Indian Medicinal Plants with Antidiabetic Potential

Many medicinal plants and herbs are used to treat diabetes due to their antidiabetic activity. Various clinical studies confirm that medicinal plant extracts help reduce high blood sugar levels and restore the action of pancreatic β- cells. Some of these herbs are mentioned below:

Acacia arabica

Acacia arabica, commonly known as Babool or Babul, Kikar, and Indian gum, belongs to the Fabaceae family and is found all over India, mainly in the wild habitat. The plant extract acts as an antidiabetic agent and induces a hypoglycemic effect by initiating the release of insulin from pancreatic beta cells. Regular use of Acacia significantly reduces fasting and post-prandial blood glucose, triglyceride, LDL, total cholesterol, and blood pressure.

Aegle marmelos

Aegle marmelos, commonly known as Bilwa, Bael, and Stone Apple, belong to the Rutaceae family. It is an important medicinal plant in Ayurveda and has been widely used in indigenous systems of medicine due to its various medicinal properties. Studies indicate that the aqueous extract of Aegle marmelos leaves improves digestion and reduces blood sugar and serum cholesterol. Along with exhibiting hypoglycemic activity, this extract also prevents increased blood glucose in the oral glucose tolerance test. The data obtained indicate that the Aegle marmelos leaf extract has some bioactive molecules, such as umbelliferone, a coumarin, which act as hypoglycemic, antihyperglycemic, and hypolipidemic agents.

Allium cepa

Allium cepa, commonly known as Onion and Pyaz, belongs to the Liliaceae family. Various fractions of dried onion show antihyperglycemic activity in diabetics. Allium cepa also has antioxidant and hypolipidaemic properties. Various clinical studies and researches provide information that onions are used to treat asthma, diabetes, cancer, and various viral diseases. Administration of Allium cepa to people with diabetes significantly controls blood glucose and lipids in serum and normalises the activities of liver hexokinase, glucose 6-phosphatase and HMG Co-A reductase (rate-limiting enzyme of cholesterol biosynthesis). Onion juice significantly controls post-prandial glucose levels in diabetic patients. It contains allyl propyl disulphide (APDS) that stimulates insulin production from the pancreas, enhances insulin concentration, and decreases glucose levels in the blood. Oil extracted from red onion shows antihyperglycemic activity and antioxidant effects.

Allium sativum

Allium sativum, commonly known as Garlic and Lahsun, belongs to the Liliaceae family and is a perennial herb cultivated throughout India. Allium contains Allicin, a sulphur-containing compound responsible for its pungent odour, and has been shown to have significant hypoglycemic activity. This effect is due to increased insulin release from pancreatic beta cells and increased hepatic metabolism. Aqueous garlic extract significantly increases hepatic glycogen, and free amino acid content decreases fasting blood glucose and triglyceride levels in serum. S-allyl cystein sulfoxide (SACS), the precursor of allicin, is a sulphur-containing amino acid, which controls lipid peroxidation and improves diabetic conditions.

Aloe vera

Aloe vera, commonly known as Ghritkumari and Ghikanvar, is a popular household plant, belongs to the Liliaceae family, and has a long history as a multipurpose folk remedy. Aloe Vera gel has various therapeutic effects, including antidiabetic and antioxidant effects. Aqueous extract of aloe vera significantly lowers the blood glucose level. Extract of aloe gum effectively increases glucose tolerance in both normal and diabetic persons. This action of Aloe vera is through stimulation of synthesis and insulin release from pancreatic beta cells. Aloe also improves wound healing in people with diabetes due to its anti-inflammatory property.

Azadirachta indica

Azadirachta indica, commonly known as Neem, belongs to the family Meliaceae and is available throughout India. Extract of Azadirachta shows anti-hyperglycemic activity. Aqueous extract of Azadirachta indica improves blood circulation by enlarging the blood vessels and reduces blood glucose levels. Studies show that good results are obtained when neem is given in combination with allopathic drugs in type 2 diabetic patients, whose diabetes is not maintained by allopathic drugs alone.

Catharanthus roseus

Catharanthus roseus, commonly known as Sadabahar, Periwinkle, and Vinca rosea, belongs to the Apocynaceae family. Extract of leaves and twigs of Catharanthus exhibits antihyperglycemic activity and significantly decreases blood sugar levels in diabetic patients. Administration of Catharanthus results in prolonged action of reduction of blood glucose level. It induces glucose-stimulated insulin secretion from pancreatic beta cells that were otherwise impaired. Catharanthus also reverses diabetes-induced damage to blood and tissues and ameliorates the defects in the activities of key enzymes of the glycolytic path. Catharanthus prevents diabetes complications and can be used as a possible herbal cure for diabetes mellitus.

