Phytochemicals for Diabetes Management
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Send Orders for Reprints to [email protected] Pharmaceutical Crops, 2014, 5, (Suppl 1: M2) 11-28 11 Open Access Phytochemicals for Diabetes Management Switi B. Gaikwad*, G. Krishna Mohan and M. Sandhya Rani Centre for Pharmaceutical Sciences, Institute of Science and Technology, Jawaharlal Nehru Technological University Hyderabad, Andhra Pradesh, India Abstract: Diabetes mellitus is a complex metabolic disorder resulting from either insulin insufficiency or insulin dysfunc- tion. Diabetes mellitus affects most of the people in both developed and developing countries. The treatment of diabetes with synthetic drugs is costly and chances of side effects are high. Phytomedicine has been used since ancient times in various parts of the world where access to modern medicine is limited. Medicinal plants and phytoconstituents play an important role in the management of diabetes mellitus especially in developing countries where resources are meagre. Phytochemicals identified from medicinal plants present an exciting opportunity for the development of new types of therapeutics for diabetes mellitus. Most prevalent among phytochemical groups are the alkaloids, glycosides, polysaccha- rides, and phenolics such as flavonoids, terpenoids and steroids. Despite considerable progress in the development of syn- thetic drugs, the discovery of phytomedicine as an alternative therapy is progressing. This article aims to provide a com- prehensive review on various plant species from globe and their constituents, which have been shown to display potent hypoglycemic activity. Keywords: Antidiabetic, diabetes management, diabetes mellitus, hyperglycemia, hypoglycemia, insulin, phytochemicals. INTRODUCTION Diabetic retinopathy is an important cause of blindness, and occurs as a result of long-term accumulated damage to the The World Health Organization (WHO) defined diabetes small blood vessels in the retina. One percent of global mellitus as “a metabolic disorder of multiple etiologies char- blindness can be attributed to diabetes. Diabetes is among acterized by chronic hyperglycemia with disturbances in the leading causes of kidney failure [3]. With increasing carbohydrate, fat and protein metabolism resulting from de- rates of childhood and adult obesity, diabetes is likely to fects in insulin secretion, insulin action, or both” [1]. Diabe- become even more prevalent over the coming decades. The tes is a disorder of carbohydrate, fat and protein metabolism drugs which lower the blood sugar level or treat the symp- attributed to diminished production of insulin or mounting toms of diabetes mellitus are known as hypoglycemic drugs. resistance to its action. Diabetes is a chronic disease that It can be categorized into insulin and insulin preparations, occurs either when the pancreas does not produce enough which are employed only parenterally, and oral hypoglyce- insulin or when the body cannot effectively use the insulin mic drug which can be administered orally [4]. that it produces. Insulin is a hormone that regulates blood sugar. The increased production and ineffective scavenging Plants have always been a good source of drugs. The eth- of reactive oxygen species may play a critical role in diabe- nobotanical information reports about 800 plants that may tes mellitus. The disturbance of antioxidants defence system possess anti-diabetic potential. The beneficial uses of me- in diabetes is mainly because of alteration in antioxidant dicinal plants in traditional system of medicine of many cul- enzymes, impaired glutathione metabolism, and decreased tures are extensively documented. Several plants have been ascorbic acid levels. It is becoming the third “killer” of the used as dietary adjuvant and in treating the number of dis- health of mankind along with cancer, cardiovascular and eases even without any knowledge on their proper functions cerebrovascular diseases [2]. Hyperglycemia, or raised blood and constituents. This practice may be attributed to the un- sugar, is a common effect of uncontrolled diabetes and over compromised cost and side effects of synthetic hypoglyce- the time leads to serious damages to many of the body's sys- mic agent. Although numerous synthetic drugs were devel- tems, especially the nerves and blood vessels. Over the time, oped for the treatment of diabetes mellitus but the safe and diabetes can damage the heart, blood vessels, eyes, kidneys, effective treatment paradigm is yet to be achieved [5]. and nerves. Diabetes increases the risk of heart disease and WHO has recommended the evaluation of traditional stroke. 