Scope of Hydrolysable Tannins as Possible Antimicrobial Agent.
Nitric oxide (NO) is a pleiotropic regulator, critical to numerous biological processes, including vasodilatation and macrophage-mediated immunity. Macrophages express inducible NO synthase (iNOS) and produce NO after lipopolysaccharide (LPS) stimulation. Gallotannins are water-soluble polyphenols with wide-ranging biological activities. Various chemical structures of gallotannins occurring in medicinal and food plants that are used worldwide showed several remarkable biological and pharmacological activities. In the present study, we examined the inhibitory effects of gallotannin 1,2,3,6-tetra-O-galloyl-beta-D-allopyranose (GT24) isolated from Euphorbia jolkini on the LPS-induced NO production and underlying mechanisms of action. GT24 dose-dependently decreased LPS-induced NO production and iNOS expression in J774A.1 macrophages. In addition, GT24 inhibited LPS-induced activation of nuclear factor (NF)-kappaB as indicated by inhibition of degradation of I-kappaBalpha, nuclear translocation of NF-kappaB, and NF-kappaB dependent gene reporter assay. Our results suggest that GT24 possesses an inhibitory effect on the LPS-induced inflammatory reaction.