Anti-inflammatory monoterpenes from morinda (Morinda officinalis How.)

Morinda (Morinda officinalis How.) is widely consumed as a functional food owing to its potential to promote health. This study investigated the anti-inflammatory phytochemicals of morinda and isolated 30 monoterpenes, including 6 undescribed iridoids (1, 6, 9-11 and 25), 2 undescribed acyclic monoterpenoids (28, 29), a known acyclic monoterpenoid and 21 known iridoids. Their chemical and stereo-structures were elucidated based on HR-ESI-MS, NMR, ¹³C-NMR calculations, ECD data and ECD calculations. Notably, compounds 11, 12 and 20 exerted pronounced inhibitory effects on lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophages, with IC₅₀ values of 28.51 ± 1.70, 25.45 ± 4.17 and 29.17 ± 3.71 μM respectively (indomethacin, IC₅₀ of 33.68 ± 2.19 μM). The same compounds exert anti-inflammatory effects by blocking nuclear translocation of nuclear factor κ-B, and down-regulating the expression of inflammatory cytokines such as cyclooxygenase-2, inducible nitric oxide synthase, interleukin-1β and interleukin-6 at mRNA and protein levels in a dose-dependent manner. These results suggest that moderate consumption of morinda helps prevent and reduce the occurrence of inflammatory-related diseases.