Alves Susana P, Bessa Rui J B
CIISA, Faculdade de Medicina Veterinária (FMV), Universidade de Lisboa (ULisboa), Av. da Universidade Técnica, 1300-477, Lisbon, Portugal,
Lipids. 2014 Jun;49(6):527-41. doi: 10.1007/s11745-014-3897-4. Epub 2014 Mar 28.
The "trans-10 shifted" biohydrogenation pathway is frequently established in the rumen when high starch diets are fed to ruminants, resulting in the accumulation of trans-10 18:1 in ruminant products. It has been proposed that the "trans-10 shifted" biohydrogenation pathway of α-linolenic acid generates two intermediates, the trans-10,cis-15 18:2 and trans-10,cis-12,cis-15 18:3, although none of these have been found in the rumen. We analyzed digestive contents and meat samples from two trials, where animals were fed: a compound feed diet supplemented with 8% oil blend containing linseed oil (samples A); and a forage based diet supplemented with 6% linseed oil (samples B). The use of the new SLB-IL111 chromatographic column allowed the detection of two different 18:2 isomers in each sample trial, which could not be resolved when the CP-Sil 88 column is used. The two 18:2 isomers were characterized by mass spectrometry using 4,4-dimethyloxazoline derivatives. However, because they were subject to higher temperatures and present different chromatographic properties compared with the fatty acid methyl esters, we also used the "covalent adduct chemical ionization" technique to confirm the identity of both 18:2 isomers. We detected and identified the 10,15-18:2 in samples A and the 11,15-18:2 in samples B. The geometry of both isomers was tentatively assigned as trans,cis taking in account their elution order and biologic plausibility. As far as we know, this is the first time that the trans-10,cis-15 18:2 has been found in ruminant digestive contents and meat samples associated with the "trans-10 shifted" biohydrogenation pathway of α-linolenic acid.
当给反刍动物饲喂高淀粉日粮时，瘤胃中常常会形成“反式-10 位转移”生物氢化途径，导致反刍动物产品中反式-10 18:1 积累。有人提出，α-亚麻酸的“反式-10 位转移”生物氢化途径会产生两种中间体，即反式-10,顺式-15 18:2 和反式-10,顺式-12,顺式-15 18:3，尽管在瘤胃中均未发现这些中间体。我们分析了两个试验中的消化物和肉类样本，试验动物分别饲喂：补充 8%含亚麻籽油的混合油的配合饲料日粮（样本 A）；以及补充 6%亚麻籽油的草料型日粮（样本 B）。使用新型 SLB-IL111 色谱柱能够在每个样本试验中检测到两种不同的 18:2 异构体，而使用 CP-Sil 88 柱时则无法分离。使用 4,4-二甲基恶唑啉衍生物通过质谱对这两种 18:2 异构体进行了表征。然而，由于它们要承受更高的温度，并且与脂肪酸甲酯相比具有不同的色谱特性，我们还使用了“共价加合物化学电离”技术来确认这两种 18:2 异构体的身份。我们在样本 A 中检测并鉴定出 10,15-18:2，在样本 B 中检测并鉴定出 11,15-18:2。考虑到它们的洗脱顺序和生物学合理性，将这两种异构体的构型初步确定为反式,顺式。据我们所知，这是首次在与α-亚麻酸的“反式-10 位转移”生物氢化途径相关的反刍动物消化物和肉类样本中发现反式-10,顺式-15 18:2。
