10 バラ花弁の新規色素Rosacyanin類の構造(口頭発表の部) 10 Structures of two novel pigments, Rosacyanin A and B isolated from petals of Rosa hybrida
Rose breeders have failed to make blue roses. This has been attributed to the lack of blue pigment in the petals. We revealed that mauve rose such as "M'me.Violet" and "Lavande" contain a small amount of blue pigment other than a red anthocyanin, cyanidin 3,5-diglucoside. The major blue pigment of the rose named Rosacyanin A and the minor red one was named Rosacyanin B. The structures of these pigments were elucidated. A high-resolution mass spectrometry showed that Rosacyanin B had the molecular weight of 419.0409 and molecular formula of C_<22>H_<11>O_9. The NMR data showed that Rosacyanin B had an extremely unique structure whose C-1 position of gallic acid is bound to the C-4 position of cyanidin by C-C bond formation. (Fig.2) Rosacyanin A has λ max 590nm (MeOH) of the ultraviolet and visible absorption spectrum, and a molecular formula of C_<56>H_<37>O_<31> which is calculated from the molecular weight of 1205.1319 obtained from high-resolution mass spectrometry. As a result of the observation of the isotope shift by the DH exchange of the solvent using a coaxial sample tube in ^<13>C NMR, it was found that the 3-position of flavylium of Rosacyanin B is bonded to the hexahydroxydiphenoyl part of Tellimagrandin II which is a kind of ellagitannin with ether linkage. (Fig.4) To our knowledge, this is the first report of the compound whose gallic acid binds to C-4 position of polyhydroxyflavylium. The only similar compound which binds gallic acid to catechin was obtained from Burkea africana and Peltophorum africanum. The dream of blue roses will come true if we can accumulate Rosacyanin A in rose petals.
天然有機化合物討論会講演要旨集 42(0), 55-60, 2000