Lipid classes, fatty acid composition and triacylglycerol molecular species in the kernels of pumpkin (Cucurbita spp) seeds

The lipids extracted from the kernels of pumpkin (Cucurbita spp) seeds of three cultivars were classified by thin layer chromatography into six fractions: steryl esters (SEs, 0.5-1.2%), triacylglycerols (TAGs, 92.7-93.4%), free fatty acids (FFAs, 2.9-3.S%), sn-1,3-diacylglycerols (1,3-DAGs, 0.4-0.9%), sn-1,2-diacylglycerols (1,2-DAGs, 0.7-0.9%) and phospholipids (PLs, 1.5%). Fatty acids derivatised as methyl esters were analysed by gas chromatography with flame ionisation detection. Molecular species and fatty acid distributions of TAGs, isolated from the total lipids in the kernels, were analysed by a combination of argentation thin layer chromatography (TLC) and gas chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total chain length of fatty acid groups. With a few exceptions, SM2 (5.8-20.1%), S2D (8.8-11.2%), M-3 (6.7-24.8%), SMD (6.8-16.7%), M2D (16.7-23.6%), SD2 (4.6-15.1%) and MD2 (4.9-18.6%) were the main TAG components. These results suggest that there are significant differences (P < 0.05) not only in fatty acid distributions of acyl lipids but also in molecular species of TAGs among the three cultivars. The differences in pumpkin cultivars could be appreciable, based on the distribution of molecular species in TAGs. However, pumpkin seed kernels could be utilised successfully as a source of edible oils for human consumption. (C) 2004 Society of Chemical Industry.