Inhibitory Effects of New Epicatechin Oligomers on Nitric Oxide Production

The primary aim of this research was to identify the structural characteristics of three newly derived procyanidins from cold plasma-treated (-)-epicatechin, known for their anti-inflammatory properties. The newly generated compounds were isolated through column chromatography, and their chemical structures were elucidated through spectroscopic data analyses, including both one-dimensional and two-dimensional nuclear magnetic resonance (NMR) and mass spectrometry (MS) techniques. Furthermore, their absolute configurations were determined via circular dichroism (CD) spectroscopy. The inhibitory activity of the isolated compounds on nitric oxide (NO) production and expression levels of inducible NO synthase (iNOS) in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages was evaluated. Three new procyanidins-methylenetrisepicatechin (<b>2</b>), isomethylenetrisepicatechin (<b>3</b>), and methylenebisepicatechin (<b>4</b>)-along with two reported dimeric flavan-3-ols (<b>5</b> and <b>6</b>), were identified from plasma-treated (-)-epicatechin (<b>1</b>). The unique oligomerized products <b>2</b> and <b>3</b> linked by methylene bridges significantly suppressed both NO production and iNOS expression, demonstrating higher anti-inflammatory activities in LPS-stimulated RAW 264.7 cells compared with the parent compound. The newly oligomerized procyanidins have potential applications in the treatment of inflammatory diseases owing to their significant anti-inflammatory properties.