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The popular zobo drink made from the calyx (flower part) of roselle (Hibiscus sabdariffa) has been successfully used in traditional medicine to treat various diseases such as cough, hypertension, stomach disorders, loss of appetite, upper respiratory congestion, nerve and heart disorders and menstrual difficulties. But recent studies suggest that although it could be used to reduce the risk of kidney damage in diabetics, high doses could lead to kidney damage. CHUKWUMA MUANYA writes.

CAN drinking high doses of the popular zobo drink lead to kidney damage? Results of a recent study suggest that aqueous extract of Hibiscus sabdariffa (HSE) has no harmful effect on the liver but when consumed in high doses could be harmful to the kidney. “Further research aimed at identifying the chemical composition and potential toxic agent(s) in HS is recommended,” the researchers wrote.

Commonly called zobo or roselle in Nigeria, Hibiscus sabdariffa belongs to the plant family malvaceae.

The study titled: “Toxicilogical effects of aqueous extract of Hibiscus Sabdariffa on the liver and kidney,” was published in Journal of College of Medicine.

The aim of the study is to show the effect of graded doses of aqueous extract of HS on major excretory organs (liver and kidney) of albino Wistar rats. This may be helpful in determining the safety or otherwise of its consumption at different concentrations.

The researchers wrote: “There were no significant changes in the histology of the liver throughout the period of HS administration in all the groups. However, there were significant histological changes in the kidney, which were more pronounced at higher doses (80 and 160mg/kg). There was shrinkage of glomerular tuft, increase in urinary pole, increase in size of tubular lumen and tubular damage. These effects were more marked as the duration of administration of the extract progressed with greatest effect observed at 12th week.”

Another study found that Hibiscus sabdariffa might help treat kidney stones via uricosuric activity. The study titled: “Uricosuric effect of Roselle (Hibiscus sabdariffa) in normal and renal-stone former subjects,” was published in Journal of Ethnopharmacology.

Uricosuric agents are used to lower the uric acid level in the blood and to prevent the formation of uric acid crystals in the joints and kidneys. These drugs are often used to treat gout, a disease in which uric acid crystals deposit in joints and cause pain. By decreasing plasma uric acid levels, these drugs decrease the deposition of crystals in joints, eventually decreasing inflammation and thereby reducing the pain of gout.

Researchers from Thailand conducted a study with nine subjects with no history of kidney stones and nine with a history of kidney stones. A cup of tea made from 1.5 grams of dry roselle was provided to subjects twice daily (morning and evening) for 15 days.

After taking the tea, both groups showed increases in oxalate and citrate. In the non-kidney stone group, increases in uric acid excretion and clearance were observed. In the patients with kidney stones, both uric acid excretion and clearance were significantly increased.

The study authors concluded that roselle has a uricosuric effect and they suggested that the chemical constituents exerting this effect should be identified.

Also, researchers have shown that aqueous (water) extracts of HSE is capable of reducing lipid peroxidation, increasing catalase and glutathione activities significantly in diabetic kidney, and decreasing the plasma levels of triglyceride, low-density lipoprotein (LDL) and increasing high-density lipoprotein (HDL) value.

Lipid peroxidation is a well-defined mechanism of cellular damage in both animals and plants that occurs in vivo during aging and in certain disease states.

Catalase is an antioxidant enzyme found in living organisms that changes hydrogen peroxide to water and oxygen. Hydrogen peroxide is formed as a toxic waste product of metabolism. It must be quickly converted into other, less dangerous, chemicals. To manage this problem, the enzyme catalase is frequently used to rapidly catalyse the decomposition of hydrogen peroxide into harmless oxygen and water.

Glutathione is an antioxidant compound found in living animal and plant tissue. Glutathione is the major endogenous antioxidant produced by the cell. Glutathione participates directly in the neutralization of free radicals, reactive oxygen compounds, and maintains exogenous antioxidants such as vitamins C and E in their reduced (active) forms. In addition, through direct conjugation, glutathione plays a role in the detoxification of many xenobiotics (foreign compounds) both organic and inorganic. Glutathione is an essential component of the human immune response.

