38 植物中のC-配糖体型タンニンおよび加水分解性タンニンオリゴマーの形成について : フウのタンニンその他(口頭発表の部)

抄録

1)Four new hydrolyzable tannins, liquidambin (3), isorugosin A (12), isorugosin B (9) and isorugosin D (13), were isolated from the leaves of Liquidambar formosana. 2) Liquidambin (3), which could be a biogenetic precursor of C-glucosidic tannins, was isolated as an equilibrium mixture. The equilibration was found to be due to hydration of the aldehyde group at C-1 of the glucose residue in 3. 3) Isorugosin D (13), biogenetically producible from two molecules of tellimagrandin II (17), had a valoneoyl group of the orientation different from that of rugosin D (6). Isorugosins A (12) and B (9), monomeric tannins from the same plant, were isomers of rugosins A (4) and B (5) concerning the orientation of valoneoyl group. 4) Rugosins A (4), B (5) and D (6) were absent in L. formosana, and isorugosins A (12), B (9) and D (13) have not been found in Rosa rugosa and Coriaria japonica, which contain 4, 5 and 6. The C-O oxidative coupling in the formation of valoneoyl group in L. formosana, therefore will have been effected by an enzyme different from that of R. rugosa and C. japonica. 5) Cornusiin A, a major component of the fruits of Cornus officinalis, should be formulated as 19, on the basis of the chemical conversion of 19 to isorugosin B (9). Structures of camptothins A and B, which were isolated from the leaves of Camptotheca acuminata, and that of cornusiin C from the Cornus and Camptotheca species, were determined to be 20, 21 and 22, respectively.