Management of Diabetes with Medicinal plants and Dietary control (part 2)

An important research area is the discovery and development of more effective and safer antidiabetic agents. In this context, medicinal plants and diet continue to play an important role in the treatment of diabetes, particularly in developing countries where most people have limited resources and do not have access to modern treatment. A recent survey of the frequency of use of complementary and alternative medicine (CAM) in diabetes patients found that most of the patients using CAM are better educated, born in cities, live in large families and were suffering from diabetes for longer duration.

One should note that metformin, the single most prescribed agent for the treatment of diabetes, originated from herbal medicine and was derived from galegine. Experimental and clinical evaluations of galegine, isolated from Galega officinalis provided the pharmacological and chemical basis for the subsequent discovery of metformin. 1- Deoxynojirimycin (DNJ), a potent α-glucosidase inhibitor which helps in prevention of diabetes, was isolated from the water extract of leaves of mulberry trees (Morus alba L.).

Diet has long been the keystone in the treatment of diabetes and various other diseases. Diet and lifestyle play an important role in the management of several diseases, including diabetes. Before the introduction of the therapeutic use of insulin, diet was the main form of treatment and dietary measures included the use of traditional medicines mainly derived from plants.

Many studies have confirmed the benefits of medicinal plants with hypoglycemic effects in the management of diabetes mellitus. The effects of these plants may delay the development of diabetic complications and correct metabolic abnormalities. Moreover, during the past few years, some of the new bioactive drugs isolated from plants showed antidiabetic activity with more efficacy than oral hypoglycemic agents used in clinical therapy.

The folk medicines used for the treatment and prevention of diabetes include garlic, onion, ginseng, bitter melon, fenugreek, Gymnema sylvestre, Pterocarpus marsupium, bilberry and aloe vera. The active ingredients derived from plants used for antidiabetic preparations have been identified, and potentially beneficial effects on the rate of food ingestion, glucose transport, potentiation of insulin release, inhibition of insulin clearance, insulin-mimetic effects, reduced gluconeogenesis, and β-cell protection have been attributed to these agents.

Some plants, such as G. sylvestre, M. charantia and P. marsupium, may also help in regeneration of β cells in the pancreas, which is an important discovery because none of the conventional oral hypoglycemic agents shows this action. Several common spices such as fenugreek, cumin, turmeric are some other spices with beneficial antidiabetic properties. Experimental data indicated that dosages of 25- 50 grams of fenugreek seeds, 5-6 garlic cloves, 1 onion bulb, and 1 gram of turmeric powder incorporated into the daily diet of diabetics were effective as a support therapy in the prevention and management of diabetes and related complications like hypertension and obesity.

The mechanisms of action are recognized as stimulation of the pancreas to secrete insulin, interference with dietary glucose absorption and insulin sparing action of bioactive compounds. Ginger, curry leaf, mustard and coriander also improved glucose tolerance in experimental diabetic animals. The National Diabetes Education Program of the National Institutes of Health (NIH) recommends that eggplant should be included in the diet for the management of Type II diabetes.

The anti-diabetic potential of two plants, leaves of agrimony (Agrimony eupatoria), avocado (Persea americana), were evaluated by an in vitro dialysis model of glucose movement. The glucose movement was decreased by more than 50% by agrimony and avocado. It was concluded that agrimony and avocado have the ability to inhibit glucose diffusion using an in vitro model of glucose absorption and represented potential dietary supplements that may be useful for allowing flexibility in meal planning for management of Type II diabetes.

Other nutraceutical compounds which reduce the risk of diabetes are found in diets rich in fibres, legumes, coffee (chlorogenic acid), barley malt, biotin, magnesium, chromium picolinate, calcium/vitamin D, bitter melon, cinnamon extracts.

Hot water extracts of coffee seeds showed significant inhibition against both the enzymes α-glucosidase and α-amylase and reduced postprandial hyperglycemia as assessed by in vivo assays on Wistar rats for Oral Saccharinity tolerance test (OST).

