[Synopsis] The structures of glycolipids isolated from mushrooms, Hypsizigus marmoreus (Bunashimeji) and Pleurotus citrinopileatus (Nireouma) were determined to be (4E,8E)-N-2-hydroxyhexadecanoyl-1-O-β-glucopyranosyl-9-methyl-C_-sphinga-4,8-dienine (1), phosphodihexose N-(2-hydroxyoctadecanoyl)-4-hydroxy-C_-sphinganine (2), phosphodihexose N-(2-hydroxyhexadecanoyl)-4-hydroxy-C_-sphinganine (3), phosphodihexose N-(2-hydroxytetracosanoy1)-4-hydroxy-C_-sphinganine (4), and phosphodihexose N-(2-hydroxydocosanoy1)-4-hydroxy-C_-sphinganine (5). In particular, location of the double bonds in the long-chain base of 1 was clearly determined by the B/E constant linked scan method. The structure of cerebroside having a long-chain base of 9-methyl-C_-sphinga-4,8-dienine could be determined in general by the presence of characteristic fragment ions of [C_-sphingadienine + H-H_2O]^+at m/z 276 and [C_-sphingadienine + H]^+ at m/z 294, and the fatty acid carbon number could be calculated from the characteristic fragment ion of [ceramide - 180]^+ ([MH - GlcOH - 180]^+) in positive ion mode FAB mass spectrometry. In the structural determination of 2-5, the ions of m/z 421 and 720 in the negative ion mode analyses are assigned to be characteristic peaks of phosphodihexose and phytosphingosine containing phosphodihexose, respectively. This method proved to be useful for the structural determination of unstable natural products such as lipids. （摘要） 機能性天然物分子探索の一環として、食用キノコに含まれる糖脂質の構造解析について研究を行っている。本稿では、ブナシメジ (Hypsizigus marmoreus) および楡黄麻 (Pleurotus citrinopileatus) から得た糖脂質のFAB/MSの構造特性について紹介する。得られた糖脂質の構造は、(4E, 8E)-N-2-hydroxyhexadecanoyl-1-O-β-glucopyranosyl-9-methyl-C_-sphinga-4,8-dienine (1), phosphodihexose N-(2-hydroxyoctadecanoyl)-4-hydroxy-C_-sphinganine (2), phosphodihexose N-(2-hydroxyhexadecanoyl)-4-hydroxy-C_-sphinganine(3), phosphodihexose N-(2-hydroxytetracosanoyl)-4-hydroxy-C_-sphinganine (4) および phosphodihexose N-(2-hydroxydocosanoyl)-4-hydroxy-C_-sphinganine (5) と決定した。特に、これらの構造特性において、長鎖アルキルの不飽和結合の位置、極性部および脂肪酸の種類はB/E一定リンクドスキャン法を用いたFAB/MSを測定することにより容易に決定された
