Scientists endorse herbs for diabetes’ treatment

By Chukwuma Muanya

Scientists have endorsed some local plants used in the management of diabetes. Top on the list are Gongronema latifolium, Ocimum gratisimum, Vernonia amygdalina, and Piper guineense (Uziza in Ibo) Gongronema latifolium is known by the Ikales of Ondo State of Nigeria as Iteji. The Ibos call the plant Utazi, the Efik/ Ibibio call it Utasi while the Yorubas call it Arokeke.

Botanically called Vernonia amygdalina, bitter leaf is of the plant family Compositae. It is called Ewuro in Yoruba and Onugbu in Ibo.

Botanically called Ocimum gratissimum, scent leaf or Basil belongs to the mint family Lameacea. It is called Effirin in Yoruba and Nchuanwu or Arigbe in Ibo.

Commonly called West African Black Pepper or Ashanti pepper, Piper guineense, is called Uziza in Igbo and Ata iyere in Yoruba.

Other local plants endorsed for the treatment of diabetes include: Allium cepa (onion), Allium sativum (garlic), Aloe vera, Cinnamomum cassie, Coccinia indica, Gymmema slyvestre (Gurnar), Momordica charantia (Bitter melon), Catharanthus roseus (Madagascar Periwinkle), Muurrayi komingii (curry leaf), Ocimum sanctum (Nchuanwu in Ibo and Effirin nla in Yoruba), Panax ginseng, Trigonella foemum-graecum (Fenugreek) Pterocarpus marsupium (Indian Kino) and Syzigium cumini (Java plum).

The study published in Journal of Diabetes & Metabolism is titled “Overview of Anti-Diabetic Medicinal Plants: The Nigerian Research Experience.”

The researchers from the Department of Biochemistry, Imo State University, Owerri, and Federal University of Technology, Owerri, Imo State, include: Paul C. Chikezie, Okey A. Ojiako, Kanayo C. and Nwufo noted that a survey of several medicinal plant research findings showed that the polysaccharides, sterols, terpenoids, alkaloids, saponins, flavonoids, amino acids and their derivatives are the most encountered bioactive principles that exhibited glycemic control in experimental animals.

Previous studies have shown that a combination of daily intake of coconut oil, local spices, banana, Zobo (sorrel), local bitters such as bitter leaf, scent leaf as well as exercise training would reduce the risk of developing chronic and non communicable diseases like blood pressure, blood sugar (diabetes) and heart diseases.

Earlier studies suggest that a combination of bitter leaf and scent leaf extracts could not only reduce the blood glucose level, but protects the heart and testes against impairment and complete destruction due to diabetes.

A study by researchers at the University of Calabar published in February 2012 edition of The Internet Journal of Tropical Medicine concluded, “we therefore conclude that extracts of Vernonia amygdalina and Ocimum gratissimum apart from their hypoglycemic actions could protect the heart against impairment and complete destruction due to diabetes.”

Also, a Nigerian born Professor of Biology, Ernest Izevbigie has patented a formula made from bitter leaf. This bitter leaf-based formula is a proven anti-diabetic and anti-cancer formula in laboratory and clinical trials. This formula product can also benefit Human Immuno-deficiency Virus (HIV)/Acquired Immune Deficiency Syndrome (AIDS) patients. It has been patented: U.S. Patent 6,713,098 in 2004 and the second 6,848,604 in 2005.

Onion and garlic

Oral administration of onion (A. cepa L.) and garlic (A. sativum L.) to alloxan-induced diabetic rats for 30 days ameliorated hyperglycemia, reversed weight loss and depletion of liver glycogen. The anti-diabetic bioactive principles of A. cepa L. and A. sativum L. were S-methylcysteinesulfoxide (SMCS) and S-allylcysteinesulfoxide (SACS) respectively.

The studies showed that SMCS and SACS exerted their anti-diabetic properties by stimulating insulin secretion as well as compete with insulin for insulin inactivating sites in the liver. Specifically, SACS inhibited gluconeogenesis in the liver. In addition, SACS from A. sativum L impeded lipid peroxidation due to its antioxidant and secretagogue actions. The capacities of A. cepa L. and A. sativum L. to alleviate Diabetes Mellitus (DM) in the experimental rats were comparable with diabetic rats treated with glibenclamide and insulin. The study also noted that SMCS and SACS caused significant increase in the biosynthesis of cholesterol from acetate in the liver, which was an indication of low capacities of allium products to protect the rats against risk factors associated with DM.

