Effect of polyphenols on the performance of spectrophotometric assays for the determination of total sugars

Abstract

Polyphenols, naturally present in plants and some foods, exhibit beneficial effects on human health due to their antioxidant capacity, acting as reducing species. Within the context of circular economy, polyphenols are being recovered from agri-food by-products. In these recovery processes, it is necessary to track the target compounds, but also possible residues, being sugars the principal concern. This project is focused on the impact of polyphenols on spectrophotometric methods to quantify sugars. Most of these methods are based on redox reactions, with sugars acting as reducing agents. This work assesses the effect of the presence of polyphenols in sugar assays in this context. DNS and BCA methods were tested showing sugar and polyphenol responses. BCA showed low LOD and LOQ compared to DNS but presented a short linearity range. Also, it has been observed that polyphenols are contributing to sugar response on both colorimetric assays. The interference of polyphenols is important when polyphenol concentration is higher or even similar to sugars concentration so, the obtained results reveal none of the methods are suitable to quantify sugars when extract purification is performed. When analysing extracts from plant samples, the comparison of results from spectrophotometric methods with those obtained by HPLC confirms that the presence of polyphenols can lead to an overestimation of total sugars