Onion may provide next novel drug for asthma, diabetes, liver damage

Can onion extracts provide the next novel drug for asthma, diabetes, ‘bad’ cholesterol, liver damage and prostate enlargement? CHUKWUMA MUANYA writes

researchers have provided the first evidence that onion (Allium cepa) may have an anti-allergic effect more intense than quercetin, and may be a future target for new molecules to treat allergic asthma.

The study, published in DARU Journal of Pharmaceutical Sciences 2015, concluded: “Our work may also validate and explain the long-held traditional use of this species by folk Brazilian medicine to treat asthma. This work also opens new perspectives in the context of elucidating the cellular and molecular mechanisms involved in the mechanism of action of Allium cepa as a way to enable clinical trials to evaluate its efficacy in humans.”

The study is titled “Potential therapeutic effect of Allium cepa L. and quercetin in a murine model of Blomia tropicalis induced asthma.”

Meanwhile, an earlier study published in March 6, 2015, in The Endocrine Society indicates that the extract of onion bulb, Allium cepa, strongly lowered high blood glucose (sugar) and total cholesterol levels in diabetic rats when given with the anti-diabetic drug metformin.

Asthma is an inflammatory condition characterized by airway hyper-responsiveness and chronic inflammation. The resolution of inflammation is an essential process to treat this condition.

The researchers investigated the effect of Allium cepa L. extract (AcE) and quercetin (Qt) on cytokine and on smooth muscle contraction in vitro and its therapeutic potential in a murine model of asthma.

The researchers obtained the AcE by maceration of Allium cepa and it was standardized in terms of quercetin concentration using high performance liquid chromatography (HPLC). In vitro, using AcE 10, 100 or 1000 μg/ml or Qt 3.5, 7.5, 15 μg/ml, the researchers measured the concentration of cytokines in spleen cell culture supernatants, and the ability to relax tracheal smooth muscle from A/J mice. In vivo, Blomia tropicalis (BT)-sensitized A/J mice were treated with AcE 100, 1000 mg/kg or 30 mg/kg Qt.

The researchers measured cell influx in bronchoalveolar lavage (BAL), eosinophil peroxidase (EPO) in lungs, serum levels of Bt-specific IgE, cytokines levels in BAL, and lung histology.

They observed a reduction in the production of inflammatory cytokines, a relaxation of tracheal rings, and a reduction in total number of cells in BAL and EPO in lungs by treatment with AcE or Qt.

The researchers performed an ethno-pharmacological survey, and one of the herbs described was Allium cepa L., commonly used to treat inflammatory conditions such as asthma.

Several plant-derived secondary metabolites have been shown to interfere directly with molecules and mechanisms, such as the mediation of inflammatory responses and activity of second messengers, as well as the expression of transcription factors and key pro-inflammatory molecules.

The main compounds found in Allium cepa L. extract (AcE) are the flavonoids such as quercetin, which are natural phenolic compounds present in fruits and vegetables, exhibiting many pharmacological properties such as its anti-inflammatory and antioxidant effects. Along with flavanols, the major bioactive constituents in Allium cepa L. are sulfurous compounds.

In previous studies, using mass spectrometry for direct analysis of volatile sulfurous compounds has described the presence of propanethiol, dipropyl disulfide and thiosulfinates. The sulphoxides, which are responsible for the onion flavour and odor, might also be responsible in part for the onion biological activity of different Allium spp. species. The propanethiol is suggested to be the main source of the characteristic onion odour.

In previous studies, the anti-allergic potential of the extracts of Allium cepa L. and its flavonoid quercetin has been reported using a mouse model of ovalbumin (OVA)-induced asthma.

This study is the first, which was conducted using extracts of Allium cepa L. (AcE) and quercetin treatment in murine model of allergic airway disease induced by the sensitization to the clinically relevant aeroallergen Blomia tropicalis mite. This mite is a major house dust mite in dust worldwide. In addition, it has been shown that flavonoids, typically found in Allium cepa, have a relaxing effect on the smooth muscle of isolated trachea and may have bronchodilator effect.

