Tropical Herbs and Spices as Functional Foods with Antidiabetic Activities

ABSTRACT

The high biodiversity of herbs and spices are concomitant with the ethno- botanical medicines that are used as natural food preservatives, herbal medicine, cosmetics, crop protection, etc. Herbs and spices (such as: celery, clove, cumin, garlic, ginger, nutmeg, onion, red pepper, tamarind, and turmeric) as functional foods can reduce the risk factors related to diabetes mellitus that is associated with cardiovascular illness, stroke, diabetic retinopathy (eye damage), diabetic nephropathy (kidney damage), diabetic neuropathy (nerve damage) and diabetic foot (ulcers). These plants are rich in bioactive compounds, such as, phenolics, terpenoids, flavonoids, and xyloglucan. This chapter highlights phytochemicals in herbs and spices for anti-diabetic activity.

INTRODUCTION

Diabetes is one of the main metabolic disorders of the endocrine system, which is usually attributed by increasing blood sugar levels [109]. According to the WHO report, 1.6 million deaths in 2016 were due to diabetes. International Diabetes Federation Atlas (IDFA) indicated that approximately, about 8.8% of adults (20-79 years) were living with diabetes in 2017 [40]. Traditional natural herbs have an important role to control diabetes.

Tropical herbs and spices belong to several families, namely: Achariaceae, AmaryUidaceae, Apiaceae, Asteraceae, Brassicaceae, Euphorbiaceae, Faba- ceae, Lamiaceae, Myrtaceae, Oxalidaceae, Poaceae, Rubiaceae, Rutaceae,

Solanaceae, and Zingiberaceae. Numerous investigations have been performed on the isolation, structure identification, production, and biological activities of herbs and spices with anti-diabetic activities [64, 49, 64, 66, 99].

This chapter represents comprehensive on common tropical herbs and spices with anti-diabetic activities. The chapter also includes biochemical mechanisms of biomolecules.

DIABETES MELLITUS

Diabetes has been dramatically rising during 1980 till date. According to WHO, 422 million adults suffer from type-2 diabetes. The common sign of diabetes is indicated by enhancing of blood glucose level and abnormality of glucose metabolism [109]. Diabetes is classified as:

  • Type-1 Diabetes: It referred to insulin-dependent diabetes mellitus (IDDM) and appears in the early human life and symptoms are quickly detected. Patients with Type-1 diabetes loose ability to produce adequate insulin because of the destruction of pancreatic (3-cells. Diabetic therapy is required to maintain blood glucose level. The preliminary therapies are control of dietary intake and insulin therapy.
  • Type-2 Diabetes: It is referred to non-insulin-dependent diabetes mellitus (NIDDM), which arises slowly in older and obese individuals with exhibited unrecognized symptoms. In this case, insulin is produced from the pancreatic islets but several features of the insulin-response system are failed. Characteristics in a type-2 diabetic patients are:
  • (a) inability to uptake of glucose in an efficient way from the blood,
  • (b) incomplete fatty acid oxidation in the liver, (c) accumulation of acetyl co-A, (d) overproduction of ketone bodies, acetoacetate, and p-hydroxybutyrate in the blood, (e) lowering blood pH, and (f) insulin resistance in type-2 diabetes.

Diabetic characteristic symptoms are: (a) excessive thirst and frequent urination (polyuria), (b) intake of a large volume of water (polydipsia), and excretion of glucose in the urine (glucosuria). Health management for type-2 diabetes patients involves [86]: (a) dietaiy restriction, (b) perform regular body exercise, and (c) avoid drugs that enhance insulin sensitivity or insulin production.

According to fasting plasma glucose test (FPG) values: subjects are categorized as: (1) normal fasting glucose (FPG<100 mgdL-1 (5.6 mmol L_1)]); (2) impaired fasting glucose (IFG) (FPG 100-125 mgdL-1 (5.6-6.9 mmol L-1)); and (3) provisional diagnosis of diabetes (FPG > 126 mgdL-1 (7.0 mmol L-1)).

Furthermore, oral glucose tolerance test (OGTT) also can be used to categorize subjects as: (1) normal glucose tolerance (2-h post-load glucose, 140 mg dL-1 (7.8 mmol L-1)), (2) impaired glucose tolerance (IGT) (2-h postload glucose 140-199 mg dL-1 (7.8-11.1 mmol L-1)), and (3) provisional diagnosis of diabetes 2 h post-load glucose > 200 mg dL-1 (11.1 mmol L-1)).

According to the previously mentioned information, patients with IFG and/or IGT are referred to the pre-diabetes group. Pre-diabetes patients have a high risk of encounter by diabetes mellitus (DM). In addition, IFG, and IGT are related to other metabolic syndromes, such as: obesity, dyslipidemia by abnormal behavior of high-triglyceride and/or low-high-density lipoprotein, and hypertension [7].