50% of people with diabetes die of cardiovascular plant treatments for diabetes as they are effective, non-toxic, disease. Combined with reduced blood flow, neuropathy with less or no side effects and are considered to be excellent (nerve damage) in the feet increases the chance of foot ul- aspirants for oral therapy [6]. A scientific validation of sev- cers, infection and eventual need for limb amputation. eral plant species has proved the efficiency of the botanicals in reducing the sugar level. From the reports on their poten- *Address correspondence to this author at the Centre for Pharmaceutical tial effectiveness against diabetes, it is assumed that the phy- Sciences, Institute of Science and Technology, Jawaharlal Nehru Techno- tochemicals have a major role in the management of diabe- logical University Hyderabad, Andhra Pradesh-500085, India; tes, which needs further exploration for the necessary devel- Tel: +91 9298705073, E-mail: [email protected] opment of drugs and nutraceuticals from natural resources. 2210-2906/14 2014 Bentham Open 12 Pharmaceutical Crops, 2014, Volume 5 Gaikwad et al. Herbal treatments for diabetes have been used in patients alkaloids boschniakine and 5, -hydroxyskitanthine were with insulin-dependent and non-insulin-dependent diabetes, inactive up to 100 μM [14] diabetic retinopathy, diabetic peripheral neuropathy, etc Casuarine 6-O--glucoside isolated from the methanol however many herbal remedies used today have not under- extract of the bark of Syzygium malaccense L. (Myrtaceae) gone careful scientific evaluation and some have the poten- was found to inhibit –glucosidase activity [15]. tial to cause serious toxic effects and major drug-to-drug interaction. Compounds with different structure but with the Alkaloids like catharanthine, vindoline and vindolinine same therapeutic activity isolated from different plant spe- obtained from Catharanthus roseus (L.) G. Don (Apocyna- cies act as active moieties for the treatment of various dis- ceae) also lowered blood sugar levels when tested in normal eases. The use of these plants and phytoconstituents may and streptozotocin-induced diabetic rat models. Leurosine, delay the development of diabetic complications and may vindoline, vindolinine and catharanthine, reduces blood glu- regulate the metabolic abnormalities through a variety of cose in normal and alloxan diabetic rabbits [16]. Vincristine mechanisms [7]. Moreover, during the past few years many and vinblastine, dimeric alkaloids obtained from the leaves phytochemicals responsible for anti-diabetic effects have and stems of C. Roseus are used traditionally in various re- been isolated from the plants. Several phytoconstituents such gions of the world including India, West Indies as well as as alkaloids, glycosides, flavonoids, saponins, dietary fibres, Nigeria to control diabetes [17]. polysaccharides, glycolipids, peptidoglycans, amino acids Griffiths reported a new class of nortropane polyhy- and others obtained from various plant sources that have droxylated alkaloids of a calystegine which was isolated been reported as potent hypoglycemic agents have been fur- from the fruits of Nicandra physalodes L. (Solanaceae), and ther discussed (Fig. 1, Table 1) in the following segment. the structure was determined as 3-O-D-glucopyranosyl- calystegine B1. Although calystegine B1 showed no inhibi- PHYTOCHEMICALS IN THE MANAGEMENT OF tory activity towards the enzyme Calystegine B2 which is a DIABETES MELLITUS potent inhibitor of -glucosidases and R-galactosidases. This Alkaloids glucoside was a potent inhibitor of rice R-glucosidase. The introduction of the R-glucosyl residue to calystegine B1 and Different alkaloids have been isolated from several me- of the glucosyl or galactosyl residue to calystegine B2 is dicinal plants and investigated for their possible antidiabetic resulted in a significant decrease of glycosidase inhibitory activity in different animal models. Alkaloids exert a wide activity. 4-O-R-D-Galactopyranosyl-calystegine B2 showed range of antidiabetic activities through different mecha- similar result. R-Glucosidase inhibitors have a potential for nisms. Below are some important class of alkaloids reported the treatment of diabetes because they reduce diet-induced with their mechanism of hypoglycemic or hyperglycemic hyperglycemia and endogenous insulin secretion by inhibit- activity. ing intestinal R-glucosidases [18, 19]. Berberine, an isoquinoline alkaloid is obtained from the Cryptolepine is an indoloquinolone alkaloid isolated roots and stem bark of Berberis L. (Berberidaceae). This from Cryptolepis sanguinolenta (Lindl.) Schltr. (Apocyna- compound is mostly isolated from the roots of B. aristata ceae). The Antihyperglycemic activity of cryptolepine was DC. (5% in roots and 4.2% in stem-bark), B. asiatica Roxb. measured in vitro and in a Non-insulin-dependent diabetes ex DC., B. aquifolium Pursh, B. petiolaris Wall. ex G. Don, mellitus