Theabrownins(TBs)are the characteristic functional and quality components of dark teas such as Pu’er tea and Chin-brick tea.TBs are a class of water-soluble brown polymers with multi-molecular weight distribution pro...Theabrownins(TBs)are the characteristic functional and quality components of dark teas such as Pu’er tea and Chin-brick tea.TBs are a class of water-soluble brown polymers with multi-molecular weight distribution produced by the oxidative polymerisation of tea polyphenols during the fermentation process of dark tea,both enzymatically and non-enzymatically.TBs have been extracted and purified from dark tea all the time,but the obtained TBs contain heterogeneous components such as polysaccharides and caffeine in the bound state,which are difficult to remove.The isolation and purification process was tedious and required the use of organic solvents,which made it difficult to industrialise TBs.In this study,epigallocatechin(EGC),epigallocatechin gallate(EGCG),epigallocatechin gallate(ECG),EGC/EGCG(mass ratio 1:1),EGCG/ECG(mass ratio 1:1),EGC/ECG(mass ratio 1:1)and EGC/EGCG/ECG(mass ratio 1:1:1)as substrates and catalyzed by polyphenol oxidase(PPO)and peroxidase(POD)in turn to produce TBs,named TBs-dE-1,TBs-dE-2,TBs-dE-3,TBs-dE-4,TBs-dE-5,TBs-dE-6 and TBs-dE-7.The physicochemical properties and the antibacterial activity and mechanism of TBs-dE-1–7 were investigated.Sensory and colour difference measurements showed that all seven tea browning samples showed varying degrees of brownish hue.Zeta potential in aqueous solutions at pH 3.0–9.0 indicated that TBs-dE-1–7 was negatively charged and the potential increased with increasing pH.The characteristic absorption peaks of TBs-dE-1–7 were observed at 208 and 274 nm by UV-visible(UV-vis)scanning spectroscopy.Fourier transform infrared(FT-IR)spectra indicated that they were phenolic compounds.TBs-dE-1–7 showed significant inhibition of Escherichia coli DH5α(E.coli DH5α).TBs-dE-3 showed the strongest inhibitory effect with minimum inhibitory concentration(MIC)of 1.25 mg mL–1 and MBC of 10 mg mL–1,followed by TBs-dE-5 and TBs-dE-6.These three TBs-dEs were selected to further investigate their inhibition mechanism.The TBs-dE was found to damage the extracellular membrane of E.coli DH5α,causing leakage of contents,and increase intracellular reactive oxygen content,resulting in abnormal cell metabolism due to oxidative stress.The results of the study provide a theoretical basis for the industrial preparation and product development of TBs.展开更多
[ Objective] This study aimed to provide theoretical reference for the extraction of theabrownine from Liubao tea, determination of the biological activity, and development and utilization of theabrownine. [Method] Or...[ Objective] This study aimed to provide theoretical reference for the extraction of theabrownine from Liubao tea, determination of the biological activity, and development and utilization of theabrownine. [Method] Orthogonal experimental design was adopted to investigate the effects of solid-liquid ratio, extraction temperature, extraction duration, and extraction frequency on the yield of theabrownine extracted from Liubao tea. The extraction technology was optimized, and the antioxidant activity of theabrownine was analyzed. [ Result] The results showed that extraction frequency and extraction temperature had significant effects on the yield of theabrownine extracted from Liubao tea, while solid-liquid ratio and extraction duration had no significant effect. The optimal conditions for extracting theabrownine from Liubao tea were determined as follows ： solid-liquid ratio was 1 ： 30, extraction temperature was 100℃, extraction duration was 80 min, and extraction frequency was 4 times. Under these conditions, the yield of theabrownine reached 22.92%. Results of antioxidant activity determination showed that hydroxyl radical-scavenging activity of theabrownine was as high as 74%, and the scavenging effects was significantly higher than that of Vitamin C under low concentrations; nitroso-scavenging activity of theabrownine reached 73%, with no significant difference from that of Vitamin C; superoxide anion free radical-scavenging activity of theabrownine could be above 60%, which was lower than that of Vitamin C. [Condusion] Liubao tea contains abundant theabrownine that has relatively high antioxidant activity with good prospects in antioxidant application, which lays solid foundation for in-depth development of Liubao tea.展开更多
Habitual tea consumption can reduce the risk of ASCVD morbidity and mortality and all-cause mortality in China,and long-term adherence to this habit can provide greater protection.Pu-erh tea is one of the representati...Habitual tea consumption can reduce the risk of ASCVD morbidity and mortality and all-cause mortality in China,and long-term adherence to this habit can provide greater protection.Pu-erh tea is one of the representatives of post-fermented teas,and the polymers in Pu-erh tea have anti-cancer and anti-hyperlipidemic activities,but their chemical composition is still unknown.In this study,the chemical composition of Pu-erh tea was investigated in detail and eight(1–8)known compounds were isolated.The polymers in Pu-erh tea were also degraded by thiol degradation,and the fragments of quercetin and(–)-epicatechin-3-O-gallate were found in the thiol degradation products of Pu-erh tea polymers by UPLC observation and separation and purification.This is the first time that this fragment was obtained in Pu-erh tea polymer.展开更多
基金financially supported by the National Natural Science Foundation of China(31871813).