Cinnamomum verum

Cinnamomum verum, commonly known as Cinnamon and Dalchini, belongs to the family Lauraceae. Cinnamon is well known for its hypoglycemic properties. It promotes insulin secretion, enhances insulin sensitivity, and increases glucose elimination. Also, Cinnamon has insulin-like effects by regulating the enzyme protein-tyrosine phosphatase 1B (PTP1B) and insulin receptor kinase. Cinnamon contains a compound that can act on cells by mimicking insulin, significantly improving glucose uptake by cells. Cinnamon lowers blood sugar by many other mechanisms along with the beneficial effects on insulin resistance. Cinnamon decreases post-prandial glucose levels by interfering with digestive enzymes, which slow the breakdown of carbohydrates in the digestive tract. Studies confirm fasting blood sugar levels lowering the properties of Cinnamon.

Eugenia jambolana

Eugenia jambolana, commonly known as Jamun and Indian Gooseberry, belongs to the Myrtaceae family. In India, the decoction of Eugenia jambolana kernels is used as a household remedy for diabetes and is a significant constituent of many antidiabetic herbal formulations. Extract of dried seeds contains malvidin 3-laminaribiosidea and ferulic acid as active constituents that show a reduction in blood glucose levels and are used to treat diabetes. The oral administration of the extract shows hypoglycemic activity in people with diabetes by increasing serum insulin levels.

Ficus religiosa

Ficus religiosa, commonly known as Peepal, belongs to the family Moraceae and is used in the traditional medication system to treat many diseases, including diabetes. The phytoconstituents present in Ficus, such as phytosterols, flavonoids, tannins, and furanocoumarin derivatives, namely, bergapten and bergaptol, show a significant antidiabetic effect. Decoction prepared from the bark treats diabetes as it contains Sitosterol-d-glucoside, eliciting hypoglycemic activity. Aqueous extract of Ficus religiosa elevates insulin levels and lowers blood glucose levels. Ficus extract also corrects decreased muscle and hepatic glycogen in diabetics, as skeletal muscle is an important site for insulin-stimulated glucose uptake. The aqueous extract of bark also ameliorates blood glucose levels, hepatic enzymes, and lipid parameters. Oxidative stress is one of the major causes of the pathogenesis and complications of diabetes. Ficus modulates the antioxidant enzymes, restores glutathione, and inhibits malondialdehyde content to combat oxidative stress.

Gymnema sylvestre

Gymnema sylvestre, commonly known as Gurmar, means sugar destroyer and belongs to the Apocynaceae family. It is mainly used in Indian medicines for the treatment of diabetes. The active constituents of Gymnema are alkaloids, flavonoids, and saponins. Leaf extract of Gymnema shows a significant reduction in blood sugar levels of people with diabetes. The hypoglycemic effect of the extract of Gymnema is due to an increase in insulin secretion from pancreatic β cells. Gymnema is also effective against pancreatic β cell dysfunction. Aqueous extract of Gymnema causes a reversible increase in intracellular calcium and insulin secretion in β cells. Regeneration of the cells in the pancreas raises insulin levels. Gymnema also helps prevent adrenal hormones from stimulating the liver to produce glucose, thereby reducing blood sugar levels.

Momordica charantia

Momordica charantia, commonly known as Bitter Gourd and Karela, belongs to the Cucurbitaceae family and is used as an antidiabetic and antihyperglycemic agent in India and other Asian countries. Extract of fruit pulp, leaves, seeds, and whole plant shows significant hypoglycemic activity and is used to treat diabetes. This may be due to the inhibition of glucose-6-phosphatase besides fructose-1, 6-biphosphatase in the liver and stimulation of hepatic glucose-6-phosphate dehydrogenase activities. The active constituents of Momordica charantia are cucurbitacin, and momordic I and II. It also consists of lectin, a non-protein linked to insulin receptors, and has an insulin-like activity that decreases blood sugar levels by acting on peripheral tissues.

