Tannins with LPS-induced NO production inhibitory activity from Juglans sigillata bark

Abstract

Juglans sigillata Dode (Juglandaceae), a deciduous tree indigenous to China, has been extensively used in folk medicines to cure esophageal, gastric, cardiac and lung cancer [1–3], though its chemical constituents have never been reported. The Inhibitory effect of J. sigillata bark constituents against LPS-induced NO production in murine microglial BV2 cells was investigated. Bioactivity-guided fractionation and purification of a 70% acetone extract of the bark led to the isolation of 9 tannins and their structures were elucidated as gallic acid (1), ellagic acid (2), 1,2,6-tri-O-galloyl-β-D-glucose (3), 1,3,6-tri-O-galloyl-β-D-glucose (4), 1,2,3,6-tetra-O-galloyl-β-D-glucose (5), 1,2,3,4,6-penta-O-galloyl-β-D-glucose (6), 2,3-O-4,4′,5,5′,6,6′-HHDP-(α/β)-D-glucose (7), 4,6-O-4,4′,5,5′,6,6′-HHDP-(α/β)-D-glucose (8), and pedunculagin (9) on the basis of spectral and chemical evidence. All the nine tannins exhibited significant inhibition of LPS-induced NO production compared with NAME (positive control). A structure-activity relationship analysis revealed that the introduction of galloyl and HHDP groups increased the inflammation inhibitory effect. Total tannin content of J. sigillata bark was 178mg/100g which was measured indirectly using Folin-Ciocalteu after being removed with PVPP.