This study was carried out to characterize total residual catechins and their fractions, polyphenolic contents and antioxidant activities of black teas enriched with high levels of theaflavin-3,3’-digallate. The made...This study was carried out to characterize total residual catechins and their fractions, polyphenolic contents and antioxidant activities of black teas enriched with high levels of theaflavin-3,3’-digallate. The made teas were processed from eleven selected cultivars. A comparative study was carried out between the processed teas and those from commercially grown Kenyan cultivars in relation to the above chemical parameters. A correlation matrix analysis was also conducted to find out whether a relationship existed between the antioxidant activities and the said chemical parameters. The total residual catechins were found to range between 3.10% and 8.08%. The total polyphenol levels varied between 19.00% and 28.90%, while the antioxidant activities of the teas ranged from 82.70% to 91.70%. There was a significant p < 0.001 correlation between the antioxidant activity and total polyphenols (r = 0.8948). There was also a high correlation p < 0.001 between the antioxidant activity and total catechins (r = 0.8878). Out of the four catechin fractions, the antioxidant activity correlated most with EGCG (r = 0.8774). The total polyphenolic contents and antioxidant activities for most of the cultivars were comparable to those of the green tea reference standard. From the figures obtained, it can be concluded that the most of the newly developed black teas of the selected cultivars have higher quality and enhanced antioxidant activities and that they can be recommended for commercial production.展开更多
The most daunting issue of global climate change is the deleterious impact of extreme temperatures on tea productivity and quality,which has resulted in a quest among researchers and growers.The current study aims to ...The most daunting issue of global climate change is the deleterious impact of extreme temperatures on tea productivity and quality,which has resulted in a quest among researchers and growers.The current study aims to unravel molecular programming underpinning thermotolerance by characterizing heat tolerance and sensitivity response in 20 tea cultivars.The signi fi cantly higher negative in fl uence of heat stress was recorded in a sensitive cultivar with reduced water retention(47%),chlorophyll content(33.79%),oxidation potential(32.48%),and increase in membrane damage(76.4%).Transcriptional pro fi ling of most tolerant and sensitive cultivars identi fi ed 78 differentially expressed unigenes with chaperon domains,including low and high molecular weight heat shock protein(HSP)and heat shock transcription factors(HSFs)involved in heat shock response(HSR).Further,predicted transcriptional interactome network revealed their key role in thermotolerance via well-co-ordinated transcriptional regulation of aquaporins,starch metabolism,chlorophyll biosynthesis,calcium,and ethylene mediated plant signaling system.The study identi fi ed the key role of HSPs(CsHSP90)in regulating HSR in tea,wherein,structure-based molecular docking revealed the inhibitory role of geldanamycin(GDA)on CsHSP90 by blocking ATP binding site at N-terminal domain of predicted structure.Subsequently,GDA mediated leaf disc inhibitor assay further af fi rmed enhanced HSR with higher expression of CsHSP17.6,CsHSP70,HSP101,and CsHSFA2 genes in tea.Through the current study,efforts were made to extrapolate a deeper understanding of chaperons mediated regulation of HSR attributing thermotolerance in tea.展开更多
Theanine is a non-protein amino acid representing as much as 50% of the total amino acids in black tea and 1% - 2% of dry weight in green tea. It has been shown to be able to reduce high blood pressure, promote relaxa...Theanine is a non-protein amino acid representing as much as 50% of the total amino acids in black tea and 1% - 2% of dry weight in green tea. It has been shown to be able to reduce high blood pressure, promote relaxation, and inhibit caffeine’s side effects among others. This current study explored the effects of sunlight and withering durations on theanine levels in tea shoots. Theanine content from three leaves and a bud, two leaves and a bud and internodes were detected and quantified by using High Performance Liquid chromatography (HPLC). Sunlight exposure experiment was started at dawn (0600 HRS, GMT + 3.00) when the light intensity was low and tea was collected at three-hour interval throughout the day to (1800 Hrs, GMT + 3.00) when the light intensity had dropped. At the start of the experiment, the theanine levels were significantly high but as the intensity of sunlight increased during the day there was a significant drop in theanine levels, and as the sun set the theanine levels increased significantly again in all samples. The results also showed that theanine levels were significantly increased after 15 hours of withering. Three leaves and a bud withered for 3 hours had mean theanine levels of 1.41% and those withered for 15 hours had mean theanine levels of 3.11%. Internodes exhibited higher mean theanine levels than those of leaves. In the light of these results, it’s evident that withering for a longer period of time and harvesting of tea when the light intensity is low ensure high amount of theanine in tea.展开更多
This study involved the selection of 11 cultivars out of 201 screened cultivars of fresh green and purple coloured tea leaves for use in the manufacture of black teas with optimized antioxidant activities. Individual ...This study involved the selection of 11 cultivars out of 201 screened cultivars of fresh green and purple coloured tea leaves for use in the manufacture of black teas with optimized antioxidant activities. Individual cultivars containing a combination of high leaf concentrations of the catechin fractions;epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) were used in the processing of theaflavin-3,3’ digallate (TF3) rich black tea. The black tea enrichment with TF3 was carried out through optimization of the processing conditions of each cultivar by varying the aeration times between 0 min and 80 min at an interval of 20 min. The differently processed teas were then assayed for the TF3 contents. The data analysis was carried out using the GENSTAT at p ≤ 0.05. The optimal processing time for Ejulu, TRFK 832/8, TRFK 831/11, TRFK 824/1, SC 31/37, SC 12/28, K-Purple and TRFK 6/8 was found to be 60 min while that of TRFK 301/6, TRFK 301/3 and TRFK 655/1 was 40 min. The optimal TF3 levels were found to range from 0.19% to 0.60%.展开更多
文摘This study was carried out to characterize total residual catechins and their fractions, polyphenolic contents and antioxidant activities of black teas enriched with high levels of theaflavin-3,3’-digallate. The made teas were processed from eleven selected cultivars. A comparative study was carried out between the processed teas and those from commercially grown Kenyan cultivars in relation to the above chemical parameters. A correlation matrix analysis was also conducted to find out whether a relationship existed between the antioxidant activities and the said chemical parameters. The total residual catechins were found to range between 3.10% and 8.08%. The total polyphenol levels varied between 19.00% and 28.90%, while the antioxidant activities of the teas ranged from 82.70% to 91.70%. There was a significant p < 0.001 correlation between the antioxidant activity and total polyphenols (r = 0.8948). There was also a high correlation p < 0.001 between the antioxidant activity and total catechins (r = 0.8878). Out of the four catechin fractions, the antioxidant activity correlated most with EGCG (r = 0.8774). The total polyphenolic contents and antioxidant activities for most of the cultivars were comparable to those of the green tea reference standard. From the figures obtained, it can be concluded that the most of the newly developed black teas of the selected cultivars have higher quality and enhanced antioxidant activities and that they can be recommended for commercial production.
