Studies on Biogeneration of Plant Flavor and Its Physiological Function

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A-I Group i)With investigating substrate specificities of lipoxygenase and fatty acid hydroperoxide lyase, reaction mechanism of these two enzymes were elucidated. From the results, factors who control the emission of "Green odor"could be analyzed in detail. These investigation led us to know the physiological roles of "Green odor". ii) How plants respond to stresses? Pea seedlings which were grown in a growth chamber were used. When lowest leaves of the seedlings were stressed with wounding, the upper leaves responded and formed C6-aldehydes. With these investigations, we obtained several novel findings and interesting facts which are very important to a scientific field of plant physiology. iii)Th amounts of C6-aldehydes which are major constituents of "Green odor" are very low in intact plant tissue, while, upon homogenizing the tissue, these aldehydes are rapidly formed. Because high activities of enzyme systems involved in C6-aldehyde formation could be detected in vitro, these en … More zyme systems are thought to present in intact plant tissue as latent forms. Activation of the latent-form enzyme systems should be occurred rapidly after homogenization. Precise analyses on this phenomenon revealed the mechanism controlling the activity state of this enzyme system. iv)Amounts of C6-aldehydes emitted from and formed in tea leaves have analyzed. The rate of emission of aldehydes increased temporally during May. Interestingly, the composition of aldehydes emitted from tea leaves differed from that of stored in the leaves.A-II Group Distribution of enzyme activity forming seaweeds flavor : Conversion of fatty acid to long chain aldehyde in sea algae has been extensively investigated. It has been revealed that the long chain aldehydes are emitted from tissues to sea-water. This fact indicates that these aldehydes have significant roles in sea-ecology.A-I, C Co-operative group Most of flavor compounds of plant origins are thought to be formed from carotenoids. As a model experimental system, cooxidation activity of soybean lipoxygenase has been studied with a polyene compound, retinoic acid. With these studies, reaction mechanism of cooxidation has been clarified.B, C Co-operative group The amounts of flavor compounds are generally very low. Thus, it is very difficult to determine stereo chemistry of these flavor compounds. P.Schreier and his co-workers in Wurzburg University have been tried to determine stereo chemistry of volatile compounds found in grapes as aglycons. We, with co-operating, discussed about a methodology to determine stereo chemistry of a compound of small amount, and decided to used chiral GC analyses and two-dimensional GC analyses. With this strategy, absolute configurations of a group of linalool-like compounds have been determined. Less