Obesity is a life-threatening metabolic disease, which consumes more calories from the diet than under normal conditions. It triggers several diseases, such as, type-2 diabetes, heart attack, stroke, and cancers in the colon, breast, endometrium, and prostate [69]. Therefore, obesity, and diabetes are positively correlated as the main target of metabolic disorder research. In humans, the prevention of diabetes can be achieved by the consumption of antioxidant-rich foods, (such as: herbs and spices) [12].

TROPICAL HERBS AND SPICES

Historical records indicate that the uses of herbs and spices have an important role in human nutrition, in food preservation and flavoring agents [62,75]. In 19th century, “Silk Road (a trade route connecting east and west civilization” promoted the use of herbs and spices at an affordable cost [106]. Also, herbs, and spices were utilized as the source of medicinal therapy in ancient Egypt and Assyria; and for culinary purposes [75].

The Meixiam-Webster dictionary defines “herbs as any plant or parts of plants, which are valuable for its medicinal, savory or aromatic qualities.'’'’ Often spices belong to vegetable products (such as: pepper or nutmeg) and are often used as seasonal functional or flavor foods [63]. The Food and Agriculture Organization (FAO) indicated that around 50,000 plants were used as medicinal plants in 2002 and most of them are also presently used as herbs and spices [85].

In 2016, Royal Botanic Gardens in Kew reported that 17,810 species were used for medicinal purposes among 30,000 plants [82]. A tropical environment with high humidity and rainfall has become home for millions of herbs and spices, such as: cinnamon, clove, nutmeg, pepper, ginger, citrus, saffron, tuimeric, etc.

The herbs and spices have been used to cure fever, nausea, scars, colds, headaches, arthritis, etc. Ephedra (Ma huang: Chinese herb) is used to relieve asthma, whereas willow tree bark and SaJix alba helped to relieve fever [22]. Herbal knowledge has been passed down from one generation to the next through oral conversation and daily rituals.

Research continues on usefulness of these traditional remedies, such as: (a) ginger is for relieves from nausea, (b) turmeric to help arthritis symptoms, and (c) cinnamon and saffron for reducing blood sugar levels. These days, people have faith in traditional natural remedies because of several health benefits. The World Health Organization (WHO) indicates that around 80% of the world population entrust on traditional medicine to maintain good health [31, 95].

FUNCTIONAL FOODS

The term of functional food was first coined as Foods for Specified Health Used (FOSHU) in Japan (1991). Today, functional foods are used for specific health benefits. For decades, numerous research studies on: plant- based bioactive compounds; development of functional foods in a smart way. Evidences portray that many herbs and spices show specific biological activities besides their nutritional values. Phytochemicals in herbal medicine interact with the human body, metabolic, and immune systems against several diseases. Herbs and spices are considered as functional foods [16].

HERBS AND SPICES AS ANTI-DIABETIC AGENTS

In tropical regions, herbs, and spices have received importance as therapeutic agents. These plants offer anti-diabetic activities. Figure 3.1 shows tropical herbs and spices that have anti-diabetic activities.

CELERY

Celery (Apium graveolens) is a commercial seed spice for use in flavoring and seasoning of the food. Celery leaves are ordinarily used in cooking to add a balmy flavor to foods. Celery leaves are commonly dried and are sprinkled in soups, stews, and baking puiposes, fried, and roasted foods, and even the uncooked celery is an edible item. It is introduced in a salad or as a garnish. This plant possesses many health benefits, such as: antioxidant, anti-diuretic, hypolipidemic, hypoglycemic, etc.

Tropical herbs and spices with anti-diabetic activities. Source

FIGURE 3.1 Tropical herbs and spices with anti-diabetic activities. Source: Self-developed with concepts from Refs. [64, 105].

Gelodar et al. [34] reported that celery reduced blood glucose in diabetic mice. For the purpose of the experiment, 20 out of 25 mice were induced by alloxan (170 mg kg-1) and divided into 4 groups (5 mice per group). Another 5 mice were chosen as control group receiving neither alloxan nor celery-based diet. Following this, 3 groups of alloxan-induced mice were treated with a celery-based diet (6.25% of the bodyweight) for 15 days. The remaining 5 mice were chosen as a negative control group receiving an only intraperitoneal injection of alloxan. As a result, the concentration of glucose, cholesterol, and creatinine and the activities of ALT, AST, and ALP were lower in the celery-treated group (P<0.05) [34].

