Other experts indicated than only 800 plants are used in the management of Diabetes
and only 30% of plants used in folk medicines for Diabetes have been biologically
assayed (Chinsembu 2019). Therefore, the potential to discover new antidiabetic
drugs from plants is still untapped.
15.2 Mechanisms of Action of Antidiabetic Substances
Hypoglycemic drugs exert antidiabetic effects through different mechanisms,
namely, sulfonylureas (reduce blood sugar, mostly by elevating insulin release from
islets of Langerhans), biguanides (improve the body’s sensitivity towards insulin and
reduce the amount of sugar absorbed by the intestine), a-glucosidase inhibitors
(reduce the absorption rate of carbohydrates in the body), thiazolidinediones (improve muscle and adipose tissue sensitivity to insulin and reduce liver glucose
production. Also augment b-cell function by lowering free fatty acid levels that
ultimately lead to b-cell death), and non-sulfonylureas secretagogues (increase the
secretion of insulin from active b-cells). These drugs alongside with insulin are the
main way for controlling diabetes; however, they have different side effects. The
antidiabetic action of plant materials has been accredited to the mixture of phytochemicals (alkaloids, phenolic acids, flavonoids, glycosides, saponins, polysaccharides, stilbenes, and tannin) or to a single component of plant extracts through
various mechanisms such as regulation of glucose and lipid metabolism, insulin
secretion, stimulating b cells, NF-jB signaling pathway, inhibition of gluconeogenic
enzymes (pyruvate carboxylase, PEP carboxykinase, fructose-1, 6-bisphosphatase,
and glucose 6-phosphatase), and reactive oxygen species (ROS) protective action
(Salehi et al. 2019).
He et al. (2019) summarize naturally antidiabetic drugs and identified their
molecular targets. a-Glucosidase and a-amylase are crucial enzymes that hydrolyze
complex dietary carbohydrates to glucose or monosaccharides in the digestive
system. Glycosidase inhibitors decrease the digestion process and postprandial
blood glucose levels through the blockage of various amylases and glycosidases.
The inactivation of DPP4 prolong the degradation rate of glucagon-like peptide-1
(GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) normalizing
insulin release. GLP-1 and GIP can modulate b-cell differentiation, insulin
biosynthesis and release, gastric emptying, and execute some other functions.
Plasma levels of GLP-1 and GIP promote insulin secretion, reduce glucagon
secretion, and in this way, control blood glucose levels. The stimulation of PPAR c
(a family of nuclear receptors and ligands activated by transcription factors that
modulate adipocyte differentiation, lipid metabolism, inflammatory processes, and
glucose homeostasis) serves as an insulin sensitizer in adipose tissue and muscle
throughout the improvement of glucose and lipid metabolism and inflammatory
processes. The antidiabetic effect of alkaloids glycosides, polyphenols, carotenoids,
terpenoids, flavonoids, anthocyanins, tocopherols, peptidoglycans, steroids, saponins, xanthones, and polysaccharides may also be related to these other
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537
and only 30% of plants used in folk medicines for Diabetes have been biologically
assayed (Chinsembu 2019). Therefore, the potential to discover new antidiabetic
drugs from plants is still untapped.
15.2 Mechanisms of Action of Antidiabetic Substances
Hypoglycemic drugs exert antidiabetic effects through different mechanisms,
namely, sulfonylureas (reduce blood sugar, mostly by elevating insulin release from
islets of Langerhans), biguanides (improve the body’s sensitivity towards insulin and
reduce the amount of sugar absorbed by the intestine), a-glucosidase inhibitors
(reduce the absorption rate of carbohydrates in the body), thiazolidinediones (improve muscle and adipose tissue sensitivity to insulin and reduce liver glucose
production. Also augment b-cell function by lowering free fatty acid levels that
ultimately lead to b-cell death), and non-sulfonylureas secretagogues (increase the
secretion of insulin from active b-cells). These drugs alongside with insulin are the
main way for controlling diabetes; however, they have different side effects. The
antidiabetic action of plant materials has been accredited to the mixture of phytochemicals (alkaloids, phenolic acids, flavonoids, glycosides, saponins, polysaccharides, stilbenes, and tannin) or to a single component of plant extracts through
various mechanisms such as regulation of glucose and lipid metabolism, insulin
secretion, stimulating b cells, NF-jB signaling pathway, inhibition of gluconeogenic
enzymes (pyruvate carboxylase, PEP carboxykinase, fructose-1, 6-bisphosphatase,
and glucose 6-phosphatase), and reactive oxygen species (ROS) protective action
(Salehi et al. 2019).
He et al. (2019) summarize naturally antidiabetic drugs and identified their
molecular targets. a-Glucosidase and a-amylase are crucial enzymes that hydrolyze
complex dietary carbohydrates to glucose or monosaccharides in the digestive
system. Glycosidase inhibitors decrease the digestion process and postprandial
blood glucose levels through the blockage of various amylases and glycosidases.
The inactivation of DPP4 prolong the degradation rate of glucagon-like peptide-1
(GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) normalizing
insulin release. GLP-1 and GIP can modulate b-cell differentiation, insulin
biosynthesis and release, gastric emptying, and execute some other functions.
Plasma levels of GLP-1 and GIP promote insulin secretion, reduce glucagon
secretion, and in this way, control blood glucose levels. The stimulation of PPAR c
(a family of nuclear receptors and ligands activated by transcription factors that
modulate adipocyte differentiation, lipid metabolism, inflammatory processes, and
glucose homeostasis) serves as an insulin sensitizer in adipose tissue and muscle
throughout the improvement of glucose and lipid metabolism and inflammatory
processes. The antidiabetic effect of alkaloids glycosides, polyphenols, carotenoids,
terpenoids, flavonoids, anthocyanins, tocopherols, peptidoglycans, steroids, saponins, xanthones, and polysaccharides may also be related to these other
15 Role of Natural Bio-active Compounds …
537