Molecular mechanisms underlying health benefits of tea compounds

Tea polysaccharide conjugates (TPS conjugates) are receiving worldwide attention in the recent decades, after they were recognized as critical components of coarse tea, and were responsible for their therapeutic effects in patients with diabetes. Existing evidences indicate that TPS conjugates not only benefit human health, but also can be used as carriers for drugs and as films for food packaging, and as emulsifiers. Despite their many practical applications, molecular structures of TPS conjugates are not well worked out yet, making their mechanisms of action difficult to understand. Their structural variations are attributed mainly to the differences in the processing of different tea. This comprehensive review summarises the compositions, structural characteristics, and bioactivities of TPS conjugates from different tea-leaf products, discusses the relationships between their compositions and structures, and the specific functions, and suggests the conjugation among polysaccharides, proteins and polyphenols occurring in tea leaves during processing which is mainly responsible for the alteration in composition and structure of TPS conjugates derived from different kinds of tea.

A comprehensive review on polysaccharide conjugates derived from tea leaves: Composition, structure, function and application

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.

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

Natural polysaccharides are critical to a wide range of fields (e.g., medicine, food production, and cosmetics) for their various remarkable physical properties and biological activities. However, the bioactivities of naturally acquired polysaccharides may be unsatisfactory and limit their further applications. It is generally known that the chemical structure exhibited by polysaccharides lays the material basis for their biological activities. Accordingly, possible structural modifications should be conducted on polysaccharides for their enhancement. Recently, polysaccharides complexed with metal ions (e.g., Fe, Zn, Mg, Cr, and Pt) have been reported to be possibly used to improve their bioactivities. Moreover, since the properties exhibited by metal ions are normally conserved, polysaccharides may be endowed with new applications. In this review, the synthesis methods, characterization methods, and bioactivities of polysaccharide metal complexes are summarized specifically. Then, the application prospects and limitations of these complexes are analyzed and discussed.

Synthesis, Characterization, and Bioactivities of Polysaccharide Metal Complexes: A Review.

Deep eutectic solvent as a new green and safe solvent system has attracted more and more attention in recent years. In this study, three deep eutectic solvents (DES) were combined with ultrasound irradiation to extract tea polysaccharides (TPs) from Anji white tea, which was compared with conventional hot water extraction (HW). The physicochemical, structural, and biological properties of TPs extracted by ultrasound-assisted DES and hot water (HWP) were further investigated. Results showed that the DES system composed of choline chloride and 1,6-hexanediol (CH) with the molar ratio of 1:2 exhibited the optimal extraction yield (19.18%) and in vitro antioxidant activities for TPs (CHP). Furthermore, compared to the HWP, the CHP had a higher extraction yield and total carbohydrate content and a lower molecular weight. Monosaccharide composition analysis displayed that the molecular structure of CHP exhibited more arabinose but less glucose, mannose, galacturonic acid, and glucuronic acid than HWP. Little difference was observed in the preliminary structural characteristics between HWP and CHP from Fourier transform infrared analysis. Besides, CHP possessed better α-glucosidase inhibitory and hypoglycemic activity in L6 cells than HWP. Therefore, the ultrasound-assisted DES extraction method can be a promising strategy for extracting TPs with excellent bioactivities for future applications in functional foods.

/pdf/ultrasound-assisted-deep-eutectic-solvent-extraction-of-tqcgup11.pdf

Ultrasound-Assisted Deep Eutectic Solvent Extraction of Polysaccharides from Anji White Tea: Characterization and Comparison with the Conventional Method

The effects of purity of tea polysaccharides (TPS) on its five antioxidant activities and hypoglycemic activities in vitro were studied The results showed that the higher the purity of TPS, the lower the antioxidant capacity The purity of FTPSI is the highest (sugar content 8072%), but its antioxidant activities were lower than those of Fujian tea polysaccharides (FTPS) and FTPSII The antioxidant activity of tea polysaccharide is related to its protein and polyphenol content (Pearson r > 90) The protective effect of Zhejiang tea polysaccharides and FTPS on human umbilical vein endothelial cells (HUVEC) was better than that of its purified fractions The inhibition rates of FTPSII (5 and 2 mg/ml) on α-glucosidase (3276%) and α-amylase (-1193%) were higher than those of FTPS and FTPSII Purification does not change the basic structure of TPS This study has certain reference value for the study of the antioxidant activities of TPS Meanwhile, TPS can be used as a potential resource with hypoglycemic function PRACTICAL APPLICATIONS: A large number of studies have shown that TPS have antioxidant activity However, several studies considered that the antioxidant activity of TPS mainly comes from the residues of tea polyphenols Therefore, the in vitro and cell antioxidant activities of TPS were studied in this paper We believe that both glycoprotein and tea polyphenol are antioxidants of tea, and tea polysaccharide perform preferable effect on hypoglycemic HUVEC cell model and four in vitro antioxidant test methods were used to study the antioxidant activities of TPS, and two enzyme inhibition activities were used to study the hypoglycemic effect of TPS, in order to provide a theoretical basis for the study of biological activity of TPS

Effect of purity of tea polysaccharides on its antioxidant and hypoglycemic activities.

