Studies from D.C. Marino and co-researchers in the area of agriculture and food science published.

"A spectrophotometric method is proposed for the determination of the polyphenols content in aqueous extracts of plants. The method is based on the reduction of Cu(II) to Cu(l) by polyphenols, in the presence of bicinchoninic acid in a buffered medium (ammonium acetate, pH 7.0) with the formation of Cu(I)/BCA complexes," investigators in Santo Andre, Brazil report.

"A calibration curve of absorbance (at 558 nm) vs tannic acid concentration is linear (r = 0.995; n = 7) with tannic acid from 0.1 to 0.7 mu mol L-1. The limit of detection and relative standard deviation were 40 nmol L-1 (99% confidence level) and 3.8% (0.4 mu mol L-1 tannic acid, n = 7), respectively," wrote D.C. …