73 紅麹変異株由来の新規天然色素の構造と生合成(ポスター発表の部)

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In Japan, a red natural coloring material, which is produced by Monascus anka, has been used as a food additive. During the course of selection of a high yield strain, one mutant strain, M. anka U-1, was found to produce new yellow pigments designated as Y-1 and Y-2. Before using this coloring material as a new food additive more information is needed. Therefore, we attempted the isolation and structural elucidation of the pigments. Physico-chemical properities of Y-1 and Y-2, except for NMR data are shown in Table 1. In addition to the FAB-MS data ^1H-NMR analyses revealed the structural similarity of Y-2 and Y-1 except for the longer side chain (C_7H_<11>) on Y-2. Since NMR studies including CH COSY (Table 2) could not afford further correlations than the subset of the partial structures of Y-1 (Fig. 2), 2D-INADEQUATE experiments were employed to complete the carbon skeleton (Fig. 3). On the basis of the spectroscopic studies the two possible structures of Y-1 were proposed (Fig. 4). Although the structures of Y-1 involved a novel skeleton, which has never been reported, an oxidative cleavage and a successive rearrangement of rubropunctatin, which is normally one of the major pigment in Monascus family, yields the structure of Y-1 (Chart 1). To confirm the structure of Y-1 and the above biosynthetic hypothesis, incorporation experiments of [1-^<13>C] sodium acetate (AcONa) and [1,2-^<13>C_2 AcONa into Y-1 were carried out. The incorporation ratios of carbons in both experiments were almost the same (1.1-1.4%). In the incorporation experiments of [1-^<13>C] AcONa the expected carbons (C, E, I, M, P, Q, R, S, T, U) were enriched. The 2D-INADEQUATE analyses of Y-1 enriched by [1,2-^<13>C_2] AcONa is consistent with the cleavage between carbons J and R and the rearrangement involving carbons J and I. The simultaneous labellings of the adjacent acetate units were observed except for the adjacent units L-S and Q-N (Fig. 5,6). The ratio calculated was about 50%. The lack of C-C coupling between both acetate units suggests that two polyketide chains are biosynthesized independently.
天然有機化合物討論会の論文
1991-09-07

73 紅麹変異株由来の新規天然色素の構造と生合成(ポスター発表の部)

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