Inhibitory effects of flavonol glycosides from Cinnamomum osmophloeum on inflammatory mediators in LPS/IFN-γ-activated murine macrophages Original Research Article

Four kaempferol glycosides were isolated from the leaves of Cinnamomum osmophloeum Kaneh, a Taiwan endemic tree. These compounds namely, kaempferitrin (1), kaempferol 3-O-β-d-glucopyranosyl-(1→4)-α-l-rhamnopyranosyl-7-O-α-l-rhamnopyranoside (2), kaempferol 3-O-β-d-apiofuranosyl-(1→2)-α-l-arabinofuranosyl-7-O-α-l-rhamnopyranoside (3), and kaempferol 3-O-β-d-apiofuranosy-(1→4)-α-l-rhamnopyranosyl-7-O-α-l-rhamnopyranoside (4). The structure of compound 2 was determined by spectroscopic analyses and acid hydrolysis. The isolates 1–4 were evaluated as inhibitors of some macrophage functions involved in the inflammatory process. These four compounds inhibited lipopolysaccharide (LPS) and interferon (IFN)-γ-induced nitric oxide (NO), and cytokines [tumor necrosis factor (TNF)-α and interleukin (IL)-12] in a dose-dependent manner. The concentration of 50% inhibition (IC50) of NO by compounds 1, 3, 4 were 40, 15, 20 μM, respectively. In parallel, these concentrations were approximately in a similar manner to that observed for TNF-α and IL-12 production. However, compound 2 inhibited NO and cytokines production by 30% at 100 μM concentration. On the other hand, compounds 3 and 4 showed no inhibitory effect on the production of NO from macrophages, when inducible NO synthase was already expressed by the stimulation with LPS and IFN-γ. Taken together, our results provide evidence that isolates of C. osmophloeum possess an anti-inflammatory potential which constitutes a previously unrecognized biological activity.