Bitter gourd or bitter melon (Momordica charantia L.) is consumed as a vegetable and herbal medicine in various parts of the world is considered to prevent and help in the management of diabetes and its related complications. It has been proved by a cell culture and glucose uptake assay that the hypoglycemic potential of bitter gourd was due to activation of AMP-Activated protein kinase. Leaves of Tamarindus indicus showed 90% inhibition of α-amylase. Other fruits and vegetables which have been reported as helping to decrease hyperglycemia are the rind of bitter cucumber (Citrullus colocynthis Schard), roots of cabbage (Anthocleista voglii), leaf extract of mango (Mangifera indica),flowers and fruits of banana (Musa sapientum Kuntze), leaves of olive (Olea europea L.), leaves of jackfruit (Atrocarpus heterophyllus Lam.), roots of ginger (Zingiber officinalis), husk of isphagula (Plantago ovate), bitter gourd (Momordica Charantia), Ivy gourd (Coccinia indica), leaves of mustard (Brassica juncea), cinnamon (Cinnamomi cassia).

In addition, other well-known plants with this activity are Aloe barbedensis, Ocimum album, Withania somnifera, Cryptolepis Sanguinolenta, Ocimum sanctum Linn, Stevia rebaudiana Bertoni, Cantharanthus roseus, Azadirachta indica, Opuntia steptacantha, Lantana camara, Agrimony eupatoria L., Eucalyptus globules Labill, Semecarpus anacardium Linn., Chamaemelum nobile, Pterocarpus marsupium, Asparagus adscendens, Phyllanthus amarus, Tinospora cardifolia, Acanthopanax senticosus, Silybum marianum and Panax ginseng.

An extract of leaves of guava (Psidium guajava Linn.) have all shown good hypoglycemic potential. An aqueous extract of unripe plantain (Musa paradisiaca) was shown to possess hypoglycemic activity, as it reduced glucose levels in normal and alloxan-induced diabetic rats.It is suggested that daily consumption of chamomile tea can prevent hyperglycemia and diabetic complications. Roselle tea extract is made from the dried flowers of Hibiscus sabdariffa Linn. (Sobolo) and is a popular beverage in Ghana. Roselle tea extract showed significant inhibition of porcine pancreatic amylase.

From the scientific evaluation of phytochemicals, it is clearly seen that the majority of foods traditionally used to reduce hyperglycemia and related disorders (obesity etc) are rich in polyphenolic compounds and flavonoids.

Conclusion
As α-amylase is a key enzyme for starch hydrolysis and α-glucosidase for intestinal absorption, these enzymes help in digestion and uptake of carbohydrates. Inhibition of these enzymes significantly decreases the postprandial increase of blood glucose level and can therefore be an important strategy in the management of hyperglycemia linked to Type II diabetes. Currently available drugs, acarbose and voglibose, which inhibit these enzymes, have associated side effects of abdominal distention, flatulence, meteorism and diarrhea, which might be caused by the excessive inhibition of pancreatic α- amylase resulting in the abnormal bacterial fermentation of undigested carbohydrates in the colon.

Natural inhibitors from dietary sources have shown lower inhibitory effects against α- amylase activity and stronger inhibitory activity against α-glucosidase, which can be a good strategy to reduce postprandial hyperglycemia with minimal side effects. Lifestyle modifications and proper diet management are also important factors in the treatment and prevention of diabetes mellitus and its related complications. Omega-3-fatty acids and regular consumption of fish helps in diabetes by reducing the chances of getting cardiovascular diseases and cinnamon may also have some affect in reducing blood glucose. Exercise and physical activity are the other important factors to manage diabetes to increase energy expenditure, as physical inactivity and a sedentary lifestyle are associated with metabolic disorders such as diabetes, obesity and other cardio-vascular disorders.

By MH/Dr Ernest Aggrey, 0543999776/[email protected]

Reference:
Gulati, V., Harding, I., & Palombo, E. (2009), Medicinal Plants: Classification, Biosynthesis and Pharmacology, Management of Diabetes with Diet and Plant-Derived Drugs. Nova Science Publishers, Inc. New York.pg 167-182