The olive leaf (Olea europea) has been widely used by the Greeks and Romans since antiquity. In the early 1990s olive leaf extract was introduced as dietary supplement for its antiviral and antibacterial activities.
Calcium elenolate (CE) a hydrolysed synthetic product of oleuropein, was extensively studied by the pharmaceutical giant Upjohn Co. in the late 60s. CE was shown to have profound antiviral activities.
However, in-vivo CE was found to quickly bind to plasma proteins, negating its activity. The research was abandoned.
Chemistry
The pharmacologically active constituents in olive leaves are secoridoids, such as: oleuropein, oleuroside, ligstroside. Other ingredients include flavonoids, apigenin, caffeic acids and triterpenes. Oleuropein, a bitter glucoside found in highest concentrations in the leaves, has been well researched:
Pharmacological properties / Clinical applications
Antihypertensive. Oleuropein possesses a vasodilator effect. Moreover, a recent study has found that the aqueous extract of olive leaves inhibited Angiotensin converting enzyme (ACE), an enzyme that converts angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor. Antithrombosis. The phenolic compound 3,4-di-hydrophenyl ethanol inhibited aggregation of platelet and production of thromboxane A2 (a stimulator of platelet aggregation with vasoconstrictor activity).
Prevention of development of atherosclerotic lesions. The secoridoid and phenolic compounds were found to protect vascular endothelium cells from damage.
Antioxidant activity. Caffeic acid and oleuropein were found to inhibit iron toxicity in rat hepatocytes by their antioxidant activity through the scavenging of superoxide radical.
Hypoglycemic effect. Oleuropein has a hypoglycemic effect possibly due to potentiation of glucose-induced insulin release and/or increased peripheral glucose uptake.
Antimicrobial Activity
1.) Antibacterial. Oleuropein has been shown to inhibit growth and the production of enterotoxin B by Staphylococcus. Oleuropein also inhibits the growth of Bacillus cereus, E. coli, pseudomar, Bacillus subtilis, etc.
2.) Antiviral. Olive leaf extract (calcium elenolate) eliminates the viruses by interfering with certain amino acid production processes. The interference stops the virus from shedding, budding, or assembling at the cell membrane. Laboratory tests suggest that the compound has the ability to penetrate infected host cells and irreversibly inhibit viral replication. Oleuropein possesses antiviral activity against a number of viruses including parainfluenza 3, herpes, influenza A, polio 1,2, and 3, etc.
References
i. Furneri PM, Marino A, Saija A, Uccella N, Bisignano G. “In vitro antimycoplasmal activity of oleuropein.”
Int J Antimicrob Agents. 2002 Oct; 20(4): 293-6.
ii. Ma SC, He ZD, Deng XL, But PP, Ooi VE, Xu HX, Lee SH, Lee SF. “In vitro evaluation of secoiridoid glucosides from the fruits of Ligustrum lucidum as antiviral agents.” Chem Pharm Bull (Tokyo). 2001 Nov; 49(11): 1471-3.
iii. Bisignano G, Tomaino A, Lo Cascio R, Crisafi G, Uccella N, Saija A. “On the in-vitro antimicrobial activity of oleuropein and hydroxytyrosol.” J Pharm Pharmacol. 1999 Aug; 51(8): 971-4.
iv. Aziz NH, Farag SE, Mousa LA, Abo-Zaid MA. “Comparative antibacterial and antifungal effects of some phenolic compounds.” Microbios. 1998; 93(374): 43-54.
v. Tassou CC, Nychas GJ. “Inhibition of Salmonella enteritidis by oleuropein in broth and in a model food system.” Lett Appl Microbiol. 1995 Feb; 20(2): 120-4.
vi. Tranter HS, Tassou SC, Nychas GJ. “The effect of the olive phenolic compound, oleuropein, on growth and enterotoxin B production by Staphylococcus aureus.” J Appl Bacteriol. 1993 Mar; 74(3): 253-9.
vii. Tassou CC, Nychas GJ, Board RG. “Effect of phenolic compounds and oleuropein on the germination of Bacillus cereus T spores.” Biotechnol Appl Biochem. 1991 Apr; 13(2): 231-7.
viii. Fleming HP, Walter WM Jr, Etchells JL. “Antimicrobial properties of oleuropein and products of its hydrolysis from green olives.” Appl Microbiol. 1973 Nov; 26(5): 777-82.
ix. Gonzalez M, Zarzuelo A, Gamez MJ, Utrilla MP, Jimenez J, Osuna I. “Hypoglycemic activity of olive leaf.” Planta Med 1992 Dec; 58(6): 513-5.
x. Cherif S, Rahal N, Haouala M, Hizaoui B, Dargouth F, Gueddiche M, Kallel Z, Balansard G, Boukef K. “A clinical trial of a titrated Olea extract in the treatment of essential arterial hypertension.” J Pharm Belg 1996 Mar-Apr; 51(2): 69-71.
xi. Zarzuelo A, Duarte J, Jimenez J, Gonzalez M, Utrilla MP. “Vasodilator effect of olive leaf.” Planta Med 1991 Oct; 57(5): 417-9.
xii. Fehri B, Aiache JM, Memmi A, Korbi S, Yacoubi MT, Mrad S, Lamaison JL. “Hypotension, hypoglycemia and hypouricemia recorded after repeated administration of aqueous leaf extract of Olea europaea L.” J Pharm Belg 1994 Mar-Apr; 49(2): 101-8.
