Spectrophotometric Folin-Ciocalteu and Aluminium Chloride Method Validation for the Determination of Phenolic Acid, Flavan-3-ol, Flavonol, and Anthocyanin Content

Spectrophotometric methods for the determination of total polyphenols and total flavonoids are often used because they are simple, sensitive, and precise. Before using these methods, they must be validated to ensure the quality of the obtained data and to prove that the method is suitable for its purpose. The aim of this study was to validate the spectrophotometric methods for total polyphenols and total flavonoids. The method for total polyphenols has been validated according to polyphenol standards, which belong to the groups of phenolic acids (p-hydroxybenzoic acid, sinapic acid, ferulic acid), flavan-3-ols ((-)-epicatechin), flavonols (myricetin, kaempferol), and anthocyanins (cyanidin-3-glucoside). For the validation of the method for total flavonoids, the same polyphenol standards belonging to flavan-3-ols, flavonols, and anthocyanins have been used. The validation parameters were linearity, sensitivity, limit of detection, limit of quantification, precision, and accuracy. The results of the validation for both methods were in acceptable ranges, except for kaempferol in the method for total flavonoids. In conclusion, these methods can be used for the determination of total polyphenols and total flavonoids by using calibration curves of studied polyphenol standards, except for the kaempferol standard in the method for total flavonoids, due to lower sensitivity