According to some researchers, the antidiabetic effects of polysaccharides are primarily due to their antioxidant properties. The antioxidant activity of polysaccharides helps to reduce the degree of damage to β-cells in the pancreas
. Pumpkin polysaccharides have antioxidant, antitumor, immunoregulatory, hypoglycemic, and hepatoprotective activity.
Alkaloids are a class of naturally occurring chemical compounds derived from plants, animals, bacteria, and fungi. They have a wide range of pharmacological activities such as antimalarial, antiasthma, anticancer, antihypertensive, oxytotic, CNS stimulant, muscle relaxant, antispasmodic, cholinomimetic, vasodilator, antiarrhythmic, analgesic, antibacterial, and antihyperglycemic. Several alkaloids, including berberine, boldine, and sanguinarine, have been demonstrated to be potentially effective against various diabetes models 
Medicinal species such as capsicum (Capsicum annuum
), turmeric (Curcuma longa
), barberry (Berberis vulgaris
), and garden cress (Lepidium sativum
) are among the most common and therapeutic plants used to control diabetes and have been the subject of several experimental and clinical studies. Alkaloids isolated from these plants (berberine, capsaicin, and trigonelline) are of great interest in this area. Interestingly, the therapeutic effect of alkaloids on blood glucose pathogenesis is mediated through various signaling cascades and pathways, such as inhibition of the α-glucosidase enzyme, blockade of PTP-1B, deactivation of DPP-IV, increased insulin sensitivity, and oxidative stress modulation 
4. Complications of DM and the Effect of Medicinal Plants and Their Phytocomponents on Them
The absolute or relative deficiencies of insulin and insulin resistance contribute to the development of various metabolic and vascular diseases, neuropathies, and pathological changes in internal organs and tissues, including the digestive system 
. The diabetic syndrome is characterized mainly by lesions of the lower extremities. The main pathogenetic factors leading to the development of diabetic foot are peripheral nephropathy and damage to the large arteries of the lower extremities, leading to infection 
. A decisive role in the development of diabetic retinopathy is played by chronic hypoglycemia and associated biochemical disorders (formation of sorbitol, non-enzymatic glycosylation of retinal vascular proteins, increased oxidative stress).
Due to their antioxidant and membrane stabilizing effects, flavonoids can reduce vascular wall permeability and inflammation, as well as determine the antioxidant, anti-inflammatory, and diuretic effects of preparations containing these substances 
. Polyphenolic compounds in phytocomponents react with free radicals to form less active phenolic radicals, facilitating the utilization of oxidized sugars and rapidly slowing the sugar oxidation process in the body. The inhibitory effect of preparations stabilizes the structure of cell membranes, normalizes permeability, improves microcirculation and accelerates the utilization of toxic substances. The end result is the prevention of severe organ damage and the activation of regenerative processes 
The blueberry, a member of the lingonberry family, is a plant that may help to reduce the side effects of DM. It contains tannins, myrtilene, a mixture of delphidin monomethyl ether and malvidin chloride, vitamins C, B, and carotenes, and it has recently been used to treat diabetes. Neomyrtilene in the leaves of the plant significantly reduces blood glucose levels in experimental diabetic patients 
Soy contains flavonoids, amino acids, beta-carotene, and vitamins E, B, and C. Studies have shown that soy extract dissolved in water reduces blood sugar levels by 30–40%, has a diuretic effect and improves pancreatic function 
. This makes the use of soy in DM highly beneficial, in addition to its use as a diuretic and renal drug 
. Vitamin K, uric acid glycosides, formic acid, tannins and proteins, vitamins C and B2, trace elements, flavonoids, chlorophyll, and carotenoids are all present in fresh nettle leaves 
. Kuril tea extract has an anti-inflammatory effect, manifested by a decrease in blood sugar and lipid levels, a protective effect against diabetes, and functional activity of the liver and kidneys. The plant’s therapeutic effects on experimental diabetes have been tested on laboratory animals and it contains flavonoids, vitamin C, carotenes, and tannins. It has been established that it reduces the degree of damage to the islets of Langerhans, slows down the development of diabetes and hypoglycemia, and increases resistance to the toxic effects of DM. Dandelion is an insulin-containing plant that increases the activity of the pancreas, increases insulin secretion, and improves digestion and metabolism 
. Fennel root contains tryptophan compounds, sterols, and 24% of insulin. It is customary to collect the rhizomes along with the aerial parts of the plant for medicinal purposes.
The use of plant extracts and phytochemicals is currently popular for the prevention or treatment of various health problems; though this creates problems when classifying them as dietary supplements or nutraceuticals, because they do not require proof of effectiveness 
. The use of herbal medicines or herbal ingredients in combination with traditional medicines requires product approval, including safety measures, quality control, and efficacy data 
The bioavailability of a plant extract or plant component is critical to its full effect on the body and includes the steps of delivery, absorption, distribution, metabolism, and clearance of the extract/component. The crude plant extracts or plant components showed good biological activity (such as antioxidant activity) in vitro, and a slight decrease in activity was observed in in vivo studies. One of the main reasons why plant extracts or plant compounds work more effectively in vitro is the use of higher effective concentrations than those commonly used in in vivo studies. When used in vivo, effective concentrations reach target tissues or organs after absorption, distribution, metabolism, and degradation, and exhibit biological responses at concentrations lower than those tested in vitro