Diabetes mellitus is characterized by hyperglycemia that is induced by decreased cellular glucose uptake and metabolism. Control of plasma glucose concentration is vital to decrease the incidence and severity of long term diabetic complications. Currently, dietary changes, oral hyperglycemic agents or insulin injections are utilized to prevent hyperglycemia.
Many synthetic antidiabetic agents were developed. But they produce some serious side effects and are relatively expensive for developing countries. Therefore searching for effective, low cost and hyperglycemic agents with less side effects is important.
More than 400 plants world wide have been documented as beneficial in the treatment of diabetes. The majority of traditional antidiabetic plants await proper scientific and medical evaluation for their ability to improve blood glucose control. However, a few comprehensive studies of traditional antidiabetic plants have been carried out. Traditional antidiabetic plants might provide a useful source for developing new oral hyperglycemic compounds as pharmaceutical entities to the existing therapies1.
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Evaluating the effect of such traditional medicines might offer an alternative and natural key to unlock diabetologistâ€™s pharmacy. Glucose transport through biological membranes requires specific transport proteins . Passive transport (facilitated diffusion) of glucose through the cell membrane is otherwise catalysed by glucose carriers (GLUT). GLUT 2, a transmembrane carrier protein of GLUT family, located in basolateral membrane of small intestine is very efficient carrier of glucose across small intestine. Studies have revealed that the hypoglycemic effect can be attributed to certain medicinal plant extracts which reduced the glucose uptake by retarding the glucose transport function.
The antihyperglycemic activity of these plants in vivo can be associated with the ability of soluble components to increase glucose uptake and metabolism in muscle or to stimulate insulin secretion. Decreasing gastrointestinal glucose convection and diffusion is now thought to be the reason why viscous plant components have antihyperglycemic properties3.
Glucose is diffused through passive transport across a cellular membrane by passing through specific transmembrane integral proteins. Glucose is absorbed in the small intestine by the transcellular and paracellular pathways. Transcellular absorption is mediated by membrane bound transporter proteins such as the sodium dependent glucose transporter (SGLT-1), found on the apical membrane of enterocytes, that actively absorbs glucose from the gut lumen2.
In diabetes mellitus the management of blood glucose concentration is of fundamental importance and a large number of plants are known to contribute towards achieving this goal. A large number of plants that have been identified to have antihyperglycemic activity have diverse modes of action, either through physical or biochemical means. Some of these plants are known for their influence on the process of glucose diffusion by physical means4. The antihyperglycemic activity of some plants in vivo can be associated with their ability to increase glucose uptake and metabolism. Decreasing gastrointestinal glucose convection and diffusion can also be a reason why some plant components reduce blood glucose levels 1.
The metabolic energy for mammalin cells are obtained from oxidation of glucose. However, as the plasma membrane is impermeable to polar molecules such as glucose, the cellular uptake of this nutrient is accomplished by membrane-associated carrier proteins that transfer it across the lipid bilayer. The Na(+) glucose co-transporter and the facilitative glucose transporter were the two classes of glucose carriers described in mammalian cells. The Na(+)-glucose cotransporter transports glucose against its concentration gradient by coupling its uptake with the uptake of Na+ that is being transported down its concentration gradient.
The glucose transport is accelerated by facilitative glucose carriers down its concentration gradient by facilitative diffusion.
Studies have revealed that the hypoglycemic effect of many antidiabetic plants can be attributed to the flavanoid component of the plant extracts which reduces glucose uptake by retarding glucose transport functions6.
Chalcone , an aromatic ketone that forms the central core for a variety of important biological compounds.
It has antibacterial, antifungal, antitumor and anti-inflammatory properties. Some have antihyperglycemic activity .They are also intermediates in the synthesis of flavanoids, which are substances widespread in plants and have an array of biological activities. Hypoglycemic activity of chalcones:
The antioxidant property of chalcones attracted to explore hybrid structures as anti-hyperglycemic agents, because oxidative stress also plays an important role in diabetic patients leading to vascular complications. 3,4-dimethoxy compound displayed significant antihyperglycemic effect. Mono methoxy series showed blood glucose lowering activity. Compounds vicinally deoxygenated as dimethoxy and methylenedioxy substitution showed the best antihyperglycemic activity when compared to the corresponding monomethoxy compounds. Compounds containing propanolamine chain at para position showed significant activity as compared to meta and ortho substituted compounds7,8.
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The activity of chalcones on serum glucose-lowering in hyperglycemic normal rats is mainly due to insulin secretion and indicates these chalcones as novel compounds with strong anti-hyperglycemic properties9.
Naphthylchalcones were found to possess antihyperglycemic activity.In addition some chalcones (figure 1 and 2) stimulated significantly by the insulin secretion given by glucose. These results suggested that the presence of nitro group and their position in the phenyl rings are responsible for antihyperglycemic activity of chalcones.The effect of chalcones on serum glucose-lowering seems to be a resultof chalcones shows the insulin secretion and these chalcones represent potential compounds with strong antihyperglycemic properties10.
Sulfonamide 4- methoxy chalcones were found to possess antihyperglycemic activity37.
Herbal medicine involves the use of plant products (include leaves,stems,flowers,fruits,seeds,roots,rhizomes and bark) for medicinal purposes.In some cases animal and mineral products are also used.In ancient time the plants are used for healing purposes.The use of herbal products for medicinal purpose is 60,000 years old13.
The World Health Organization (WHO) estimates that 4 billion people,ie; 80% of the world population, use herbal medicine for primary health care. Herbal medicine is a major component in all indigenous natural products.Traditional medicine is a common element in Ayurvedic, Homeopathic, Naturopathic, Traditional oriented and Native American Indian Medicine. According to WHO reports, 74% of the modern medicines are derived plant products.Even major pharmaceutical companies are currently conducting extensive research on plant materials of medicinal values14.
Major Chemical Components In Herbs:11,12
1 . Alkaloids
i) Flavanoid glycosides
ii) Anthraquinone glycosides
iii) Saponin glycosides
iv) Cardioactive glycosides
v) Coumarin glycosides
3. Essential oils
4. Organic acids
6. Amino acids
7. Protein and Enzymes
9. Wax and Lipids