An extraction solvent optimum for analyzing polyphenol contents by Folin-Denis assay

"An optimum solvent is described for analyzing total polyphenol contents by the procedure of Folin-Denis assay. We used water, ethanol, methanol, acetone or dimethyl sulfoxide (DMSO) as the extraction solvent for the polyphenol analysis of several food materials. All these sol-vents provided excellent calibration curves for ( + )-catechin in the range of 62.5 to 1000 microg/ml (r**2 = 0.998-0.999). DMSO gave the highest value of total polyphenol contents compared to the other solvents. Therefore, DMSO was proved to be the best solvent for the extraction of polyphenols from food samples. This improved method can be applied to the analysis of polyphenol contents in other food samples. (Received Jan. 9, 2002 ; Accepted Apr. 4, 2002)"