Lipid Components of Winged Beans

Abstract

Total lipids were extracted from four varieties of winged beans (Psophocarρus tetragonolobus) introduced from Indonesia, Papua New Guinea, and Ishigaki Jima, and separated into neutral, glycolipid and phospholipid fractions. The yields of the total lipids were 16-18%, and the neutral lipid fraction usually amounted to more than 90% of the whole. The ratios of the glycolipid and phospholipid fractions were 1:7:9. The compositions of the lipid classes and fatty acids in the fractions as well as of total sterols were analyzed by thin-layer chromatography on silica gel G followed by densitometry, and gas-liguid chromatography. The neutral lipid fraction consisted of seven lipid classes. Triacylglycerol was predominant among them; free fatty acid and sterols, the next adundant ones, were present at a low level, As polar lipis, eight glycolipids and nine phospholipids were found; the major ones were acylglycosylsterol, glycosylsterol and cerebroside in the former group and phosphatidylethanolamine, phosphatidylcholine and phosphatidylinositol in the latter. Eleven fatty acids from C14 to C24 were identified, among which oleic, linoleic and palmitic acids, particularly the former two, were commonly predominant. Notable amounts of fatty acids with long carbon chains more than C20 such as behenic, lignoceric and eicosenic acids were also detected in the neutral lipid and glycolipid fractions. Proportions of saturated fatty acids (behenic acid, palmitic acid and so on) in the glycolipid fraction were high compared to those in other fractions. As for the positional distribution of fatty acids in triacylglycerol, unsaturated fatty acids, especially Iinoleic acid, were predominant at C-2 of the molecule; behenic and palmitic acids as well as oleic acid were the principal components at C-1 and C-3. The longer chain fatty acids were exclusively located at the C-1 and C-3 positions. Seven component sterols were characterized, among which sitosterol and stigmasterol were predominant.