Olive leaf (Olea europaea L.)
Traditional Indications
Olive oil has been taken orally to treat hypertension and agitation, as a laxative and vermicide in the United States. Boiled extract of fresh or dried leaves is taken orally to treat asthma and hypertension and to induce diuresis. Infusion of leaves are taken orally to reduce fever. O. europaea leaf preparations are used as a common remedy for gout in Mediterranean folk medicine. Leaves of O. europaea are used in Tunisian folk medicine as a remedy for many inflammation types and bacterial infections such as gingivitis, otitis, icterus, and cough. Fruits and leaves of O. europaea are used to treat haemorrhoids and rheumatism, and as vasodilator in vascular disorders. Infusions of leaves are used as ointment to treat eye infections or as mouthwash to relieve sore throat. Hot water extract of the fresh leaves of O. europaea is taken orally to treat hypertension and to induce diuresis in Algeria, Brazil and Palestine a decoction of leaves is used in Morocco to treat hypertension and diabetes. Olive oil is mixed with lemon juice and is used to treat gallstones (1).
Pharmacognosy
The plant materials and isolated components have shown a wide spectrum of in vitro and in vivo pharmacological activities like antidiabetic, anticonvulsant, antioxidant, anti-inflammatory, immunomodulatory, analgesic, antimicrobial, antiviral, antihypertensive, anticancer, antihyperglycemic, antinociceptive, gastroprotective, and wound healing activities (1). Olive leaves are rich in polyphenolic compounds that are known to have antioxidant, antimicrobial, and anti-inflammatory activities. The phytochemical oleuropein is responsible for the major antiinflammatory effects of olive leaf extract (2).
The antimicrobial properties of oleanolic and maslinic acid have been known for years. These acids present in olives are not only harmless to the cells in our body, but also, bacteria are not resistant to them. Olive polyphenols could contribute in inhibiting the growth of Helicobacter pylori and that of some foodborne pathogens, such as Escherichia coli, Listeria monocytogenes and Salmonella enteriditis oleanolic and maslinic acid have shown antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) (3, 4).
In addition to ACE2 protein, cell surface heat shock protein A5 (HSPA5) act as another receptor that assists SARS-CoV-2 entry into host cells. HSPA5 is also called glucose-regulated protein 78 (GRP78). GRP78 is one member of the heat shock protein family of chaperone proteins. GRP78 is a host auxiliary factor for SARS-CoV-2 and GRP78 depleting antibody blocks viral entry and infection (5). GRP78 forms a complex with SARS-CoV-2 S protein and host receptor ACE2 and is a potential therapeutic target to combat SARS-CoV-2 (6). The bioactive phytochemical, hydroxytyrosol, in olive leaf extract shows good binding affinity to the GRP78 SBDβ in silico.
1. Hashmi MA, Khan A, Hanif M, Farooq U, Perveen S. Traditional Uses, Phytochemistry, and Pharmacology of Olea europaea (Olive). Evidence-based complementary and alternative medicine : eCAM. 2015;2015:541591.
2. Qabaha K, Al-Rimawi F, Qasem A, Naser SA. Oleuropein Is Responsible for the Major Anti-Inflammatory Effects of Olive Leaf Extract. J Med Food. 2018;21(3):302-5.
3. Blanco-Cabra N, Vega-Granados K, Moya-Andérico L, Vukomanovic M, Parra A, Álvarez de Cienfuegos L, et al. Novel Oleanolic and Maslinic Acid Derivatives as a Promising Treatment against Bacterial Biofilm in Nosocomial Infections: An in Vitro and in Vivo Study. ACS Infectious Diseases. 2019;5(9):1581-9.
4. Nazzaro F, Fratianni F, Cozzolino R, Martignetti A, Malorni L, De Feo V, et al. Antibacterial Activity of Three Extra Virgin Olive Oils of the Campania Region, Southern Italy, Related to Their Polyphenol Content and Composition. Microorganisms. 2019;7(9):321.
5. Carlos AJ, Ha DP, Yeh DW, Van Krieken R, Tseng CC, Zhang P, et al. The chaperone GRP78 is a host auxiliary factor for SARS-CoV-2 and GRP78 depleting antibody blocks viral entry and infection. The Journal of biological chemistry. 2021;296:100759.
6. Carlos AJ, Ha DP, Yeh D-W, Van Krieken R, Tseng C-C, Zhang P, et al. The chaperone GRP78 is a host auxiliary factor for SARS-CoV-2 and GRP78 depleting antibody blocks viral entry and infection. Journal of Biological Chemistry. 2021;296.