Onion protects against testicular, kidney damage, diabetes, stroke, AIDS, others

Botanically called Allium cepa, onion belongs to the plant family Liliaceae, which consists of over 250 genera and 3700 species.

Until now, Allium species such as onion has attracted particular attention of modern medicine because of its widespread health use around the world, and the cherished belief that it helps in maintaining good health, warding off illnesses and providing vigour.

Phtochemical analysis shows that onion is rich in flavonoids such as quercetin and sulphur compounds, such as cysteine and allyl propyl disulphide. The bulb contains Kampferol, β- sitosterol, ferulic acid, myritic acid, prostaglandins and several compounds of secondary metabolism that have perceived benefits to human health.

Several studies have shown that these compounds possess antidiabetic, antibiotic, hypocholesterolaemic, fibrinolytic, antioxidant, antihypertensive, antithrombotic, hypoglycemic, antihyperlipidemic and other various beneficial biological effects.

Meanwhile, Nigerian researchers have in a new study, using aqueous extracts of onion (Allium cepa) bulbs, demonstrated the ability of plant extracts rich in antioxidative principles to reverse testicular damage associated with Artesunate toxicity in endemic malaria zones of the country.

In traditional medicine in Eastern Nigeria, the bulb extract had reportedly been used to alleviate and improve low sperm count in male human subjects. The extract has also been shown in traditional medicine to improve male erectile function and ameliorate groin and testicular pains associated with prostate inflammation.

Nigerian researchers from the Department of Biochemistry, Faculty of Basic Medical Sciences, University of Calabar, and Department of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Abuja, concluded: “… It is concluded in this study that populations living in endemic malaria zones be encouraged to regularly take water extracts of red onions, as well as eat them raw. Further researches are on-going to evaluate the effect of Allium cepa extract on microbial load in the cervix region in female reproductive area and also on sex hormone regulation.”

The researchers added: “Animals were humanely euthanized, testes collected, homogenized and used for sperm count, motility and oxidative stress evaluation.

“Artesunate mediated testicular damage caused a significant reduction in sperm count compared to normal control. Extract treatment of groups 1, 2 and 3 caused a dose-dependent reversal of sperm count, motility and morphology after seven weeks. Treatment with the highest dose (300 mg/kg) of the extract reversed testicular oxidative induced lesions as shown by levels of enzymatic antioxidants; CAT, SOD and GPx and non-enzymatic antioxidants; MDA and GSH relative to normal control, respectively.

“These results demonstrated the potential beneficial effects of Allium cepa in the management of prostrate inflammation and testicular lesions.”

The study titled “The Protective Role of Extract of Allium cepa Linn. (Liliaceae) (Red Onion) Bulb in Artesunate-induced Testicular Damage in Male Wistar Rats” was published 2014 in British Journal of Pharmaceutical Research.

The researchers include: Nwaehujor Chinaka O., Igile Godwin O., Nwinyi Florence C. and Ode Julius O.

Also, according to a new study presented at The Endocrine Society’s 97th annual meeting in San Diego, United States, the extract of onion bulb, Allium cepa, strongly lowered high blood glucose (sugar) and total cholesterol levels in diabetic rats when given with the antidiabetic drug metformin.

Lead investigator, Dr. Anthony Ojieh, of Delta State University in Abraka, said: “Onion is cheap and available and has been used as a nutritional supplement. It has the potential for use in treating patients with diabetes.”

To three groups of rats with medically induced diabetes, Ojieh and his colleagues gave metformin and varying doses of onion extract—200, 400 and 600 milligrams per kilograms of body weight daily (mg/kg/day)—to see if it would enhance the drug’s effects. They also gave metformin and onion extract to three groups of nondiabetic rats with normal blood sugar, for comparison. Two control groups, one nondiabetic and one diabetic, received neither metformin nor onion extract. Another two groups (one with diabetes, one without) received only metformin and no onion extract. Each group contained five rats.

Ojeil reported: “Two doses of onion extract, 400 and 600 mg/kg/day, strongly reduced fasting blood sugar levels in diabetic rats by 50 percent and 35 percent, respectively, compared with “baseline” levels at the start of the study before the rodents received onion extract.”

Allium cepa also reportedly lowered the total cholesterol level in diabetic rats, with the two larger doses again having the greatest effects.

