Recent Progress in Natural Anticancer Agents Discovery from Tea (Camellia sinensis): A Review

Background: Tea, as the bud from the plant Camellia sinensis, is the most consumed popular beverage just next to water; especially green tea has gained much attention because of its health effects. The anticancer effects of tea components including tea polyphenols, in particular epigallocatechin gallate and tea polysaccharides, are widely investigated in recent years. Objective: Based on the articles and patents published in the last 10 years, this review focuses on the structural activities and molecular mechanisms of the anticancer effects of tea components (mainly tea polyphenols and tea polysaccharides), with a view to providing references for future anticancer studies of tea. Methods: In the database, a literature search was conducted with “tea polyphenols”, “tea polysaccharides”, “theanine” and “anticancer” as the key words, and the limited time range was “2010-2021”. After sorting out and analyzing the retrieval results, the structure, activity and molecular mechanism, as well as the research progress on the structural modification, drug delivery system and toxicology of natural agents in tea in recent years were summarized. Results: We found that the natural anticancer agents in tea mainly include tea polyphenols, tea polysaccharides, theanine, caffeine and other components by summarizing the literature. The anticancer mechanisms can be divided into the induction of cell apoptosis, inhibition of cell proliferation, metastasis and invasion, and inhibition of angiogenesis. In the past 10 years, there were few literatures on the structural modification, drug delivery system and toxicological evaluation of natural anticancer agents in tea, and there were reports of novel research on nano preparations. The studies showed that nano preparation technology could effectively improve the bioavailability and targeting treatment of tea anticancer components. In addition, in the past decade, patents on tea and natural anticancer agents in tea were relatively rich, among which pharmaceutic preparation patents were the majority, and tea polyphenols were the main ones. Conclusion: This paper concluded that there are many kinds of natural anticancer agents in tea, and the anticancer mechanism is complex. Further research on the structural modification, drug delivery system and toxicological evaluation of relevant anticancer active components can be carried out. In general, tea components as new anticancer substances have a certain potential for development. In addition, future research can be focused on the comprehensive study of the structure-activity relationship, the in-depth study of the molecular mechanism, the in-depth understanding of the anticancer effects in vivo, and the verification of large-scale production.

Dynamic Evolution and Correlation between Metabolites and Microorganisms during Manufacturing Process and Storage of Fu Brick Tea

Fu brick tea (FBT) is one of the major brands of dark tea. Microbial fermentation is considered the key step in the development of the special characteristics of FBT. The systemic corelationship of the microbiome and metabolomics during manufacture of Fu brick tea is not fully understood. In this study, we comprehensively explored the microbiome and metabolite dynamic evolution during the FBT manufacturing processes, and revealed decisive factors for the quality and safety of FBT based on the grouped methods of metabolomics combined with biochemical measurements, microbiome sequencing combined with quantitative polymerase chain reaction (PCR), and multiplex analysis. Both the microbiome and quantitative PCR showed that fungi displayed concentrated distribution characteristics in the primary dark tea samples, while bacterial richness increased during the flowering processes and ripening period. All microorganism species, as well as dominant fungi and bacteria, were identified in the distinct processes periods. A total of 178 metabolites were identified, and 34 of them were characterized as critical metabolites responsible for metabolic changes caused by the corresponding processes. Metabolic analysis showed that most metabolites were decreased during the FBT manufacturing processes, with the exception of gallic acid. Multivariate analysis verified that the critical metabolites were correlated with specific dominant microbial species. All the top fungal species except unclassified_g_ Aspergillus showed positive correlations with six critical metabolites (L-The, epigallocatechin (EGC), Gln, tea polyphenol (TP), tea polysaccharides (TPs) and caffeine). Five of the top bacteria species (Cronobacter, Klebsiella, Pantoea, Pluralibacter, and unclassified_ f_Entero-bacteriaceae) showed positive correlations with epigallocatechins and tea polyphenols, while the other 11 top bacterial species correlated negatively with all the critical metabolites. The content of amino acids, tea polyphenols, tea polysaccharides, and flavonoids was reduced during microbial fermentation. In conclusion, our results reveal that microbial composition is the critical factor in changing the metabolic profile of FBT. This discovery provides a theoretical basis for improving the quality of FBT and enhancing its safety.

