Iridoid derivatives from Vitex rotundifolia L. f. with their anti-inflammatory activity

Three undescribed iridoid glucosides and nine known compounds were isolated from Vitex rotundifolia L. f. Their structural elucidation was performed based on their spectroscopic data or acid hydrolysis followed by HPLC analysis and comparison of their NMR data with those reported in the literature. These iridoids were then evaluated for inflammatory effects through inhibition on NO production level in LPS-stimulated RAW264.7 cells. The active compounds, rotundifoliin C, isonishindacin A, agnuside, and eurostoside, were further investigated for their anti-inflammatory mechanisms of action on expression levels of iNOS and COX-2 proteins. In addition, V. rotundifolia fractions also significantly inhibited LPS-induced IL-8 production, with IC₅₀ values ranging from 9.81 to 54.31 μg/mL. Rotundifoliin A, agnuside, VR-I (10-O-vanilloyl aucubin), and eurostoside showed inhibition rates of 55.5%, 94.6%, 55.6%, and 81.9% on IL-8 production at concentrations of 100 μM, respectively, compared to those of control without sample addition. The therapeutic properties of the plant might give rise to develop the functional products to treat inflammatory diseases.