Aloe vera

Aloe vera (Aloe barbedensis)

A 1.0 μg of five phytosterols- lophenol, 24-methyl-lophenol, 24-ethyl-lophenol, cycloartanol, and 24-methylene-cycloartanol from A. vera exhibited comparable capacities to lower blood glucose levels in Type II diabetic BKS.Cg-m+/+Leprdb/J (db/db) mice following 28 day treatment. The five phytosterols caused significant decrease in blood HbA1c levels by 15 to18 per cent.

Additionally, severe diabetic mice treated with the five phytosterols did not suffer weight loss because of rapid excretion of glucose in the urine. The findings suggested that phytosterols derived from A. vera gel have a long-term blood glucose lowering effect, which could be applied as agents of glycemic control in Type 2 DM. Studies showed that phytosterols stimulate the biosynthesis and/or release of insulin as well as alter the activity of carbohydrate metabolizing enzymes.

Catharanthus roseus

The Madagascar periwinkle (C. roseus), is a traditional remedy and was marketed in England as ‘Vinculin’ for the treatment of DM. Earlier studies showed that leaf aqueous extracts of C. roseus administered orally to rabbits and dogs caused hypoglycemic response. Similar studies using variety of laboratory animals and limited clinical trials gave negative or at best equivocal results.

Alkaloids, notably, catharanthine, leurosine, lochnerine, tetrahydroalstonine, vindoline, and vindolinine are the major anti-diabetic principles present in C. roseus. Specifically, studies showed that vincamine and (-)-eburnamonine caused extensive decrease in rat brain tissue glucose concentration, with concomitant increase in lactate and pyruvate concentrations as well as the lactate pyruvate ratio and increase in tissue ATP contents. In vitro studies showed that the quinoline derivatives, quinolate and 3-mercaptopicolinate, inhibited hepatic gluconeogenesis from lactate or alanine by inhibiting muscle cytosolic/mitochondrial phosphoenolpyruvate carboxykinase and cytosolic aspartate aminotransferase activities. Certainly the active alkaloids analogs of C. roseus exhibited oral hypoglycemic activity of one-third capacities when compared with tolbutamide.

Piper guineense

Oral administration of dichloromethane:methanol (1:1) leaf and twig extracts of C. roseus at dose = 500 mg/kg to streptozotocin (STZ)-induced diabetic rats for seven and 15 days gave 48.6 and 57.6 per cent hypoglycemic activity, respectively. The same dose for 30 days exhibited protective effect against STZ challenge. The anti-diabetic action of C. roseus was as a result of inhibition of hepatic glycogen synthase, glucose 6-phosphate-dehydrogenase, succinate dehydrogenase and malate dehydrogenase activities coupled with increased mobilization of glucose following treatment of the experimental rats.

Similarly, the same dose of C. roseus extracts ameliorated oxidative stress as exemplified by lower levels of 2-thiobarbituric acid reactive substances (TBARS) in diabetic rats following treatment.

Cinnamomum cassie (Chinese cinnamon)

Cinnamon methylhydroxychalcone polymer (MHCP) from cinnamon functions as a mimetic for insulin in 3T3-L1 adipocytes. Therefore, MHCP may be useful in the treatment of Type II DM and in the study of the pathways leading to glucose utilization in peripheral cells.

Coccinia indica

Orally administered pectin materials isolated from fruit extracts of C. indica at dose = 200 mg/100 g body weight/day caused hypoglycemia in normal rats. The study noted that pectin materials caused significant reduction in blood glucose and an increase in the liver glycogen as a result of increase in hepatic glycogen synthetase activity and corresponding reduction in phosphorylase activity.

Hypoglycemic effect of ethanolic extract of C. indica is partly due to the repression of the key gluconeogenic enzyme (glucose-6-phosphatase), but did not affect alanine aminotransferase and aspartate amino transferase activities, in starved male rats.

Fiscus bengalensis

Leucopelargonidin-3-0-alpha-L rhamnoside from dimethoxy ether extract of Indian Banyan tree F. bengalensis Linn bark at a medium effective dose = 100 mg/kg caused hypoglycemia and increased blood insulin levels in normal and moderately alloxan-induced diabetic dogs following two hours oral administration. The bioactive glycoside stimulated insulin secretion in the experimental animals. Furthermore, acute (doses = 0.2-1.8 g/kg) administration to mice and chronic (doses = 100, 250 and 500 mg/kg) daily administration to rats for a period of one month respectively did not elicit toxic effects even at the high dose of 1.8 g/kg in experimental animals.