Onion extract led to an increase in average weight among nondiabetic rats but not diabetic rats.

“Onion is not high in calories,” Ojieh said. “However, it seems to increase the metabolic rate and, with that, to increase the appetite, leading to an increase in feeding.”

Histologic study of the pancreas removed from each diabetic rat showed that neither metformin nor onion extract healed the damage that resulted from the drug-caused diabetes.

“We need to investigate the mechanism by which onion brought about the blood glucose reduction,” Ojieh said. “We do not yet have an explanation.”

The onion extract used for the experiment was a crude preparation from onion bulb, which is available in the local market. If this were to be administered to humans, it would usually be purified so that only the active ingredients would be quantified for adequate dosing, Ojieh said.

Meanwhile, mammalian spermatozoa is particularly vulnerable to lipid peroxidation because of the molecular anatomy of its plasma membrane. Unlike somatic cells, mammalian sperm cells present highly specific lipid composition with high content of polyunsaturated fatty acids (PUFA), plasmalogenes and sphingomyelins. This unusual structure of sperm membrane is responsible for its flexibility and the functional ability of sperm cells to migrate through the uterus to fertilize ovum in the fallopian tube.

Unfortunately, spermatozoa lipids especially PUFA are the main substrates for peroxidation, that may provoke severe functional disorder of sperm, sperm membrane disruption, testicular lesions and potential infertility in susceptible males.
Quiles et al., Chularojmontri et al. and Prahalathan et al. have attempted to study the effects of chemotherapeutic drugs on the reproductive system. It was established that anti-malarial drugs induce oxidative damage to spermatozoa by generating free radicals either by the enzymatic pathway of redox cycling or by the non-enzymatic process. In both pathways, molecular oxygen is reduced to superoxide anion (O .), which is converted to two other forms of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and the more toxic hydroxyl radical (OH•). These free radicals then cause membrane and macromolecular damage by three basic mechanisms involving lipid peroxidation, DNA fragmentation and protein oxidation.

Therefore, Artesunate-induced testicular damage occurs at molecular level. Under biological conditions, the anthracycline and semiquinone (which are metabolites in urine of Artesunate biotransformation) or reduced metal ions selectively cleaves H2O2 to produce the hydroxyl radical (OH•) which is the most reactive and destructive chemical species ever known [27]. This ultimately leads to lipid peroxidation, causing irreversible damage to membrane structure and function.

Phytochemical screening revealed the presence of glycosides, saponins and flavonoids which are potent antioxidants and free radical scavengers from Allium cepa bulb [29,30]. It is likely the extract improves spermatogenesis and produces testicular protection by scavenging free radicals produced by Artesunate and its metabolites. This is observed in the improved sperm count, sperm motility, sperm morphology and increased levels of enzymatic and non- enzymatic antioxidants in the testicular homogenates. This potential protection is further observed in the lowering of the MDA levels in groups treated with the different doses of the extract when compared with the negative control group.

These results showed that the groups treated with the extract, especially at high doses (300mg/kg b.w) gave similar results with the normal control group and elicited recovery of all parameters tested.

The researchers concluded: “Anti-malarial drugs seem to have major side effects on both male and female reproductive systems, as well as being teratogenic and hepatotoxic in human subjects. The ability of plant extracts rich in antioxidative principles to reverse testicular damage associated with Artesunate toxicity in endemic malaria zones in Nigeria has been demonstrated using aqueous extracts of Allium cepa bulbs.

“It is concluded in this study that populations living in endemic malaria zones be encouraged to regularly take water extracts of red onions, as well as eat them raw. Further researches are on-going to evaluate the effect of Allium cepa extract on microbial load in the cervix region in female reproductive area and also on sex hormone regulation.”

Nigerian researchers have also shown that onion extract prevents cadmium induced kidney (renal) dysfunction.

The study was published in Indian Journal of Nephrology.

Cadmium (Cd), a heavy metal, is known for its adverse effects on the body. The researchers investigated the lowering effect of Cd on renal clearance (RC), and Allium cepa extract (AcE) (an antioxidant) was pre-administered orally to prevent Cd’s adverse effects.

Seventy-two Wistar rats, grouped into three (n = 24), were used for this study. While Group C was given 1.0 ml of AcE daily (orally), Group A and Group B were given distilled water. AcE administration was done for eight weeks. Afterwards B and C were then given 1.5 ml/kg BW of 0.3 mg/L 3CdSO4.8H2O intraperitoneally for three consecutive days.

