Methodological Aspects to the Determination of Phenolic Compounds in Tea

Tea is rich in polyphenol compounds, which possess antioxidant and anticarcinogenic activity, and are becoming increasingly popular because of their potential role in contributing to human health. Responding to the increasing interest in the health promoting properties of tea as well as a significant rise in scientific investigation, we have given an overview of the current analytical methods for determination of polyphenol compounds in tea samples of different origins. For this purpose, the extraction from the sample, separation and quantitative analysis of phenolic compounds involving catechins and the products of their oxidative transformations such as theaflavins and thearubigins, are covered in this review. Extraction methods evaluated include extraction at room temperature as well as heat reflux, Soxhlet, ultrasonic, supercritical carbon dioxide, microwave-assisted and high hydrostatic pressure extraction techniques. The analytical separation techniques widely employed are high-pressure liquid chromatography, gas chromatography and capillary electrophoresis. However, colorimetric or spectrophotometric methods are still the most widely used, due to their simplicity in the determination of total phenolic content, theaflavins and thearubigins, of tea.