Cyclooxygenase-2 enzyme inhibitory triterpenoids from Picrorhiza kurroa seeds

A bioassay guided phytochemical study of the ethyl acetate extract of the seeds of Picrorhiza kurroa afforded a new triterpenoid, 2α, 3β, 19β, 23-tetrahydroxyolean-12-en-28-O-β-d-glucoside (1), along with five known triterpenoids, 2α, 3β, 19β, 23-tetrahydroxyolean-12-en-28-oic acid (2), 2α, 3β, 23-trihydroxyolean-12-en-28-O-β-d-glucoside (3), 2α, 3β, 23-trihydroxyolean-12-en-28-oic acid (4), 2α, 3β, 19β, trihydroxyolean-12-en-28-oic acid (5), and 2α, 3β, 6β, 23-tetrahydroxyolean-12-en-28-oic acid (6). Their structures were established by extensive NMR spectral studies. The acetyl derivatives, compounds 7 and 8, were prepared from compounds 1 and 2, respectively, to aid in their structure elucidation. The inhibition of cyclooxygenase-2 (COX-2) enzyme by compounds 1–6 at 100 μg/mL was 38.3%, 39%, 37%, 49.6%, 25%, and 45.0%, respectively. However, compounds 1–6, at 100 μg/mL, did not inhibit cyclooxygenase-1 (COX-1) enzyme. Compound 1 is a novel triterpenoid and compounds 1–6 are isolated for the first time from the seeds of P. kurroa.