Inhibition of cyclooxygenase activity by standardized extract of Givotia rottleriformis Griff. ex Wight bark

Abstract

A standardized ethanol extract of Givotia rottleriformis Griff. ex Wight bark was tested in vitro for anti-inflammatory activity on key pro-inflammatory enzymes, cyclooxygenase (COX-1 and COX-2) and membrane stabilizing potential. The extract was standardized in terms of the presence of flavonoids by HPLC, total phenolics by Folin-Ciocalteu method, flavonoid content using AlCl₃ method, and free radical scavenging activity using inhibition of hydroxyl, 2, 2-diphenyl-1-picrylhydrazyl (DPPH), and nitric oxide radical. The anti-inflammatory effect was screened using cyclooxygenase inhibition and membrane stabilizing potential. In the HPLC analysis, 4 flavonoids were identified by comparing with the calibration curve derived from the standard rutin, quercetin, kaempferol, and luteolin. The total phenolic content and flavonoid contents were found to be 13.80 and 5.7 % w/w, respectively. Significant hydroxyl, DPPH, and nitric oxide radical scavenging activity was observed with IC50 values of 230, 220, and 180 µg/mL, respectively. The ethanol extract significantly protected the rat erythrocyte membrane against lysis induced by hypotonic solution. The ability of the extract to inhibit cyclooxygenase enzymes (COX-1 and COX-2) was determined by calculating percent inhibition of PGE2 production measured by enzyme immunoassay. The extract inhibited both enzymes with IC50 value of 45 and 37 µg/mL, respectively. The anti-inflammatory activity of G. rottleriformis bark could be at least in part due to free radical-scavenging activity and cyclooxygenase enzyme inhibition.