Oleander is a drought-tolerant small-sized evergreen plant. This plant name is enlisted under the Chinese traditional medicinal system. Mediterranean countries are the native place of this plant. This wild plant is found in subtropical Asian countries (Indo-Pak subcontinent area), the southern United States and other warmth climatic regions. Scientifically known as Nerium oleander L., which belongs to the Apocynaceae family.[1]
In general, the toxic potential of the plant is well-established. But in our folk medicinal practice, Oleander is used to treat different disease conditions, including skin disorders, eczema, ringworm infections, malaria, epilepsy, eyesight disturbance, gastrointestinal ailments, and cancer. Oleander leaves and bark act as a cardiac tonic, diuretic, anti-emetics and antibacterial. However, the application of this plant and plant parts have confusion due to its toxic property. It is evidential that the toxic effect of this plant is significant in both animals and humans. Animals had cardiac dysfunction followed with death after toxic exposure to the Oleander plant. However, death is very rare in human after exposure to the Oleander plant. [2]
The two most important cardiostimulatory phytochemicals present in Oleander plant are neriin, and oleandrin. Neriin acts as a cardiac glycoside, whereas oleandrin is an alkaloid. The glycoside composition of Oleander leaves contains gentiobiosyl-beaumontoside, gentiobiosyloleandrin, and gentiobiosylnerigoside. This plant also a rich source of vitamins, minerals, and anti-oxidants. α-tocopherol, Vitamin C are two important micronutrients present in this plant. Other phytochemicals include cardenolides, adyregenin, triterpenoids, ursolic acid, tannins, glucose, a resin, and essential oil, etc. adigoside, oleandrine, and odorosides, are glycosides present in seeds of this plant and corteneroside, nerioside, and rosaginoside are certain glucosides composition of bark. The roots contain steroids. [3]
Oleander plant is poisonous due to its chemical composition of this plant causes cardiac dysfunction. Certain toxic cardiac glycosides, such as oleandrin and neriine inhibits Na+, K+-ATPase and provide poisoning effect. In some cases, this plant is also used for suicidal or murderous intention. Domestic as well as wild animals like cattle, horses, sheep, goats, donkeys, camels, cats, dogs, monkeys, budgerigars, geese, ducks, turkeys, toed sloths and bears have affected with accidental and/or experimental N. oleander toxicities.
Hematological changes
An animal study reported oral intake of oleander leaves extract can increase RBCs, Hb, Hct and MCV levels in blood.
Increase of Erythropoietin
There is a significant enhancement of red blood cell production that occurs in the bone marrow. Oleander leaves may regulate the Erythropoietin hormonal secretion by acting on the liver and kidney. In general, Erythropoietin produces in liver and kidney tissue.
But this benefit converts to toxic effect when high dose exposure leads to increase expression of Erythropoietin, as Oleander directly or indirectly acts on liver and kidney tissue. Excess release of Erythropoietin makes the blood thick by increasing the production of RBC. This increases the chances of a blood clot and subsequently causes heart attack and stroke.
Increase of HCT
Oleander enhances the production of erythropoietin in the kidneys subsequently increase the Hct levels in the blood. There are many disease condition associated with HCT enhancement which includes Dengue Shock Syndrome, polycythemia, myeloproliferative disorders, COPD chronic obstructive pulmonary diseases, and hypoxia. It has also found that Hct enhancement leads to raising of MCV level, which consequently reduces the plasma level in the blood. This physiological condition is termed as macrocytosis, which causes a liver problem, folate deficiency.
Induce oxidative stress
Administration of Oleander leaf extract causes neutrophil count, which can cause an increased rate of free radical formation. Oleander leaf extract causes liver damage due to the increase in oxidative stress. Oleander leaf extract mediates pro-inflammatory cytokinine release may cause inflammation. [2]
There are very limited dosage forms available in the market due to the toxic property of Oleander.
Capslim: This herbal medicine contains Oleander seed powder. This medicine is available in Mexico as a natural anti-obesity treatment. [4]
Oleander flower extract: This is a natural remedy, study research has proven its anticonvulsant activity. [5]
The active phytochemical Oleandrine has different pharmacological actions, such as anti-inflammatory, emollient, induce apoptosis and anti-tumor. The Oleander flowers have cardiotonic and anti-nociceptive functioning. The leaves and seeds of Oleander have a poisonous effect by inducing nausea, vomiting, bradycardia, mental confusion and potassium imbalance in blood lead to mortality.
Both, flower and leave extract have anti-nociceptive activity, which can cause pain relief by calming nervous stimulation. However, for therapeutic purposes, only flower extract is used. Although the leaves extract has a potent antinociceptive effect, but it induces gastric ulcer in experimental mice. Therefore, the selection of oleander dosage form is tough.
The phytochemical compositions of flowers can reduce inflammation and the Anti-inflammatory is comparable with the drug indomethacin (conventional anti-inflammatory medicine).
Oleander plants have both antibacterial and antifungal property. Herbal researchers found that leaves and roots of Nerium oleander were effective against Aspergillus niger, Bacillus pumilus, B.subtilis, Escherichia coli, and Staphylococcus aureus.
Fresh oleander leaves extract has CNS depressant activity, which obstructs locomotor activity. This plant extract also provides pain relief due to its analgesic effect. The research study also assessed this by thermal test. [3]
Oleandrin, the principal active ingredient present in the oleander plant has a diuretic effect.
Oleander containing oleandrin and neriodin both have cardiac functioning stimulating effect. An animal study reported that odorin has a similar type of effect as a digitalis group of cardiotonic, whereas neriodin provides double cardiac stimulating action than digitoxin. [3]
oleandrin and oleandrigenin are two active ingredients of Oleander have Antitumor activity effective against prostate cancer cell line. Anvirzel and oleandrin can cause human cancer cell death. Clinical studies had conducted on oleander aqueous extract reported that this herb acts as an anticancer agent. The bioactive compounds Oleandrin and oleandrigenin have anticancerous properties. Anvirzel is one of the poisonous substance present in this plant can induce apoptosis, which leads to cancer cell death. [3]
There are many new phytochemicals identified in this plant. Researchers reported some of these phytochemicals obtained from Oleander leaves lead to CNS depressant activity. [3]
Oleander plant is historically considered as a poisonous plant. The active composition of oleandrin and oleandrigenin have cardiac glycoside property but a narrow therapeutic index. Therefore, exceeding dose can cause severe morbidity and even mortality. [6]