Significance of Chromatographic and Voltammetric Data for the Classification of Green Teas in Türkiye: A Principle Component Analysis Approach

Abstract

Tea (Camellia sinensis) is one of the most popular beverages in Anatolia; it provides a significant source of phenolic compounds in the Turkish diet. All around Anatolia, tea traditionally is usually served black but in recent years green tea is becoming a popular alternative, mostly due to its higher content of antioxidant compounds. The growing green tea consumption resulted in the appearance of commercial green tea brands with different additives. In this study, the flavonoid content of methanol extracts of various commercial green tea samples was determined by HPLC analysis. Rutin, apigenin, luteolin, luteolin-4-glucoside, naringenin, quercetin, isoquercitrine, and quercetin-4-glucoside were studied as model bioactive flavonoid compounds successfully separated and detected. HPLC detection was performed under isocratic conditions through a C18 analytical column with methanol and 0.01 M orthophosphoric acid (pH 7) (50:50, v/v) as the mobile phase. Variable wavelength UV-Vis (230 nm), fluorescence (Ex: 250 nm, Em: 450 nm), and a programmable electrochemical detector (+ 1.30 V vs. Ag/AgCl) were employed for detection. Based on the chemometric tools (principle component analysis, PCA), the flavonoid patterns of the samples were used successfully to identify and classify the commercial brands with additives from unmodified ones. This might help to make a very easy and rapid classification simply based on rough data without focusing on detailed analysis methods. Additionally, cyclic voltammetry (CV) data of the samples was obtained and used again in PCA to identify the commercial brands. Also, based on the CV data, the samples were sorted according to their anodic oxidation potential, which is a measure of the free radical scavenging (antioxidant) capacity of the samples.