1.0 INTRODUCTION
Medicinal plants constitute an effective source of both traditional and modern medicine. These plants have been shown to have genuine utility and about 80% of the rural population depends on them as primary health care (Akinyemi, 2000). Plants have been used as sources of remedies for the treatment of many diseases since ancient times and people of all continents especially Africa have this old tradition. Infections caused by pathogenic bacteria and fungi remain an important public health concern particularly in developing countries because of factors such as: emergence of bacterial and fungal strains that are resistant to most useful antibiotics (Abad et al., 2007; WHO, 2007), HIV/AIDS pandemic (Wagate et al., 2008) and unavailability of vaccine (Assob et al., 2011). Conventional drugs are expensive and the western health facilities are also inaccessible to rural people (Matu and Staden, 2003; Wagete et al., 2008). Medicinal plants have been used since time immemorial to treat and prevent human ailments because they have components of therapeutic value (Hassan et al., 2006; Gulluce et al., 2006; Parekh and Chanda, 2007). Domesticated and non-domesticated animals in ordinary settings unconsciously treat themselves when sick by eating various parts of medicinal plants such as leaves, stems, barks and roots (Sindiga et al., 1995). They may also treat their skin conditions by briskly rubbing themselves against suitable plants with curative properties (Sindiga et al., 1995). WHO estimates that up to 80% of the world`s population relies on plants for their primary health care needs (Doughari, 2006; Turker and Usta, 2008; Verma et al., 2011). Such a large population depends on traditional medicine due to factors such as: Increase in resistance to the commonly used antibiotics, high cost and inaccessibility to antibiotics especially in rural areas. It is however noted that medicinal plants are readily available, they have little side effects and there is extensive local knowledge on herbal medicine amongst the communities (Rojas et al., 2006; Doughari et al., 2008). There are about 20,000 plant species used for medicinal purposes (Gulluce et al., 2006). From which at least 121 chemical substances are extracted (Olila et al., 2007). Some of the known good sources of pharmacologically active compounds are natural products from fungi and higher plants (Olila et al., 2001). Many of the effective drugs such as anti-malarial, anticancer, anti-diabetic and antibiotics such as atropine and ergometrine compounds have been purified from medicinal plants (Olila et al., 2001; Samie et al., 2005). Medicinal plants are also sources of many active ingredients in the pharmaceutical industries (Maundu and Tengnas, 2005). The popularity of plants medicine is increasing because of their biodegradability, least persistence and less toxic to non-target organisms, economic and easy availability. Guava plant (Psidium guajava) Linn.belonging to family Myrtaceae, a traditionally used plant because of its food and nutrition value. Guava is widely grown in tropical and many areas like India, Bangladesh, Florida, and West Indies. Different parts of the Psidium guajava are reported to be used in folk medicine. Various parts of the plant like root, bark, leaves and fruits are found to possess many pharmacological properties as it is used in the treatment of various disorders. Various evidences depict that the leaves and bark of P. guajava tree possess a long history of medicinal uses. The aqueous extract of guava leaves has been reported to be efficacious in the treatment of various types of gastrointestinal disturbances such as diarrhoea, inhibition of the peristaltic reflex and gastroenteritis. Moreover the whole plant is used as skin tonic and is employed in the treatment of female related disease like dysmenorrhoea, miscarriages, uterine bleeding and premature labour. Recent studies on the pharmacological properties of the bark, fruit and leaves depicts antibacterial, hypoglycaemic, anti-inflammatory, antipyretic, spasmolytic and central nervous system depressant activities. Bark tincture showed fungicidal activity at different concentrations but exhibit only fungistatic property in case of Candida albicans. Leaf extract of psidium guajava also reported for the anti-bacterial activity on staphylococcus aureus due to the protein degrading activity of the leaf extract. The aqueous extract was more potent in inhibiting the growth of E.coli, staphylococcus aureus and Pseudomonas aeroginosa than the organic extracts. The Gram negative bacteria were less susceptible to the effect of crude drugs. The genus Citrus belongs to the family of Rutaceae and is native tropical and subtropical areas in Southeast Asia. The citrus plants are grown worldwide and ranks top in production and trade among the fruit trees. Citrus fruits are richer sources of bioactive compounds having beneficial effect on human health such as vitamin C, carotenoids, flavonoids, limonoids, essential oils, acridone alkaloind, minerals and vitamin B complex. Majority of citrus fruits are eaten fresh such as sweet orange, mandarins, grapefruits etc (metallurgy 2011).
Aim
The aim of this study is to determine the antimicrobial efficacy of two medicinal plants (Psidium guajava and Citrus x sinensis) against two microorganisms (Streptococcus mutans and Candida aldicans).
OBJECTIVES