Lipid composition of winged bean (Psophocarpus tetragonolobus).

The lipids were extracted from the winged bean (Psophocarpus tetragonolobus) seed with water-saturated n-butanol. Lipids were separated into groups by preparative TLC on silica gel G. The amount of each lipid type was determined by analysis of the fatty acid constituents in each lipid type. Glyceride was the major lipid accounting for 89.6% of the total, followed by an unknown lipid 4%, free fatty acid of 2.3%, 1,3-diglyceride, 1,2-diglyceride and steryl ester as 1% each and finally a polar lipid as 0.2%. The results show that winged bean oil should be suitable for edible purposes. Triglycerides showed a similar profile of fatty acids to those of whole lipid: the major fatty acids were palmitic (10.9%), stearic (4.5%), oleic (37.1%), linoleic (19.0%), eicosenoic (3.6%), behenic (18.5%) and lignoceric (4.2%) acids. Compared to soybean oil, winged bean oil contained long chain fatty acids and a fairly small amount of linolenic acid which is favorable regarding oil stability against autoxidation.