EVALUATION OF HYPOGLYCAEMIC EFFECTS OF LEAF EXTRACTS OF MISTLETOES (Globimetula oreophila OLIV. AND Globimetula braunii ENGL. Van Tiegh) IN ALLOXAN INDUCED DIABETIC RATS

ABSTRACT

Folklore medicine has it that some mistletoes are used in the management of diabetes in Nupeland. The aqueous and ethylacetate extracts of two mistletoe plants, Globimetula braunii and Globimetula oreophila were investigated for hypoglycaemic effects in diabetic rats. Diabetes was induced intraperitoneally in rat with 100mg/kg body weight (b.w) of alloxan and rats with blood glucose >135 mg/kg b.w were considered diabetic. The design consisted of twenty one (21) rats with each group having three rats. The diabetic rats were given 500mg/kg b.w of respective extracts once daily for fourteen days. Blood glucose was monitored every five days and it reduced during the period of treatment when compared with diabetic untreated group (DNT). The experiment lasted for twenty one (21) days, the blood serum and fresh organs were collected after euthanizing the animals.   The extracts showed significant (P<0.05) hypoglycaemic effects with 58.37%, 50.46%, 65.50% and 50.65% for Aqueous Globimetula braunii (AGB), Aqueous Globimetula oreophila (AGO), Ethylacetate Globimetula Braunii (EGB) and Ethylacetate Globimetula oreophila (EGO) respectively. There was no significant (P>0.05) gain in body weight for all the groups treated with the extracts but normoglyceamic group (NNT) showed significant (P<0.05) increase (8.04%) in total body weight. The mean percentage ratio of fresh organs to whole body weight for liver and heart reveals no significant (P>0.05) difference between the groups. While lungs and pancreas show significant (P<0.05) reduction for all the groups treated with the extracts. The kidney of the AGB treated group showed a significant (P<0.05) increase when compared with NNT groups. There was no significant difference (P<0.05) in serum total protein and cholesterol levels between the groups. Triglyceride level significantly (P<0.05) increased (173.50+16.57) in the Diabetes untreated group (DNT) alone when compared with the NNT group. Only EGO group showed a significant (P<0.05) increase (1.57+0.2) in the level of direct bilirubin, total bilirubin was not significantly (P>0.05) increase in all the groups when compared with the NNT group. AGB group showed significant increase in the activities of Alkaline phosphatase. EGB, EGO and DNT, showed significant (P<0.05) increase (78.90+8.90, 63.30+6.10 and 73.07+2.40 respectively) in the activities of Alanine aminotransferase when compared with the NNT group. All groups showed significant (P<0.05) increase in the activities of Aspartate aminotransferase when compared with the NNT groups. Thus, the research work has shown that all the extracts of G.braunii and G.oreophila at 500mg/kg b.w have significant anti-diabetic effects on the diabetic animal model (rats) in addition to ameliorating the biochemical abnormalities arising from diabetes.

CHAPTER ONE

1.0       INTRODUCTION

1.1       Background of the Study

The number of people with diabetes mellitus was estimated in 2011 to be 336 million adults aged 20-79 years of the world’s 7 billion population. This gives a comparative prevalence of 8.5% (International Diabetes Federation (IDF), 2011). Accord to the International Diabetes Federation (IDF) data of 2003, shows that West Africa, Nigeria has the highest number of people living with diabetes with approximate estimate of 1,707,000 people affected (IDF, 2003).

Diabetes mellitus is a group of metabolic diseases characterized by hyperglycaemia resulting from defects in insulin secretion, insulin action, or both (American Diabetic Association (ADA), 2000). The chronic hyperglycaemia of diabetes is associated with long-term  damage,  dysfunction,  and  failure  of  different  organs,  especially  the  eyes, kidneys, nerves, Liver, heart, and blood vessels (Zeller, Whittaker, Sullian, Raskin, and Jacob, 1991; Pedrini, Levey, Lau, Chalmers, and Wang, 1996).

