Anti-inflammatory naphthoates and anthraquinones from the roots of Morinda officinalis

Morinda (Morinda officinalis) is widely consumed as a health-care herb in Asia and reported to possess various biological activities. In this study, anti-inflammatory phytochemicals were investigated and two pairs of new methyl-2-naphthoate enantiomers (1a/1b, 2a/2b), one new anthraquinone (3), three new natural unknown anthraquinones (5-6, 23), and eighteen known anthraquinones were isolated and elucidated from the roots of morinda. Anti-inflammatory activities of the isolated compounds were assessed in lipopolysaccharide-stimulated RAW 264.7 macrophages. Compounds 2b and 19 significantly inhibited the production of NO with IC₅₀ values of 34.32 ± 4.87 and 17.17 ± 4.13 μM (indomethacin, IC₅₀ 26.71 ± 6.32 μM), and they were further corroborated via immunoblotting, quantitative real-time PCR and immunofluorescence staining assays. They could dose-dependent suppress lipopolysaccharide-stimulated pro-inflammatory factors (COX-2 and iNOS) production and block nuclear translocation of NF-κB. The results implied that reasonable consumption of morinda may be beneficial for preventing and reducing the occurrence of inflammatory-associated diseases.