Selective biotransformation of coumarins by Cunninghamella elegans

Coumarins (1,2-benzopyrones) are ubiquitous in plants and comprising a vast array of biological properties. The great variety of applications of these compounds, combined to the difficulties in their isolation from natural sources, make them attractive for chemical synthesis and biotechnological studies. The biotransformation by microorganisms can generate chemical analogues with high selectivity, under mild and ecofriendly conditions. The aim of this study was to investigate the biotransformation of nine coumarins scaffolds (Figure 1) by the filamentous fungus Cunninghamella elegans ATCC 10028b. Firstly, the fungus was cultured in malt agar, for seven days, at 28°C. After this, C. elegans was transferred to 125 mL-Erlenmeyer flask containing 50 mL of Koch´s medium (glucose 0.18%; peptone 0.06%; yeast extract 0.04%) and 5 mg of each substrate separately dissolved in 200 μL of DMSO. All coumarins were previously synthetized through Pechmann reaction. The biotransfomation was carried out under agitation (120 rpm), at 28°C and during three days. Control flasks were incubated at the same conditions. Extraction using ethyl acetate yielded the crude extracts, which were analyzed by HPLC (reverse phase). C. elegans transformed the coumarins 4 and 7, revealing the importance of only one hydroxyl group in the aromatic ring and a bulky group in the lactone ring to biotransformation of this compounds class. Taking into account that C. elegans is an important enzymatic system both for derivatives achievement and for mimic the mammalian metabolism, our results open new possibilities for the coumarins studies.