IN-VITRO HYDROLYSIS OF NATURAL AND SYNTHETIC GAMMA-LINOLENIC ACID-CONTAINING TRIACYLGLYCEROLS BY PANCREATIC LIPASE

The present study compared the in vitro hydrolysis of two 18:3n-6-rich oils-evening primrose oil (EPO) and borage oil (BO)-and different syn thetic 18:3n-6-containing triacylglycerols (TC). Incubation of EPO and BO with pancreatic lipase lipolyzed 18:3n-6 from the TC species. The rate of lipolysis of TC species containing two or three molecules of 1 8:3n-6, which comprised 36% of total 18:3n-6 in 80 and only 7% in EPO, was significantly slower than those containing only one molecule of 1 8:3n-6. This was round especially in those with two molecules of linol eic acid, which constituted 20% of total 18.3n-6 in BO, whereas over 8 0% were present in EPO. In a separate study, various synthetic 18:3n-6 -containing TC were also subjected to in vitro hydrolysis by pancreati c lipase. Results showed that release of 18:3n-6 from the sn-1/sn-3 po sitions was significantly slower when two other stereospecific positio ns in the same ic molecule were occupied by either palmitic acid (16:0 ) or monounsaturated (18:1 and 20:1) fatty acids than when occupied by 18:2n-6. The rate of hydrolysis of sn-2-gamma-linolenyl-sn-1(3)-diacy lglycerol to form sn-2-mono-gamma-linolenyl glycerol was also signific antly slower when both the sn-l and sn-3 positions in TG molecules wer e occupied by either saturated fatty acids (16:0 and 18:0) or long-cha in monounsaturated fatty acids than when occupied by 18:2n-6. These fi ndings suggest that the stereospecific position of 18:3n-6 in TC molec ules and the constituent of its neighboring fatty acids modulated avai lability of 18:3n-6 from 18:3n-6-containing TG or 18:3n-6-rich oils.