Investigation of the anti-inflammatory and antioxidant activities of luteolin, kaempferol, apigenin and quercetin

Luteolin, kaempferol, apigenin and quercetin are four common flavonol glycoside compounds found in many plants that possess multiple biological activities. The current study focused on their anti-inflammatory and antioxidant activities in vitro by assaying the NO content, phagocytosis, DPPH and ABTS radical scavenging activities and ferric reducing antioxidant power. This study indicated that all four compounds at concentrations of 50, 100 and 200 μM could reduce both the concentration of NO and phagocytosis; their antioxidant activities increased as the concentration increased from 0.5 to 32.0 μg/ml; the IC50 DPPH values were 2.099, 5.318, 1.84, 10.5 and 3.028 μg/ml for luteolin, kaempferol, quercetin, BHT and VC, respectively; the IC50 ABTS values were 0.59, 0.8506, 0.8243, 0.5083, 1.4497 and 2.1563 μg/ml for luteolin, kaempferol, apigenin, quercetin, BHT and VC, respectively; and the FRAP values ranged from 0.0101 to 0.0402 mmol Fe2+/μg/ml for the six compounds. Compared with the test results, quercetin is a perfect anti-inflammatory and antioxidant agent that has potential as an adjuvant treatment for inflammatory diseases and oxidative stress. In addition, this research preliminarily revealed that antioxidant activity is directly proportional to the number of phenolic hydroxyl groups, and after comparison of the anti-inflammatory and antioxidant activities, the compounds with enol groups were superior to those without enol groups, which will be further verified in future in vivo experiments.