It is generally agreed that the oil palm (
This review intends to provide information on the documented medicinal uses of oil palm including laboratory studies on the plant. Earlier review by Obahiagbon (2012) was limited to an aspect of the plant. This present review covers both the traditional as well as the scientific uses of the oil. The review however does not extend to the core botanical aspect of the plant. The literatures used for this review were obtained from Medline and Google Scholar search carried out from September, 2013 to April, 2014.
The traditional theory about the uses of oil palm in many parts of Nigeria is that products from oil palm are antidotes that can be used in the treatment of many ailments especially gastrointestinal disorders and poisons.
The African oil palm (
Ekwenye and Ijeomah (2005) reported that traditionally, palm oil has been used in the South Eastern Nigeria for the treatment of various diseases and skin infections. This was confirmed by their experiment carried out at the Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria using five microorganisms namely;
Palm oil provides a rich source of beta-carotene and vitamin E, namely tocopherols and tocotrienols which are recognized nutritional anti-oxidants that act as scavengers of the oxygen atom or free radicals (Chong and Ng, 1991; Ekwenye and Ijeomah, 2005; Goh et al., 1985). The oxygen atom or free radicals can arise during the body’s normal oxidative metabolism or from the action of toxic pollutants that contaminate our food and have been implicated in ageing, heart disease and cancer (Ekwenye and Ijeomah, 2005).
Research has shown that consumption of red palm oil significantly enhanced vitamin A levels in humans, and it is beneficial in preventing vitamin A deficiency (Manorama and Rukmini, 1991; Roo, 2000; Solomons, 1998) and it is used for combating vitamin A deficiency in developing countries (Rukmini, 1994). Additionally, some workers have advised that nursing mothers should take red palm oil as supplement with their food in order to prevent vitamin A deficiency (Lietz et al., 2000). Vitamin A deficiency may lead to blindness, skin disease and weakened immune function. The vitamin A content of the red palm oil plays important roles in growth, development and in visual process (Edem, 2009). The human body is able to convert provitamin-A carotenoids (alpha- and beta-carotene) when there is a deficiency, hence it is safer to supplement with carotenes than consuming vitamin A (retinoids) directly. Excessive consumption of retinoids may lead to toxicity with symptoms ranging from mild, such as headache, nausea and dry, itchy skin to severe, such as liver damage (Solomons, 1998).
Tocotrienols are members of the vitamin E family. In the body, vitamin E acts as an anti-oxidant that protects lipid from peroxidation and help quench free radicals. However, there is a difference in anti-oxidant potency between tocotrienol and its sibling tocopherol. Tocotrienol has been shown to be 40 to 60 times more potent than tocopherol as an anti-oxidant. Palm oil is the only vegetable oil available on the world market that naturally contains tocotrienols (Cottrell, 1991; Ebong et al., 1999; Elson, 1992; Van Rooyen et al., 2008) and is the richest natural source of beta - carotene (500 - 700 mg/l) which is responsible for the characteristic colour of the oil. Similar to the tocopherols, tocotrienols consist of 4 members: alpha, beta, gamma, and delta isomers (Serbinova, 1991). Alpha toco pherols and gamma tocotrienols have anti-oxidative effects on lipid peroxidation, in the presence of a xenobiotic metabolizing enzyme that induces lipid peroxidation (Zuzana et al., 2005). The vitamin E, particularly the tocotrienol present in palm oil can suppress the synthesis of cholesterol in the liver (Mcintosh et al., 1991; Qureshi et al., 1991; Qureshi et al., 1980). Some scientists in South Africa have been able to establish that oxidative stress plays a role in inflammatory and chronic disease such as HIV/AIDS and TB and contribute significantly to depletion of immune factors, micronutrients and progression of disease and that red palm oil could potentially retard the process because of rich anti-oxidants (Oguntibeju et al., 2009).
