Original Article

Lipids

, Volume 43, Issue 6, pp 533-548

First online:

The Identification of Mono-, Di-, Tri-, and Tetragalactosyl-diacylglycerols and their Natural Estolides in Oat Kernels

  • Robert A. MoreauAffiliated withUS Department of Agriculture, Agricultural Research Service, Eastern Regional Research CenterCrop Conversion Science and Engineering Research Unit, ERRC, ARS, USDA Email author 
  • , Douglas C. DoehlertAffiliated withUS Department of Agriculture, Agricultural Research Service, Cereal Crops Research Unit
  • , Ruth WeltiAffiliated withKansas Lipidomics Research Center, Division of Biology, Kansas State University
  • , Giorgis IsaacAffiliated withKansas Lipidomics Research Center, Division of Biology, Kansas State University
  • , Mary RothAffiliated withKansas Lipidomics Research Center, Division of Biology, Kansas State University
  • , Pamela TamuraAffiliated withKansas Lipidomics Research Center, Division of Biology, Kansas State University
  • , Alberto NuñezAffiliated withUS Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center

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Abstract

Oat kernels were extracted with methanol, and glycolipid-enriched fractions were prepared using silica solid phase extraction. Using direct infusion electrospray ionization (ESI) tandem mass spectrometry (MS), high performance liquid chromatography (HPLC)-ESI-MS, and HPLC-atmospheric pressure chemical ionization (APCI)-MS, we confirmed previous reports that digalactosyldiacylglycerol (DGDG) was the most abundant glycolipid in oat kernels and confirmed a previous report of the presence of a DGDG mono-estolide in oat kernels. In the current study we also identified several additional natural galactolipid estolides: two new DGDG estolides (di- and tri-estolides), two trigalactosyldiacylglycerol (TriGDG) estolides (mono- and di-estolides), and one tetragalactosyldiacylglycerol (TetraGDG) estolide (mono-estolide). The levels of total galactolipid estolides in oat kernels were estimated to be about 29% of the total glycolipid fraction. To our knowledge, this report is the first evidence of natural di- and tri-estolides of polar lipids.

Keywords

Oat kernels Estolides Digalactosyldiacylglycerol Trigalactosyldiacylglycerol Tetragalactosyldiacylglycerol Galactolipid Mass spectrometry