Triglycerides are a type of lipid found in blood. When food is consumed, calories are released by the oxidation of food. The calories, which the body does not exhaust, are converted into energy resources called triglycerides which are stored in the fat cells of the body and are used to supply energy when required. Under the action of certain hormones these triglycerides are broken into simpler, absorbable forms of fatty acids to liberate energy.

LDL is “bad” cholesterol, while HDL is “good” cholesterol.

According to the study published in Evidence-Based Complementary and Alternative Medicine, HSE, in histological examination, improves hyperglycemia-caused osmotic diuresis in renal proximal convoluted tubules (defined as hydropic change) in diabetic rats.

Hyperglycemia or Hyperglycæmia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma.

Osmotic diuresis is increased urination caused by the presence of certain substances in the small tubes of the kidneys.

The proximal convoluted tubule is the most proximal segment of the renal tubular portion of the nephron. It is responsible for the reabsorption of glucose, amino acids, various ions and water.

The study also reveals that up-regulation of Akt/Bad/14-3-3? and NF-?B-mediated transcription might be involved.

The researchers concluded: “In conclusion, our results show that HSE possesses the potential effects to ameliorate diabetic nephropathy via improving oxidative status and regulating Akt/Bad/14-3-3? signaling.”

The study is titled: “Aqueous extract from Hibiscus sabdariffa linnaeus ameliorate diabetic nephropathy via regulating oxidative status and Akt/Bad/14-3-3? in an experimental animal model.”

Several studies point out that oxidative stress maybe a major culprit in diabetic nephropathy. Diabetic nephropathy is kidney disease or damage that occurs in people with diabetes. HSE has been demonstrated as having beneficial effects on anti-oxidation and lipid-lowering in experimental studies.

This study investigated the effects of Hibiscus sabdariffa L. on diabetic nephropathy in streptozotocin induced type 1 diabetic rats.

Diabetic mellitus (DM) is a consequence of chronic metabolic aberrations including hyperlipidemia. High glucose facilitating the glycolysis and adenosine triphosphate generation would cause huge reactive oxygen species (ROS) production. Under physiological circumstances, ROS involve some signaling molecules and follow defense mechanisms such as phagocytosis, neutrophil function and shear-stress induced vasorelaxation.

However, excessive oxidative stress could damage proteins, lipids, and DNA and eliminate anti-oxidative enzymes or molecules. Ujihara et al. observed that oxidized LDL level was significantly higher in diabetic patients with macroalbuminuria. They suggested that oxidized-LDL might play an important role in diabetic nephropathy.

Experimentally, the oxidative level of LDL can be determined by detecting lipid peroxidation. Antioxidant defense mechanisms include free radical scavengers and enzyme systems, such as superoxide dismutase (SOD), glutathione peroxidase (GSH) and catalase (CAT). Previous studies showed that these anti-oxidative molecules were reduced in diabetes.

In addition to the devastating damage effect on macromolecules, oxidative stress can be involved in cellular signal transduction including Akt signaling pathway. Akt is a principal mediator of biological functions of insulin in glucose metabolism. Phosphorylated Akt can regulate apoptosis via activating Bad to associate with 14-3-3? protein and also to activate nuclear factor-kappa B (NF-?B) to regulate transcription.

Recent studies showed the importance of phosphoinositide 3-kinases (PI3-K) and Akt signaling pathway in diabetic nephropathy including regulation of renal mesangial hypertrophy and renal tubular cells proteolysis. It has been well known that hyperglycemia and insulin could modulate Akt activity in diabetic renal tissue. However, the results are not compatible. Furthermore, the correlation between oxidative stress and Akt signaling in diabetic renal tissues has not been well clarified.

A wide variety of natural products have been found to possess capacity to control metabolic problems and oxidative stress in diabetes. Hibiscus sabdariffa Linnaeus is usually used as a beverage. The constituents in the flowers of Hibiscus species are polyphenolic acids, flavonoids, and anthocyanins.

Previous studies found that HSE possessed anti-oxidative characteristics and had anti-atherosclerotic effects. Recent pharmacological studies also showed that HSE significantly reduced blood pressure in humans and in experimental animals.

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Updated 7 Years ago

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