Rapid microplate high-throughput methodology for assessment of Folin-Ciocalteu reducing capacity.
In the present work, a rapid and high-throughput Folin-Ciocalteu (F-C) reducing capacity assay adapted to routine/screening analysis was developed. In order to attain a fast F-C reducing kinetic reaction, the reaction conditions of the classical time-consuming F-C assay were modified and the influence of alkali and F-C reagent concentration was evaluated using gallic acid as standard. The proposed method was performed in a 96-well microplate format and it was applied to several phenolic compounds and food products (wines, beers, infusions and juices) providing F-C reducing capacity results after 3 min of reaction similar to those obtained by the time-consuming (120 min) conventional method. The additive and synergistic effect of reducing nonphenolic compounds usually found in food samples was also investigated. Ascorbic acid and ferrous sulfate provided an additive effect, while for fructose, glucose and sodium sulfite a synergistic effect was obtained. The detection limit was 0.25 mg L(-1) (as gallic acid) and the repeatability was <1.6% (n=12).
REQUIMTE, Departamento de Química, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal Cunha 164, 4099-030 Porto, Portugal. luismagalhaes@ff.up.pt
Luís M
LM
Magalhães
Fernando
F
Santos
Marcela A
MA
Segundo
Salette
S
Reis
José L F C
JL
Lima
D001205:Ascorbic Acid / Q000032:analysis; D001515:Beer; D001628:Beverages; D002138:Calibration; D002623:Chemistry Techniques, Analytical; D005296:Ferrous Compounds / Q000032:analysis; D005502:Food; D005504:Food Analysis / Q000379:methods*; D005506:Food Contamination / Q000032:analysis*; D005632:Fructose / Q000032:analysis; D005707:Gallic Acid / Q000032:analysis; D005947:Glucose / Q000032:analysis; D013447:Sulfites / Q000032:analysis; D013997:Time Factors; D014920:Wine
D005296:Ferrous Compounds; D013447:Sulfites; D005632:Fructose; C020748:ferrous sulfate; D005707:Gallic Acid; D005947:Glucose; D001205:Ascorbic Acid; C025026:sodium sulfite