A PRELIMINARY STUDY ON THE ACTIVE CONSTITUENTS OF TEA MODIFYING N-NITROSATION REACTION / 营养学报

ABSTRACT

The contents of tea polyphenolic compounds, ascorbic acid, flavones and tea catechins in 17 kinds of Chinese tea were reported.In multivariable analysis, both factor analysis and regression technique were used to assess the realationship between blocking rate (transferred into In odd, dependent variable) and tea active constituents (independent variable) . It has been shown that the correlation coefficient between each pair of independent variables is comparatively high. One main factor could explain 80% of variation among independent variables, of which the factor loadings were 0.951 (tea catechins), 0.88 (tea polyphenolic compounds), 0.842 (ascorbic acid). It has been found that tea polyphenolic compounds had a higher contribution to the blocking rate. The blocking rates on NPRO formation were 88% for 2 ml green tea extract, 74% for tea polyphenolic compounds extracted from 2 ml green tea, and 75% for 20 mg of tea catechins, the same amount as contained in 2ml of tea extract. The blocking rate -was 28% for the same amount of ascorbic acid contained in 2 ml of tea extract, and therefore ascorbic acid in tea didn't play an important role in the blocking of NPRO formation. Tea polyphenolic compounds and tea catechin affected NPRO formation in the same manner as tea extract, i.e. inhibtion in higher level and promotion in lower level. Thus, it might be concluded that blocking effect on NPRO formation was mainly due to tea polyphenolic compounds especially tea catechin in tea.