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SCREENING OF SENNA ALATA LEAVES FOR BIOCHEMICAL AND HYPOGLYCEMIC ACTIVITY

ABSTRACT

This study intends to validate the local use of Senna alata in the management of diabetes by quantitatively analyzing the phytochemicals present and its effect on blood sugar level and the histology of destroyed pancreatic islet cells.  50g of fresh leaves of Senna alata were used for phytochemical and nutritional analyses while the remaining leaves were dried and blended into fine powder. Bioactive substances in the herb were extracted with 80% ethanol. The herb extract was reinstituted with normal saline before administration to the rats.  Twenty-four wistar rats of both sexes with average weight of 160g were used in this study. The rats were randomly divided into three parallel groups of diabetic and non-diabetic rats. The non-diabetic groups were designated AN, BN and CN while the diabetic groups were designated AD, BD and CD. Rats in groups A (AN and AD) served as control for each parallel group and received 0.4ml of normal saline. Rats in the 2 parallel groups of B(BN and BD) received singe daily doses of 500mg/kg body weight of ethanolic leaf extract of Senna alata via orogastric tube while rats in groups C (CN and CD) received subcutaneous injection of 5IU/kg body weight of human insulin daily. All the rats received water freely and normal rat feeds. The experiment lasted for twenty-eight days. The rats were sacrificed and pancreatic tissue taken for histological studies. Histological sections were stained with Haematoxylin and Eosin staining techniques. Experimental diabetes was induced using a single intraperitoneal injection of 65mg/kg body weight of streptozotocin. Results revealed the presence of varying quantities of saponins, flavonoids, tannins, oxalate and alkaloids. Blood sugar level also reduced in both the diabetic and non-diabetic groups and histology revealed regeneration of destroyed pancreatic islet cells. It can be inferred that Senna alata potentiates the regeneration of beta cells in the pancreas of diabetic rats and has hypogycaemic effect. These antidiabetic effects may have been brought about by its rich phytochemical composition.

CHAPTER ONE

INTRODUCTION

BACKGROUND TO THE STUDY

The use of plants for the treatment of certain illnesses dates back to many centuries, by our ancestors who not only used plants as food and shelter but also for the treatment of certain illnesses (Akinyemi et al., 2000). Plants serve as food for man and animals, since man and animals cannot manufacture their own food and so rely solely on plants to provide them with nutrients such as vitamins, proteins, carbohydrates, lipids and essential minerals that are required for growth, development and proper body functions, (Selvi et al., 2012).

Apart from the nutrients provided by plants, man discovered that by consuming some plants their health conditions improved. This gave rise to the medicinal use of plants and it was discovered that some of these plants contained certain chemical substances that have therapeutic values (Masuda et al., 2003). Plant parts used for medicinal purposes vary among plant species and also dependent on the location of the medically active components. Some plants have their active component in their roots, others in their leaves while some others bear theirs in their seed, fruits, and flowers or stem bark, (Selvi et al., 2012).

The increasing use of plant for the production of natural products for maintaining human health which has been observed over the last decades, has led to the increased studies by scientists to discover more medicinal plants, and according to the World Health Organization (WHO), medicinal plants would be the best source of a variety of drugs as 80% of individuals in developing countries use traditional medicine, which has compounds derived from medicinal plants, (W.H.O., 2006).

One of such plants is Senna alata an erect tropical perennial herb that grows up to 6ft tall and it belongs to the family; fabaceae. It is a plant originally grown in South America but due to its medicinal value, is now found in other countries, such as India where it is called Dadmari and in Nigeria it is called Rai-dore in Hausa, Asuwon oyinbo in Yoruba and Omirima in Igbo, (Arbonnier, 2004). Senna alata is used in traditional medicine for the treatment of a variety of infections and diseases including ringworm, eczema, wounds, constipation, burns and food poisoning, hemorrhoids, inguinal hernia, intestinal parasitosis, syphilis and diabetes; and the leaves have also been reported to be useful in treating convulsion, gonorrhoea, heart failure, abdominal pains, oedema and also used as a laxative (Zhongguo, 2009 and Adebayo et al., 2001, ebayo et al., 2001). It was reported that ethanol leaf extracts of the Senna alata plant showed high activity against dermophytes, like Trichophyton mentagrophytes which attacks the skin and scalp of man and Trichophyton rubrum and Microsporium gypseum and Microsporium canis, (Owoyale et al., 2005) and the aqueous leaf extracts showed higher activity on Escherichia coli than the ethanol extract (Timothy et al., 2012). The methanol extracts of Senna alata leaves, flowers, stem and root showed a range of antimicrobial activity against Bacillus cereus, Micrococcus luteus, Citrobacter freundii, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumonia, Neisseria gonorrhea, Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella typhimurium, Serratia marcescens and Trichomonas vaginalis (Somchit et al.,2003).

Diabetes mellitus is a chronic metabolic disease and for now there is no substantive cure. Many plant products have been used locally to bring about beneficial antidiabetic effects but most have not been screened to know the bioactive components that may be responsible for these effects. Recently the search for appropriate hypoglycaemic agents has been focused on plants used in traditional medicine. Natural compounds with antidiabetic activity include complex carbon hydrates, alkaloids, glycopeptides, amines, flavonoids, sulphur compounds and inorganic ions. The antidiabetic mechanisms are numerous including activation of regeneration of functional pancreatic beta cells thereby increasing the number of insulin producing pancreatic beta cells, inhibition of insulinase activity, possession of insulin-like polypeptide which will mimic the action of insulin, interference with carbohydrate absorption by the plant fibre, stimulation of insulin secretion in pancreatic beta cells and increase in glycogen storage.  Senna alata is a beautiful flowering shrub, a member of genus cassia belonging to the family of caesalpiniaceae. It is commonly known as candle bush. Different parts of the plant have been used for a wide spectrum of diseases. The leaves have been reported to possess anti-inflammatory and hypoglycaemic actions. 

Statement of the Problem

Several traditional uses of Senna alata have been reported in several places. In Indo China and Philippines, the leaves are considered most effective against herpes and is also used as a mild laxative. In Guinea, the pounded fresh leaves are used for all kinds of skin infections. In Ghana, the leaves are used in the treatment of lesions and ringworm on the forehead or on the skin. This is one of the most effective treatments amongst traditional medicines. The leaves are also boiled and drunk by women to hasten delivery during birth, (Alalor, et al., 2012). Despite the numerous reports in the literature of the antimicrobial activity of Senna alata, not much work has been reported from Nigeria. It is the paucity of information as regards this plant that necessitates this study, the need of which cannot be over emphasized.

Aim and Objectives of the Study

The aim of this study is to validate the traditional use of Senna alata herb by screening for the bioactive components of the leaves and its effect on destroyed beta cells of the pancreas.

Specific objectives include;

i.  To evaluate the antimicrobial activity of the aqueous and ethanol extracts of Senna alata leaves on clinically important micro-organisms such as, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella pneumoniae, Trichophyton species, Aspergillus species and Alternaria species.

ii.  To encourage the medicinal use of plants in the treatment of infections caused by micro-organisms.