1.1 Background of the Study

The use of medicinal plants in the treatment of diseases has generated renewed interest in recent times, as herbal preparations are increasingly being used in our health care system despite advances in modern medicine (Masibo and Mango, 2009).

Diabetes mellitus is an important human ailment affecting many people from various walks of life in different countries.  Though there are various approaches to reduce the ill effect of diabetes mellitus and its secondary complications, “crude drugs” (herbal formulations) are preferred due to their lower cost and lesser side effects (Aderibigbe et al., 1999)

More than 800 plants are used traditionally in the treatment of diabetes around the world and approximately 30 % of these traditionally-used anti-diabetic plants have been pharmacologically and chemically investigated (Alarcon-Aguilar et al., 2002).  Traditional treatments may provide valuable clues for the development of new oral hypoglycemic agents and simple dietary adjuncts. Diabetes mellitus is treated with diet, physical exercise and medicinal plants (Ayyanar et al.,2008). Medicinal plants such as Allium cepa, Allium sativa, Aloe vera, Cajanus cajan, Coccinia indica, Caesalpinia bonducella, Ficus banghalensis, Gymnema sylvestre, Momordica charantia, Ocimum sanctum, Pterocarpus marsupium, Syzygium cumini, and Tinospora cordifolia, have been studied in relation to diabetes and its complications (Alarcon-Aguilar et al., 1998).

Diabetes mellitus was first reported in Egypt about 3500 years ago. From the 16th– 18thcentury diabetes mellitus was diagnosed and treated more methodically starting in Europe, but a remedy was only discovered in the last century.  The discovery of insulin for the treatment of diabetes remains one of the major humanitarian and scientific milestones of the 20th century (Lasker et al., 2006).

1.2     What is Diabetes Mellitus?

          Diabetes mellitus is a complex metabolic disorder characterized by high blood glucose levels resulting from either insulin insufficiency or insulin dysfunction (Khan et al., 2009). It is a multi-factorial disease that affects the metabolism of carbohydrates, fats, proteins, and electrolytes in the body climaxing to severe complications such as hyperglycemia, diabetes ketoacidosis, polyuria, weight loss, etc. (Baynes and Thorpe 1997; Silink 2006).  Diabetes mellitus is a multi-factorial disease leading to several complications, patients of diabetes mellitus either do not make enough insulin or their cells do not respond effectively to insulin.

1.3     Prevalence

          The prevalence of diabetes mellitus is increasing rapidly and standing as a major threat to mankind.  There are about 100 million (3 % of the world’s population) diabetic patients in the world today (Krall, 1986; Crawford and Cortran, 2003). By the year 2025, it is estimated that 6.3 % of the global population will have diabetes mellitus (Silink, 2006). It is now recognized as the third leading cause of death in adults after heart diseases and cancer (Stuart, 1988).

1.4     Etiologic Classification of Diabetes Mellitus

          On the basis of etiology and clinical presentation, diabetes mellitus is classified into four:

Type I: Type 1diabetes is also referred to as insulin-dependent diabetes.  It is characterized by pancreatic islet beta cell destruction and absolute Insulinopenia (Stuart, 1988).  These individuals are ketosis-prone under basal conditions.  The onset of the disease is generally in youth, but it can occur at any age.  Patients have a dependence on daily insulin administration for survival. Type 1 Diabetes is found in all ethnic groups, but the highest incidence is in people from northern Europe and from Sardina.

Type 2: (Non-insulin dependent diabetes mellitus). It is characterized by both impaired insulin secretion and insulin resistance which is often associated with obesity and hereditary disposition (Mehta, 1982). It is the most common form of diabetes, accounts for 90 – 95 % of the diabetic population.  Most researchers seem to agree that genetic factors are mostly responsible for its prevalence but it is probably not caused by defects at a single gene locus.

Gestational Diabetes (GDM): It is defined as any abnormality in the glucose level noted for the first time during pregnancy. During pregnancy, the placenta and placental hormones create an insulin resistance that is most pronounced in the last trimester. Gestational diabetes is diagnosed in approximately 4 % of all pregnancy in Nigeria (Iwu, 1980)

Obesity, diet, physical activity, intra-uterine environment, stress are among the most important environmental factors which play a role in the development of the disease.

1.5     Symptoms

 Symptoms of diabetes conditions may include:

  1. High level of sugar in the blood
  2. Unusual thirst
  3. Frequent hunger and loss of weight
  4. Blurred vision
  5. Nausea and vomiting
  6. Extreme weakness and tiredness
  7. Irritability and mood changes

          Though path physiology of diabetes remains to be fully understood, experimental evidence suggests the involvement of free radicals in the pathogenesis of diabetes and more importantly in the development of diabetic complications (Oberlay, 1988; Baynes and Thorpe, 1997; Lipinski, 2001).

1.6     Oxidative Stress in Diabetes Mellitus

          Oxidative stress depicts the existence of products called free radicals and reactive oxygen species (ROS) which are formed under normal physiological conditions but become deleterious when not being quenched by the antioxidant system (Gregus et al., 1996).

There is convincing experimental and clinical evidence that the generation of reactive oxygen species is increased in both types of diabetes and that the onset of diabetes is closely associated with oxidative stress (Grover et al., 2000; Grodsky et al., 2001). Free radicals are formed disproportionately in diabetes by glucose autoxidation, polyol pathway and non-enzymatic glycation of proteins (Guillochou et al., 1986). Abnormally high levels of free radicals and the simultaneous decline of antioxidant defense systems can lead to the damage of cellular organelles and enzymes, increased lipid peroxidation and development of complications of diabetes mellitus (Halliwell and Gutteridge, 1997). Free radicals may play an important role in the causation and complications of diabetes mellitus (Halliwell and Gutteridge, 1989). In diabetes mellitus, alterations in the endogenous free radical scavenging defense mechanisms may lead to ineffective scavenging of reactive oxygen species, resulting in oxidative damage and tissue injury.  Oxidative stress is currently suggested as the mechanism underlying diabetes and diabetic complications (Hammouda et al., 1995). Enhanced oxidative stress and changes in antioxidant capacity, observed in both clinical and experimental diabetes mellitus, are thought to be the etiology of chronic diabetic complications (Hiramatsu and Arimori, 1988).