THE GUARDIAN: Thursday, 20 May 2010 02:00 By Chukwuma Muanya
THEY are known for their juices. They are bigger than their relatives – orange, tangerine, lime and lemon. But the seeds are showing promise in the control of non-communicable diseases like diabetes, obesity, infertility and heart diseases, CHUKWUMA MUANYA writes.
CAN increasing the intake of grapefruit juice and seed extract lower blood sugar, fats, heart disease, urinary tract infections, testicular damage and obesity risk?
Nigerian researchers have found that methanol seed extract of grapefruit (Citrus paradise) Macfad lowers blood glucose, lipids and cardiovascular disease risk indices in normal Wistar rats. The study was published in Nigeria Quarterly Journal of Hospital Medicine by Adeneye A. A. of the Department of Pharmacology, Faculty of Basic Medical Sciences, Lagos State University College of Medicine (LASUCOM), Ikeja, Lagos.
Until now, alcoholic decoction of grapefruit seed, which belongs to the plant family Rutaceae is traditionally used for the management of diabetes mellitus and obesity by the natives of South-West Nigeria. Despite its ancestral use, scientific validations of its therapeutic uses in the management of these conditions are lacking.
However, a previous study had suggested that a substance in grapefruit could prove to be the key to fighting obesity and diabetes. The substance, a flavonoid called “naringenin,” is a naturally occurring compound in all citrus fruit, but especially in grapefruit, giving it its characteristic bitter taste.
Grapefruit is a tropical and subtropical citrus tree grown for its fruit which was originally named the forbidden fruit of Barbados. Phytochemical analysis indicates that grapefruit seed extract contains high levels of Vitamin C, Vitamin E and the polyphenolic flavonone glycosides hesperidin, neohesperidin, nariratin and naringin.
These compounds have been shown to be powerful antioxidants individually and collectively. Grapefruit seed extract has therefore since been regarded as one of the most powerful natural antioxidants.
The preliminary study by LASUCOM researchers was undertaken to evaluate blood glucose and lipid lowering effects as well as cardiovascular disease risk factor-reducing effect of Citrus paradisi Macfad (100 per cent methanol seed extract) in male Wistar rats.
The rats were divided into groups I - V, with six rats in each group, were gavaged at the dose levels of 10 ml/kg/day of distilled water, 10 ml/kg of body weight/day of dimethyl sulphoxide (DMSO), 100, 300, and 600 mg/kg of body weight/ day of the extract dissolved in 10 ml/kg DMSO, in that order for 30 days.
On day 31, blood samples obtained were assayed for fasting plasma glucose (FPG), total cholesterol (TC), high density lipoprotein (HDL-c), low density lipoprotein (LDL-c), and very low density lipoprotein (VLDL-c) using standard procedures. HDL-c is termed good cholesterol, while LDL-c is called bad cholesterol.
Cardiovascular disease risk assessing factors such as obesity or body mass index (BMI), atherogenic index (AI), coronary risk index (CRI) were calculated. Results showed significant dose related lowering effects of the extract on FPG, cardiovascular disease risk assessing indices and lipid parameters except HDL-c fraction, which was significantly elevated. The extract also induced significant dose related weight loss in the treated rats in the latter 15 days of their treatment
The researcher concluded: “These results, therefore, lend support to its therapeutic potentials in the management of suspected type 2 diabetic patients.”
Nigeria researchers have also demonstrated the effectiveness of grapefruit seeds in treating urinary tract infections.
The study was published in the Journal of Alternative and Complementary Medicine by O. A. Oyelami, E. A. Agbakwuru, L. A. Adeyemi, and G. B. Adedeji of the Obafemi Awolowo University, Ile Ife, Osun State.
According to the study, three middle-aged males and one female were diagnosed as having urinary tract infections (UTIs) between 2001 and 2003 in the Wesley Guild Hospital, Ilesa, a unit of Obafemi Awolowo University Teaching Hospitals Complex, Ile Ife. Of the four patients, only the female was asymptomatic. The three males had Pseudomonas aeruginosa, Klebsiella species, and Staphylococcus aureus, respectively, in their urine samples, while the female had Escherichia coli.
All four patients were treated with grapefruit seeds orally for two weeks and they all responded satisfactorily to the treatment except the man with P. aeruginosa isolate. However, the initial profuse growth of Pseudomonas isolate in the patient that was resistant to gentamicin, tarivid, and augmentin (conventional antibiotics) later subsided to mild growth with reversal of the antibiotic resistance pattern after two weeks' treatment with grapefruit seeds.
The researchers concluded: “These preliminary data thus suggest an antibacterial characteristic of dried or fresh grapefruit seeds when taken at a dosage of five to six seeds every eight hours, that is comparable to that of proven antibacterial drugs.”
According to a study by Roberts Research Institute at the University of Western Ontario, Canada, naringenin, in concentrations far above levels found naturally, makes the liver burn fat instead of storing it.
The study used two groups of mice that were fed a typical western high-fat diet, a diet known to induce symptoms of metabolic syndrome. One group’s diet, however, was treated with naringenin.
The researchers found that the naringenin corrected elevations in tryclycerides and cholesterol, prevented the onset of insulin resistance, and otherwise normalised the metabolism of insulin.
Also, the naringenin completely reprogrammed the livers of the mice so that excess fat was burned rather than stored. The “marked obesity that develops in these mice was completely prevented by naringenin,” said study leader, Murray Huff.