Gymnema Sylvestre (Gurnar)

G. sylvestre extracts at various doses caused decreased blood sugar level in STZ-induced diabetic rat models, which was comparable with the standard anti-diabetic drug-tolbutamide. Also, human experiments showed that GS4 (dose = 400 mg/day), a water-soluble extract from leaves of G. sylvestre, administered to patients suffering from insulin-dependent diabetes mellitus (IDDM) and placed on insulin therapy, caused the normalization of their serum lipid profiles, whereas insulin requirements together with fasting blood glucose and glycosylated haemoglobin (HbAlc) and other glycosylated plasma protein levels remained higher than that of the control subjects. Nevertheless, GS4 therapy appears to enhance endogenous insulin biosynthesis, possibly by regeneration/revitalization of the residual β-cells of IDDM individuals.

Ginseng (Panax ginseng) and Fenugreek (Trigonella foenum-graecum L.)

In vivo experiments using STZ-induced diabetic rats chronically administered with food mixed with steroid saponins from the seeds of fenugreek (T. foenum-graecum L) (dose = 12.5 mg/300 g body weight per day) showed significantly increase in food intake as well as the motivation to eat in normal rats. it also stabilized the food consumption in diabetic rats, which resulted in a progressive weight gain in these animals, in contrast to untreated diabetic controls. Aerobic exercise in combination with ginsenosides from P. ginseng promote lower serum lipid, regulate lipid metabolism, promote anti-oxidation, and enhance immune activity.

Momordica cymbalaria (Bitter melon)

Oral and intra-peritoneal administration of aqueous fruit extracts of M. charantia to normal rats lowered the glycemic response without altering the insulin response. Also, aqueous extract and the residue after alkaline chloroform extraction reduced hyperglycemia in diabetic mice after one hour. The recovered plant matters by acid water wash of the chloroform extract following alkaline water wash engendered a slower hypoglycemic effect. These findings suggested that orally administered M. charantia extracts lower glucose concentrations independently of intestinal glucose absorption and involved an extra-pancreatic effect.

In another study, M. cymbalaria fruit powder caused reduction in blood sugar concentrations in alloxan-induced diabetic rats following 15 days treatment. Elevated serum cholesterol and triglycerides levels were lowered with significant improvement in hepatic glycogen level in treated diabetic rats. The study showed the anti-diabetic and hypolipidemic properties of M. cymbalaria fruit powder.

Ocimum gratissimum

Muurrayi komingii (Curry leaf)

A single oral administration of aqueous leaf extracts of M. koenigii (doses = 200, 300 and 400 mg/kg) lowered blood glucose level in normal and alloxan-induced diabetic rabbits. The reduction on blood glucose levels in normal and mild diabetic rabbits corresponded to 14.68 per cent and 27.96 per cent following four hours of oral administration of 300 mg/ kg of the leaf extract.

Likewise, 300 mg/kg of the leaf extract caused a marked improvement in glucose tolerance by 46.25 per cent in sub-diabetic and 38.5 per cent in mild diabetic rabbits at two hours post prandial test. The study suggested that the aqueous leaf extracts of M. koenigii may be prescribed as adjunct to dietary therapy and treatment of DM. Aegle marmelos possess anti-diabetic and hypolipidemic effects in diabetic rats.

Ocimum sanctum (Holy basil)

Alcoholic leaf extract O. sanctum ameliorates hyperglycemia in normal-glucose fed hyperglycemic and streptozotocin-induced diabetic rats by potentiating the action of exogenous insulin in the rats. The anti-diabetic action of alcoholic leaf extract O. sanctum was comparable with that of the standard anti-diabetic drug-tolbutamide.

The researchers noted: “Allium cepa, Allium sativum, Aloe vera, Cajanus cajan, Coccinia indica, Caesalpinia bonducella, Ficus bengalenesis, Gymnema sylvestre, Momordica charantia, Ocimum sanctum, Pterocarpus marsupium, Swertia chirayita, Syzigium cumini, Tinospora cordifolia and Trigonella foenum-graecum.

All the above named plants stimulate insulin release from isolated pancreatic Islets cells by virtue of their phytochemical contents, especially the saponins and glycosides fractions.”

Gongronema latifolium

Gongronema latifolium

Ethanolic leaf extract of G. latifolium has antihyperglycemic potency, which is thought to be mediated through the activation of hepatic hexokinase (HK), phosphofructokinase (PFK) and glucose- 6-phosphate dehydrogenase (G6PDH) and inhibition of glucokinase (GK) activity in the liver.

The findings of the study, as in the case of numerous indigenous Nigerian research exercises on anti-diabetic medicinal plants, fell short in establishing the molecular structure of the bioactive compound(s) and its/their mechanism of action.

The article first appeared on The Guardian