Effects of pH and Micelle on the Radical Scavenging Ability of Puerarin

Abstract

The radical scavenging properties of puerarin are investigated in buffered hydroalcoholic media and Triton X-100 micellar solutions using the free-radical diphenylpicrylhydrazyl (DPPH•) method. The reactions, which follow the mixed second-order rate law, are investigated under pseudo-first-order condition by use of a large excess of puerarin. The rate constants (k ₂) observed for puerarin show notable pH dependence. These differences in reactivity of puerarin toward the oxidants at different acidity of the solution have been assumed to arise from the acid-base equilibrium of puerarin. The influence of acid-base equilibrium on bond dissociation energy for puerarin has also been investigated by means of DFT calculations. It has been concluded on the basis of these calculations that monoanionic form of puerarin is more powerful radical scavenger than the neutral molecule. When the reactions take place in Triton X-100 micelles, the radical scavenging properties of puerarin are enhanced. The results may be due to the special location of puerarin in Triton X-100 micelles.

Keywords:

• Antioxidants
• DFT calculations
• DPPH
• puerarin
• Triton X-100

This work is supported by the National Natural Scientific Foundation of China (No. 20633010 and No. 20773106).

Notes

Part of the special issue, Surface and Colloid Chemistry Without Borders: An International Festschrift for Professor Per Stenius on the Occasion of His 70th Birthday.