Studies have indicated that the potential mechanism of action for the improvement in glucose metabolism with
Peer review journals have documented palm tocotrienol complex’s promising hypocholesterolemic properties (Qureshi et al., 1991, 1995). Also, the daily consumption of tocotrienols-enriched fraction of palm oil (200 mg palmvitee capsule) can result in a significant reduction of serum cholesterol, Low Density Lipoprotein cholesterol, APOB, thromboxane, platelet factor 4 and glucose of hyper cholesterolemic subjects within four weeks of administration (Qureshi et al., 1991; Packer, 1992; Song and DeBose-Boyd, 2006). A number of human feeding studies reported that palm oil diets showed a reduction of blood cholesterol values ranging from 7 to 38% (Mattson and Grundy, 1985; Bonanome and Grundy, 1988). A comparative study in young Australian adults showed that the total blood cholesterol, triglycerides and High Density Lipoprotein (HDL) - cholesterol levels of those fed on palm oil (palm olein) and olive oil were lower than those fed on the usual Australian diet (Choudhury et al., 1995). A number of studies have also shown that palm oil increased HDL cholesterol and Apo A-1 levels (Sundram et al., 1992; Truswell et al., 1992). Other studies have also shown the beneficial effects of palm oil on the cholesterol level of the body (Marzuki et al., 1991; Ng et al., 1992, 1991; Zhang et al., 1997). The position of the saturated and unsaturated fatty acid chains in a triglyceride backbone of palm oil molecule determines whether the fat will elevate cholesterol level in the blood (Kritchevsky, 1988, 1996). High blood pressure or hypertension is one of the major risk factors of cardiovascular diseases and strokes. In a human clinical trial, patients supplemented with palm tocotrienol complex for two months resulted in significant reduction in aortic systolic blood pressure (Rasool et al., 2006). In an earlier review by Obahiagbon (2012), he pointed out that Tocotrienol-rich Fraction (TRF) of palm oil exhibited cardio-protective ability in animal trials (Das et al., 2008). The cardio-protective effects produced by the isomers of tocotrienol were of the order of: γ > α >δ. The inhibition of normal cellular gene, C-Src activation and proteosome stabilization were found to be reasons behind the cardio-protective properties of TRF (Das et al., 2008). Feeding experiments using various animal models have highlighted that red palm oil is beneficial to health by reducing oxidative stress (Ebong et al., 1999). Many studies have demonstrated the protective effects of red palm oil in an ischemia/reperfusion model of oxidative stress (Bester et al., 2006; Engelbrecht et al., 2006; Esterhuyse et al., 2005)
Palm oil has been shown to possess anti-clotting effect and it prevents the formation of thrombus in the blood vessels (Oguntibeju et al, 2010). A human study (Kooyenga et al., 1997) showed that tocotrienol (from palm oil) supplementation can reduce stenosis of patients with carotid atherosclerosis. Vitamin E in palm oil has been linked with inhibition of platelets from sticking to each other. Other reports showed that palm oil diets increases the production of prostacyclin or thromboxane (Ng et al., 1992; Sundram et al., 1990). Thus scientific evidence indicates that the palm oil diet is anti-thrombotic. Studies in animals confirmed that palm oil do not promote the formation of plaques in the arteries. A study was conducted on rabbits to test the effect of palm oil on atherosclerosis. After feeding the rabbits for one and a half years, palm oil and sunflower oil diets caused the lowest degree of atherosclerosis in comparison with fish oil, linseed oil and olive oil. Similarly, the effects of palm oil was also compared with other types of plants derived oils and at the end of the 14-month feeding period, coconut oil fed rabbits had the most atherosclerosis lesions, while in palm oil-fed rabbits; the number of lesions was no different from that with the other oils (Oguntibeju et al., 2010).
