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
气候变化对自然环境和经济社会发展的影响日益加剧,威胁人类可持续发展的进程。进行应对气候变化技术研究不仅可以加深人类对于气候变化科学的认知,而且可以为未来缓解和适应气候变化的政策和措施提供重要依据。本文利用文献计量方法对1...气候变化对自然环境和经济社会发展的影响日益加剧,威胁人类可持续发展的进程。进行应对气候变化技术研究不仅可以加深人类对于气候变化科学的认知,而且可以为未来缓解和适应气候变化的政策和措施提供重要依据。本文利用文献计量方法对1988—2018年来自Web of Science数据库中应对气候变化技术研究的科学文献进行了系统的数据统计与分析,通过气候变化研究的发文历程、主要研究机构分布、研究主题的发展与演变等方面的数据揭示了现阶段全球应对气候变化技术的总体科研状况,并一定程度上预估了其未来发展趋势。主要研究结果表明:(1)在所有研究国家当中,美国和英国在应对气候变化技术领域长期处于领先地位,而中国虽然发文量和H指数相对靠前,但篇均被引频次较低,需要注重整体发文质量的提高。(2)基金资助论文在论文总数中所占比例越来越大,截止到2018年,其比例已经占到了75. 28%。(3)全球发文主要机构中,美国仍然占据了首位,而中国的主要发文机构中仅中国科学院发文量、H指数、篇均被引频次较高,中国其他发文机构还需进一步提升科研实力和在应对气候变化领域的影响力。(4)在主要研究方向梳理中,中国和全球的主要研究方向基本一致,但工程学、技术与科学和能源燃料等研究方向在中国的起步较晚、发展较慢,还需要继续加大投入,向世界先进水平靠拢。(5)从关键词随时间的变化可以看出,生物质技术、CCS技术和太阳能、风能、氢能源等可再生能源技术是应对气候变化的关键性技术,也会是未来全球的主要发展方向。展开更多
The antioxidant effects of quercetin were studied in vitro and in vivo.In vitro,vitamin C was used as a positive control to evaluate the antioxidant capacity of quercetin in three aspects:scavenging free radicals,prot...The antioxidant effects of quercetin were studied in vitro and in vivo.In vitro,vitamin C was used as a positive control to evaluate the antioxidant capacity of quercetin in three aspects:scavenging free radicals,protecting biological macromolecules and the total reducing power.In vivo,a total of 240 AA broilers(1-day age)with similar body weight were randomly divided into four groups with six replicates in each group,and 10 broilers in each replicate.The four groups were fed with corn-soybean basal diet supplemented with 0.00%,0.02%,0.04%and 0.06%quercetin to study its effects on antioxidant indexes of AA broilers,and to explore the optimal dose of quercetin as a dietary additive.The results showed that quercetin scavenged superoxide anion,hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl(DPPH)in vitro,the scavenging effects of quercetin on O_(2)-and•OH first increased and then decreased with the increase of the concentrations(P<0.01),and its maximum scavenging effect was observed at concentrations of 40 and 300 mg·L^(-1).The scavenging effects of quercetin on DPPH was increased constantly with increasing concentrations.The scavenging effect of quercetin on three free radicals was DPPH>•OH>O_(2)-.The inhibition of vitelline lipoprotein peroxidation by quercetin was increased with increasing concentrations(P<0.01)and the inhibitory effect was higher than that of vitamin C.The inhibition of red blood cell hemolysis by quercetin was increased with increasing concentrations at 0.05-1.25 mg·L^(-1)(P<0.01);however,the inhibition tended to decrease when the concentration was too high(31.25 mg·L^(-1)),and the inhibitory effect was higher than that of vitamin C.The inhibition of mitochondrial expansion by quercetin was increased with increasing concentrations,according to the degree of mitochondrial expansion at 60 min,the integrity of mitochondria in the experimental groups was significantly higher than that in the model group(P<0.01).The total reducing power of quercetin was increased with increasing concentrations(P<0.01);however,the total reducing power was less than that of vitamin C.In vivo,malondialdehyde(MDA)and nitric oxide(NO)were significantly decreased with increasing quercetin(P<0.01).Quercetin supplementation had no effect on the content of lipid peroxidation(LPO)in livers(P>0.05);however,superoxide dismutase(SOD)activity was significantly increased,whereas glutathione peroxidase(GSH-Px)and catalase(CAT)activities were significantly decreased in livers with increasing quercetin(P<0.05).These results suggested that quercetin exhibited strong antioxidant effects in vitro and in vivo.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.
