Direct Microwave Transesterification of Fingertip Prick Blood Samples for Fatty Acid Determinations

Abstract

Omega-3 polyunsaturated fatty acid (PUFA) dietary intakes and tissue levels are positively associated with various health benefits. The development of cost efficient, high throughput methodologies would enable research in large clinical and population studies, and clinical fatty acid profiling. Microwave heating for the transesterification of blood fatty acids was examined. Samples were collected by venous puncture and fingertip prick onto chromatography paper. Aliquots of serum, plasma, erythrocytes and whole blood were prepared from venous blood. Boron trifluoride in methanol was used for transesterification but sample preparation and heating varied. Fatty acid determinations and markers of omega-3 fatty acid status including the sum of eicosapentaenoic acid and docosahexaenoic acid, the ratio of total n-3 PUFA to n-6 PUFA, and the percentage of n-3 highly unsaturated fatty acids (HUFA, >or=20 carbons and >or=3 carbon-carbon double bonds) in total HUFA were compared. Quantitative determinations indicate that microwave transesterification results in significantly lower estimates of monounsaturates and polyunsaturates, possibly through incomplete transesterification of triacylglycerols. However, qualitative estimates of omega-3 fatty acid status were relatively similar. Fingertip prick blood collection combined with direct transesterification by microwave may be a very rapid method to estimate omega-3 fatty acid status for selected applications.

Microwave Energy Increases Fatty Acid Methyl Ester Yield in Human Whole Blood Due to Increased Sphingomyelin Transesterification

“…Contrary to our findings with sphingomyelin, at least three previous studies have shown a reduced yield for very-long chain SFA and MUFA with the use of microwave-assisted transesterification both in serum/plasma and whole blood [1,6,16]. Most recently, two studies from one research group using a similar but multi-modal microwave system from the same company found yields of 70-90 % for 20:0, 22:0, 24:0 and 24:1n-9 [6] and 20-70 % for the same fatty acids in an earlier study [16].…”

“…Dried blood spots (DBS) collected by fingertip prick provide fatty acid determinations similar to venous whole blood sampling [1,2], and in recent years have gained in acceptance and been adopted for use in a variety of populations including infants [3,4], the elderly [5] and military personnel [6], among others [2,[7][8][9]. In addition, the % sum of eicosapentaenoic acid (EPA, 20:5n-3) + docosahexaenoic acid (DHA, 22:6n-3) in whole blood can be used as a predictor for risk of sudden cardiac death [10].…”

“…More recently, microwave-assisted direct fatty acid transesterifications have been reported for the conversion of DBS by fingertip prick [1,6,9] and serum [16] lipids into FAME. Although microwave-assisted direct transesterification may fail to fully transesterify triacylglycerols when using 14 % boron trifluoride (BF 3 ) in methanol [1], this may be a limitation of the kitchen-grade microwave utilized in two of the previous studies [1,9]. This potential limitation may be overcome by systems such as the CEM Discover SP-D single-mode [16] or MARS multi-mode [6,16] microwaves specifically designed for laboratory processes (CEM Corporation, Matthews, North Carolina, USA).…”

Biomarker and Dietary Validation of a Canadian Food Frequency Questionnaire to Measure Eicosapentaenoic and Docosahexaenoic Acid Intakes from Whole Food, Functional Food, and Nutraceutical Sources

“…Blood samples were collected by fingertip prick, which has been shown to be an equally good measure of whole blood EPA and DHA as samples collected by conventional venous puncture 30 and reflective of dietary EPA and DHA intake. 31 Participants were asked to consume no food or beverage with the exception of water for 8 to 12 hours and no alcohol for 24 hours before blood sampling.…”

Comprehensive lipidome profiling of Sauvignon blanc grape juice

“…Although a number of methods have been described for fatty acid profiling (Abdulkadir & Tsuchiya, 2008;Akoto, Vreuls, Irth, Pel, & Stellaard, 2008;Armstrong, Metherel, & Stark, 2008;Cantellops, Reid, Eitenmiller, & Long, 1999;Connerth, Grillitsch, Kofeler, & Daum, 2009;Glaser, Demmelmair, & Koletzko, 2010;Mazalli & Bragagnolo, 2007;Paterson & Amado, 1997;Quehenberger et al, 2011;RodriguezPalmero, Lopez-Sabater, Castellote-Bargallo, Dela Torre-Boronat, & Rivero-Urgell, 1997;Ulberth & Henninger, 1995;Wiesman & Chapagain, 2009), they often involve laborious procedures with several extraction steps and a combination of different solvents, anhydrous conditions and freezing cycles, which make sample preparation very time consuming. Moreover, the high sugar content in grape juice poses a significant problem to profile and quantify lipids at their trace levels due to the matrix effect.…”