The Biogeneration of Green Odour by Green Leaves and It’s Physiological Functions - Past, Present and Future

(3Z)-Hexenol, which is commonly called leaf al­ cohol, and (2£)-hexenal, also called leaf aldehyde, are widely distributed in fresh leaves, vegetables and fruits. They are mainly responsible for the socalled “green odour” characteristic of leaves, along with other C6-compounds such as (3£")-, and (2£)-hexenols, their corresponding aldehydes (3Z)-, (3£")-hexenals, «-hexanol and «-hexanal. Thus, green odour of green leaves arises from a mixture of the eight volatile C6-compounds. (2E)Hexenal was first isolated from the green leaves of certain bushes by Curtius at Heidelberg Univer­ sity in 1912 (Curtius, 1912). On the other hand, (3Z)-hexenol was found in green tea leaves by A. H ’s former teacher Sankichi Takei at Kyoto Uni­ versity in 1933 (Takei and Sakato, 1933). His inves­ tigations on green odour were carried on until 1942. Since 1957, we have been conducting studies on leaf alcohol, leaf aldehyde and other volatile C6-compounds found in tea leaves, using multidis­ ciplinary approaches including synthetic chemistry, natural products chemistry and physiological bio­ chemistry (Hatanaka, 1993). In the course of our extensive studies, it has also been revealed that the young and fresh green odour of fruits results from a mixture of not only the eight volatile C6-compounds but also eight C9-compounds consisting of (3Z, 6Z)-, (2£, 6Z)-nonadienols and (3Z)-, (2E)nonenols, and their corresponding aldehydes (Ha­ tanaka et al., 1975). (3Z, 6Z)-Nonadienol is char-