Michiyo Tsujimura

What sort of research did Dr. Tsujimura do?

After two years doing research in Hokkaido, Tsujimura entered the Riken Foundation (Institute of Physical and Chemical Research). There she had the good fortune to work under the celebrated agricultural chemist Umetaro Suzuki, who had only recently discovered vitamin B₁ and extracted it from rice bran. At Suzuki's urging, Tsujimura focused her research efforts on the green tea commonly drunk in Japan and discovered that it was a source of vitamin C. She proved it by using green tea to cure a guinea pig of scurvy, an ailment caused by vitamin C deficiency and characterized by bleeding from mucous membranes and other symptoms.

What other discoveries did she make?

Michiyo Tsujimura (front center) and Umetaro Suzuki (front right) in a photo circa 1925.

After discovering vitamin C in green tea, Tsujimura took an interest in the uniquely bitter and astringent flavor of green tea and began to search for the ingredient responsible for that taste. In 1929 she succeeded in extracting the component in crystalline form by boiling down a large quantity of tea, and she determined that it was a chemical compound known as a catechin. Catechins, which have properties midway between water-soluble and fat-soluble substances, are released into the hot water from the green tea leaves placed in it. She called this particular catechin "tea catechin," since it had been found in tea and was responsible for its pleasant astringent flavor and sweet aftertaste. In 1934 she found another catechin in tea and named it "tea catechin II." These were later renamed epicatechin and epigallocatechin, respectively, on the basis of their chemical structure.

Tsujimura extracted and crystallized two other substances with a strongly astringent taste and named them tea tannin I and tea tannin II (they were later renamed epicatechin gallate and epigallocatechin gallate). In her paper "On the Chemical Components of Green Tea," she detailed her findings, including the effect of varying quantities of catechins on the taste of different types of teas. Thanks to this highly regarded paper, in 1932 Tsujimura became the first woman in Japan to be awarded a doctorate in agriculture.