-1 associated changes in cellular signaling. Treating HIV-1 infected cells with OLE upregulates expression of apoptosis inhibitor proteins, calcium and protein kinase C pathway signaling, and ornithine decarboxylase ODC1, suppressing cell-to-cell transmission of HIV-1 and acute infection.16
Anecdotal reports of OLE’s therapeutic effect in AIDS patients date back to 1996. Some reports involve its use as a monotherapy, while others report its use in conjunction with naltrexone, an immune modulator. All report significant decreases in viral load, some after taking olive leaf extract for only 2-3 weeks. Some patients report increases in CD4, CD8, and white blood cell counts; others report a change in HIV status from positive to negative on ELISA and Western Blot tests for AIDS.35 These anecdotal reports would require randomized, controlled trials for substantiation.
Colds/Influenza
Anecdotal reports indicate when taken at the onset of cold or flu symptoms, olive leaf extract prevents or shortens the duration of the infection. For viral sore throats, gargling with olive leaf tea may alleviate symptoms, possibly by decreasing inflammation and viral infectivity. In 1977 the effect of olive leaf constituents against influenza A in hamsters was demonstrated. Calcium elenolate administered to infected hamsters as nose drops shortly after influenza A inoculation reduced viral titers of nasal washes and cured infection.37
Bacterial, Protozoan, and Fungal Infections
In vitro research demonstrates the effectiveness of OLE against a wide range of pathogens, including Escherichia coli, Pseudomonas fluorescens, Corynebacterium sp., Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Salmonella typhimurium, Erwinia carotovora, Candida albicans, and Plasmodium falciparum.18 Although clinical trials have not evaluated the therapeutic effect of olive leaf extract against these pathogens, anecdotal reports demonstrate clinical efficacy against some organisms.
Diabetes
In vitro and animal studies demonstrate a hypoglycemic effect for olive leaf extracts. In alloxan-induced diabetic rats, OLE was shown to increase peripheral glucose uptake, raise insulin levels, and decrease blood glucose levels at doses of 16 and 32 mg/kg body weight.26 In diabetic rabbits, oleuropein given at 20 mg/kg body weight for 16 weeks restored blood glucose values to normal and decreased diabetes-associated oxidative stress compared to nondiabetic rabbits.40
Hypothyroidism
Olive leaf extract given to mature male rats in 100-, 250-, and 500-mcg doses increased T3 levels in a dose-dependent manner and significantly reduced circulating thyroid stimulating hormone levels at all doses after 14 days of treatment.41 This animal study suggests a possible use of OLE for hypothyroidism.
Botanical-Drug Interactions
Due to the hypotensive and antiplatelet aggregating properties of olive leaf extract, concomitant use with blood-pressure lowering medications and blood thinners may have a potentiating effect; so caution is advised. Theoretically, olive leaf extract could also have an additive effect when taken in conjunction with antidiabetic medications, although this has not been reported in humans.
Side Effects and Toxicity
Olive leaf properties appear to be quite safe. In animal experiments, researchers observed no toxicity in rats, even at high doses (1g/kg body weight) for seven days.42 In vitro studies on human cell lines found no toxicity at 1 mg/mL of extract.16 Studies have not been conducted on the safety of olive leaf extract in pregnant and lactating women. Olive leaf extracts are best taken with food to avoid gastrointestinal irritation.
Dosage
Oral dosages range from 500-2,000 mg powdered OLE daily. Extracts are usually standardized to 17-20 percent oleuropein.
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References
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