文摘Theabrownins(TBs)are the characteristic functional and quality components of dark teas such as Pu’er tea and Chin-brick tea.TBs are a class of water-soluble brown polymers with multi-molecular weight distribution produced by the oxidative polymerisation of tea polyphenols during the fermentation process of dark tea,both enzymatically and non-enzymatically.TBs have been extracted and purified from dark tea all the time,but the obtained TBs contain heterogeneous components such as polysaccharides and caffeine in the bound state,which are difficult to remove.The isolation and purification process was tedious and required the use of organic solvents,which made it difficult to industrialise TBs.In this study,epigallocatechin(EGC),epigallocatechin gallate(EGCG),epigallocatechin gallate(ECG),EGC/EGCG(mass ratio 1:1),EGCG/ECG(mass ratio 1:1),EGC/ECG(mass ratio 1:1)and EGC/EGCG/ECG(mass ratio 1:1:1)as substrates and catalyzed by polyphenol oxidase(PPO)and peroxidase(POD)in turn to produce TBs,named TBs-dE-1,TBs-dE-2,TBs-dE-3,TBs-dE-4,TBs-dE-5,TBs-dE-6 and TBs-dE-7.The physicochemical properties and the antibacterial activity and mechanism of TBs-dE-1–7 were investigated.Sensory and colour difference measurements showed that all seven tea browning samples showed varying degrees of brownish hue.Zeta potential in aqueous solutions at pH 3.0–9.0 indicated that TBs-dE-1–7 was negatively charged and the potential increased with increasing pH.The characteristic absorption peaks of TBs-dE-1–7 were observed at 208 and 274 nm by UV-visible(UV-vis)scanning spectroscopy.Fourier transform infrared(FT-IR)spectra indicated that they were phenolic compounds.TBs-dE-1–7 showed significant inhibition of Escherichia coli DH5α(E.coli DH5α).TBs-dE-3 showed the strongest inhibitory effect with minimum inhibitory concentration(MIC)of 1.25 mg mL–1 and MBC of 10 mg mL–1,followed by TBs-dE-5 and TBs-dE-6.These three TBs-dEs were selected to further investigate their inhibition mechanism.The TBs-dE was found to damage the extracellular membrane of E.coli DH5α,causing leakage of contents,and increase intracellular reactive oxygen content,resulting in abnormal cell metabolism due to oxidative stress.The results of the study provide a theoretical basis for the industrial preparation and product development of TBs.
基金Supported by Scientific and Technological Development Project of Guangxi Zhuang Autonomous Region(GKN1348022-4)General Project of Scientific Research Fund of the Education Department of Guangxi Zhuang Autonomous Region(201012MS138)
文摘[ Objective] This study aimed to provide theoretical reference for the extraction of theabrownine from Liubao tea, determination of the biological activity, and development and utilization of theabrownine. [Method] Orthogonal experimental design was adopted to investigate the effects of solid-liquid ratio, extraction temperature, extraction duration, and extraction frequency on the yield of theabrownine extracted from Liubao tea. The extraction technology was optimized, and the antioxidant activity of theabrownine was analyzed. [ Result] The results showed that extraction frequency and extraction temperature had significant effects on the yield of theabrownine extracted from Liubao tea, while solid-liquid ratio and extraction duration had no significant effect. The optimal conditions for extracting theabrownine from Liubao tea were determined as follows ： solid-liquid ratio was 1 ： 30, extraction temperature was 100℃, extraction duration was 80 min, and extraction frequency was 4 times. Under these conditions, the yield of theabrownine reached 22.92%. Results of antioxidant activity determination showed that hydroxyl radical-scavenging activity of theabrownine was as high as 74%, and the scavenging effects was significantly higher than that of Vitamin C under low concentrations; nitroso-scavenging activity of theabrownine reached 73%, with no significant difference from that of Vitamin C; superoxide anion free radical-scavenging activity of theabrownine could be above 60%, which was lower than that of Vitamin C. [Condusion] Liubao tea contains abundant theabrownine that has relatively high antioxidant activity with good prospects in antioxidant application, which lays solid foundation for in-depth development of Liubao tea.
基金supported by the National Natural Science Foundation of China(31660099)。
文摘Habitual tea consumption can reduce the risk of ASCVD morbidity and mortality and all-cause mortality in China,and long-term adherence to this habit can provide greater protection.Pu-erh tea is one of the representatives of post-fermented teas,and the polymers in Pu-erh tea have anti-cancer and anti-hyperlipidemic activities,but their chemical composition is still unknown.In this study,the chemical composition of Pu-erh tea was investigated in detail and eight(1–8)known compounds were isolated.The polymers in Pu-erh tea were also degraded by thiol degradation,and the fragments of quercetin and(–)-epicatechin-3-O-gallate were found in the thiol degradation products of Pu-erh tea polymers by UPLC observation and separation and purification.This is the first time that this fragment was obtained in Pu-erh tea polymer.
