Anti-inflammatory activity of phenylpropyl triterpenoids from Osmanthus fragrans var. aurantiacus leaves

Osmanthus fragrans var. aurantiacus has been used for the treatment of menopausal pain, foul breath, and intestinal bleeding. Four phenylpropyl triterpenoids, 3-O-trans-p-coumaroyltormentic acid (1), 3β-trans-p-coumaroyloxy-2α-hydroxyl-urs-12-en-28-oic acid (2), 3β-cis-p-coumaroyloxy-2α-hydroxyl-urs-12-en-28-oic acid (3), 3-O-cis-coumaroylmaslinic acid (4), were isolated from the leaves of O. fragrans var. aurantiacus and the inhibitory effect on nitric oxide (NO) production in lipopolysaccharide (LPS)-induced macrophages were evaluated. Among them, compounds 2–4 concentration dependently showed NO production inhibitory effects. To determine the signaling factors involved in the inhibition of NO production by compounds 2–4, we assessed anti-inflammatory activity. Western blot analysis revealed compounds 2–4 significantly decreased the expression of LPS-stimulated protein, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, nuclear factor-kappa B (NF-κB) and phosphorylated extracellular regulated kinase (pERK)1/2. Also, compounds 2–4 downregulated tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-8 levels in LPS-induced macrophages and colonic epithelial cells. This study demonstrated that phenylpropyl triterpenoids 2–4 isolated from O. fragrans var. aurantiacus leaves can be used as potential candidates for the prevention and treatment of inflammatory bowel disease.