INTRODUCTION

The use of herbal mixtures or phytomedicine predates human history (Andrew et al, 2009). Plants produce a diverse range of bioactive molecules making them rich source of different types of medicines (Roy et al., 2004). Most of the drugs today are obtained from natural sources or semi-synthetic derivatives of natural products used in traditional systems of medicine. Medicinal plants are finding their way into pharmaceuticals, cosmetics and neutraceuticals. In pharmaceutical field medicinal plants are mostly used for a wide range of substances present in plants which have been used to treat chronic as well as infectious diseases (Schultz et al., 2008). Plants have been utilized as source of medicine for thousands of years and continue to play an important role globally in primary health care, mostly in developing countries. The use of medicinal plants is increasing because people believe they are safe for human consumption (Roy et al., 2004). Herbal mixtures are prepared and used not only for primary health care of the poor in developing countries, but also in countries where conventional medicine is predominant in the national health care system. Herbal mixtures serve the health needs of about 80% of the world’s population, especially for millions of people in the vast rural areas of developing countries. More than 65% of the global population uses medicinal plants and their herbal mixtures for their primary health care needs. World Health Organization (WHO) has described traditional medicine as one of the surest means to achieve total health care coverage of the world’s population in pursuance of its goal of providing accessible and culturally acceptable health care for the global population. World Health Organization has encouraged the rational use of traditional plant based medicines by member states and has developed technical guide lines for the assessment of herbal medicine (Kunle et al, 2012). In Nigeria, there appears to be an overwhelming increase in the public awareness and usage of herbal mixtures in the treatment and/or prevention of diseases. This may not be unconnected to the active mass media advertisement embarked upon by the producers and marketers of the herbal mixtures. World Health Organization have taken the advantage of the relatively high cost of the conventional pharmaceutical dosage forms, inaccessibility of the orthodox medical practices to a vast majority of people particularly in the rural areas and the reservations by the public due to the prevalence of fake, substandard or counterfeit drugs in the market. These placed the herbal mixtures as a ready alternative to conventional dosage forms in the treatment of diseases. With this increased usage, the safety efficacy and quality of these medicines have been important concern for health authorities and health professionals. Although herbal mixtures are often perceived as being natural and therefore safe, they are not free from microbial contaminants which may be due to preparatory, handling and environmental factors (McDonald et al, 2010). Nigeria is endowed with wide varieties of indigenous medicinal plants. These plants are used by the local herbalists for treatment of a number of diseases, both bacterial and non-bacterial types (Schoop et al. , 2006). These plants such as Asmina triloba (paw paw), Citrus aurantifolia (lime), Psidium guajava (Guava), Azadirachta indica (Neem/dogoyaro). Others include Aspilia africana (Haemorrhage plant), Venonia amagdalina (Bitter leaf), Gongronema latifolia (Utazi) etc are naturally distributed in most autonomous communities in Mbaitoli Local Government Area. Most plant parts (extract) eg. (bark root, seeds, fruit, leaf) serve as major source of active ingredient and products of secondary metabolites. For instance, Azadirachta indica (Dogoyaro/Neem) is commonly known for treating malaria scourge, though it could also be used to treat ailments like hepatitis and intestinal problems when mixed with the bark and leaves of Mangifera indica with some fruits of Citrus aurantifolia. The methods of harvesting, drying, storage, transportation and processing such as mode of extraction and the polarity of the extracting solvent, instability of constituents, also affect herbal quality. These may serve as the sources of contamination of the herbal mixtures (Bodeker et al, 2005).