Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, Bari, Italy.
Centro Interdipartimentale SMART, Università degli Studi di Bari Aldo Moro, Bari, Italy.
Electrophoresis. 2018 Jul;39(13):1634-1644. doi: 10.1002/elps.201700475. Epub 2018 Mar 12.
Hydrophilic interaction liquid chromatography coupled to negative-ion electrospray linear ion-trap multiple-stage MS (HILIC-ESI-MS , n = 2,3) was used to characterize polar lipids occurring in donkey milk. Besides the detection of abundant phospholipids, the structural characterization and content evaluation of minor glycosphingolipids (GSLs) were assessed. We report an unprecedented characterization of 11 hexosyl-ceramides (HexCer), 10 Hex Cer, and 4 Hex Cer. CID-MS/MS spectra in negative ion mode mainly afford information on the monosaccharide number and ceramide constitution (i.e., N-acyl residue and long-chain base), whereas MS/MS/MS spectra on the ceramide anions allow to recognize for each GSL the sphingoid base. The occurrence of sphingosine (S), sphinganine (DS), and phytosphingosine (P) was inferred from the fragmentation patterns. The milk samples exhibit a relatively high number of phytosphingosine substitutes, perhaps because of the feeding of donkeys, mainly based on pasture grass. However, the incidence of hydroxylated species on the α-carbon of the acyl chain was also revealed. The fatty acid composition of N-acyl chains showed high values of long-chain saturated fatty acids such as 20:0, 22:0, 23:0, and 24:0. An average content of GSL is also provided and three representative mono-, di-, and tri-HexCer in donkey milk are the following: HexCer 18:0/24:1 phytosphingosine nonhydroxylated [PN] at m/z 862.6 as chloride adduct [M+Cl] , and content 225.9 ± 2.8 μg 100 mL ; Hex Cer 18:0/16:0 sphinganine nonhydroxylated [DSN] at m/z 862.7 as deprotonated adduct [M-H] , and content 70.8 ± 1.4 μg 100 mL ; and Hex Cer 18:1/24:1 [SN] at m/z 1132.8 as [M-H] , and content 38.5 ± 0.7 μg 100 mL .
采用亲水相互作用液相色谱与负离子电喷雾线性离子阱多级质谱联用（HILIC-ESI-MS，n=2,3）对驴乳中的极性脂质进行了表征。除了检测丰富的磷脂外，还评估了少量糖鞘脂（GSL）的结构特征和含量评估。我们首次报道了 11 种己糖神经酰胺（HexCer）、10 种 Hex Cer 和 4 种 Hex Cer 的特征。负离子模式下的 CID-MS/MS 谱主要提供关于单糖数量和神经酰胺结构（即 N-酰基残基和长链碱基）的信息，而关于神经酰胺阴离子的 MS/MS/MS 谱则允许识别每种 GSL 的鞘氨醇碱基。根据裂解模式推断出鞘氨醇（S）、二氢鞘氨醇（DS）和植物鞘氨醇（P）的存在。从断裂模式中还揭示了 α-碳上羟基化物种的存在。N-酰基链的脂肪酸组成显示出长链饱和脂肪酸如 20:0、22:0、23:0 和 24:0 的高含量。还提供了神经酰胺 GSL 的平均含量，并且在驴乳中发现了三种代表性的单、二和三己糖神经酰胺：HexCer 18:0/24:1 植物鞘氨醇非羟基化[PN]，在 m/z 862.6 处为氯化物加合物 [M+Cl]，含量为 225.9±2.8μg 100mL；Hex Cer 18:0/16:0 二氢鞘氨醇非羟基化[DSN]，在 m/z 862.7 处为去质子加合物[M-H]，含量为 70.8±1.4μg 100mL；Hex Cer 18:1/24:1 [SN]，在 m/z 1132.8 处为[M-H]，含量为 38.5±0.7μg 100mL。
