The emulsification properties of alkaline-extracted polysaccharide conjugates from Apocynum venetum L. tea residues

Valorization of cell wall polysaccharides extracted from Liubao brick tea residues: chemical, structural, and hypoglycemic properties

BACKGROUND

Tea dregs, typically generated during the production of instant tea or tea beverages, have conventionally been regarded as waste material and routinely discarded. Nevertheless, contemporary research endeavors are concentrating on discovering efficient methods for utilizing the potential of this discarded resource.

RESULTS

In this study, we employed a sequential extraction method using chemical chelating agents to extract and isolate four distinct cell wall polysaccharides, designated as CWTPS-1 through CWTPS-4, from the tea dregs of Liubao brick tea. A comprehensive investigation into their physicochemical, structural, and hypoglycemic properties was conducted. The analysis of chemical composition and physicochemical characteristics revealed that all four CWTPSs were characterized as acidic polysaccharides, albeit with varying chemical compositions and physicochemical attributes. Specifically, the xyloglucan fractions, CWTPS-3 and CWTPS-4, were found to be rich in glucose and xylose, displaying a more uniform molecular weight distribution, greater structural stability, and a more irregular surface compared to the others. Moreover, they exhibited a higher diversity of monosaccharide residues. Importantly, our research unveiled that all four CWTPSs exhibited the capacity to modulate key glucose-regulated and antioxidant enzyme activities within HepG2 cells via the IRS-1-PI3K/AKT signaling pathway, thereby ameliorating cellular insulin resistance. Furthermore, our correlation analysis highlighted significant associations between monosaccharide composition and neutral sugar content with the observed hypoglycemic activity of CWTPSs.

CONCLUSION

This study highlights the potential of utilizing tea dregs as a valuable resource, making a significant contribution to the advancement of the tea industry. Furthermore, CWTPS-4 exhibits promising prospects for further development as a functional food ingredient or additive. © 2024 Society of Chemical Industry.

Two novel polysaccharides from Huangshui: Purification, structure, and bioactivities

In this study, the novel polysaccharides named HSP-0 M and HSP-0.1 M were successfully purified from Huangshui (HS), and their structural properties and bioactivities were investigated. Structural analysis revealed that HSP-0 M had a molecular weight of 493.87 kDa and was composed of arabinose, galactose, glucose, xylose, and mannose in a molar ratio of 1.48:1.09:26.52:1.33:1.00. On the other hand, HSP-0.1 M was made up of fructose, arabinose, galactose, glucose, xylose, mannose, ribose, galacturonic acid and glucuronic acid in a ratio of 2.67:26.00:29.10:36.83:16.22:30.53:1.00:1.43:3.64 with a molecular weight of 157.6 kDa. Methylated and 2D NMR analyses indicated that T-Glcp-(1 → 4)-Glcp-(1 → 2)-Glcp-(1 → 3)-Glcp was the primary chain of HSP-0 M, and the backbone of HSP-0.1 M was made up of →3)-Galp-(1 → 6)-Manp-(1 → 3)-Glcp-(1 → 6)-Glcp-(1 → 2)-Manp-(1 → 6)-Glcp-(1 → 3)-Galp. Morphological research showed that both polysaccharides were homogeneous as well as exhibit a web-like structure and an irregular lamellar structure. Furthermore, HSP-0 M demonstrated the capacity to safeguard Lactococcus lactis from damage caused by low temperatures and freeze-drying, while HSP-0.1 M exhibited noteworthy antioxidant activity. These results established a theoretical foundation for the applications of HSPs in food products, cosmetics, and medicines.

Structural and flow rheological properties of pumpkin pectic polysaccharide extracted by citric acid

The present study aimed to investigate the structural and physicochemical characteristics of acid-extracted pumpkin pectic polysaccharide (AcPP) and to evaluate their flow rheological properties. AcPP was extracted from pumpkin pulp using the citric acid extraction method. The physicochemical and structural properties were analyzed by chemical methods and instrumental analyses. The obtained results showed that AcPP consisted predominantly of GalA (85.99 %) and small amounts of Rha, Gal, and Ara, with the ratio of HG/RG-I being 81.39/16.75. In addition, AcPP had medium DE (45.34 %) and contained four macromolecular populations with different Mw of 106.03 (main), 10.15, 4.99, and 2.90 kDa. The NMR analysis further confirmed that AcPP contained a linear backbone consisting of α-1,4-linked GalA residues, some of which were partially methyl-esterified. Furthermore, AcPP was amorphous in nature and had favorable thermal stability. The effects of extrinsic factors on the flow rheological properties of AcPP were evaluated. In particular, the high concentrations of CaCl2 (8 mM) and MgCl2 (10 mM) were effective in enhancing the viscosity and non-Newtonian shear-thinning behavior of the AcPP solution. This study elucidates the unique molecular structure of AcPP and suggests the potential of AcPP as a rheology modifier in low-viscous and mineral-reinforced beverages.

