Microbial Transformation of the Sesquiterpene Lactone, Vulgarin, by Aspergillus niger .

The biotransformation of vulgarin , an eudesmanolides-type sesquiterpene lactone obtained from , by the microorganism, , was carried out to give three more polar metabolites; 1--tetrahydrovulgarin (1α,4α-dihydroxy-5αH,6,11βH-eudesman-6,12-olide , 20% yield, 1α,4α-dihydroxyeudesm-2-en-5αH,6,11βH-6,12-olide , 10% yield, and C-1 epimeric mixture , 4% yield, in a ratio of 4:1, . The structures of vulgarin and its metabolites were elucidated by 1 and 2D NMR spectroscopy in conjunction with HRESIMS. Metabolites and are epimers, and they are reported here for the first time as new metabolites obtained by biotransformation by selective reduction at C-1. Vulgarin and its metabolites were evaluated as anti-inflammatory agents using the human cyclooxygenase (COX) inhibitory assay. The obtained data showed that exhibited a good preferential inhibitory activity towards COX-2 (IC50 = 07.21 ± 0.10) and had a moderate effect on COX-1 (IC50 = 11.32 ± 0.24). Meanwhile, its metabolite retained a selective inhibitory activity against COX-1 (IC50 = 15.70 ± 0.51). In conclusion, the results of this study revealed the necessity of the presence α, β unsaturated carbonyl group in for better COX-2 inhibitory activity. On the other hand, the selectivity of as COX-1 inhibitor may be enhanced via the reduction of C-1 carbonyl group.