Structural Characteristics of Crude Polysaccharides from 12 Selected Chinese Teas, and Their Antioxidant and Anti-Diabetic Activities

Twelve representative edible Chinese teas (Camellia sinensis L.) from six categories (dark tea, black tea, oolong tea, white tea, yellow tea, and green tea) were selected in this study. Tea polysaccharides (TPs) were extracted with hot water, and their structural properties and biological activities, mainly antioxidant and anti-diabetic activities, were systematically evaluated. Results revealed that the extraction yields of TPs ranged from 1.81% to 6.38%, and Pu-erh tea polysaccharides had the highest extraction yield (6.38 ± 0.28%). The chemical compositions, molecular weight, and compositional monosaccharides of TPs varied among the six categories of tea. It appeared that all TPs were protein-bound acid heteropolysaccharides, and all TPs exhibited obvious antioxidant and anti-diabetic (e.g., α-glucosidase inhibitory and antiglycation) activities. Particularly, Pu-erh tea polysaccharides also contained the highest total phenolic and protein contents, and also exhibited the best antioxidant and anti-diabetic activities. Moreover, for the structural-function relationship, the heat map analysis found that total phenolic and protein contents in TPs were positively correlated with their antioxidant and anti-diabetic activities, indicating that the presence of phenolic compounds and proteins in the TPs might be the main contributors to their bioactivities. The conclusion from this study can help understand the structural-function relationship of crude tea polysaccharides.

Valorization of Polysaccharides Obtained from Dark Tea: Preparation, Physicochemical, Antioxidant, and Hypoglycemic Properties

The structure and hypoglycemic activity of tea polysaccharides has been extensively studied, while there are few reports on the characterization and hypoglycemic activity of dark tea polysaccharides. The crude dark tea polysaccharide (CDTPS) was optimally extracted from Fuzhuan dark tea. Six polysaccharide fractions (namely DTPS-1, DTPS-2, DTPS-3, DTPS-4, DTPS-5, and DTPS-6) were isolated from CDTPS, and their physicochemical, structural, and biological properties were compared and analyzed. The results revealed that the compositions, structural characteristics, and biological properties of the six DTPSs were different. Therein, DTPS-4 and DTPS-6 had looser morphology, faster solubility, and a more stable structure. Additionally, DTPS-4 had the optimum in vitro antioxidant capabilities, and DTPS-6 had the strongest in vitro hypoglycemic capabilities. In addition, a correlation analysis revealed that the molecular weight and uronic acid content were significantly related to their antioxidant and hypoglycemic activities. Our results indicated that DTPS-4 and DTPS-6 could be further developed into functional foods or additives, respectively.

Correction: In-vitro antidiabetic activities, chemical compositions, antioxidant activities, and toxicity of black tea polysaccharides as a potential source of dietary ingredients

There is an error in Table 2 in the published article, Journal of Food Bioactives, 2021;13:93–101, doi: 10.31665/JFB.2021.13263. The correct value in column “mg/100 g” under “D-glucose” is “59.50 ± 7.80”, not “9.50 ± 7.80”. The authors have included a corrected version of the table below.

Influencing Factors on the Physicochemical Characteristics of Tea Polysaccharides

Tea polysaccharides (TPSs) are one of the main bioactive constituents of tea with various biological activities such as hypoglycemic effect, antioxidant, antitumor, and immunomodulatory. The bioactivities of TPSs are directly associated with their structures such as chemical composition, molecular weight, glycosidic linkages, and conformation among others. To study the relationship between the structures of TPSs and their bioactivities, it is essential to elucidate the structure of TPSs, particularly the fine structures. Due to the vast variation nature of monosaccharide units and their connections, the structure of TPSs is extremely complex, which is also affected by several major factors including tea species, processing technologies of tea and isolation methods of TPSs. As a result of the complexity, there are few studies on their fine structures and chain conformation. In the present review, we aim to provide a detailed summary of the multiple factors influencing the characteristics of TPS chemical structures such as variations of tea species, degree of fermentation, and preparation methods among others as well as their applications. The main aspects of understanding the structural difference of TPSs and influencing factors are to assist the study of the structure and bioactivity relationship and ultimately, to control the production of the targeted TPSs with the most desired biological activity.

Polysaccharides and polyphenol in dried Morinda citrifolia fruit tea after different processing conditions: Optimization analysis using response surface methodology

The increasing popularity of Morinda citrifolia has many medical and health benefits because of its rich polysaccharides (PSC) and polyphenols (PPN). It has become popular to brew the dry M. citrifolia fruit slice as tea in some regions of China. In this study, optimize the extraction parameters of M. citrifolia fruit tea polysaccharides and polyphenols using response surface methodology. The results indicated the highest PSC yield of 17% at 46 °C for 11 min and the ratio of water/M. citrifolia fruit powder was 78 mL/g. The optimum extraction of PPN was at 95 °C for 10 min and the ratio of water/M. citrifolia fruit powder 90 mL/g, with 8.93% yield. Using dry M. citrifolia fruit slices as a tea is reported for the first time. Based on the results, the maximum level of PSC can be obtained under condition by infusing about four dried M. citrifolia fruit slice with average thickness and size in warm boiled water for 11 min, taking a 300 mL cup (300 mL of water) for example. The maximum level of PPN can be obtained by adding three slices of dried M. citrifolia fruit slice to boiled water for 10 min. Considering the powder used in our study, the further pulverization of cutting into powder is more conducive to material precipitation. This study provides a scientific basis for obtaining PSC and PPN from dry M. citrifolia fruit slice tea by brewing.