Synthetic cytokinin forchlorfenuron (FCF) is a plant growth regulator widely used in agricultural industry to promote fruit growth in grapes and kiwifruit. Despite the fact that many toxicological and environmental properties of FCF are known, little is known about the toxicology effects its secondary metabolites have on humans. Microbial biotransformation provides an efficient, cost effective, and ethical means for conducting metabolic studies that offer valuable insight into human metabolism. Cunninghamella elegans, a filamentous fungus, is an important model organism used in the biotransformation of drugs and other xenobiotics due to its ability to mimic mammalian drug metabolism. Acting as an alternative approach to the traditional mammalian model, the fungal model can reproduce the effect of mammalian metabolism while minimizing the usage of animals and human subjects in the drug discovery and development process. In this study, a panel of fungi were screened for their ability to catalyze the biotransformation of FCF. Of the organisms screened, C. elegans (ATCC 9245) was selected for further studies. A time trial study indicated maximum conversion of the parent drug on the 26^thday of the study as measured by HP-LC UV absorption. Metabolites were isolated and further characterized by LC-MS and NMR studies to determine their structures. Furthermore, in an effort to definitively identify the proposed structure of the metabolites, the two metabolites were prepared synthetically and compared to the samples produced by C. elegans. The preparation of the synthetic metabolites confirmed the proposed structures of the metabolites isolated from the biotransformation of FCF by C. elegans as 3-hydroxyphenyl-forchlorfenuron and 4-hydroxyphenyl-forchlorfenuron. Currently these metabolites are being evaluated for their toxicological properties with human cells.

Paulo Carvalho

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