A new cyclooxygenase (COX) inhibitory pterocarpan from Indigofera aspalathoides: structure elucidation and determination of binding orientations in the active sites of the enzyme by molecular docking

A new compound indigocarpan (1) and the known compound mucronulatol (2) were isolated from chloroform extracts of Indigofera aspalathoides. Their structures were established by spectroscopic methods, including single-crystal X-ray analysis (in the case of 1). The isolates were evaluated for cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) inhibitory activities and antioxidant properties. The new compound 1 showed significant COX-1 inhibition (IC50 30.5 μM) and its in vivo anti-inflammatory activity was found to be comparable to that of ibuprofen. Molecular docking studies revealed the binding orientations of 1 in the active sites of COX-1 and COX-2.