Triterpenoids Isolated from Alnus japonica Inhibited LPS-Induced Inflammatory Mediators in HT-29 Cells and RAW264.7 Cells

Alnus japonica (Betulaceae) is a broad-leaved tree easily found in damp regions within the mountains of Korea and Japan. Four triterpenoids (1–4) from the fruits of A. japonica, including the newly isolated 3β-hydroxy-lanost-9(11),23(24)-dien-25,26-diol (3), inhibited the lipopolysaccharide (LPS)-induced expression of the chemotactic cytokine interleukin (IL)-8 and nitric oxide (NO) production in HT-29 colon epithelial cells and RAW264.7 macrophages, respectively. Among these triterpenoids, compound 4, which showed the most potent inhibitory activity, effectively down-regulated LPS-induced protein expression of inducible nitric oxide synthase (iNOS) in RAW264.7 cells and in HT-29 cells. Also, compound 4 concentration-dependently inhibited the levels of LPS-induced pro-inflammatory cytokines, IL-1β and IL-6 in macrophage cells. These triterpenoids isolated from A. japonica fruits are thought to contribute to the anti-inflammatory activities of macrophage and colon epithelial cells, which are important for regulating the colon immune system. They are expected to be potential candidates for therapeutic agents against inflammatory bowel disease.