Traditional Antidiabetic Plants (Introduction)

Molecules. 2022 Jul 3;27(13):4278. doi: 10.3390/molecules27134278

Pharmacologically Active Phytomolecules Isolated from Traditional Antidiabetic Plants and Their Therapeutic Role for the Management of Diabetes Mellitus

Prawej Ansari 1,2,*, Samia Akther 1, J M A Hannan 1, Veronique Seidel 3, Nusrat Jahan Nujat 1, Yasser H A Abdel-Wahab 2

Editors: Rudolf Bauer, Jelena S Katanic Stankovic

             Introduction

Diabetes mellitus is one of the most common endocrine metabolic disorders characterized by chronic hyperglycemia caused by varying degrees of insulin resistance, 

deficiency in insulin secretion, or both [1].

 Nearly 10.5% of the worldwide population is affected by diabetes, with its prevalence increasing at an alarming rate. According to data collected from the International Diabetes Federation (IDF), about 783.2 million people are estimated to be diagnosed with diabetes by 2045 [2].

Diabetes mellitus can be classified into two major categories: Type 1 and Type 2 diabetes, where Type 2 diabetes accounts for about 90% of all cases. 

Type 1 diabetes, previously known as insulin-dependent diabetes, is an autoimmune disorder that occurs due to the destruction of the pancreatic beta cells leading to significantly reduced secretion of insulin [3]. 

It is a non-hereditary genetic condition that mainly affects the juvenile under thirty years of age.

 Type 2 diabetes, also known as non-insulin-dependent diabetes, is the most common form of diabetes, with its prevalence rapidly rising worldwide [4]. 

It is a hereditary condition caused as a result of insulin resistance, insufficient insulin secretion, or a combination of both, largely affecting an older population than Type 1 diabetes [5]. 

Both forms of diabetes alter carbohydrate, protein, and fat metabolism.

 The effect of insulin resistance leads to high blood sugar levels by hindering the uptake and efficient use of glucose by most cells of the body [6]. 

KeThe progression of the disease is accompanied by tissue or vascular damage resulting in severe complications,

 including retinopathy, diabetic neuropathy, nephropathy, cardiovascular, pulmonary, cerebral, and peripheral vascular diseases, ulcers, and thyroid gland disorders, leading to serious morbidity and mortality [1,7,8,9]. 

Available therapies currently in use for the treatment and management of diabetes include insulin and several oral hypoglycemic agents such as metformin, sulfonylureas, α-glucosidase inhibitors, meglitinide analogues, thiazolidinediones, DPP-IV inhibitors, SGLT-2 inhibitors, and GLP-1 mimetics. However, these drugs, intended to boost insulin sensitivity and increase insulin secretion together with the reduction in circulatory plasma glucose levels by increasing glucose excretion or uptake in adipose tissue, are usually associated with many side effects. 

These include, among others, weight gain, hypoglycemia, gastrointestinal tract disturbances, liver injury, renal failure, hypersensitivity reactions, flatulence, diarrhea, and abdominal bloating [1,10,11]. 

In addition, these drugs have been known to have other major disadvantages, including drug resistance, and there is also a lack of therapies to prevent the long-term complications of the disease.

The complications associated with insulin and oral antidiabetic agents, together with limited drug tolerability, adverse effects, and cost, have accelerated the search for alternative medicines with better efficacy, potency, and fewer side effects [12]. 

Interestingly, there has been an increase in popularity surrounding drug discovery research into natural antidiabetic agents, especially those derived from medicinal plants, which could enhance β-cell function and treat diabetes-associated complications with fewer adverse side effects [13].

Herbal medicines contain a diversity of phytochemicals and have been traditionally used for treating a wide variety of diseases. 

They are considered to be naturally safe and efficacious with fewer side effects [12]. 

The control and management of diabetes using herbal drugs have proven to be more advantageous over synthetic medicines due to their accessibility, reduced cost, lesser complications, and lower side effects. Herbal medicines act via different mechanisms aiming at reducing insulin resistance, increasing insulin secretion, protecting pancreatic beta cells, and thereby lowering circulating blood glucose levels [14].

Throughout the years, thousands of plant species have been used for their medicinal uses as integrative medicines for various diseases, of which more than 800 plants have been reported to exhibit antidiabetic effects [15]. 

Such plants have been examined for their use in the treatment of the different types of diabetes and could be potential sources for new natural antidiabetic drug discovery research [16]. 

A number of medicinal plants used traditionally for their antidiabetic activity are currently under investigation to be formulated commercially as modern drugs.

 This is particularly the case in developing countries where the cost of allopathic medicine is high, and the traditional use of plants to treat diabetes is common practice [15].

 Traditional natural medicines are extensively prescribed in Asian countries (e.g., China, India, Bangladesh, Pakistan, Sri Lanka, Thailand, Nepal, Bhutan, Japan, and others) [17].

 Among the medicinal plants possessing hypoglycemic effects, the most common ones used as remedies for diabetes include Acacia arabica, Aegle marmelos, Allium cepa, Allium sativum, Aloe vera, Annona squamosa, Azadirachta indica, Berberis vulgaris, Camellia sinensis, Capsicum frutescens, Cassia alata, Cinnamomum zeylanicum, Eucalyptus globulus, Eugenia jambolana, Helicteres isora, Momordica charantia, Panax ginseng, Punica granatum, Swertia chirayita, Trigonella foenum-graecum, and others [15,16,18,19].

 The antidiabetic activity of these plants is thought to be mediated via various mechanisms, including the stimulation of insulin secretion from pancreatic β-cells, increasing insulin binding to receptors, reduction in insulin resistance, and improving glucose tolerance. 

Other modes of action include enhancing glucose metabolism, improving β-cell mass and function, and increasing plasma insulin, thus decreasing circulating blood glucose levels [20,21,22,23]. 

In addition to being used to treat diabetes, these plants have also been traditionally employed to treat other conditions such as ulcers, wounds, inflammation, infections, diarrhea, dysentery, malaria, rheumatism, hypertension, obesity, pneumonia, and kidney diseases [12,19,24,25,26].

 The main objective of this review is to explore the traditional plant-based therapies and/or their phytoconstituents available for the treatment of diabetes. These could provide the basis for the discovery of new antidiabetic drugs with fewer side effects and stronger efficacy than currently available medicines.

To be continued