Copper-Granule-Catalyzed Microwave-Assisted Click Synthesis of Polyphenol Dendrimers
作者:Choon Young Lee、Rich Held、Ajit Sharma、Rom Baral、Cyprien Nanah、Dan Dumas、Shannon Jenkins、Samik Upadhaya、Wenjun Du
DOI:10.1021/jo401603d
日期:2013.11.15
Syringaldehyde- and vanillin-based antioxidant dendrimers were synthesized via microwave-assisted alkyne-azide 1,3-dipolar cydoaddition using copper granules as a catalyst. The use of Cu(I) as a catalyst resulted in copper contaminated dendrimers. To produce copper-free antioxidant dendrimers for biological applications, Cu(I) was substituted with copper granules. Copper granules were ineffective at both room temperature and under reflux conditions (<5% yield). However, they were an excellent catalyst when dendrimer synthesis was performed under microwave irradiation, giving yields up to 94% within 8 h. ICP-mass analysis of the antioxidant dendrimers obtained with this method showed virtually no copper contamination (9 ppm), which was the same as the background level. The synthesized antioxidants, free from copper contamination, demonstrated potent radical scavenging with IC50 values of less than 3 mu M in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. In comparison, dendrimers synthesized from Cu(I)-catalyzed click chemistry showed a high level of copper contamination (4800 ppm) and no detectable antioxidant activity.
Effect of electron donating groups on polyphenol-based antioxidant dendrimers
作者:Choon Young Lee、Cyprien N. Nanah、Rich A. Held、Amanda R. Clark、Uyen G.T. Huynh、Marina C. Maraskine、Rebecca L. Uzarski、John McCracken、Ajit Sharma
DOI:10.1016/j.biochi.2015.02.001
日期:2015.4
EDG groups. Similar results were obtained when the dendrimers were used to protect DNA and human LDL against organic carbon and nitrogen-based freeradicals. In addition, the antioxidant dendrimers did not show any pro-oxidant activity on DNA in the presence of physiological amounts of copper. Although the dendrimers showed potent antioxidant activities against carbon and nitrogen freeradicals, EPR