Lipid Classes and Subclasses of Cold-Pressed and Solvent-Extracted Oils from Commercial Indian Niger (Guizotia abyssinica (L.f.) Cass.) Seed

Lipid classes and subclasses of cold-pressed and solvent-extracted (hexane and ethanol) oils from commercially available niger (Guizotia abyssinica (L.f.) Cass.) seeds were investigated. The oil yield of niger seeds obtained by cold pressing was 28.3 g/100 g while by hexane and ethanol extractions was 38.3 and 29.7 g/100 g respectively. The lipid classification of the extracted niger seed oils showed neutral lipids (65.9–95.5 %), glycolipids (2.7–24.6 %) and phospholipids (1.8–9.5 %). The acylglycerol composition of neutral lipids of extracted niger seed oils showed triacylglycerols (76.9–91.6 %), diacylglycerols (3.9–7.3 %) and monoacylglycerols (0.6–2.5 %). The fatty acid composition of tri-, di-, and monoacylglycerols of extracted niger seed oils showed linoleic acid (66.7–71.6 %) as the major fatty acid. The triacylglycerol composition of neutral lipids of extracted niger seed oils showed trilinolein (39.2–40.3 %) as the major triacylglycerol. The extracted niger seed oils contained 1289.9–6215.8 ppm of total phytosterols with β-sitosterol (41.9–43.7 %) as the major phytosterol. Acylated steryl glucoside (39.5–52.2 %) was the major glycolipid in extracted niger seed oils. Phosphatidylcholine (49.6 and 47.9 %) was the major phospholipid in cold-pressed and hexane-extracted niger seed oils and phosphatidylethanolamine (57.1 %) was the major phospholipid in ethanol-extracted niger seed oil. This is probably the first report on the variations in lipid classes and subclasses of Indian niger seed oil as affected by different modes of oil extraction.     

Regiospecific Enzymatic Oxygenation of <Emphasis Type="Italic">cis</Emphasis>-Vaccenic Acid in the Marine Phototrophic Bacterium <Emphasis Type="Italic">Erythrobacter</Emphasis> sp. strain MG3

The fatty acid composition of the marine phototrophic bacterium Erythrobacter sp. strain MG3 was analysed. The involvement of an unusual enzymatic peroxidation of the allylic carbon 10 of cis-vaccenic acid in this strain was confirmed. This process, which seems to be a characteristic of some aerobic and anaerobic phototrophic bacteria, appeared to also act on the allylic carbon 10 of octadeca-5,11-dienoic acid. Enzymatic degradation of 10-hydroperoxyoctadec-11(cis)-enoic acid resulting from the peroxidation of cis-vaccenic acid mainly involves reduction to the corresponding hydroxy acid (probably catalysed by peroxygenases) and cleavage to the corresponding oxoacid, which is then biohydrogenated. Abiotic degradation of this hydroperoxide involves allylic rearrangement to 10-hydroperoxyoctadec-11(trans)-enoic and 12-hydroperoxyoctadec-10(trans)-enoic acids and cyclisation to the very unusual 7,10-epoxyoctadec-11(cis)-enoic acid. Several tests carried out at different periods of growth and under different growth conditions allowed to show that the induction of this enzymatic peroxidation process strongly depends on the physiological state of the cells and is enhanced during C-limitation and at low temperatures.