Structure Identification of Triacylglycerols in the Seed Oil of Momordica Charantia L. Var. Abbreviata Ser.

Abstract

AbstractTriacylglycerols (TGs) in the seed oil of Momordica charantia L. var. abbreviata Ser. (MCV) were separated by non‐aqueous reversed‐phase (NARP)‐HPLC. Many of the TGs contain two different fatty acyl chains, such as palmitic (P), stearic (S), oleic (O), linoleic (L), and conjugated linolenic acid (CLn). Seven pairs of AAB/ABA‐type TGs might present in the seed oil of MCV, namely CLnCLnP/CLnPCLn, CLnCLnS/CLnSCLn, CLnCLnO/CLnOCLn, CLnCLnL/CLnLCLn, SSCLn/SCLnS, OOCLn/OCLnO and LLCLn/LCLnL. The positional isomers of a AAB/ABA‐type TGs pair yielded mass spectra showing a significant difference in relative abundance ratios of the fragment ions [AA]+ to [AB]+, which were produced by preferred losses of the fatty acid from the 1/3‐position compared to the 2‐position of the glycerol backbone. The precise stereospecific structures of the predominant regioisomers of TGs in AAB/ABA pairs were identified by atmospheric pressure chemical ionization mass spectrometry (APCI‐MS) according to the special relative abundance ratios of the fragment ions [AA]+ to [AB]+. TGs with CLn occupying the sn‐2 position in seven pairs of AAB/ABA might be major constituents of the oil, such as CLnCLnS, LCLnL, CLnCLnP, and so on. Some of the TGs which were isolated and collected as fractions from the seed oil of MCV by NARP‐HPLC were further analyzed by 13C‐NMR. 13C‐NMR data of type‐AAA TGs containing α‐eleostearic acyl have been complemented.