Ocimum sanctum

Ocimum sanctum, commonly known as Tulsi or Holy Basil, belongs to the Lamiaceae family and is widely found all over India. Since ancient times, it has been used in Indian medicines to treat various diseases. Holy basil's nutritional and chemical composition makes it a plant of immense importance. Eugenol, the active constituent in Ocimum, is responsible for its therapeutic potential. Various studies prove that the aqueous extract of Ocimum sanctum leaves shows a hypoglycemic effect. A significant reduction in fasting blood glucose, glycosylated haemoglobin, urea, total amino acid, total cholesterol, triglyceride, and total lipid, and a simultaneous increase in glycogen, hemoglobin, and protein levels, indicates the hypoglycemic and hypolipidemic effects of tulsi in people with diabetes. Leaf extract of Ocimum stimulates the physiological pathways of insulin secretion.

Panax ginseng

Panax ginseng, commonly known as Ginseng, is a slow-growing perennial plant that belongs to the family Araliaceae. Ginseng has a blood glucose-lowering property that stimulates insulin secretion, protects pancreatic islet cells, stimulates glucose uptake, and increases insulin sensitivity. Ginseng has been used in Indian and traditional Chinese medicine for centuries, and the hypoglycemic activity of ginseng extract and its active ingredients came into the limelight in the 1980s. Ginseng improves fasting blood glucose and glycosylated hemoglobin (HbA1c). Data from various studies have shown that ginseng extract has a beneficial effect on glucose and lipid metabolism. Benefits of using ginseng as part of a treatment program for type 2 diabetes include improved fasting and postprandial (after meal) glucose levels and insulin resistance. The resulting meta-analysis reveals that ginseng supplementation significantly improves fasting blood glucose levels.

Phyllanthus amarus

Phyllanthus amarus, commonly known as Bhuiavla or Bhumi Amla, belongs to the family Phyllanthaceae and is a leafy herbal plant scattered throughout the hotter parts of India. Traditionally it is used in diabetes therapeutics. Extract of Phyllanthus amarus has potent antioxidant activity and reduces blood sugar levels. Research has found that Phyllanthus has the potential to treat diabetes. Extract of the plant helps lower fasting blood sugar and prevents blood sugar spikes. Results show that the extract also suppresses the postprandial rise in blood glucose, reduces hemoglobin glycation, and increases liver glycogen content in people with diabetes. Treatment with the extract also ameliorates the decrease in body weight caused by diabetes. Findings suggest that aerial parts of Phyllanthus amarus have blood glucose-lowering properties due to the inhibition of glucose absorption and enhancement of glucose storage.

Pterocarpus marsupium

Pterocarpus marsupium, also known as Malabar kino, Indian kino, and Vijayasar, belongs to the Fabaceae family and is a deciduous moderate tree found in India. The blood sugar-lowering activity of Pterocarpus marsupium is due to the presence of tannates in the plant extract. It contains marsupin, pterosupin, and liquiritigenin, which show antihyperlipidemic activity. Epicatechin, the active principle of Pterocarpus, is insulinogenic as it enhances insulin release and converts proinsulin to insulin. Flavonoid fraction of Pterocarpus marsupium not only has a hypoglycemic effect but also shows pancreatic protective and regenerative properties.

Tinospora cordifolia

Tinospora cardifolia, also known as Guduchi, belongs to the Menispermaceae family and is a large, glabrous, deciduous climbing shrub. It is mainly used in Indian medicines for the treatment of diabetes. The active constituents of Tinospora are diterpene compounds which consist of tinosporone, tinosporic acid, berberine, and giloin. Oral administration of Tinospora cordifolia root extract results in a significant reduction in blood and urine sugar, and it also prevents a decrease in body weight caused due to diabetes. Studies show that the daily administration of an aqueous extract of Tinospora decreases blood glucose levels and increases glucose tolerance.

Trigonella foenum graecum

Trigonella foenum-graecum, commonly known as Fenugreek and Methi, belongs to the family Fabaceae and is found all over India. The fenugreek seeds are one of the major constituents of Indian spices. Studies have proved that fenugreek has strong antidiabetic, antioxidant, and lipid-lowering properties. 4-hydroxyleucine, a novel amino acid found in fenugreek seeds, increases glucose-stimulated insulin release by islet cells of the pancreas. Oral administration of fenugreek seeds decreases blood glucose levels, improves glucose metabolism, and normalises creatinine kinase activity in the heart, skeletal muscles, and liver.

Conclusion

All the herbs discussed in this review have exhibited significant pharmacological and clinical activities. The herbal drugs have powerful potency with negligible side effects compared to synthetic antidiabetic drugs. There has been an increasing demand to use natural products having antidiabetic activity. Isolation & identification of active constituents from these plants and preparation of a standardised dose plays a significant role in improving the hypoglycaemic activity. Interest in plant-based remedies has rekindled in recent times, and plants hold definite promise in managing diabetes.