| 摘要: | Hasegawa and co-workers2) have isolated phellamurin and amurensin from the leaves of Phellodendron amurense Ruprecht, and have offered their chemical structures asⅣ andⅤ, respectively, and after that the structure of phellamurin was corrected as I by enzymatic cleavage method3) and synthetic method4), but there is not any further trial for the structure of amurensin. In order to compare the constituents with the leaves of Phellodendron amurense, the leaves of Phellodendron wilsonii growing in Taiwan were examined, and both phellamurin and amurensin were isolated too. On the other hand, the structure of amurensin was reexamined, and established as 8-isopentenylkaempferol-7-glucoside, epimedoside C (Ⅲ)5), by some color reactions and spectral data, and by identification with the oxidation product of phellamurin.
Amurensin, a yellow needle crystal, showed positive to the reactions with Mg- HC1, FeCl3, and ZrOCl2-Citric acid, and the solution after acid hydrolysis of this substance reduced the Fehling's solution. These properties were characterized for a phenolic flavonoid glycoside with a free hydroxyl group at 3-position. The spectral studies on the UV region of amurensin revealed that the structure was similar to kaempferol. In the presence of sodium acetate, the UV spectrum showed a considerable hypsochromic shift in Band Ⅱand a bathchromic shift in BandⅠ. These properties were characterized for a flavonol which has two hydroxyl groups at 3- and 4′-, but is absent in 7-position6). On the other hand, in the presence of aluminium chloride or aluminium chloride-HCl, the UV spectum of amurensin showed a bathochromic shift, which allowed to presume existence of two hydroxyl groups at 3-and 5-position6) The decoloration of 2% bromine solution by amurensin revealed that it contains an olefinic alkyl substituent. The NMR spectrum of the amurensin acetate: δ1.69 (6H, s, vinyl methyl). 3.49 (2H, d, J=6Hz, arylmethylene), 5.20 (1H, t, J=6Hz, olefinic proton), and 2.43, 2.34, 2.33, 2.06-2.02 (21H, 7×acetyl group), showed that it contains an isopentenyl group, four glucosyl hydroxyl and three phenolic hydroxyl groups. The oxidation of phellamurin (Ⅰ) by Oyamad's method a yellow needle crystal with mp. 275° which was identical with amurensin. Therefore amurensin was recognized as 8-isopentenylkaempferol-7-glucoside (Ⅲ), epimedoside C, which was reported by Takemoto and co-workers5). |
