PHYTOCHEMICAL AND ANTIMICROBIAL STUDIES OF Spermacoce verticillata (Rubiaceae)

ABSTRACT

The plant Spermacoce verticillata is used in ethnomedicine for the treatment of itches, diarrhoea, sores and other ailments. The hexane soluble fraction of acetone extract of the whole plant Spermacoce verticillata was subjected to phytochemical and antimicrobial screening. The phytochemical techniques employed were dry column vacuum chromatography and preparative thin layer chromatography. The antimicrobial activity was studied using agar diffusion, and broth dilution methods. The result of preliminary phytochemical screening carried out on the crude acetone extract revealed the presence of carbohydrates, Flavonoids, Anthraquinone, terpenoids, Tannis and Steroids; Tannins flavonoids, and Steroids/terpenes were also found to be present in the hexane fraction. Extensive chromatographic separation of the hexane soluble fraction using silica gel, dry column chromatography, followed by preparative thin layer chromatography led to the isolation of stigma sterol. The structure of this compound was established by spectral analysis including 1D and 2D NMR. The result suggest that the hexane fraction of Spermacoce verticillata plant possess phytochemical constituents that may be useful in the management of microbial diseases.

CHAPTER ONE

INTRODUCTION

1.0 General Introduction

The use of plants and their preparations to treat infectious diseases is an age‐old practice and in the past possibly the only method available (Peach, 1995). However, the systemic study of plants for detecting antimicrobial activity is of comparatively recent origin. These investigations have been triggered by the emergence and spread of antibiotic resistant microorganisms causing the effective life‐span of existing antibiotics limited. Hence the plant kingdom is being screened for newer and effective chemotherapeutic agents. Higher plants can serve both as potential antimicrobial crude drugs as well as a source of new anti‐infective agents (Peach, 1995).

It is evident, that even though scientific advances have been made in our quest to understand the physiology of the body, biotechnology and the treatment of diseases, natural products remain a crucial, cheap and uncontroversial component of the comprehensive health care strategy for the future (Patwadhan, 2005). Natural products such as plant extracts, either as pure compounds or as standardized extracts, provide unlimited opportunities for new drugs discoveries because of the unmatched availability of chemical diversity (Cosa et al., 2006).

In the last decades, various studies have demonstrated that plants serve as reservoirs for innumerable microorganisms known as endophytes; these microorganisms live in the host plant at least for one period of their life cycle, without causing apparent harm to them (Petrini, 1991; Bacon and White, 2000). Even with the existence of uncountable epiphytic and soil microorganism, diverse studies have shown the potential of endophytes as a promising source of natural products for the discovery of a variety of different classes of bioactive molecules to be applied in medicine, industry and Agriculture (Schulz et al., 2002; Joseph and Priya, 2011). Investigations have shown that the search for microorganisms of biotechnological interest based in the ethno botanical pharmacology represents an alternative to discover new microorganisms and bioactive molecules (Li et al., 2005, Qin et al; 2011). Based on these principles, the bio prospection of microorganisms isolated from new ecological niches constitutes an important strategy for obtaining more efficient and less toxic antibiotics, which may ultimately control pathogenic bacteria that are resistant to the diverse antibiotics commonly used in current time (Appelbaum and Jacobs, 2005).

The use of the plant to treat diseases continue to play a key role in health care. According to the World Health Organization (WHO), 80% of the developing world’s rural population depends on traditional medicines for its primary healthcare needs (Bannerman et al; 1993). In some African countries such as Ghana, Mali, Nigeria and Zambia, the first line treatment for 60% of the children with high fever resulting from malaria is the use of herbal medicines at home (WHO, 2003). In these societies, the tradition of collecting, processing, and applying plants and plant-based medications have been handed down from generation to generation. Traditional Medicine, with medicinal plants as their most important components are sold in market places and prescribed by traditional healers in their homes (VonMaydell, 1996).

The development of resistance to most of the available antimicrobial agents and the high costs of treatment consequent upon this resistance has necessitated a search for new, safe, efficient and affective agents for the management of infection (Okwu and Uchenna, 2009). These research for new effective agents against infectious diseases and other diseases such as cancers, diabetes, cardio-vascular, neurological, respiratory disorders, among others; has led to increased interest in existing information about the remedies of these diseases from natural sources, principally the plants (Karou et al., 2007; Ouattara et al., 2007). Because of this strong dependence on plants as medicines, ethno pharmacological studies have been conducted to determine their safety and efficacy and on the other hand to find out new active principles from plants (Zongo et al., 2010; Ouattara et al., 2011).

Herbal medicine is now globally accepted as a valid alternative system of therapy in the form of pharmaceuticals, functional foods, a trend recognised and advocated by the World Health Organisation (WHO, 2003). Various studies around the world, especially in Europe, have been initiated to develop scientific evidence-based rational herbal therapies. Though ancient medical treatises have remained largely undocumented as the knowledge of their use are mainly being passed down from generation by word of mouth. New plants sources of medicine are also being discovered (WHO, 2003).

Herbal medicine can be valuable to modern medicine in many ways. Plants in the tropics are often used as direct source of drugs, e.g. the alkaloid tubercurarine (I), is used as muscle relaxant in surgery, and till date chemists are unable to produce it synthetically, although its analogue atracurium besylate (II) was syntheses (WHO, 2003).

In medicine, trees of the genus Cinchona are of great interest because of their alkaloids, the most familiar being quinine, (III) the first effective agent in treating malaria (WHO, 2003).