Calculation of the molar absorptivity of polyphenols by using liquid chromatography with diode array detection: the case of carnosic acid

Antioxidant activity of vegetable extracts is related to the nature and the amount of active components, mainly polyphenols; therefore, a correct quantification of these molecules should be required to define their concentration in such kind of vegetable extracts. A fast and accurate method to calculate molar absorption coefficients ( ε), by using HPLC, has been tested on standard polyphenols and caffeine, and should be widely adapted for standardless quantitative analysis. Molar absorptivity ( ε) of carnosic acid (CA) was determined from 200 to 300 nm, by the proposed method and those values were compared to tert-butyl-hydroxytoluene (BHT) ones for further comparative quantification.