38 



Plant Derived Bioactive Chemicals 



H avail 



Figure 1 : Regions of the USA Sampled by the Missouri Botanical Gardens for 

 Monsanto-Searle 



been obtained by botanists from regions in the USA which are rich in plaint 

 biodiversity (Figure 1). They are collected from public, government and private 

 land after obtaining the necessary authority and permits. Endangered species 

 are identified before hand and are not collected. Samples are shipped to 

 Monsanto, extracted and screened for the desired biological activity. The USA 

 was chosen for this work because of its large resources of native plants growing in 

 diverse environments, easy access £ind well documented flora. Over the past four 

 years, Monsanto has spent over $1 million on sourcing plaints for their screens 

 and plans to continue the program. 



The next challenge is to develop and supply the analytical technology to screen the 

 collected plants in a reasonable time. Devising the screen to test large numbers of 

 samples requires a major commitment and considerable analj^ical skill. Cell 

 biology and biotechnology advances provide sufficient quantities of the protein 

 based targets to support large scale random screens. High throughput screens 

 are devised and resxilts analyzed using microanalytical methods combined with 

 computerized data heindling. When a 'hit' is identified, advanced separations 

 and structure elucidation methodologies are used for the isolation of natural 

 product chemicals and the assignment of structure. In order to obtain sufficient 



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