Thus, the objective of this study was to assess the therapeutic potential (anti-inflammatory and bronchodilator) of the methanolic extract of Allium cepa L. (AcE) and its flavonoid quercetin (Qt) in a murine model of respiratory allergy to Blomia tropicalis mite.

Asthma is described an inflammatory condition characterized by airway hyper-responsiveness, mucus cell hyperplasia, inflammatory cell infiltration and reversible bronchoconstriction, which may progress to airway remodeling with fibrosis and an increase in smooth muscle reactivity.

Studies have shown that in allergic asthma, exposure to allergens causes an imbalance between the T helper type (Th) 1 and Th2 responses. Cytokines produced by the Th2-type CD4 + T cells (interleukin (IL-4, IL-5, IL-13) in asthma have a central role in orchestrating the inflammatory response.

Strong support for this T-cell-centric paradigm has been enriched by the identification of Treg cells with the capacity to control both Th1 and Th2 responses.

It has been shown that the synthesis and release of IL-4 (which stimulates B cells to synthesize IgE), IL-13 (which stimulates mucus production) and IL-5 (which is necessary for eosinophilic infiltration to the lung tissue) increase vascular permeability and chemotaxis, which amplify the inflammatory response. Additionally, activated mast cells are able during an allergen challenge to release several inflammatory and broncho-constrictor mediators.

Several studies indicate that the prevalence of asthma continues to rise worldwide, and treatment of asthma faces many challenges, including under diagnosis, access to care, ability of health-care workers to manage asthma, education of healthcare providers and patients, and availability and affordability of inhaled therapy. Treatment with inhaled steroids and bronchodilators often results in good control of symptoms.

However, the treatment for patients with severe asthma with uncontrolled and frequent exacerbations still contributes to morbidity and mortality of asthma in all age groups and remains a challenge. The safety concerns and the obstacles for the asthmatic patients justify continued efforts to find new alternative therapies.

Historically, herbal medicine has been studied in asthma treatment, and some of the drugs currently used to treat this disease such as the inhaled corticosteroids, sympathomimetics, anti-cholinergics, methylxanthines and cromones have origins in herbal treatments.
Onions for diabetes and ‘bad’ cholesterol

Meanwhile, the extract of onion bulb, Allium cepa, strongly lowered high blood glucose (sugar) and total cholesterol levels in diabetic rats when given with the anti-diabetic drug metformin.

The study results were presented on March 6, 2015, at The Endocrine Society’s 97th annual meeting in San Diego, United States.

“Onion is cheap and available and has been used as a nutritional supplement,” said lead investigator Anthony Ojieh, MBBS (MD), MSc, of Delta State University in Abraka, Nigeria. “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 non-diabetic rats with normal blood sugar, for comparison. Two control groups, one non-diabetic 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.

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, Ojieh reported.

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 non-diabetic 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.
Onion and garlic waste from the food industry could be used to mop up hazardous heavy metals

Also, according to a research paper published in the International Journal of Environment and Pollution, onion and garlic waste from the food industry could be used to mop up hazardous heavy metals, including arsenic, cadmium, iron, lead, mercury and tin in contaminated materials.

Biotechnologists Rahul Negi, Gouri Satpathy, Yogesh Tyagi and Rajinder Gupta of the GGS Indraprastha University in Delhi, India, explain how waste from the processing and canning of onion (Allium cepa L.) and garlic (Allium sativum L.) could be used as an alternative remediation material for removing toxic elements from contaminated materials including industrial effluent. The team has studies the influence of acidity or alkalinity, contact time, temperature and concentration of the different materials present to optimize conditions for making a biological heavy metal filter for industrial-scale decontamination.

Onion extracts protect liver against paracetamol-induced damage

Researchers have also examined the hepatoprotective effects of Allium cepa (onion) extracts against paracetamol-induced liver damage in rats.

The study was published in African Journal of Biotechnology.

