Hydrophobic Fractions of Triticum aestivum L. Extracts Contain Polyphenols and Alleviate Inflammation by Regulating Nuclear Factor-kappa B

Abstract

As a nutritional supplement, wheatgrass (Triticum aestivum L.) is well-known for its anti-inflammatory effects that are exerted through signal transduction pathways. Wheatgrass was extracted in 80% ethanol (WGE), and the ethanol extracts were further fractionated using ethyl acetate, n-butanol, and water. To determine the antioxidant activity, WGE was tested using various radical-scavenging assays. To explain the anti-inflammatory mechanisms, western blotting, reverse-transcription polymerase chain reaction, luciferase assay, immunofluorescence staining, and the inhibition of mitogen-activated protein kinase (MAPK) phosphorylation were performed using mouse macrophage cells (RAW 264.7). Inhibition of proinflammatory and Th2 cytokines was analyzed using a 2,4-dinitrochlorobenzene-induced contact dermatitis mouse model. WGE exhibited a strong antioxidant activity in radical scavenging-assays conducted using artificial and natural substrates. The ethyl acetate and n-butanol fractions (hydrophobic fractions) obtained from the 80% ethanolic extract, inhibited the expression of inducible nitric oxide synthase gene, whereas the aqueous layer (the hydrophilic fraction) showed no inhibitory effects. In addition, the hydrophobic fractions inhibited nuclear factor-kappa B (NF-κB) and reduced phosphorylation of MAPK, indicating that inflammation was alleviated possibly by the regulation of NF-κB signaling. This mechanism was further elucidated using the RAW 264.7 cell line and mouse model. Using high-performance liquid chromatography, the hydrophobic fractions were separated into over 10 phenolic compounds, among which benzoic acid, quercetin, and luteolin were abundant. The study demonstrated that wheatgrass is a potential nutraceutical candidate with antioxidant and anti-inflammatory properties for future use in health foods and cosmetics.