Huff added: “What was unique about the study was that the effects were independent of caloric intake, meaning the mice ate exactly the same amount of food and the same amount of fat. There was no suppression of appetite or decreased food intake, which are often the basis of strategies to reduce weight gain and its metabolic consequences.”
The famous grapefruit diet apparently headed in the right direction, but the levels of naringenin found in grapefruit were not high enough to produce the results obtained in the study. People wanting to try naringenin for obesity and diabetes benefits will have to wait until a concentrated supplement is developed. The study team is trying to develop a naringenin treatment for humans.
Nigerian researchers have also evaluation the influence of grapefruit seed extract on doxorubicin-induced testicular oxidative stress and impaired sperm formation (spermatogenesis).
Several studies have suggested that the therapeutic value of Doxorubicin (DOX) as anticancer antibiotic is limited by its organotoxicity. It has been shown that free radicals are involved in doxorubicin-induced toxicity. Doxorubicin causes the generation of free radicals and the induction of oxidative stress, associated with cellular injury. Because of the great importance of DOX in cancer therapy, researchers have expended great efforts trying to prevent or attenuate the side effects of DOX administration. There has, however, been only a little success in this regard.
The study published in Asian Journal of Scientific Residency investigated the ameliorating role of antioxidant-rich ethanolic seed extract of Citrus paradisi (CP) on DOX-induced testicular oxidative stress and impaired sperm parameters. Three experimental groups of Wistar rats were used; CP-alone group that received orally CP 10 mg kg-1 b.wt. daily for 14 days followed by intraperitoneal (i.p.) Normal Saline (NS) 2.5 mg kg-1 b.wt. DOX-alone group that had ip DOX 10 mg kg-1 b.wt. as a single dose. CP plus DOX-group that were similarly given DOX, but also had oral CP 10 mg kg-1 b.wt. pretreatment for 14 days. There was also a corresponding control group. The animals were autopsied eight weeks after DOX or NS injections.
Results showed that DOX-induced reduction in sperm motility and epididymal sperm concentrations as well as increase in total abnormal sperm rates were all normalised in the group pretreated with CP. Pretreatment with CP ameliorated the testicular content of Glutathione (GSH) and Auperoxide Dismutase (SOD), Catalase (CAT) and Glutathione Peroxidase (GPx) activities. Similarly, CP treatment attenuated the DOX-induced increase in testicular lipid peroxidation reflected by malondialdehyde (MDA) levels. These data indicate that CP protects the rat testis against DOX-induced oxidative stress and deranged sperm characteristics.
The study is titled: “An evaluation of influence of Citrus paradisi seed extract on doxorubicin-induced testicular oxidative stress and impaired spermatogenesis.”
Indeed, DOX is one of the most potent broad-spectrum antitumor anthracycline antibiotics, widely used to treat a variety of cancers. On the other hand, the clinical use of DOX is restricted because of its serious toxicity. The cytotoxic effect of DOX on malignant cells and its toxic effects on various organs (heart, liver, lung, kidney, blood cells and testis) are thought to be related to the nucleotide base intercalation and the cell membrane lipid-binding activities of DOX. So, the present work was designed to investigate the potential testiculoprotective effect of seed extract of CP as antioxidant-rich nutraceutical.
It is well documented that, long-term treatment by DOX causes irreversible, severe male infertility. The mechanisms involved in such toxicity have been documented by many investigators. The involvement of oxygen free radical, superoxide radical and oxidative stress have been strongly accepted as crucial factors in the pathogenesis of DOX-induced cytotoxicity.
The results of the present study indicate that administration of DOX in a dose of 10 mg kg-1 b.wt. i.p. decreased the absolute testicular weights, testicular weight b.wt.-1 ratio and testicular volumes of rats. This agrees with the findings by many investigators, who provide well documented evidences of testicular morphologic impairment following DOX challenge in animal models.
Assessment of lipid peroxidation, GSH content as well as SOD, CAT, GPx and other antioxidant enzyme activities in biological tissue have been always used as markers for tissue injury and oxidative stress.
The researchers wrote: “In our study, testiculotoxicity and oxidative damage induced by DOX administration are also manifested by a significant increase in the activities of antioxidant enzymes, SOD, CAT, GPx and the testicular content of MDA and a significant decease of GSH. More interestingly, pretreatment of animals with seed extract of CP markedly modulates the oxidative damage induced by DOX administration.
“DOX exerts its antitumor effects as well as other organ toxicity by generation of free radicals and reactive oxygen species. This increased oxidative stress damages the sperm membranes, proteins and deoxyribonucleic acid (DNA). This explains the reduced sperm concentration, sperm motility and sperm progressivity, with accompanying increase in abnormal sperm rates as seen in DOX alone group of rats. Pretreatment with CP containing phenolics and other potent antioxidants resulted in a remarkable normalisation of these parameters.
“Attempts have been made to explain the mechanisms of antioxidant effect of phenolics. These include the binding of metal ions, scavenging of reactive oxygen species (ROS); reactive nitrogen species (RNS); or their precursors, up-regulation of endogenous antioxidant enzymes, or the repair of oxidative damage to biomolecules.
“Clearly, present study proves the beneficial effect of the CP seed extract in protecting animals against DOX-induced testicular oxidative damage. This protecting potential of CP could be at least in part due to its free radicals scavenging capability. The fact that CP seed extract exerts profound ameliorating effects on doxorubicin-induced testicular toxicity in laboratory animals warrants a further approach for its testiculoprotective potential during DOX chemotherapy in clinical practice.”