The  basis  of  the  abnormalities  in  carbohydrate,  fat,  and  protein  metabolism  noted in diabetes is as a result of the deficient action of insulin on target tissues which then lead to abnormalities of lipoprotein metabolism, hypertriglyceridemia and hypercholesterolemia (Granner, 2000). There is also marked elevation in the activities of some enzymes in a diabetic  condition  (Eskander,  Won  Jun,  Ibrahim,  and  Abdelal,  1995;  Hassan,  2007). Several pathogenic processes are involved in the development of diabetes. These range from autoimmune destruction of the β-cells of the pancreas with consequent insulin deficiency to abnormalities that result in resistance to insulin action (Lernmark, Haggloff, Freedman, Irvine, Ludvigsson and Holmgren, 1981).

Today, medicinal plants are increasingly being used in most parts of the world as antidiabetic regimen because of their hypoglycaemic effects (Saidu, Mann and Onuegbu 2012). Mistletoe plants are well known for their medicinal importance from time immemorial which has been highly revered in different cultures (Marzell, 1923). They have been reported for their anticancer, antihypertensive, and fertility functions (Obatomi, Bikomo and Temple, 1994). A tea prepared from leaves of the Viscum album mistletoe is used traditionally to treat diabetes in the West Indies (Peters 1957). This treatment has been shown also to relieve the diabetic symptoms of severely hyperglycaemic streptozotocin-diabetic mice, including polydipsia, polyphagia and body weight loss (Swanston-Flatt, Day, Bailey and Flatt, 1989).

Mistletoe,  which  is  called  ‘Afomo’  in  Yoruba,  ‘Kauchi’  in  Hausa,  ‘Apari’  in  Igbo, ‘Osuochi’ in Ebira, and ‘Etu’ in Nupe, is ethnomedicinally used by various ethnicities in Nigeria as a remedy for several human and animal ailments such as diarrhea, dysentery, wound, cancer, hemorrhage, convulsion (Adesina, 1979; Adesina and Ojewole, 1983), gynaecology problems and cardiovascular diseases (Adodo, 2004). The genus Globimetula is in the major group Angiosperms (Flowering plants) and it has about twelve (12) known species which are anguliflora, assiana, braunii, cornutibracteata, Cupulata, dinklagei, elegantiflora, mayombensis, mweroensis, oreophila, pachyclada and rubripes. G.braunii and G.oreophila medicinal importance is well documented (Le and Zam, 2008; Ochuko, Joseph, Adeniyi, Rabiat and Michael, 2011; Huaxing and Micheal, 2012). G.braunii and G.oreophila are also used as folkloric treatment for diabetes by the Nupe speaking people of Niger state.  The medicinal efficacy of mistletoe has been proven to be dependent on several factors (Bako, 2001; Wahab, Ayodele and Moody, 2010). Thus it is of the interest of this research to investigate and compare the varying degree of the antidiabetic properties of G.braunii and G.oreophila which are different species from different host plant.

1.2       Justification for this Research

Folkloric usage of mistletoe plants for the treatment of diabetes is well known and highly revered by many cultures all over the world. The Nupe speaking people of Niger state of Nigeria use the plant locally for the treatment of many illnesses including diabetes. The varying degree of the medicinal properties of mistletoe and its efficacy depend on the extract, the species and the host plant it parasitized. Hence the need to scientifically appraise the antidiabetic property of selected species from two different host plants (Locust beans and shea butter plant).

1.3       Aim and Objectives

1.3.1    Aim

To investigate the hypoglycemic properties of aqueous and ethylacetate leaves extracts of Globimetula braunii (grown on Locust beans) and Globimetula oreophila (grown on shea butter) in alloxan induced diabetic wistar rats.

1.3.2    Objectives

I.      To determine the phytochemical constituents of the plants extracts

II.      To  investigate  the  LD50    of  aqueous  and  ethylacetate  extracts  of  G.braunii  and G.oreophila in Wistar rats

III.     To investigate the effect of the crude aqueous and ethylacetate extracts on the blood glucose level of diabetic rats.

IV.      To determine the effects of the extracts on the relative organs weights of diabetic rats.

V.        To check the effects of extract on selected marker enzymes and on some biochemical parameters of diabetic rats.

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