Effect of subcritical water temperature on the chain conformation and immune activity of ginger polysaccharides

In this study, the ginger polysaccharides extracted from hot water (HW-G) were modified with subcritical water (SW-G) to effectively regulate their immune activity, and the relationship between polysaccharide chain conformation and immune activity at different subcritical water temperatures was investigated. The results indicated that, compared with HW-G, the xylose and mannose were degraded at high temperatures. The molecular weight of ginger polysaccharide decreased from 1.083 × 106 g/mol to 3.113 × 105 g/mol after subcritical water modification (100-160 °C). The chain conformation transitioned from rigid rod chain to semi-rigid chain and eventually to random coil. The degree of relaxation of the polysaccharide chains showed a continuous increase trend. Additionally, ginger polysaccharide modified by subcritical water at 130 °C was found to promote the proliferation and phagocytosis of 264.7 cells more obviously and signally increase the secretion levels of NO, IL-6, TNF-α and IL-1β. When the subcritical water temperature exceeds 130 °C, the activity of ginger polysaccharide begins to decline rapidly. These findings demonstrate a close correlation between polysaccharide chain conformation and immunomodulatory activity, confirming the feasibility of the subcritical water temperature effect as a means of immune activity regulation, which opens up a new approach to obtaining highly active polysaccharides.

Green tea polysaccharide conjugates and bovine serum albumin have a synergistic effect in improving the emulsification ability

Our previous study revealed that green tea polysaccharide conjugate (gTPC) has emulsion effect, but its emulsifying ability is weak. In order to improve the emulsification ability of gTPC, gTPC and bovine serum albumin (BSA) were combined to form five different mass proportions of the TPC/BSA (TB) complex: TPC/BSA: 5:1, 5:2, 5:3, 5:4, and 5:5 w/w. We observed that the 5:5 w/w TB emulsion was more hydrophobic and surface-active. Furthermore, the emulsions prepared using 50.00 wt% medium-chain triglycerides exhibited the best stability. In addition, the TB emulsion exhibited stability in adverse environments of pH, salt, and heat; in particular, under salt conditions, no significant changes were observed in zeta potential. Subsequently, in vitro simulated digestion experiments were performed to investigate the use of TB emulsions for β-carotene encapsulation. We observed that the encapsulation efficiency for β-carotene was approximately 90.0 %; it was subsequently released in the intestine.

Physicochemical stability and antibacterial mechanism of theabrownins prepared from tea polyphenols catalyzed by polyphenol oxidase and peroxidase

Tea polyphenols were used as substrates and oxidized successively by polyphenol oxidase and peroxidase to prepare theabrownins (TBs-dE). The conversion rate of catechins to TBs-dE was 90.91%. The ultraviolet and infrared spectroscopic properties and zeta potential of TBs-dE were characterized. TBs-dE is more stable at pH 5.0-7.0, about 25 °C or in dark environment. Ultraviolet light and sunlight can deepen its color due to the further oxidative polymerization. Mg2+, Cu2+, and Al3+ had a significant effect on the stability of TBs-dE. The inhibitory rates of TBs-dE (1 mg/mL) against Staphylococcus aureus and Escherichia coli DH5α were 51.45% and 45.05%, respectively. After TBs-dE treatment, the cell morphology of both bacteria changed, some cell walls were blurred, and the cytoplasmic content leaked. The research results can provide theoretical support for the industrialization of theabrownins.

