Phenolic Constituents from Platycodon grandiflorum Root and Their Anti-Inflammatory Activity

Six lignols (1-6), including two new compounds (+)-(7R,8R)-palmitoyl alatusol D (1) and (+)-(7R,8R)-linoleyl alatusol D (2), along with four phenolics (7-10), a neolignan (11), three alkyl aryl ether-type lignans (12-14), two furofuran-type lignans (15-16), three benzofuran-type lignans (17-19), a tetrahydrofuran-type lignan (20), and a dibenzylbutane-type lignan (21) were isolated from the ethyl acetate-soluble fraction of the methanol extract of Platycodon grandiflorum (Jacq.) A. DC. root. The chemical structures of the obtained compounds were elucidated via high-resolution mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy analyses. The obtained spectroscopic data agreed well with literature. Among the isolated compounds, eighteen (1-7 and 11-21) were isolated from P. grandiflorum and the Campanulaceae family for the first time. This is the first report on lignol and lignan components of P. grandiflorum. The anti-inflammatory effects of the isolated compounds were examined in terms of their ability to inhibit the production of pro-inflammatory cytokines IL-6, IL-12 p40, and TNF-α in lipopolysaccharide-stimulated murine RAW264.7 macrophage cells. Nine compounds (4-6, 12, and 15-19) exhibited inhibitory effects on IL-12 p40 production, eleven compounds (1-6, 12, 15-17, and 19) exhibited inhibitory activity on IL-6 production, and eleven compounds (1-6 and 15-19) exhibited inhibitory effects against TNF-α. These results warrant further investigation into the potential anti-inflammatory activity and general benefits of the phenolic constituents of P. grandiflorum root.