ABSTRACT
A large number of human, animal and plant disease are caused by pathogenic microbes (fungi bacteria and algae). Infection due to fungi and bacteria have been a major cause of death in higher organisms. The discovery of antibiotic penecillin by Fleming is therefore considered to be one of most important discoveries in the world. Historically many of the new antibiotics were isolated from natural sources (soil microbes, plants, etc). Many more were later synthesized and introduced in clinical practices. Unfortunately human struggle against pathogenic microbes is far from over due to many reasons. Most important of them time to time discovery of new pathogens, and remarkable abilities of microbes to develop resistance against used antibiotic. The discovery and development of new antimicrobial agent is therefore a on going process. Remarkable diversity of chemicals present in biological sampleshave tremendous potential in search of new antimicrobial agents.