Effect of hydrophobic property on antibacterial activities of green tea polysaccharide conjugates against Escherichia coli

We previously found that green tea polysaccharide conjugates (gTPCs) have antibacterial activity against Escherichia coli. In this study, the effect of hydrophobic property on the antibacterial activities of gTPCs was evaluated to elucidate their property-activity relationship. Three gTPCs (gTPCs-5 h, gTPCs-12 h and gTPCs-24 h) were extracted from green tea with the ethanol precipitation time of 5 h, 12 h and 24 h, respectively. These three gTPCs did not differ significantly in terms of molecular weight distribution, amino acids composition and zeta potentials. Fourier transform infrared spectroscopy results revealed that gTPCs-5 h and gTPCs-12 h processed more hydrogen bonds than gTPCs-24 h. The surface hydrophobicity and contact angle of gTPCs-5 h were larger than that of gTPCs-12 h and gTPCs-24 h. The antibacterial activity of gTPCs against E. coli decreased in the order of gTPCs-5 h > gTPCs-12 h > gTPCs-24 h. There wasn't significant difference among the zeta potentials of E. coli treated by gTPCs-5 h, gTPCs-12 h and gTPCs-24 h, but the bacterial contact angles of E. coli treated by gTPCs-5 h were higher compared with those of the other two gTPCs. Furthermore, gTPCs-5 h exhibited higher activity to decrease bacterial membrane proteins, and increase bacterial membrane permeability than the other two gTPCs. In conclusion, gTPCs with higher hydrophobicity property exhibited stronger antibacterial activity against E. coli.

Regulating effects of phytosterol esters-loaded emulsions stabilized with green tea polysaccharide conjugates and Tween on lipids in KKAy mice

Phytosterol esters (PSE) have been shown to have cholesterol-lowering effects, but their insolubility in water limits their applications. Green tea polysaccharide conjugates (gTPC) have hypoglycemic and emulsifying effects. To address lipid dysregulation in diabetic patients, we developed PSE-loaded emulsions stabilized with gTPC and Tween-20 (gTPC-PSE emulsions) and evaluated their physicochemical properties. We subsequently investigated the lipid-regulating potential of these emulsions to in KKAy mice. The KKAy mice were randomly assigned to eight groups: the model group, the Lipitor (10 mg·kg^-1)-acarbose (30 mg·kg^-1) combination group, two gTPC groups, two PSE groups, and two gTPC-PSE groups with a 1:2 mass ratio of gTPC to PSE. The administered doses were 90 and 270 mg kg^-1, respectively. Administration of a 270 mg·kg^-1 dose of gTPC-PSE emulsions led to the most significant effects including increased levels of liver and serum high-density lipoprotein cholesterol (HDL-CH), reduced serum leptin and insulin, and improved liver superoxide dismutase (SOD) and reduced malondialdehyde (MDA). In general, gTPC and PSE demonstrated a synergistic effect on lipid regulation in mice. Our results indicate that gTPC-PSE emulsions hold potential as a nutritional intervention for diabetes by modulating lipid levels.

Apocynum venetum, a medicinal, economical and ecological plant: a review update

Apocynum venetum L. is an important medicinal perennial rhizome plant with good ecological and economic value. Its leaves have many pharmacological effects such as anti-inflammatory, anti-depression, anti-anxiolytic, etc., while its fibers have the title of "king of wild fibers". Furthermore, it was suitable for the restoration of degraded saline soil in arid areas. An increasing studies have been published in the past years. A scientometric analysis was used to analyze the publications of Apocynum venetum L. to clearly review the pharmacology, fiber application of Apocynum venetum L. and the potential value with its similar species (Apocynum pictum Schrenk) to the environment.

Sustainable Food Systems: The Case of Functional Compounds towards the Development of Clean Label Food Products

The addition of natural components with functional properties in novel food formulations confers one of the main challenges that the modern food industry is called to face. New EU directives and the global turn to circular economy models are also pressing the agro-industrial sector to adopt cradle-to-cradle approaches for their by-products and waste streams. This review aims to present the concept of “sustainable functional compounds”, emphasizing on some main bioactive compounds that could be recovered or biotechnologically produced from renewable resources. Herein, and in view of their efficient and “greener” production and extraction, emerging technologies, together with their possible advantages or drawbacks, are presented and discussed. Μodern examples of novel, clean label food products that are composed of sustainable functional compounds are summarized. Finally, some action plans towards the establishment of sustainable food systems are suggested.

