Polyphenols (Folin Ciocalteu) Assay
This assay is based on Folin-Ciocalteu method. The FC reagent contains phosphomolybdic/ phosphotungstic acid complexes. The method relies on the transfer of electrons in alkaline medium from phenolic compounds to form a blue chromophore constituted by a phosphotungstic/phosphomolybdenum complex where the maximum absorption depends on the concentration of phenolic compounds. The reduced Folin-Ciocalteu reagent is detectable with a spectrophotometer in the range of 690 to 710 nm. The reaction temperature has been used to reduce the time necessary to attain the maximum color (T= 37°C). Generally, gallic acid is used as the reference standard compound and results are expressed as gallic acid equivalents (mg/mL).
The assay has been used as a measure of total phenolics in natural products, but the basic mechanism is an oxidation/reduction reaction. In the original Folin-Ciocalteu assay, the carbonate buffer is used for pH adjustment and the end-point of the reaction was attained after 120 min at room temperature, which makes its implementation for routine analysis difficult. 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, juices).
Polyphenols have become an intense focus of research interest because of their perceived health-beneficial effects. They occur in a variety of fruits, vegetables, nuts, seeds, flowers, bark, beverages, and even some manufactured food, as a component of the natural ingredients used. They have been reported to exhibit anti-carcinogenic, anti-atherogenic, anti-ulcer, anti-thrombotic, anti-inflammatory, immunomodulating, anti-microbial, vasodilatory and analgesic effects.
Interest in the research of polyphenols from different natural sources has grown because polyphenols can be utilized as antioxidants in the food industry, and they benefit human health in various ways. The beneficial effects of polyphenols on human health could be due to their free radical scavenger properties, blocking the deleterious action of these molecules on cells.