The results obtained showed that Cd exposure causes renal dysfunction, but oral administration of onion could prevent it.

The researchers concluded: “It can be concluded that exposure to cadmium adversely affects renal functions (using renal clearance as a marker) due to cadmium’s ability to cause oxidative stress by interfering with the activities of SOD and that of CAT, and thereby given freedom to free radicals [for example reactive oxygen species, (ROS)] to cause oxidation which manifests as increase in the concentration of MDA (in the case of lipid peroxidation). Allium cepa, however, prevents cadmium from adversely affecting renal functions. This would be a result of the anti-oxidant properties of Allium cepa, which ensures reduced activity of ROS.”

Nigerian researchers from Nnamdi Azikiwe University, Agulu campus, Anambra state, have also established the antidiabetic efficacy of combined aqueous extract of Gongronema latifolium (utazi in Ibo, arokeke in Yoruba) and Allium cepa a popular polyherbal therapy in treatment of diabetes mellitus in South Eastern Nigeria.

The study was published in Journal of Pharmaceutical and Biomedical Sciences.

Alloxan induced diabetic rats were used for the study. Surviving diabetic rats were divided into treatment and control groups. Treatment groups received the combined extracts (1:1, 1:2 and 2:1) orally at three different doses (100, 200 and 400mg/kg).

Control groups received Glibenclamide (5mg/kg, oral) and normal saline. After oral administration of the combined extracts/drug, invivo measurement of blood glucose was taken hourly for six hours. Thereafter, oral administration was continued for 28 days and blood glucose measurement was taken every seven days.

Single dose treatment and 28 days treatment caused blood glucose reduction over the intervals monitored with different doses and ratios of the combined extracts. Increasing dosages of 1:1 and 2:1 of combined aqueous extracts produced a dose-dependent significant (p < 0.05) reductions in the blood glucose levels. These effects were comparable with antidiabetic effect of glibenclamide.

This study showed that the combination of Gongronema latifolium and Allium cepa as a polyherbal antidiabetic remedy expressed good actions in reducing blood glucose when combined in the ratio of 1:1 or 2:1 than 1:2.

Nigerian researchers from the Department of Science Technology, Microbiology unit, Federal Polytechnic, Ado-Ekiti, Ekiti State, have demonstrated the antibacterial Activities of aqueous and ethanolic extract of onion bulb against some selected pathogenic microorganisms.

The study was published in the International Journal of Scientific and Research Publications, Volume 4, Issue 11, November 2014.

The researchers wrote: “Antibacterial activities of aqueous and ethanolic extracts of Allium cepa (onion bulb) were investigated against Escherichia coli, Salmonella spp., Streptococcus pneumoniae, Shigella spp., and Staphylococcus aureus with the minimum inhibitory concentration (MIC) of 0.2 g/ml by agar dilution technique.

“The antibacterial potency of the extract as evaluated by broth dilution technique, showed diameter of inhibition zone of 17.08 mm, 0.00 mm, 19.00, 19.00 and 15.0 mm for E. coli, Salmonella spp., S. pneumoniae, Shigella spp., and Staph. aureus respectively at a concentration of 0.2 mg/ml for aqueous extract and diameter of inhibition zone of 23.0 mm, 20.00 mm, 20.00 mm, 21.00 mm and 21.00 mm for E. coli, Salmonella spp., S. pneumoniae, Shigella spp., and Staph. aureus respectively at a concentration of 0.2 mg/ml for ethanolic extract.

“The result obtained using the ethanol and hot water extract of the plant showed that the local use of medical plant are based on the efficacy of their active principle which can be discovered scientifically; orthodox medical practices can therefore be complemented with traditional practices.”

Researchers have also found, in clinical studies, that crude onion produced hypoglycemic effects and could be used as a dietary supplement in management of type 1 and type 2 diabetes mellitus.

The study published in the journal Environmental Health Insights is titled “Preliminary Study of the Clinical Hypoglycemic Effects of Allium cepa (Red Onion) in Type 1 and Type 2 Diabetic Patients.”

