Discovery of cyclooxygenase inhibitors from medicinal plants used to treat inflammation

Eleven authenticated botanicals used in the traditional Chinese medicine Huo-Luo-Xiao-Ling Dan were screened for ligands to cyclooxygenase (COX) using pulsed ultrafiltration liquid chromatography–mass spectrometry, and a mass spectrometry-based enzyme assay was used to determine the concentration of each of 17 ligands that inhibited COX-1 or COX-2 by 50% (IC₅₀). Acetyl-11-keto-β-boswellic acid, β-boswellic acid, acetyl-α-boswellic acid, acetyl-β-boswellic acid, and betulinic acid were COX-1 selective inhibitors with IC₅₀ values of approximately 10 μM. Senkyunolide O and cryptotanshinone were COX-2 selective inhibitors with IC₅₀ values of 5 μM and 22 μM, respectively. Roburic acid and phenethyl-trans-ferulate inhibited COX-1 and COX-2 equally. COX inhibition and the IC₅₀ values of most of these natural product ligands have not been reported previously.