Tea polysaccharide (TPS) is a bioactive compound that has attracted increasing attention for its health effect on regulating the metabolism of glucose and lipid. Moreover, due to their good biocompatibility and biodegradability, TPS-based nanoparticles have emerged as effective nanocarriers for the delivery of bioactive molecules. In this study, we developed a TPS-based biocarrier system for the orally targeted administration of Mn(II) ions and investigated their antidiabetic effects in C57BL/6 mice with HFD/streptozotocin (STZ)-induced T2DM. Mn(II)-loaded TPS-based nanoparticles (MTNPs) were synthesized, in which negatively charged functional groups in protein and uronic acid in TPS conjugates would act as binding sites for Mn(II) ions, which is responsible for the cross-linking reaction of MTNP. The resulting MTNP had a spherical shape and a mean particle size of around 30 nm with a Mn(II) ion content of 2.24 ± 0.13 mg/g. In T2DM mice, we discovered that MTNP treatment significantly lowered blood glucose levels and improved glucose intolerance. Furthermore, the impact of MTNP on the recovery of FINS, the homeostatic index of insulin resistance (HOMA-IR), and the homeostatic index of β-cell (HOMA β-cell) levels was significantly larger (p < 0.05) than TPS alone, demonstrating that Mn(II) ions can enhance TPS's ability to repair HFD/STZ-induced β-cell damage. Mn(II) ions in MTNP not only acted as cofactors to increase the exocytosis of insulin secretory cells by upregulating the expression of Ca(II)/calmodulin-dependent protein kinase II (CaMK II) but also promoted TPS's lipid-lowering effect in T2DM mice by inhibiting glucogenesis and regulating the lipid metabolism. Our findings suggest that Mn(II) ions can be used not only as cross-linkers in the formation of nanoparticulated TPS but also as cofactors in improving the functional role of TPS in regulating the glucose and lipid metabolism, which will provide insights into the development of TPS-based drug delivery systems for the prevention of type 2 diabetes.

Mn(II)-Mediated Self-Assembly of Tea Polysaccharide Nanoparticles and Their Functional Role in Mice with Type 2 Diabetes.

The preparation method and the sources of metal elements may affect the activity of the metal-polysaccharide complex. In this study, four Fe-tea polysaccharide complexes were prepared and three tea polysaccharides (TPSs) from different seasons were extracted. Moreover, the binding mode of TPSs with internal and external metallic elements as well as their inhibitory effect on α-glucosidase was explored. The results revealed that the binding mode (-C-O-Fe and -C-Fe) of the Fe-TPS complex prepared at pH 5.0 was closer to TPS with internal metallic elements. The TPS with the least amount of internal metallic elements (61.72 mg/g) exhibited a high inhibitory activity on α-glucosidase (37.90%). The inhibitory activity of Fe-TPS on α-glucosidase was lower than that without Fe. But the quenching effect and the inhibition type of TPSs on α-glucosidase were not affected by metallic elements. Therefore, the metallic elements have the potential to reduce the hypoglycemic activity of TPS. PRACTICAL APPLICATIONS: In this paper, TPS was extracted from crude tea in different seasons, and the effects of metallic elements in TPS on hypoglycemic activity, physicochemical properties, and structure of TPS were discussed. TPS metal complexes were prepared by adding Fe3+ or removing metallic elements, and the differences of internal metallic elements in TPS were discussed. It is of great academic significance to use tea pruned leaves and crude tea as potential resources to develop polysaccharide hypoglycemic products and to reveal the relationship between TPS metal ions and their structure and activity. In addition, it has guiding value for consumers to choose tea-producing regions and growers to choose chemical fertilizer.

Preparation and characterization of metal-tea polysaccharide complexes and their inhibition on α-glucosidase.

Purpose: To determine the characteristic chemical components of the ethanol extract of Chenopodium ambrosioides and evaluate their antioxidant and anti-tumor effects in vitro. 
Methods: The plant powder (5 g) was extracted with 1 L of 80 % ethanol at room temperature for 45 min, and then placed at 60 oC at varying microwave power and duration to obtain optimal extraction conditions. Characteristic chemical components were detected using ultra-high performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS/MS). Kaempferitrin was isolated from the 80 % ethanol extract using a D101 macroporous resin column, and its content was assessed by high performance liquid chromatography (HPLC). The antioxidant effect of kaempferitrin was evaluated by its ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radicals, while its anti-proliferation activity in human liver cancer cells SMMC-7721 was determined using cell counting kit-8 (CCK-8) reagent. 
Results: Three characteristic components of ethanol extract of C. ambrosioides were obtained, namely, kaempferitrin, kaempferol-3-O-apigenin-7-O-rhamnoside and kaempferol-3-O-acetylapigenin-7-O-rhamnoside. Kaempferitrin was shown to possess strong DPPH radical and moderate ABTS radical scavenging activities. Kaempferitrin significantly inhibited the proliferation of SMMC-7721 cells at doses of 4 and 8 μg/mL, with half-maximal concentration (IC50) of 0.38 μM (p < 0.05). 
Conclusion: Kaempferitrin extracted from C. ambrosioides has antioxidant and anti-tumor activities. The results reported here indicate that C. ambrosioides may have potential use in herbal medicine practice.

/pdf/identification-of-the-chemical-components-of-ethanol-extract-64e7l2q7.pdf

Identification of the chemical components of ethanol extract of Chenopodium ambrosioides and evaluation of their in vitro antioxidant and anti tumor activities

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Papers

Effect of purity of tea polysaccharides on its antioxidant and hypoglycemic activities.

Mn(II)-Mediated Self-Assembly of Tea Polysaccharide Nanoparticles and Their Functional Role in Mice with Type 2 Diabetes.

Preparation and characterization of metal-tea polysaccharide complexes and their inhibition on α-glucosidase.

Identification of the chemical components of ethanol extract of Chenopodium ambrosioides and evaluation of their in vitro antioxidant and anti tumor activities