Location: Market Quality and Handling ResearchTitle: Antioxidant and Anti-inflammatory Effects of Peanut Skin Extracts Author
Submitted to: Food and Nutrition Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2013
Publication Date: 8/1/2013
Citation: Lewis, W.E., Harris, G.K., Sanders, T.H., White, B.L., Dean, L.L. 2013. Antioxidant and Anti-inflammatory Effects of Peanut Skin Extracts. Food and Nutrition Sciences. 4:22-23. Interpretive Summary: Waste material from peanut shelling plants includes the redskins that coat the peanut seeds inside the shells. This material is currently used as a component in animal feed in limited quantities due to its antinutritional properties and bitter taste. It has been found that peanut skins contain large amounts of compounds with antioxidant and anti-inflammatory properties. This study involved extracting peanut skins with mixtures of water and organic solvent and testing the extracts for phenolic compounds, specifically procyanidins. The extracts were found to have antioxidant properties in chemical tests. Their ability to decrease inflammation in cells being raised in culture that had exposed to chemical agents that had caused inflammation was determined. The mechanism of this action was discussed.
Technical Abstract: Peanut skins are regarded as a low economic value by-product of the peanut industry; however, they contain high levels of bioactive compounds including catechins and procyanidins, which are known for their health-promoting properties. The in vitro antioxidant activity of peanut skin extracts (PSE) has been reported but the associated anti-inflammatory properties have not been widely reported. This study investigates the anti-inflammatory effects of PSE on the pro-inflammatory enzyme, Cyclooxygenase-2 (COX-2) and its downstream product, prostaglandin E2 (PGE2). Nitrous oxide (NO) levels produced by the stimulated cells were also measured. Defatted peanut skins were extracted using two aqueous solvent mixtures (50 % acetone and 90% ethanol), in order to compare the effects of the two solvent systems on antioxidant and anti-inflammatory properties. PSE antioxidant activity was determined by the hydrophilic oxygen radical absorbance capacity (H-ORAC) assay, the total phenolics were determined by the Folin-Ciocalteu assay and flavan-3-ols and procyanidins were quantified by HPLC. Acetone extracted PSE (A-PSE) exhibited numerically, but not statistically higher H-ORAC and total phenolic values than the ethanol extracted PSE (E-PSE) (1,836 µmol Trolox/100g and 67.9 mg GAE/g, and 1,830 µmol Trolox/100g and 51.8 GAE/g respectively). A-PSE also had higher levels of flavan-3-ols and procyanidins than E-PSE. RAW 264.7 were pretreated with 1.0, 2.5 and 5.0% (v/v) of A-PSE or E-PSE and induced with the inflammatory marker, lipopolysaccharide (LPS) for 12 hours. COX-2 protein expression, measured by Western blotting was significantly (p<0.05) inhibited by A-PSE and E-PSE at 2.5% and 5.0% concentrations. PGE2 and NO levels measured by ELISA, were significantly (p<0.05) decreased with increasing added levels of A-PSE and E-PSE suggesting that A-PSE and E-PSE not only possess similar antioxidant properties, but also exhibit similar anti-inflammatory properties.