Plants as potential source of antimicrobial agents

Abstract

For microbial infections, either caused by bacteria or fungi, antibiotics are employed. After the discovery of antibiotics it was thought that infectious diseases will no longer exist. But due to irrational use of antibiotics, a number of bacterial strains with multi-drug resistance have emerged (khan et al., 2009) and due to infectious diseases millions of people die every year (Dubey et al., 2012). It is a bitter fact that infectious diseases are the leading cause of the premature deaths which result in approximately fifty thousand deaths annually around the globe (Ahmad and Beg, 2001). The unnoticeable use of antimicrobials both in developing and developed countries led to the creation of microbial resistance problems. It also makes the treatment difficult especially in immunocompromised patients (Ahmad and Beg, 2001).Plants and plant products have been used as medicines since the start of history. Many researchers have conducted research on the plant products to check their antimicrobial effects (Abu-shanab et al., 2004). The oldest known method for healing is the use of plant. Using higher plants for treatment of diseases had started since the man started to live on this planet (Onyeagba et al., 2004). Traditional medicines including the herbal medicines are used at least for primary health care in some domains in almost every country. In the developing countries about 70-95% patients depends on the natural medicines. In 2008 the worldwide market of natural medicine was of 83 billion US$ and on annual basis there is exponential increase in this bill. Legal concerns about the herbal/natural medicines vary widely from state to state and country to country and these medicines are used as self-medicines, health foods, functional foods, homes care remedies, over the counter medicines, prescription medicines etc. The quality of the herbal/traditional medicines is very difficult to control and maintain consistently. WHO in cooperation with its local and regional offices has made Good Agricultural and Collection Practices (GACP) and Good Manufacturing Practices (GMP) in addition to technical support and assistance for standardization for creation of high quality products. For understanding the approaches of quality, safety and efficacy which are based on research are needed to evaluate the traditional or herbal medicines (Robinson and Zhang, 2011). Search for the relief from infection from natural resources (plants etc.) is not a new idea. People from all over the world use the plant products for healing e.g. it is evident that Neanderthals who lived 60,000 years ago in the present day Iraq used hollyhock, and these plants are still widely used in the ethanomedicine all around globe. Hippocrates mentioned 300-400 medicinal plants in the late 5th century B.C (Cowan, 1999). A number of plants contain compounds that have antibacterial property (Khan et al., 2011). Compounds such as emetine, berberine and qunine which are derived from plants are very effective for the infectious microbes (Iwu et al., 1999). On the earth there are more than 3, 00,000 plant species and only about 2% of plants have been checked so for, for their antimicrobial properties. Plants extracts from more than 157 plant families have been described which have potential antimicrobial properties (Narayan et al., 2010). In United States of America (USA) about 1/4th to 1/2th of the pharmaceuticals dispensed have their origin of higher plants (Cowan, 1999). Medicine which in near past had been derived from natural resources include taxol, camptothecin (anticancerous) and artemisinin (antimlarial). These and many other drugs clearly show that plants serve the potential source of medicine even today.