Microbial biotransformation—A novel approach for modification on coumarin substrates

Microbial biotransformation, one of the tools of green chemistry, is widely used in organic synthesis to cutshort number of organic intermediates in obtaining the final required compounds. In the present study, an approach was made for preparing substituted derivatives of coumarin as therapeutic agents. Nine biotransformation experiments were performed where random combination of four microorganisms and five substrates (JSN1-9), showing optimum recovery of the final compounds, were selected. The conditions suitable for the growth of the organisms using the test substrate and products were standardized. Quantitative analysis of the transformed product was done by HPTLC technique and characterized by mass spectra. Of the nine test compounds, two transformations were found to be successful; O-deethylation of 7-ethoxy-4methyl coumarin gave 7-hydroxy-4-methyl coumarin using Streptomyces griseus with a yield of 4.2% (JSN8) and O-methylation of 7-hydroxy-4-methyl coumarin gave 7-methoxy-4-methyl coumarin using Candida tropicalis with a yield of 5.5% (JSN3). The crude transformed extracts were then screened for their antioxidant activity by DPPH radical scavenging method. Further, the test extracts were subjected for their antibacterial activity.