ABSTRACT
Merck has maintained an active natural products research program continuously since the early days of antibiotic research in the 1940’s. The primary focus of the effort has been the discovery of new microbial metabolites with biological activity. Cultures which are inactive in all of the assays are usually destroyed, while those found to be active in one or more screening assay are regrown under conditions similar to the original small-scale fermentation. Dereplication is the process of determining whether a particular active constituent has been encountered previously in a screening program. The newer methods available in biology, biochemistry and chemistry have produced the current peak in interest in natural products, but they have also resulted in the advent of other kinds of screening. In a typical microbial products program, microbiologists isolate pure cultures of microorganisms from environmental samples which have been collected in the biosphere.
