Quantification of Antioxidant Properties in Popular Leaf and Bottled Tea by High-performance Liquid Chromatography (HPLC), Spectrophotometry, and Voltammetry

Antioxidant activity study and GC-MS profiling of Camellia sinensis Linn

The antioxidant activity of tea leaves extract is a widely researched topic. Tea leaves, particularly those from the Camellia sinensis Linn plant, have garnered attention due to their potential health benefits attributed to their antioxidant properties. Antioxidants are compounds that can neutralize harmful free radicals in the body, which can damage cells and contribute to various health issues, including cancer, cardiovascular diseases, and aging. In this research, the matured tea leaves which has been considered as agricultural waste in Moulovibazar area of Bangladesh have been investigated as a potential source of antioxidant. Methanol was used as solvent for the extraction of antioxidant. DPPH (1,1-diphenyl-2-picryl hydrazyl) scavenging free radical assay method was used to assess the antioxidant activity of the extracts and ascorbic acid was used as positive control. Gas chromatography with mass spectrometric (GC-MS) analysis method was conducted on this extract to investigate the principal components. The half inhibitory concentration (IC50) values of methanol extract and ascorbic acid were found to be 69.51 μg/mL and 10.70 μg/mL, respectively. Caffeine is the main compound (74.47%) among the eight bioactive compounds was identify and quantified by GC-MS.

Electrochemical Sensors and Biosensors for the Analysis of Tea Components: A Bibliometric Review

Tea is a popular beverage all around the world. Tea composition, quality monitoring, and tea identification have all been the subject of extensive research due to concerns about the nutritional value and safety of tea intake. In the last 2 decades, research into tea employing electrochemical biosensing technologies has received a lot of interest. Despite the fact that electrochemical biosensing is not yet the most widely utilized approach for tea analysis, it has emerged as a promising technology due to its high sensitivity, speed, and low cost. Through bibliometric analysis, we give a systematic survey of the literature on electrochemical analysis of tea from 1994 to 2021 in this study. Electrochemical analysis in the study of tea can be split into three distinct stages, according to the bibliometric analysis. After chromatographic separation of materials, electrochemical techniques were initially used only as a detection tool. Many key components of tea, including as tea polyphenols, gallic acid, caffeic acid, and others, have electrochemical activity, and their electrochemical behavior is being investigated. High-performance electrochemical sensors have steadily become a hot research issue as materials science, particularly nanomaterials, and has progressed. This review not only highlights these processes, but also analyzes and contrasts the relevant literature. This evaluation also provides future views in this area based on the bibliometric findings.

Cross-Category Tea Polyphenols Evaluation Model Based on Feature Fusion of Electronic Nose and Hyperspectral Imagery

Tea polyphenols are important ingredients for evaluating tea quality. The rapid development of sensors provides an efficient method for nondestructive detection of tea polyphenols. Previous studies have shown that features obtained from single or multiple sensors yield better results in detecting interior tea quality. However, due to their lack of external features, it is difficult to meet the general evaluation model for the quality of the interior and exterior of tea. In addition, some features do not fully reflect the sensor signals of tea for several categories. Therefore, a feature fusion method based on time and frequency domains from electronic nose (E-nose) and hyperspectral imagery (HSI) is proposed to estimate the polyphenol content of tea for cross-category evaluation. The random forest and the gradient boosting decision tree (GBDT) are used to evaluate the feature importance to obtain the optimized features. Three models based on different features for cross-category tea (black tea, green tea, and yellow tea) were compared, including grid support vector regression (Grid-SVR), random forest (RF), and extreme gradient boosting (XGBoost). The results show that the accuracy of fusion features based on the time and frequency domain from the electronic nose and hyperspectral image system is higher than that of the features from single sensor. Whether based on all original features or optimized features, the performance of XGBoost is the best among the three regression algorithms (R² = 0.998, RMSE = 0.434). Results indicate that the proposed method in this study can improve the estimation accuracy of tea polyphenol content for cross-category evaluation, which provides a technical basis for predicting other components of tea.

Synthesis and characterization of a (+)-catechin and L-(+)-ascorbic acid cocrystal as a new functional ingredient for tea drinks

Tea (Camellia Sinensis) is one of the most popular drink, consumed as infusion or bottled ready to drink beverages. Although tea leaves contain many antioxidants compounds, after processing they can drastically decrease, sometimes up to a full degradation, as in the case of catechin, a very healthy flavan-3-ol. In this context, the synthesis of a cocrystal between (+)-catechin and L-(+)-ascorbic acid, was proved to be a useful strategy to make a new ingredient able to ameliorate the antioxidant profile of both infusions and bottled teas. The obtained cocrystal showed a three-fold higher solubility than (+)catechin and its formation was elucidated unambiguously by FT-IR, thermal (DSC) and diffraction (PXRD) analyses. Antioxidant characteristics of the samples were evaluated by colorimetric assays. As expected, infusions showed much better antioxidant features than ready-to-use lemon and peach teas. The same trend was confirmed after the addition of the cocrystal at two concentration levels. In particular, supplementation at concentration of 2 mg mL-1 improved the bottled tea antioxidant values to the level showed by the not-added infusion tea.