Anti-inflammatory activity of hydroxycinnamic acid derivatives isolated from corn bran in lipopolysaccharide-stimulated Raw 264.7 macrophages

In this study, the effect of the 80% ethanolic extract of corn bran (EECB) on inhibition of nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in lipopolysaccharide (LPS)-stimulated Raw 264.7 cells was investigated. The EECB inhibited LPS-induced NO production and iNOS expression in a dose-dependent manner. Four hydroxycinnamic acid derivatives (HADs), including two free cinnamic acids, p-coumaric acid (CA) and ferulic acid (FA), and their conjugate phenolic amides, p-dicoumaroyl-putrescine (DCP) and diferuloylputrescine (DFP), were found to be present in the EECB by LC–MS analysis, and DFP (378.66 μg/g) was the predominant phenolic compound, followed by DCP (7.83 μg/g) > CA (5.58 μg/g) > FA (1.84 μg/g). The four HADs significantly inhibited NO production and iNOS expression in a dose-dependent manner. Among the four HADs tested, DFP showed the most potent inhibition on NO production and iNOS mRNA and protein expression, followed by DCP > FA ⩾ CA. DFP also exhibited the strongest inhibition on LPS-induced iNOS and NF-κB luciferase activity, which was followed by DCP ⩾ FA (CA) > CA (FA). Thus, these results suggest that phenolic amides in the corn bran may be a potential source of natural anti-inflammatory agents.