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.

A systemic review on Liubao tea: A time-honored dark tea with distinctive raw materials, process techniques, chemical profiles, and biological activities.

Liubao tea (LBT) is a unique microbial-fermented tea that boasts a long consumption history spanning 1500 years. Through a specific post-fermentation process, LBT crafted from local tea cultivars in Liubao town Guangxi acquires four distinct traits, namely, vibrant redness, thickness, aging aroma, and purity. The intricate transformations that occur during post-fermentation involve oxidation, degradation, methylation, glycosylation, and so forth, laying the substance foundation for the distinctive sensory traits. Additionally, LBT contains multitudinous bioactive compounds, such as ellagic acid, catechins, polysaccharides, and theabrownins, which contributes to the diverse modulation abilities on oxidative stress, metabolic syndromes, organic damage, and microbiota flora. However, research on LBT is currently scattered, and there is an urgent need for a systematical recapitulation of the manufacturing process, the dominant microorganisms during fermentation, the dynamic chemical alterations, the sensory traits, and the underlying health benefits. In this review, current research progresses on the peculiar tea varieties, the traditional and modern process technologies, the substance basis of sensory traits, and the latent bioactivities of LBT were comprehensively summarized. Furthermore, the present challenges and deficiencies that hinder the development of LBT, and the possible orientations and future perspectives were thoroughly discussed. By far, the productivity and quality of LBT remain restricted due to the reliance on labor and experience, as well as the incomplete understanding of the intricate interactions and underlying mechanisms involved in processing, organoleptic quality, and bioactivities. Consequently, further research is urgently warranted to address these gaps.

Preventive Effect of Raw Liubao Tea Polyphenols on Mouse Gastric Injuries Induced by HCl/Ethanol via Anti-Oxidative Stress.

Liubao tea is a type of traditional Chinese tea, belonging to the dark teas. This study is a basic research of the contained polyphenols (active substances) and detected preventive effects of polyphenols of raw Liubao tea (PRLT) on mouse gastric injuries induced by HCl/ethanol. High-pressure liquid chromatography was used to analyze the components of PRLT. Furthermore, a mouse gastric injury model was established to observe the preventive effects. PRLT was shown to contain gallic acid, EGC (epigallocatechin), catechin, caffeine, EC (epicatechin), EGCG (epigallocatechin gallate), GCG (gallocatechin gallate), and ECG (epicatechin gallate). The results of the in vivo study indicate that PRLT can inhibit the observed increase of gastric juice volume and decrease of gastric juice pH caused by gastric injury. PRLT can decrease the serum levels of IL-6 (interleukin-6), IL-12 (interleukin-12), TNF-α (tumor necrosis factor-α), and IFN-γ (interferon-γ) in mice with gastric injuries. Moreover, it can also increase the serum levels of SS (somatostatin) and VIP (vasoactive intestinal peptide) and reduce the serum levels of both SP (substance P) and ET-1 (endothelin-1). PRLT was also shown to increase SOD (superoxide dismutase) and GSH (glutathione) levels and decrease MDA (malondialdehyde) level. The detection of mRNA and protein in gastric tissues indicates that PRLT could also up-regulate the expression of Cu/Zn-SOD (copper/zinc superoxide dismutase), Mn-SOD (manganese superoxide dismutase), CAT (catalase), nNOS (neuronal nitric oxide synthase), and eNOS (endothelial nitric oxide synthase) and down-regulate the expression of both iNOS (inducible nitric oxide synthase) and COX-2 (cyclooxygenase-2). Thus, PRLT possess a good preventive effect on gastric injury, which is directly related to the contained active substance. PRLT show good anti-oxidative and preventive effect in gastric injury and offer promising application value.

Polyphenols in Liubao Tea Can Prevent CCl4-Induced Hepatic Damage in Mice through Its Antioxidant Capacities.

The present study investigated the preventive effect of polyphenols in Liubao tea (PLT) on carbon tetrachloride (CCl4)-induced liver injury in mice. The mice were initially treated with PLT, followed by induction of liver injury using 10 mL/kg CCl4. Then liver and serum indices, as well as the expression levels of related messenger RNAs (mRNAs) and proteins in liver tissues were measured. The results showed that PLT reduces the liver quality and indices of mice with liver injury. PLT also downregulates aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglycerides (TGs), and malondialdehyde (MDA), and upregulates superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the sera of mice with liver injury. PLT also reduces serum levels of interleukin-6 (IL-6), interleukin-12 (IL-12), tumor necrosis factor- α (TNF- α ), and interferon- γ (IFN- γ ) cytokines in mice with liver injury. Pathological morphological observation also shows that PLT reduces CCl4-induced central venous differentiation of liver tissues and liver cell damage. Furthermore, qPCR and Western blot also confirm that PLT upregulates the mRNA and protein expressions of Gu/Zn-SOD, Mn-SOD, catalase (CAT), GSH-Px, and nuclear factor of κ -light polypeptide gene enhancer in B-cells inhibitor- α (I κ B- α ) in liver tissues, and downregulates the expression of cyclooxygenase 2 (COX-2) and nuclear factor κ -light-chain-enhancer of activated B cells (NF- κ B). Meanwhile, PLT also raised the phosphorylated (p)-NF- κ B p65 and cytochrome P450 reductase protein expression in liver injury mice. The components of PLT include gallic acid, catechin, caffeine, epicatechin (EC), epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), and epicatechin gallate (ECG), which possibly have a wide range of biological activities. Thus, PLT imparts preventive effects against CCl4-induced liver injury, which is similar to silymarin.