ABSTRACT
The total phenolic content, flavonoid content, in vitro xanthine oxidase [XOD] inhibitory activity and antioxidant activity [AA] of Eucommia ulmoides Oliver leaf extracts were investigated. The AA investigations included 2,2-diphenyl-1-picrylhydrazyl [DPPH] assay, beta-carotene/linoleic acid bleaching assay and oxygen radical absorbance capacity [ORAC] test. The ethyl acetate fraction [EE] showed the highest AA and xanthine oxidase inhibitory activity. Whilst the lowest 50% inhibition [IC50] value of this fraction for DPPH free radical scavenging was 0.045mg/mL, its highest ORAC value was 10.57 µmol TE/mg. The highest inhibition rate against linoleic acid oxidation observed was 69.41%, and the lowest IC50 value for xanthine oxidase activity inhibition was 2.47mg/mL. These results show that E. ulmoides leaf extract is a promising source of natural antioxidants because it contains high contents of bioactive compounds, including chlorogenic acid, rutin, hyperin and astragalin, as detected by high-performance liquid chromatography coupled to HPLC-DAD-ESI-MS
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the role of p38MAPK signaling pathway in the mechanism by which glucagon-like peptide-1 (GLP-1) inhibits endothelial cell damage induced by AGEs.</p><p><b>METHODS</b>Human umbilical vein endothelial cells were divided into control group, AGEs group, GLP-1 group, AGEs+GLP-1 group, AGEs+inhibitor group, and AGEs+GLP-1+inhibitor group. The expressions of p-p38MAPK/p38MAPK and p-eNOS/eNOS protein were examined by Western blotting, and the cell apoptosis rates were tested by flow cytometry.</p><p><b>RESULTS</b>Compared with the control group, AGEs significantly enhanced the expression of p-p38 MAPK protein (P=0.001) while GLP-1 significantly inhibited its expression (P<0.001). AGEs significantly inhibited the expression of p-eNOS protein (P=0.007), which was enhanced by GLP-1 and p38 MAPK inhibitor (SB203580) (P=0.004). Both SB203580 and GLP-1 treatment decreased the apoptosis rate of AGEs-treated cells (P<0.001).</p><p><b>CONCLUSION</b>GLP-1 can protect human umbilical vein endothelial cells against AGEs-induced apoptosis partially by inhibiting the phosphorylation of p38MAPK protein and promoting the expression of p-eNOS protein.</p>