Diabetes mellitus is a heterogeneous group of disorders characterized by abnormalities of carbohydrate, protein and lipid metabolism. Type 1 diabetes mellitus is an autoimmune disease caused by destruction of pancreatic beta cells and characterized by defect in insulin secretion while type 2 diabetes mellitus results from abnormalities in insulin secretion and/or insulin action or both.

The researchers wrote: “In assessment of hypoglycaemic activity of Allium cepa in type 1 and type 2 diabetic patients, ingestion of crude Allium cepa (100 g) caused a considerable reduction in fasting blood glucose levels by about 89 mg/dl in relation to insulin (145 mg/dl) in type 1 diabetic patients and it reduced fasting blood glucose levels by 40 mg/dl, compared to glibenclamide (81 mg/dl) in type 2 diabetic patients, four hours later. The same dose of crude Allium cepa produced a significant reduction in the induced hyperglycemia (GTT) by about 120 mg/dl compared to water (77 mg/dl) and insulin (153 mg/dl) in type 1 diabetic patients and considerably reduced GTT by 159 mg/dl in relation to water (55 mg/dl) and glibenclamide (114 mg/dl) in type 2 diabetic patients, after four hours.”

Scientists have also demonstrated how onion protects kidney/renal functions in diabetic patient.

The study was published in World Journal of Life Sciences and Medical Research.

The researchers wrote: “About 90 per cent of all diabetes is type 2, wherein the body can produce the insulin needed, but cells do not respond to it. In this study we investigated the possibility that Allium cepa (a very cheap and readily available species of the genus Allium) has healing/beneficial effects on type 2 diabetics. Twenty acclimatized adult rabbits were randomly divided into four groups of five rabbits each.

“Three of the groups were made diabetic (with single intraperitoneal injection of alloxan), and two of the three groups were administered graded doses of Allium cepa extract. The results reveal that Allium cepa has renal protective effects in diabetic rabbits. This study concludes that Allium cepa contains some bioactive substances (mostly antioxidants), which could prevent renal organ damage from hyperglycemia in diabetes mellitus.”

They concluded: “This study conclude that Allium cepa (a very cheap and readily available species of the genus Allium) contains some bioactive substances mostly antioxidants which could prevent renal organ damage from hyperglycemia in diabetes mellitus.

“Further studies would, however, be required to have a comprehensive understanding of the molecular mechanism of the noted effects, and, perhaps, to answer the question as to whether or not some components of Allium cepa may affect (in this case, enhance) cell receptors for insulin.”

Novel medicinal extracts derived from onion are provided has also received a United States Patent as extracts with broad medicinal properties, especially for treatment of Human Immuno-deficiency Virus (HIV)/Acquired Immune Deficiency Syndrome (AIDS) and other viral infections.

The United States Patent: 6,340,483 is titled “Antiviral composition derived from allium CEPA and therapeutic use thereof.

The Patent reads: “It is an object of the invention to provide a novel plant extract derived from a plant species of the family Alliaceae (also known as Lilliaceae or Amaryllidaceae), preferably of the genus Allium, with the proviso that said Allium is not garlic (Allium sativum), having medicinal properties.

“It is a more specific object of the invention to provide novel plant extracts derived from an Allium species selected from the group consisting of Allium cepa, Allium ampeloprasum (“leek”), Allium fistulosa (Japanese bunching onion, scallion or Welsh onion), or Allium schoenoprasum (“chives”) having medicinal properties.

“It is an even more specific object of the invention to provide a novel plant extract derived from Allium cepa, preferably Allium cepa var. Ancasti or Southporth white glove (SWG) having medicinal properties.

“It is a more specific object of the invention to provide a novel method of treating or preventing a retroviral infection such as HIV-1 or HIV-2 or AIDS by administering a plant extract derived from an Allium species other than Allivum sativum, preferably Allium cepa, Allium fistulosa, Allium ampeloprasum or Allium schoenoprasum, and most preferably Allium cepa.

“It is a more specific object of the invention to treat wasting syndrome, especially associated with AIDS, and/or to lengthen the latency period of HIV infection, and/or to delay the latent phase of AIDS, and/or to ameliorate or eliminate the clinical symptoms associated with AIDS such as intestinal problems, diarrhea, neurological impairment and paresthesia by administering a medicinal extract derived from an Allium species other than Allivum sativum, preferably Allium cepa, Allium fistulosa, Allium ampeloprasum or Allium schoenoprasum, and more preferably Allium cepa.”