Estimation of total polyphenols content in food supplements and nutraceuticals: Antioxidant assays versus high performance liquid chromatography

Abstract

Polyphenols are molecules present in nature and synthesized mostly in plants as a product of their secondary metabolism. Depending on their structure they can be classified in phenolic acids, flavonoids, stilbenes, lignans and tannins. One of the most important effect of polyphenols is to eliminate toxic products that can harm our organism through an oxidative reaction (antioxidant capacity). In this research, antioxidant capacity is measured as the total content of polyphenols in food supplements and nutraceuticals by different methods. High-performance liquid chromatography (HPLC) and two antioxidant assays, ferric reducing antioxidant power (FRAP) and Folin-Ciocalteau (FC), were used for this purpose. On the one hand, HPLC fingerprints were obtained at different wavelengths and with those results a principal component analysis (PCA) model was built to evaluate sample distribution according to their typology. On the other hand, chromatographic fingerprints and the results obtained by the antioxidant assays were analyzed by partial least square (PLS) for correlation purposes. PCA confirms that HPLC fingerprints are acceptable sample chemical descriptors to classify the analyzed samples according to their nature and origin. Moreover, PLS shows that a model with a good prediction capacity can be obtained to predict the analytical response of the antioxidant assay in function of the HPLC chromatographic fingerprints. Determination coefficients (R2) in the model for FRAP assay and FC assay were 0.903 and 0.939, respectively. To conclude, HPLC result a better methodology than the antioxidant assays to predict natural extracts antioxidant capacity because of the simplicity of use and the presence of fewer interferences with this methodology