Direct transesterification of total fatty acids of adipose tissue, and of freeze-dried muscle and liver with boron-trifluoride in methanol

The purpose of this study was to demonstrate direct transesterification of fatty acids of tissue total lipids with boron-trifluoride in methanol. Adipose tissue, muscle, and liver samples obtained from market-weight lambs, were transesterified with 14% boron-trifluoride in methanol at 80 degrees C. Total lipids of additional samples were first solvent-extracted and then transesterified with 14% boron-trifluoride in methanol, Thin layer chromatographic evaluation revealed quantitative conversion of triacylglycerol- and polar lipid-fatty acids to fatty acid methyl esters using direct transesterification. No differences in fatty acid composition were observed for adipose tissue (p > 0.05), however, for muscle, 20:4 was greater (p = 0.01) with direct transesterification. For liver, greater concentrations of fatty acids were observed for the direct transesterification method (p < 0.02). Weight percentages of adipose and muscle fatty acids were unchanged from 15 to 180 min of direct transesterification; however, 120 and 90 min of direct transesterification were required for adipose tissue and muscle, respectively, for complete transesterification. It was concluded that for analysis of total fatty acids, one-step direct transesterification with boron-trifluoride in methanol is a useful and acceptable procedure. (C) 1997 Elsevier Science Ltd.