The investigation of ALA trans isomer profile in human plasma by silver ion HPLC in conjunction with GC-NCI-MS

Abstract: Alpha-linolenic acid (ALA) is an essential omega-3 fatty acid. It is the precursor of three long-chain omega-3 fatty acids; docosapentaenoic acid (DPA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), which were reported to be crucial for human body development and function. Furthermore, they are associated with reduction of risk of and mortality from coronary heart diseases (CHD).

Trans ALA are geometric isomers, mainly produced via trans-isomerization of ALA during the industrial refining process. Trans ALA not only pose a risk to cardiovascular health, but may also negatively impact the health benefits derived from consumption of regular ALA. However, information about trans ALA in humans is limited mainly due to the lack of reliable analytical methods.

Here we report a methodology to efficiently separate geometric isomers of ALA in human plasma using silver ion high-performance liquid chromatography (HPLC), with further separation of geometric and positional isomers by gas chromatography (GC). Identification of isomers is confirmed by the comparison of retention times and mass-to-charge ratios with compounds in synthetic standards via negative chemical ionization-mass spectrometry (NCI-MS). This approach allows us to detect and identify eight geometric isomers of ALA (9t12t15t, 9t12c15t, 9t12t15c, 9c12t15t, 9c12c15t, 9c12t15c, 9t12c15c, and 9c12c15c) in plasma samples. Initial investigations suggest that 9c12c15t is the most abundant trans isomer, while 9t12t15t is the least abundant in plasma.

This method allows for detailed analysis of ALA isomers in plasma which can help with better characterizing the effects of these isomers on human health.



Division of Laboratory Sciences, Centers for Disease Control and Prevention, Atlanta, GA, USA