A novel trace photometric titration method for the evaluation of DPPH radical scavenging activity of kaempferol

A novel trace photometric titration method for the evaluation of DPPH radical scavenging activity was proposed based on the UV- Vis spectroscopic research of the reaction of kaempferol with DPPH radical. The titration curve of kaempferol with DPPH radical was tested. The methods for the evaluation of DPPH radical scavenging capacity, and for calculation of maximal scavenging rate ( EC max) and median scavenging concentration ( EC50%) were proposed based on the stoichiometric ratio ( n D/n K) of DPPH consumption ( n D) to the addition of kaempferol ( n K) .For different initial amounts of DPPH radical, the value of n D/n K was from 1.70 to 1.78 with an EC max value of 84.32% and an EC50value of 1.99 × 10- 2mmo·lL- 1 ( according to a DPPH radical initial amount of 7.1 ×10- 7mol) , the results above were agreement well with that of conventional method, while, better precision was achieved by using the proposed method with significant decrease in the amount of sample used.