Screening of Indigofera lupatana Baker F. root extracts for antibacterial activities

Herbal remedies as cheap alternatives to conventional medicine have contributed significantly to rural livelihoods. Apart from the traditional healers practicing herbal medicine, many people are involved in collecting and trading medicinal plants. The World Health Organization (WHO) estimates that 80% of the world’s population depends on medicinal plants for their primary health care (Mothana et al, 2008; Ngoci et al, 2011). The use of traditional medicine has been explored globally and is widely used in developing countries as an alternative or to complement conventional medicine (Rates, 2001; Gupta et al, 2010). Natural products, either as pure compounds or as standardized plant extracts, provide exceptional opportunities for new drug leads because of the unmatched chemical diversity of naturally derived compounds (Cowan, 1999; Parekh and Chanda, 2007; Mariita et al, 2010; Ngoci et al, 2011). Scientific interest in medicinal plants has burgeoned due to the recognized efficacy of plant derived drugs and everpresent concerns about the side effects of modern medicinal substances. This has fuelled the intensive investigation of new molecular structures from the plant kingdom as potential medicinal compounds (Mariita et al, 2010). As a result, drugs derived from unmodified natural products or semi-synthetic drugs obtained from natural sources accounted for 78% of the new drugs approved by the United States Food and Drug Administration (FDA) between 1983 and 1994 (Suffredini et al, 2006; Ngoci et al, 2011). This underscores the importance of screening natural products. Infectious diseases are a leading cause of human and animal mortality. This is further aggravated by the rapid development of multi-drug resistance to available antimicrobial agents (Doughart and Okafor, 2007; Ngoci et al, 2011), their limited anti-microbial spectrum, their side effects (Huie, 2002), and emergence and reemergence of opportunistic infections. Therefore, studies aimed at identifying and characterizing of the substances that exhibit activity against infectious microorganisms, yet showing no cross resistance with existing antibiotics, are required (Olila et al, 2001). In recent years, pharmaceutical companies have focused on developing drugs from natural products that promises to counter the limitations of conventional antibiotics (Doughart and Okafor, 2007). The bio-activity of natural products is due to phytochemicals, a group of secondary metabolites often elaborated for the plant defense against pests and herbivores or to gain an advantage over competing agents. These phytochemicals inadvertently also protect humans against pathogens (Ngoci et al, 2011). Some phytochemicals are known to have antimicrobial properties, immune-modulative properties, provide nutrition for normal cell health and repairs, inhibit carcinogens and act as antioxidants. Indigofera lupatana Baker F. , locally called ‘mugiti’ by the Mbeere community in Kenya, is a woody shrub found in Acacia-Combretum ecological zones of Mbeere. It is widely used for its perceived medicinal value in treating coughs and diarrhea (Riley and Brokensha, 1988; Ngoci et al, 2011), gonorrhea and pleurisy (Kokwaro, 1993; Ngoci et al, 2011). There is apparently no documented scientific report on anti-microbial properties of this plant. This lack of scientific corroboration has often constituted a major constraint to the consideration of the use of herbal remedies in conjunction with or as an affordable alternative to conventional medical treatment (Okeke et al, 2001). Knowledge of the chemical constituents of plants is desirable not only for the discovery of therapeutic agents, but also because such information may be important in identifying new sources of substances of economic value such as tannins, oils, gums, and precursors for the synthesis of complex chemical substances. In addition, the knowledge of the chemical constituents of plants would further be valuable in discovering the actual value of folkloric remedies (Mojab et al, 2003). This study was therefore undertaken to determine the antibacterial properties of hexane, ethyl acetate and dichloromethane root extracts of I. lupatana Baker F.