Hamberg M, Liepinsh E, Otting G, Griffiths W
Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
Lipids. 1998 Apr;33(4):355-63. doi: 10.1007/s11745-998-0215-9.
Seeds of oat (Avena sativa L.) were recently shown to contain significant quantities of a new hydroxy acid, (15 R)-hydroxy-(9Z),(12Z)-octadecadienoic acid (trivial name, avenoleic acid). In the present work, avenoleate was found to be mainly (63%) localized in the glycolipid fraction of oat seed lipids. Fractionation of the glycolipids by thin-layer chromatography and reversed-phase high-performance liquid chromatography revealed the presence of a main molecular species which accounted for 20% of the total avenoleate content of oat seeds. Structural studies by chemical methods and mass spectrometry demonstrated that the avenoleate-containing glycolipid was a galactolipid assembled of one molecule of avenoleic acid, two molecules of linoleic acid, two molecules of D-galactose, and one molecule of glycerol. Degradation of the new galactolipid by chemical and enzymatic methods demonstrated the localization of acyl chains, i.e., linoleate at sn-1 and linoleoylavenoleate at sn-2. Nuclear magnetic resonance spectroscopy gave independent support for this structure and also demonstrated that the two galactoses formed an alpha-D-galactopyranosyl-1-6-beta-D-galactopyranosyl moiety which was bound to the sn-3 position. Based on these experiments, the new galactolipid could be formulated as 1-[(9'Z),(12'Z)-octadecadienoyl]-2-[(15''R)-[(9'''Z),(12'''Z)-o ctadecadienoyloxy]-(9''Z),(12''Z)-octadecadienoyl]-3-(alpha-D-g alactopyranosyl-1-6-beta-D-galactopyranosyl)-glycerol. Quantitatively, the amount of the avenoleate-containing galactolipid was of the same order of magnitude as those of individual molecular species of digalactosyldiacylglycerol containing nonoxygenated acyl chains. The content of the new galactolipid in oat seeds was 0.5-0.6 mg per g of seed.
燕麦（Avena sativa L.）种子最近被发现含有大量新的羟基酸，即(15R)-羟基-(9Z),(12Z)-十八碳二烯酸（俗名，燕麦油酸）。在本研究中，发现燕麦油酸酯主要（63%）存在于燕麦种子脂质的糖脂部分。通过薄层色谱和反相高效液相色谱对糖脂进行分级分离，发现存在一种主要分子种类，其占燕麦种子总燕麦油酸酯含量的20%。通过化学方法和质谱进行的结构研究表明，含燕麦油酸酯的糖脂是一种半乳糖脂，由一分子燕麦油酸酸、两分子亚油酸、两分子D-半乳糖和一分子甘油组装而成。通过化学和酶促方法对新的半乳糖脂进行降解，证明了酰基链的定位，即sn-1位的亚油酸酯和sn-2位的亚油酰燕麦油酸酯。核磁共振光谱为该结构提供了独立的支持，还表明两个半乳糖形成了一个α-D-吡喃半乳糖基-1-6-β-D-吡喃半乳糖基部分，该部分与sn-3位相连。基于这些实验，新的半乳糖脂可表示为1-[(9'Z),(12'Z)-十八碳二烯酰基]-2-[(15''R)-[(9'''Z),(12'''Z)-十八碳二烯酰氧基]-(9''Z),(12''Z)-十八碳二烯酰基]-3-(α-D-吡喃半乳糖基-1-6-β-D-吡喃半乳糖基)-甘油。从数量上看，含燕麦油酸酯的半乳糖脂的量与含有非氧化酰基链的二半乳糖基二酰基甘油的各个分子种类的量处于同一数量级。燕麦种子中这种新的半乳糖脂的含量为每克种子0.5 - 0.6毫克。
