1979 年 99 巻 2 号 p. 165-171
Various labelled compounds shown in Table I-III were fed to the aerial parts of Swertia japonica which contains four 6-C-glucosylflavones, isovitexin (1), swertisin (2), isoorientin (3) and swertiajaponin (4). Naringenin-3-14C was incorporated not only into 1 and 2 but also 3 and 4, whereas apigenin-4-14C was almost not incorporated into 1 and 2. In contrast, hemiphloin-3', 5'-T2 was incorporated into 1 and 2, but not into 3 and 4. Furthermore, caffeic acid and eriodictyol were found to be as good precursors as naringenin for 3 and 4. Isovitexin-and isoorientin-14C were incorporated into 2 and 4 respectively, but isovitexin-14C was not incorporated into 3. These results revealed that C-glucosylflavones were biosynthesized via C-glucosylflavanone and that 3'-hydroxylation of 3 and 4 occurs at the stage of naringenin prior to C-glucosylation and the 3'-hydroxyl group also can be introduced at that of p-coumaric acid. 7-O-Methylation of 2 and 4 was confirmed to take place at the last stage of their biosynthesis. C-Glucosylation of flavone was briefly discussed.