Effects Of The Aqueous Extracts Of Six Tea Types On Myocardial Contractility In Isolated Rat Hearts

Heart failure(HF)is a common cardiovascular disease,which is seriously threatening to human health.Tea is a Chinese national historical drinking for thousands of years.Recent studies has been shown that tea has multiple health benefits to prevent ailments.It could effectively reduce the prevalence of cardiovascular diseases and tea polyphenols could protect heart function.However,there are some differences in health effects among miscellaneous teas with varied active components,which are manufactured by multiple processing from different tea varieties.On the basis of previous foundings,six types of tea as green,yellow,white,oolong,black and dark tea were manufactured from the same batch of Longjing 43 fresh leaves according to their typical processing technique.The successfully made teas have their representative sensory quality evaluated by tea panelist.The main chemical quality such as polyphenols,catechins and free amino acids in those six tea types were further determined by the Folin-ciocalteu colorimetry and high performance liquid chromatography(HPLC).The results has been shown that the caffeine content of six teas had no significant difference(P>0.05),while the order of total polyphenols amount is green > yellow > white > oolong > dark > black tea.The content of total catechins is in the order as green > yellow > oolong > white >dark > black tea,while the order of free amino acids as white > yellow > oolong >green > black > dark tea.Theanine and glutamine as the two major free amino acids in those six teas has the order as yellow > oolong > green > black > white > dark tea,oolong > white > yellow > green > black > dark tea,respectively.It is indicated that the manufacturing technique has significant effects on the major chemical contents as total polyphenols,catechins and free amino acids,not caffeine.The classic Langendorff perfusion system with online Powerlab monitoring system was used to compare with the aqueous extracts of six tea types on myocardial contractility in isolated rat hearts.The results of left ventricular physiological function as LVSP,LVDP,LVEDP,±dp/dt and HR have been shown that the aqueous extracts of different teas have significant different effect on myocardial contractility in isolated rat heart.Green,yellow,oolong,white and dark tea can significantly enhance myocardial contractility(P <0.05 vs.Control).The effects of green and yellow tea arethe strongest,followed by oolong tea,white tea and dark tea,but black tea has no significant effect(P >0.05 vs.Control).Furthermore,the polyphenols from green tea without oxidation has more effects on myocardial contractility than those from black tea with fully oxidation(P<0.05).However,tea aqueous extracts without polyphenols had no significant effects.Those data suggest that the difference of myocardial contractility among those teas are caused by their different tea polyphenols.We further detected the important signaling protein of Akt and ERK1/2 by western blotting,which are important to myocardial contractility.It is found that tea could significantly increase the phosphorylation of Akt and ERK1/2.Our data provide an important clue for myocardial protection of different teas and facilitate to exploit a novel tea based on their heart protective effects.