A Comprehensive Review on Five Medicinal Plants of Bangladesh. Chemical Constituents and Uses

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Chapter 4 Pharmacological Activities of Five Medicinal Plants:
Pharmacological Activities of Gymnema sylvestre:
Anti-diabetic Activity: The hypoglycemic action of Gymnema sylvestre leaves was first documented in the late 1920s. The plants hypoglycemic action is gradual in nature, differing from the rapid effect of many prescription hypoglycemic drugs. Gymnema leaves raise insulin levels by causing regeneration of Beta cells in the pancreas that secrete insulin. Research has shown that Gymnema improves the uptake of glucose into cells by increasing the activity of glucose-metabolizing enzymes, and preventing adrenaline from stimulating the liver to produce glucose, with the net effect that blood sugar levels are reduced. Another antidiabetic effect of Gymnema is that it negates the taste of sugar, which has the effect of suppressing and neutralizing the craving for sweets. Gymnemic acid found in the leaf extracts inhibits hyperglycemia and also acts as a cardiovascular stimulant.
Oral administration of a water soluble fraction G-54 isolated from Gymnema sylvestre administered to 27 type 2 diabetic patients reduced their insulin requirement, lowered the fasting blood sugar and glycosylated haemoglobin content (Shanmugasundaram et al., 1990a). Two water soluble fractions (GS-3 and GS-4) obtained from leaves were found to double the pancreatic islets and ß-cell numbers in diabetic rats (Shanmugasundaram et al., 1990b).Alcoholic leaf extract (500mg/kg, orally) lowered maximum blood sugar in fasted, glucose fed and diabetic rats along with insulin released from pancreatic ß-cells (Chatopadhyay et al., 1993). In rats the insulin secretion from islets of Langerhans and several pancreatic ß-cell lines induced by alcoholic extract in absence of other stimulus (Persaud et al., 1999). Gymnemic acid IV, isolated from leaves produced potent hypoglycemic effect in STZ-diabetic mice (Sugihara et al., 2000). Leaf extract has been observed to produce

Pritesh Ranjan Dash, R. Ph, has earned a Bachelor's and Master's Degree in Pharmacy from Stamford University, Bangladesh, in 2010 and 2012 as well as a M. Phil Part-1 in Pharmacy from Jahangirnagar University in 2015. Currently, he is attending a PhD in Pharmacy at Jahangirnagar University, Bangladesh, and teaches at the Pharmacy Department at BRAC University, Mohakhali, Dhaka. He has already published one book and more than 17 research articles on medicinal plants in reputed national and international journals.