文摘The most daunting issue of global climate change is the deleterious impact of extreme temperatures on tea productivity and quality,which has resulted in a quest among researchers and growers.The current study aims to unravel molecular programming underpinning thermotolerance by characterizing heat tolerance and sensitivity response in 20 tea cultivars.The signi fi cantly higher negative in fl uence of heat stress was recorded in a sensitive cultivar with reduced water retention(47%),chlorophyll content(33.79%),oxidation potential(32.48%),and increase in membrane damage(76.4%).Transcriptional pro fi ling of most tolerant and sensitive cultivars identi fi ed 78 differentially expressed unigenes with chaperon domains,including low and high molecular weight heat shock protein(HSP)and heat shock transcription factors(HSFs)involved in heat shock response(HSR).Further,predicted transcriptional interactome network revealed their key role in thermotolerance via well-co-ordinated transcriptional regulation of aquaporins,starch metabolism,chlorophyll biosynthesis,calcium,and ethylene mediated plant signaling system.The study identi fi ed the key role of HSPs(CsHSP90)in regulating HSR in tea,wherein,structure-based molecular docking revealed the inhibitory role of geldanamycin(GDA)on CsHSP90 by blocking ATP binding site at N-terminal domain of predicted structure.Subsequently,GDA mediated leaf disc inhibitor assay further af fi rmed enhanced HSR with higher expression of CsHSP17.6,CsHSP70,HSP101,and CsHSFA2 genes in tea.Through the current study,efforts were made to extrapolate a deeper understanding of chaperons mediated regulation of HSR attributing thermotolerance in tea.
文摘Theanine is a non-protein amino acid representing as much as 50% of the total amino acids in black tea and 1% - 2% of dry weight in green tea. It has been shown to be able to reduce high blood pressure, promote relaxation, and inhibit caffeine’s side effects among others. This current study explored the effects of sunlight and withering durations on theanine levels in tea shoots. Theanine content from three leaves and a bud, two leaves and a bud and internodes were detected and quantified by using High Performance Liquid chromatography (HPLC). Sunlight exposure experiment was started at dawn (0600 HRS, GMT + 3.00) when the light intensity was low and tea was collected at three-hour interval throughout the day to (1800 Hrs, GMT + 3.00) when the light intensity had dropped. At the start of the experiment, the theanine levels were significantly high but as the intensity of sunlight increased during the day there was a significant drop in theanine levels, and as the sun set the theanine levels increased significantly again in all samples. The results also showed that theanine levels were significantly increased after 15 hours of withering. Three leaves and a bud withered for 3 hours had mean theanine levels of 1.41% and those withered for 15 hours had mean theanine levels of 3.11%. Internodes exhibited higher mean theanine levels than those of leaves. In the light of these results, it’s evident that withering for a longer period of time and harvesting of tea when the light intensity is low ensure high amount of theanine in tea.
文摘This study involved the selection of 11 cultivars out of 201 screened cultivars of fresh green and purple coloured tea leaves for use in the manufacture of black teas with optimized antioxidant activities. Individual cultivars containing a combination of high leaf concentrations of the catechin fractions;epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) were used in the processing of theaflavin-3,3’ digallate (TF3) rich black tea. The black tea enrichment with TF3 was carried out through optimization of the processing conditions of each cultivar by varying the aeration times between 0 min and 80 min at an interval of 20 min. The differently processed teas were then assayed for the TF3 contents. The data analysis was carried out using the GENSTAT at p ≤ 0.05. The optimal processing time for Ejulu, TRFK 832/8, TRFK 831/11, TRFK 824/1, SC 31/37, SC 12/28, K-Purple and TRFK 6/8 was found to be 60 min while that of TRFK 301/6, TRFK 301/3 and TRFK 655/1 was 40 min. The optimal TF3 levels were found to range from 0.19% to 0.60%.
