Objective: To study on the chemical constituents of Diaphragma Juglandis Fructus and investigate the antioxidant activity of their monomeric compounds. Method: Various column chromatography methods were used to isolate and purify the compounds and their structures were identified on the basis of spectral data. In addition

the antioxidant activities of compounds were evaluated by 1

1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay. Result: Seven monomeric compounds were isolated from ethanol extracts of Diaphragma Juglandis Fructus and their structures were identified as dihydrovomifoliol-9-O-β-D-glucopyranoside (1)

taxifolin-3-O-α-L-arabinofuranoside (2)

quercetin-3-O-(4"-O-acetyl)-α-L-rhamnopyranoside (3)

kaempferol-3-O-α-L-rhamnopyranoside (4)

kaempferol (5)

naringenin (6) and vanillin (7). Compounds 1-5 and 7 were isolated from Diaphragma Juglandis Fructus for the first time. As the pathogenesis of kidney disease is closely related to the body's disorder of antioxidant balance

in order to illustrate the material basis for kidney-reinforcing efficacy of Diaphragma Juglandis Fructus

three phenolic acid compounds and five flavonoids compounds were investigated for their antioxidant activity using DPPH radical scavenging assay combined with the previous experimental results. All the compounds indicated radical scavenging capacity to different extents. Conclusion: The chemical constituents of Diaphragma Juglandis Fructus have certain antioxidant activities

providing theoretical basis for the elaboration of its traditional efficacy.