Correlation between caffeine and total nitrogen in small tea leaf species (var. sinensis) and large tea leaf species (var. assamica).

The caffeine content of various kinds of tea was quantitatively analyzed by the HPLC method. Water and total nitrogen contents were also analyzed and compared with caffeine content in small leaf species (var. sinensis) and large leaf species (var. assamica). The correlation coefficient between dried-caffeine and dried-total nitrogen was 0.93 in small species and 0.92 in large species and the linear one-dimensional regression formula was y=0.47 x+0.77, and y=1.07 x-0.77, respectively. The ratio between caffeine content and total nitrogen content was larger in var. assamica than in var. sinensis. However, both of these tea varieties produced from wild plants, for example Miang, Goishi-cha and Awa-cha, showed very similar values for caffeine and total nitrogen content. Therefore, these results may provide a clue to the origin of the tea plants.