A research study indicated that leaf extract of celery has the potential to reduce blood glucose levels in elderly pre-diabetic patients. The experiment was performed with 16 elderly pre-diabetic patients (6 males and 10 females: older than 60 years). Two groups were formed: a control (placebo) group and a treated (celery leaf extract) group. The treated group was given a celery leaf extract in a capsule @ 250 mg (30 minutes before a meal, three times per day) for 12 days. This study showed that the celery capsule was able to lower the blood glucose level [113].

Celery contains alkaloids, carbohydrates, flavonoids (apigenin, apiin, isoquercitrin), glycosides, steroids, vitamin A and vitamin C [4, 53]. Other phytochemical compounds in celery leaves are: apigenin, bergapten, cliry- soeriol 7-glucosides, furanocoumarin, luteolin, isopimpinellin, phenols, phthalide, psoralen, and xanthotoxin [18, 53]. Celery has also been documented to have several hypoglycemic compounds (such as, essential oils, flavonoids (kaempferol, quercetin, triteipenes, and luteolin), phenolics, triterpenes with antidiabetic [37] antioxidant properties.

The seed extract of celery has the ability to decrease the blood glucose level and to increase insulin levels in diabetes-induced mice [27]. The celery seed is rich in flavonoids, such as: apigenin, luteolin, and phenolics [4, 51, 71]. Apigenin inhibits the aldose reductase enzyme activity [27, 42]. A diabetic patient can suffer from cataracts, retinopathy, and neuropathy due to increasing levels of sorbitol [51]. Another anti-diabetic mechanism explains the ability of celery seed in stimulating the secretion of insulin from pancreatic (3-cells and decreasing the liver gluconeogenesis pathway [5, 18, 71]. Based on the histology test, celery seeds promoted the integrity of pancreatic (3-cells [5, 71].

Flavonoid is one of the major antioxidant compounds in celery [18]. Flavonoid is able to overcome the free radicals and preclude devastation to pancreatic p-cells [2, 5, 18, 53]. Flavonoids can regulate the absorption of glucose in the intestine, carbohydrate metabolism, and glucose uptake, especially in the regulation of the cell-signaling AMP-activated protein kinase (AMPK) pathways. Flavonoid is also able to help glucose uptake in the skeletal muscle cells [5, 18, 29, 53]. Gutierrez et al. [37] reported that flavonoids as an anti-diabetic agent can diminish apoptosis, enhance pancreatic (3-cell proliferation, promote the secretion of insulin, manage glucose digest, and reduce hyperglycemia [37]. Flavonoid is also able to suppress insulin resistance, give relief from inflammation in adiposity cells, and suppress oxidative stress chain in the skeletal muscles [35]. Flavonoid plays a key role in the up-regulation of Glucose Transporter-1 (GLUT-1) expression level, which is usefi.il in the treatment of type-2 DM (T2DM).

Kaempferol, a natural flavonol, is an anti-diabetic agent due to its activity in pancreatic p-cell protection, which is correlated to T2DM [5]. It has been reported that kaempferol has the ability to reduce hyperglycemia and increase the glucose uptake through the PI3K and protein kinase С (PKC) pathways in rat’s muscle. An oral dose of kaempferol was also able to increase the fasting blood glucose (FBG), glucose tolerance, and HbAlc concentration, and depress insulin resistance [29].

Gutierrez et al. [37] reported that quercetin can reduce the levels of plasma glucose in alloxan-induced diabetic mice. Quercetin commits to GLUT-4 mRNA rearrangement in cell membranes of adipocytes and skeletal muscle cells. Also, it up-regulates GLUT-4 mRNA level, which reduces the blood glucose level. Quercetin increases the liver glucose uptake and promotes the secretion of insulin from pancreatic (3-cells.

Quercetin and naringenin can protect (3-cells from the toxicity of cytokine via Phosphatidylinositol-3-kinase (PI3K) pathway. Apigenin has anti- hyperglycemic property [39]. Apigenin-treated diabetic mice displayed an improvement in hyperglycemia levels and its antioxidant status. Apigenin treatment in alloxan-induced diabetic mice decreased the glucose blood levels and repaired pancreatic (3-cells.

Luteolin was investigated for its ability to raise the insulin action and to promote GLUT-4 activity in diabetic mice and it increased antioxidant activity in diabetic nephropathy in diabetic mice. Its antioxidant property promotes the secretion of insulin via the NF-кВ and iNOS-NO signaling pathways [107].

Apigenin and luteolin act as Sodium-glucose Cotransporter-2 (SGLT-2) inhibitors in neuropathic diabetes [39]. Several scientific facts indicate that oxidative stress affects DM pathogenesis and diabetic complications. The elaboration of glucose oxidation, glycation of proteins, and oxidative deterioration of proteins can lead to the formation and accumulation of free radicals in DM patients. This peculiarity of free radicals and chronic deterioration in endogenous antioxidants cause harm to cell organelles and oxidative enzymes [57].

 
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