The identification of mono-, di-, tri-, and tetragalactosyl-diacylglycerols and their natural estolides in oat kernels

Authors: Moreau, Robert; Doehlert, Douglas; WELTI, RUTH - KANSAS STATE UNIV; ISAAC, GIORGIS - KANSAS STATE UNIV; ROTH, MARY - KANSAS STATE UNIV; TAMURA, PAMELA - KANSAS STATE UNIV; Nunez, Alberto

Submitted to: Lipids Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2008
Publication Date: 5/15/2008
Citation: Moreau, R.A., Doehlert, D.C., Welti, R., Isaac, G., Roth, M., Tamura, P., Nunez, A. 2008. The identification of mono-, di-, tri-, and tetragalactosyl-diacylglycerols and their natural estolides in oat kernels. Lipids. 43:533-548.

Interpretive Summary: We have previously reported that oat kernels and oat oil (obtained by extracting oat flour with hexane or ethanol) contain unusually high levels of a common plant glycolipid called digalactosyldiacylglycerol (DGDG). ARS researchers at Fargo, ND have reported that baking products that include oat flour or oat oil as ingredients may contribute to improving the moisture content of the baked products. In the current study we identified several new types of glycolipids in oat kernels and in oat oil prepared by methanol extraction of oat kernels. In addition to their unique baking properties, oat glycolipids have also been used to make liposomes for pharmaceutical applications. The presence of these new types of chemical structures help to explain some of the pharmaceutical properties of liposomes prepared with oat lipids. Development of high value uses for oat lipids increases the demand and value for oats and could bring more revenue to oat producers and processors.

Technical 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), 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 glycolipids. To our knowledge, this report is the first evidence of natural di- and tri-estolides of polar lipids.