Apigenin and apigeninidin isolates from the Sorghum bicolor leaf targets inflammation via cyclo-oxygenase-2 and prostaglandin-E2 blockade

AIM: This study evaluated the anti-inflammatory properties of a species of Sorghum bicolor leaf (SBL) grown in West Africa. METHOD: Cyclo-oxygenase (COX)-2:COX-1 selectivity assay was carried out by plating isolated peripheral blood mononuclear cells in culture medium with specific SBL fractions: crude extract (J), ethyl-acetate (JE) and aqueous (JA); secondary compounds from JE (JE5, JE6, JE7 and JE8); purified (P9) and semi-purified (P8) compounds from JE5 at 5-200 μg/mL for 1 hour. Test compounds and controls ibuprofen (50 μmol/L) and CAY10404 (1 μmol/L; 10 μmol/L) were added to two sets of plates, one without lipopolyshaccharide (LPS) and the other with LPS (1 μg/mL) for 24 hour. COX-2IC50 :COX-1IC50 ratio represented 50% inhibition of the activity of COX-2 to that of COX-1 using ibuprofen as control. In separate experiments the supernatant of P8 and P9-treated fractions of SBL and controls were plated with RAW 264.7 macrophage cells to measure prostaglandin (PG)-E2 production and cell proliferation activity. RESULTS: JA fraction of SBL had the highest ratio of COX-2IC50 :COX-1IC5041.214 whereas JE had the lowest ratio COX-2IC50 :COX-1IC501.161 . Interestingly, JE5 derived from JE showed a ratio of COX-2IC50 :COX-1IC500.495 while P8 derived from JE5 showed a dose-dependent reduction in COX-2IC50 :COX-1IC50 ratio and in PG-E2 production, which was more effective compared to ibuprofen. A dose-dependent reduction in RAW 264.7 macrophage cell proliferation was also observed in P8-treated cells. The phenolic compounds identified in P8 include apigenin and apigeninidin adducts which may explain the exceptional anti-inflammatory activity and efficacy in COX-2 targeting.