Chemical perspective and criticism on selected analytical methods used to estimate the total content of phenolic compounds in food matrices

Consumers have sought for functional foods aiming to decrease the risk of various non-communicable diseases, such as diabetes, hypertension, overweight/obesity and principal cardiovascular diseases. Epidemiological and clinical studies are continuously corroborating the fact that individuals with higher intake of (poly)phenolic compounds present lower risk of incidence of non-communicable diseases, especially those related to the cardiovascular system. In this sense, food companies and regulatory health agencies together with academic bodies are investing in analytical methods to screen and typify the phenolic content of food extracts and beverages. In this scenario, this review focuses on the chemical perspective of some methods used to assess the total content of phenolic compounds, flavonoids, anthocyanins, ortho-diphenols, flavonols, and tannins (flavanols), by UV-Vis spectrophotometry, giving emphasis on the structures, reactions, overall positive aspects and limitations of the most used quantitative assays.