The anti-bacterial activity of this plant extract against different micro-organisms and anti-oxidant activity have already been reported (a; Sasidharan et al., 2009). Moreover, Chong together with Sasidharan and some others (Chong et al., 2008) described the potential of
Several studies have been conducted to confirm the nontoxicity of different parts of
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Conservation and preservation
Several literature have reported the use of palm oil in preservation purposes from various parasites including cowpea weevil,
Studies have shown that tocotrienols fractions of palm oil were able to induce an inhibitory action on the human breast cancer cells, whereas the alpha-tocopherols were not able (Nesaretnam et al., 2004, 2008; McIntyre et al., 2000). Palm oil has been reported to be with wide range of protective properties against disease, aging as well as being modulators for cellular processes / functions where photo oxidative processes predominate by acting as scavengers of oxygen and peroxyl radicals (Van Rooyen et al., 2008). It has been shown that fresh palm oil has no adverse effect on body weight and morphology of body tissues, lowers the level of serum lipids and inhibits tumour growth (Kritchevsky, 2000), enhances intestinal uptake of protein and the metabolism of sulphur-amino acids and promotes reproductive capacity (Ebong et al., 1999). Several researches have been conducted on cancer with the view to finding a lasting solution to the disease. Sundram and his colleagues (1989) were able to conduct an experiment to show that RPO significantly reduce tumor incidence in some experimental rats compared with the control groups. RPO, when compared with saturated fats and oils, may help fight cancer, especially breast cancer (Nesaretnam, et al., 1992). This may be due to tocotrienols (Nesaretnam, 1998: Elson, 1992) or other phytonutrients (Guthrie et al., 1997) present in palm oil. Indeed, Professors K. K. Carroll of the Centre for Human Nutrition at the University of Western Ontario and David Kritchevsky of the Wistar Institute recently concluded that evidence from animal and in vitro studies indicate that tocotrienols of palm oil are effective anti-cancer agents and provide adequate justification for clinical trials in human cancer patients (Nesaretnam, 1998). This oil has equally been shown to reduce the incidence of azoxymethane-induced aberrant crypt foci in rats and may therefore have a beneficial effect in reducing the incidence of colon cancer (Boateng et al., 2006).
The TRF of palm oil has been shown by Wu et al. (2008) to possess anti-inflammatory activities in a study involving the injection of lipopolysaccharide-induced inflammatory response. The mediators of cellular inflammation such as nitric oxide (NO), prostaglandin E2, and transcription of pro inflammatory cytokines were significantly reduced. The following were equally blocked; inducible NO, cyclooxygenase 2 expression and NF-kappa B expression.
A review of the health benefits of the leaf extracts of oil palm has been provided extensively by Mohammed (2014), however, the present review is to provide additional information.
Methanolic oil palm (
Sasidharan et al. (2012) reported in their article that in traditional medicine, the leaf of
The polyphenol-rich leaf extract of
Sasidharan et al. (2009) demonstrated the hepatoprotective effects of E. guineensis against paracetamol induced liver damage by looking at the histopathology of mice liver. This was subsequently followed up by a serum analysis in which the same authors (Sasidharan et al., 2012), reported that the methanol extract of the leaves of the plant also offer hepatoprotection against paracetamol induced-liver damage in mice by reducing serum markers of liver injury such aspartate aminotransferase, alanine aminotransferase, and billirubin.
Kalman et al. (2013) reported that the ethanol-derived leaf extract of
Oil palm ethanolic leaf extract (OPLE) at 150 mg/kg body weight showed significant pro-inflammatory activity with enhanced 46% late phase inflammation recovery effects. While at high dose, inflammation was significantly suppressed prior to the sixth hour compared to other groups, and did not require much inflammation suppression between the 18th and 48th hour. OPLE 150 mg/kg decreased lymphocyte counts, but was not as severely as dexamethasone treatment. This result suggests that OPLE extract possess strong in-vivo inflammatory-regulatory effects (Anyanji et al., 2013).
The main problem for the use of oil palm leaf extract as food in its natural form is its high content of insoluble fibre. The OPLE effectively reduced blood glucose and lipid oxidation in Type II diabetic humans and diabetes-induced rodents. The optimum dose in animal studies is equivalent to consuming 5 cups of 1% palm leaf extract for diabetic humans, to prevent liver and kidney damage (Mohammed, 2014).
The oil palm sap or wine can be descried as the exudates that flow when the palm is tapped (Obahiagbon, 2012). The sap of this plant is also used as a laxative and the partially fermented palm wine is administered to nursing mothers to improve lactation (Sasidharan et al., 2012). The sap has also been recorded to be involved in malaria, jaundice and measles treatment. Just like the sap of other palms like
A root decoction is used in Nigeria for headaches. The pulverized roots are added to drinks for gonorrhea, menorrhagia and as a cure for bronchitis (Sasidharan et al., 2012; Irvin, 1985). Chong et al. (2009) demonstrated the in vitro anti-microbial activity and fungitoxicity of syringic acid, caffeic acid and 4-hydroxybenzoic acid which are found in oil palm root. They also showed that of the three substances, syringic acid was the most fungitoxic against
Oil palm (