... Tetrahedron. Volume 67, Issue 37, 16 September 2011, Pages 7085–7089. ... In the radical-scavenging assay, compound 4 showed weak antioxidative activity against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, with IC 50 value of 67 μM, ascorbic acid (vitamin ...