Common medicinal plants with antiobesity potential: A special emphasis on fenugreek.

Sir,

Obesity is a major health burden, with associated increased risk of insulin resistance, type 2 diabetes, cardiovascular disease, and cancer, and due to the economic costs to healthcare providers.[1] Mechanisms underlying the progression of obesity and insulin resistance manifest dysfunction of lipid and carbohydrate metabolism.[2]

The global prevalence of obesity has nearly doubled since 1980, which is predominantly because of new dietary habits and sedentary lifestyle. Changes in the diet seem to be the major driver of the rise of the global epidemic of obesity during the past 3-4 decades.[3] According to the World health statistics 2012 report of the World Health Organization (WHO), one in six adults is obese (12% of the world's population are considered obese). Being overweight and obese are the fifth leading risk for global deaths, causing at least 2.8 million deaths each year.[4]

Pharmacological approaches to weight control have become an overriding priority. Due to obscure aetiology, the treatment of obesity is difficult and challenging. Current trends for obesity management involve multiple pharmacological strategies, including blocking nutrient absorption, modulating fat metabolism, regulating adipose signals, and modulating the satiety centre.[5] Global strategies are focused on dietary and lifestyle modifications, i.e., restricting caloric intake and increasing physical activity to slow obesity development. However, if these strategies fail, antiobesity medication is recommended.[6] Many medications have been used to manage obesity over the years, but most of them are now withdrawn due to their serious adverse effects.[7] Currently, orlistat is the only drug approved by the United States Food and Drug Administration (USFDA) for long term management of obesity. Unfortunately, this drug has adverse gastrointestinal side effects such as steatorrhea. Sibutramine, another antiobesity drug, has been recently withdrawn globally due to the increased incidence of serious, non-fatal cardiovascular events. Disappointing results of pharmacotherapy emphasize the need of other treatment modalities to prevent obesity.[8]

Natural plant products are widely used in healthcare or as dietary supplements.[9] Natural products have been used since the inception of human beings on this planet and as a result are almost as old as life itself [Table 1].[1011] Dietary phytochemicals have recently aroused considerable interest as the potential therapeutic agents for health promotion and to counteract obesity.[12] Due to their chemical diversity and ability to act on various biological targets, plant products have long been a thriving source for the discovery of new drugs, and these find use among the most common complementary and alternative medicine systems.[13] Presence of multiple-phytochemical combinations in plant drugs may result in synergistic effect by their action on multiple molecular targets, thus offering advantages over treatments which use a single constituent.[12]

Table 1

List of some common medicinal plants having antiobesity potential[1011]

Trigonella foenum-graecum L. (Fenugreek; Family: Fabaceae) is an erect annual herb native to the Eastern Mediterranean, Central Asia and Ethiopia, and is extensively cultivated in India, Pakistan, and China.[14] The name fenugreek comes from foenum-graecum, meaning Greek hay, as the plant was traditionally used to scent inferior hay. The name of the genus, Trigonella, is derived from the old Greek name, denoting ‘three-angled’, referring to the triangular shape of the flowers.[15]

The major bioactive constituents in fenugreek seeds include 45-60% carbohydrates; 20-30% proteins; alkaloids, mainly trigonelline, choline, gentianine and carpaine; flavonoids which include apigenin, luteolin, orientin, quercetin, vitexin and isovitexin; amino acids such as 4-hydroxyisoleucine, arginine, histidine, lysine, leucine, L-tryptophan; saponins such as graecunins, fenugrin B, fenugreekine, trigofoenosides A-G; steroidal sapogenins such as diosgenin, yamogenin, tigogenin, neotigogenin; minerals and vitamins; volatile oils (n-alkanes and sesquiterpenes) and fixed oils.[16]

Fenugreek is traditionally used in India, especially in the Ayurveda and Unani systems. Fenugreek seeds have been in use for over 2500 years.[17] Fenugreek is reported to possess nutritive and restorative properties,[18] and has been used in folk medicine for centuries for a wide range of diseases including diabetes, fever, and abdominal colic, as a poultice for abscesses, boils and carbuncles.[19] Fenugreek seeds are used for their carminative, tonic and aphrodisiac effects.[17] Further, seeds are used as antipyretic, anthelmentic, appetite stimulant, astringent, to cure leprosy, ‘vāta’, vomiting, bronchitis, piles, to remove bad taste from the mouth, in heart disease and is recommended for diarrhoea and also in rheumatism (as per Ayurvedic texts). The plant and seeds are suppurative, aperient, diuretic, emmenagogue, useful in dropsy, in enlargement of liver and spleen. The leaves are useful in external and internal swellings and burns, and to prevent hair fall (as per Unani practice).[2021]

Fenugreek seeds have been shown to possess hypoglycaemic, hypolipidemic and antioxidant effects in pre-clinical [Table 2] and clinical studies [Table 3]. In epidemiological studies, polyphenol and flavonoid-rich extract from fenugreek seeds have been shown to possess the hypolipidemic effect due to their antioxidant defence.[22] The presence of proteins and fibre in fenugreek seeds offers high nutritive value as it contains approximate 26% protein and 48% fibre; and might exert a lipid lowering effect.[37] Dietary fibre (galactomannan) in fenugreek seeds are polysaccharides consisting of a mannose backbone with galactose side chains attached at position C6. Galactomannan consist of linear chains of (1-4)-diequatorially linked D-mannose residues, some contain single-sugar side chains of D-galactose attached by (1-6) glycosidic bonds.[49] Galactomannan found in fenugreek seeds form a viscous gel in the intestine and inhibit glucose and lipid absorption.[23]

Table 2

Summary of Trigonella foenum-graecum seeds preclinical studies

Table 3

Summary of Trigonella foenum-graecum seeds clinical studies

Fenugreek seeds are used as an active ingredient in weight loss and anti-hypercholesterolemic Ayurvedic formulation Ayurslim (The Himalaya Drug Company, Bangalore, India) and Impair-X (Rekindle Health Care Pvt. Ltd., Karnal, India). Taxonomists suggested that as many as 260 species of Fenugreek may exist, of which a total of only 18 species of Trigonella are currently recognized.[50] Various therapeutic benefits of fenugreek seeds have been experimentally evidenced, and the daily dietary intake of fenugreek seeds may provide a higher nutritive value, in addition to high degree of efficacy and safety in obesity treatment.

Currently 80% of the world population depends on plant-derived drugs as the first line health care because plant-based drugs have no side effects.[51] The traditional system of medicine has a long history of usage in a number of diseases and disorders, but lacks recorded safety and efficacy data.[13] The development of standardized, safe and effective drugs from plant origin can provide economical alternatives for the treatment of obesity. Therefore, there is a need to develop and screen large number of plant extracts and this approach can surely be a driving force for the discovery of antiobesity drugs from medicinal plants.

Financial support and sponsorship

This work was supported by the Council of Scientific and Industrial Research, New Delhi, India, in form of Senior Research Fellowship.

Conflicts of interest

There are no conflicts of interest.