Physicochemical and Colon Cancer Cell Inhibitory Properties of Theabrownins Prepared by Weak Alkali Oxidation of Tea Polyphenols

Existing studies on the biological activity of theabrownins are not based on their free state but on the complexes of theabrownins, polysaccharides, proteins, and flavonoids. In this study, theabrownins (TBs-C) were prepared by weak alkali oxidation of tea polyphenols. The ultraviolet-visible scanning spectrum of TBs-C showed two characteristic absorption peaks at 203 and 270 nm. The zeta potential of the TBs-C aqueous solution was negative, and the values varied from - 6.26 to -19.55 mV with a solution pH of 3-9. Storage conditions of pH 5.0-7.0 and around 25 °C were beneficial for the physical and chemical stability of the TBS-C solution. Cells were treated with series concentrations and examined by MTT, HE staining, PI immunofluorescence staining, flow cytometry, and real-time PCR to investigate the antiproliferative effect of TBs-C on human colon cancer HT-29 cells. The results showed that TBs-C, particularly at 500 µg/mL, inhibited cell growth. TBs-C induced HT-29 cell apoptosis, as confirmed by morphological changes, nucleus propidium iodide staining, and distributions of the cell cycle. The apoptotic mechanism may be due to the intracellular redox imbalance induced by TBs-C.

Theabrownins Produced via Chemical Oxidation of Tea Polyphenols Inhibit Human Lung Cancer Cells in vivo and in vitro by Suppressing the PI3K/AKT/mTOR Pathway Activation and Promoting Autophagy

During the fermentation of dark tea, theabrownins (TBs), carbohydrates, and other substances get irreversibly complex. Recent research on the biological activity of TBs is not based on free TBs. In the present study, some brown polyphenol oxidized polymers, the generalized TBs (TBs-C), were prepared via alkali oxidation from tea polyphenols (TP). We also investigated the inhibitory mechanism of TBs-C on non-small-cell-lung cancer (NSCLC). TBs-C demonstrated a stronger inhibition than TP on the NSCLC cell lines A549, H2030, HCC827, H1975, and PC9. Next, A549 and H2030 cell lines were selected as subjects to explore this mechanism. TBs-C was found to inhibit proliferation, promote apoptosis, and induce G1 cell-cycle arrest in the cells. In addition, TBs-C increased autophagic flux, which in turn promoted the death of lung cancer cells. Moreover, TBs-C suppressed the PI3K/AKT/mTOR pathway activation, promoted autophagy, and increased the expression of p21 downstream of AKT, which resulted in G1 cell-cycle arrest. In xenotransplanted NSCLC nude mice derived from A549 cells, TBs-C could significantly suppress tumor growth by inhibiting the PI3K/AKT/mTOR pathway without causing hepatotoxicity, brain toxicity, or nephrotoxicity. We believe that our present findings would facilitate advancement in the research and industrialization of TBs.

Characterization of Theabrownins Prepared From Tea Polyphenols by Enzymatic and Chemical Oxidation and Their Inhibitory Effect on Colon Cancer Cells

Theabrownins (TBs) are prepared from dark tea and contain a large number of complex heterogeneous components, such as carbohydrates, proteins, and flavonoids, which are difficult to remove. In addition, some toxic and harmful extraction solvents are used to purify TBs. These obstacles hinder the utilization and industrialization of TBs. In this study, tea polyphenols were used as substrates and polyphenol oxidase and sodium bicarbonate (NaHCO₃) were used successively to prepare theabrownins (TBs-E). The UV-visible characteristic absorption peaks of the TBs-E were located at 203 and 270 nm and Fourier-transform IR analysis showed that they were polymerized phenolic substances containing the hydroxy and carboxyl groups. The TBs-E aqueous solution was negatively charged and the absolute values of the zeta potential increased with increasing pH. A storage experiment showed that TBs-E were more stable at pH 7.0 and in low-temperature environments around 25°C. HT-29 human colon cancer cells were used to evaluate the biological activity of TBs-E through 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT), H&E staining, propidium iodide immunofluorescent staining, flow cytometry, and real-time PCR assays. The TBs-E significantly inhibited cell growth and caused late apoptosis, particularly at the dose of 500 μg/ml. The TBs-E markedly reduced the expression of antioxidant enzyme genes and increased the generation of reactive oxygen species to break the redox balance, which may have led to cell damage and death. These results will promote research and industrialization of TBs.