Evaluation of Plant Phenolic Compounds as Anti-oxidative and Anti-inflammatory Agents

Abstract

Phenolic compounds are naturally occurring group of plant metabolites present widely in fruits, vegetables, wine and tea. The presumed beneficial effects of flavonoids are mainly ascribed to their inherent capacity to scavenge reactive oxygen and nitrogen species, thus counteracting conditions of oxidative stress that accompany inflammatory disorders such as cancer. In this study, we evaluated and compared major phenolic compounds for their antioxidative and anti-inflammatory activity. Phenolic compounds tested include cinnamic acid, carnosic acid, chlorogenic acid, piceatannol, apigenin, quercetin, kaempferol, hesperidine, catechin, epigallocatechin gallate, cyanidin, delphinidin, pelargonidin, piceatannol and apigenin. HT-29 human colon carcinoma cells were treated with each test compound at 10μM concentration and antioxidative activity was determined by measuring reactive oxygen species scavenging activity and the inhibition of oxidative DNA damage. Anti-inflammatory activities of phenolics were determined by measuring total nitrite, prostaglandin E2 (PGE2), tumor necrosis factor (TNF)-α and interlukin (IL)-6 in lipopolysccharide (LPS)-stimulated murine macrophage RAW 264.7 cells treated with test compounds. Results showed that apigenin (p＜0.01), piceatannol (p＜0.01), carnosic acid (p＜0.05), and delphinidin (p＜0.01) had significant ROS scavenging activity. DNA damage was suppressed by majority of the compounds tested except quercetin, catechin, piceatannol, and pelagonidine. Phenolic compounds significantly inhibited production of proinflammatory molecules. Carnosic acid, apigenin, and kaempferol belong to top 5 coumpounds possessing lowest IC50 values in all four inflammatory markers. No significant relationship was found between antioxidant and anti-inflammatory activity except tail length and IL-6. Further studies are required to understand molecular mechanisms of action by each compound, and physiological consequences of consuming diet high in polyphenol mixture. (Cancer Prev Res 13, 18-25, 2008)