A new method for quantification of total polyphenol content in medicinal plants based on the reduction of Fe(III)/1,10-phenanthroline complexes

Abstract

This paper proposes an alternative analytical spectro-photometric method for the total polyphenol quanti-fication in the aqueous extract of plants. When these extracts are added to solutions of Fe(III), in presence of 1,10-phenanthroline, the absorbance values at 551 nm (A 511nm) due to the 3 complexes form-ed are proportional to the total polyphenol concen-tration expressed as pyrogallic acid (PA). A typical calibration graph of A 511nm values vs. PA is linear from 0.16 to 0.64 mg L −1 (r = 0.994, n = 6) with a limit of detection 0.041 mg L −1 . The results of the poly-phenol content of the aqueous extracts of twenty me-dicinal Brazilian plants obtained with the proposed method were compared with values using the Folin-Ciocalteu reagent. A paired t-test revealed no statis-tically significant difference for the species analyzed. The total antioxidant capacity of the same twenty extracts was determined based on the scavenging of stable radical DPPH.   2+ Fe phen