文摘气候变化对自然环境和经济社会发展的影响日益加剧,威胁人类可持续发展的进程。进行应对气候变化技术研究不仅可以加深人类对于气候变化科学的认知,而且可以为未来缓解和适应气候变化的政策和措施提供重要依据。本文利用文献计量方法对1988—2018年来自Web of Science数据库中应对气候变化技术研究的科学文献进行了系统的数据统计与分析,通过气候变化研究的发文历程、主要研究机构分布、研究主题的发展与演变等方面的数据揭示了现阶段全球应对气候变化技术的总体科研状况,并一定程度上预估了其未来发展趋势。主要研究结果表明:(1)在所有研究国家当中,美国和英国在应对气候变化技术领域长期处于领先地位,而中国虽然发文量和H指数相对靠前,但篇均被引频次较低,需要注重整体发文质量的提高。(2)基金资助论文在论文总数中所占比例越来越大,截止到2018年,其比例已经占到了75. 28%。(3)全球发文主要机构中,美国仍然占据了首位,而中国的主要发文机构中仅中国科学院发文量、H指数、篇均被引频次较高,中国其他发文机构还需进一步提升科研实力和在应对气候变化领域的影响力。(4)在主要研究方向梳理中,中国和全球的主要研究方向基本一致,但工程学、技术与科学和能源燃料等研究方向在中国的起步较晚、发展较慢,还需要继续加大投入,向世界先进水平靠拢。(5)从关键词随时间的变化可以看出,生物质技术、CCS技术和太阳能、风能、氢能源等可再生能源技术是应对气候变化的关键性技术,也会是未来全球的主要发展方向。
基金Supposed by the National Natural Science Foundation of China(32072749)。
文摘The antioxidant effects of quercetin were studied in vitro and in vivo.In vitro,vitamin C was used as a positive control to evaluate the antioxidant capacity of quercetin in three aspects:scavenging free radicals,protecting biological macromolecules and the total reducing power.In vivo,a total of 240 AA broilers(1-day age)with similar body weight were randomly divided into four groups with six replicates in each group,and 10 broilers in each replicate.The four groups were fed with corn-soybean basal diet supplemented with 0.00%,0.02%,0.04%and 0.06%quercetin to study its effects on antioxidant indexes of AA broilers,and to explore the optimal dose of quercetin as a dietary additive.The results showed that quercetin scavenged superoxide anion,hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl(DPPH)in vitro,the scavenging effects of quercetin on O_(2)-and•OH first increased and then decreased with the increase of the concentrations(P<0.01),and its maximum scavenging effect was observed at concentrations of 40 and 300 mg·L^(-1).The scavenging effects of quercetin on DPPH was increased constantly with increasing concentrations.The scavenging effect of quercetin on three free radicals was DPPH>•OH>O_(2)-.The inhibition of vitelline lipoprotein peroxidation by quercetin was increased with increasing concentrations(P<0.01)and the inhibitory effect was higher than that of vitamin C.The inhibition of red blood cell hemolysis by quercetin was increased with increasing concentrations at 0.05-1.25 mg·L^(-1)(P<0.01);however,the inhibition tended to decrease when the concentration was too high(31.25 mg·L^(-1)),and the inhibitory effect was higher than that of vitamin C.The inhibition of mitochondrial expansion by quercetin was increased with increasing concentrations,according to the degree of mitochondrial expansion at 60 min,the integrity of mitochondria in the experimental groups was significantly higher than that in the model group(P<0.01).The total reducing power of quercetin was increased with increasing concentrations(P<0.01);however,the total reducing power was less than that of vitamin C.In vivo,malondialdehyde(MDA)and nitric oxide(NO)were significantly decreased with increasing quercetin(P<0.01).Quercetin supplementation had no effect on the content of lipid peroxidation(LPO)in livers(P>0.05);however,superoxide dismutase(SOD)activity was significantly increased,whereas glutathione peroxidase(GSH-Px)and catalase(CAT)activities were significantly decreased in livers with increasing quercetin(P<0.05).These results suggested that quercetin exhibited strong antioxidant effects in vitro and in vivo.