The researchers wrote: “Liver damage due to paracetamol hepatotoxicity is a major health challenge worldwide. It is against this background that this study was designed to determine the hepatoprotective effects of the increasing dosage of Allium cepa methanolic extracts on paracetamol induced hepatotoxic rats. Fifty-four (54) adult male albino rats comprising of nine normal and 45 paracetamol hepatotoxic rats were used for this study.

“The experimental design was the three by three Latin square design. Paracetamol hepatotoxicity was induced by single administration of paracetamol at 750 mg/kg ip on the first day of the experiment. The different biochemical parameters assessed were determined before the start of the study and subsequently monthly for the duration of the study. Blood samples were collected from the rat through the eye monthly for analysis and serum was obtained by centrifugation (5000 rpm for 10 min) and stored at -20°C prior to analysis.

“The effects of duration and increasing dosages (200, 300 and 450 mg/kg) of A. cepa methanolic extracts produced a duration dependent significant (p < 0.05) reductions in the alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and total serum bilirubin (TSB) of paracetamol hepatotoxic rats after the duration of study when compared with those of the paracetamol, normal and silymarin control rats. “A. cepa reduced alanine aminotransferase and total serum bilirubin in a dose dependent fashion whereas it reduced aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase level in a dose independent manner. A. cepa extracts studied showed potent hepatoprotective properties. It was evident that A. cepa extracts was able to reduce significantly all the elevated biochemical parameters due to paracetamol hepatotoxicity and this was collaborated by results of histopathological studies.” Onion prevents prostate enlargement Another study published in Mediators of Inflammation examined the immune-modulatory effect of red onion (Allium cepa) scale extract on experimentally induced atypical prostatic hyperplasia (prostate enlargement) in Wistar rats. The researchers from Saudi Arabia and Egypt found that red onion scales (ROS) contain large amounts of flavonoids that are responsible for the reported antioxidant activity, immune enhancement, and anticancer property. They induced atypical prostatic hyperplasia (APH) in adult castrated Wistar rats by both s.c. injection of testosterone (0.5 mg/rat/day) and by smearing citral on shaved skin once every three days for 30 days. Saw palmetto (100 mg/kg) as a positive control and ROS suspension at doses of 75, 150, and 300 mg/kg/day were given orally every day for 30 days. The researchers wrote: “All medications were started seven days after castration and along with testosterone and citral. The HPLC profile of ROS methanolic extract displayed two major peaks identified as quercetin and quercetin-4′-β-O-D-glucoside. Histopathological examination of APH-induced prostatic rats revealed evidence of hyperplasia and inflammation with cellular proliferation and reduced apoptosis Immunohistochemistry showed increased tissue expressions of IL-6, IL-8, TNF-α, IGF-1, and clusterin, while TGF-β1 was decreased, which correlates with the presence of inflammation. “Both saw palmetto and RO scale treatment have ameliorated these changes. These ameliorative effects were more evident in RO scale groups and were dose dependent. In conclusion, methanolic extract of ROS showed a protective effect against APH induced rats that may be attributed to potential anti-inflammatory and immune-modulatory effects.” They further explained: “Fruits and vegetables have health benefits and are good sources of antioxidants; therefore a lot of recent literature has focused on nutritional and herbal medicine for prostatic hyperplasia. In the present study, administration of ROS extract induced significant and dose-related reduction in both the absolute and relative weight of prostate in the APH-induced rats, an effect that was greater than that induced by saw palmetto. These effects may be due to the fact that ROS are rich in flavonols, which represent 60 per cent of the total active constituents. These mainly are kaempferol, quercetin, quercetin dimer, quercetin trimer, and other quercetin glycoside. “ Flavonols were found to be responsible for the antioxidant, hepatoprotective, anticancer, antimicrobial, antistress, and other biological activities. Among the major constituents of the ROS extract, are quercetin, which was found to be mainly responsible for the protective effects against different degenerative pathological diseases. It was reported that administration of quercetin along with finasteride resulted in reduction in prostate weight in rats, through a cell cycle-related pathway that may function independently of androgens.”