beta-carotene and trilinolein

Topics: Adenocarcinoma; alpha-Tocopherol; Antioxidants; beta Carotene; Caco-2 Cells; Carbon Dioxide; Chemical Fractionation; Cytotoxins; Fatty Acids; Flavonoids; Fruit; Humans; Lycium; Phenols; Plant Oils; Triglycerides

Lipoxygenase (LOX)-catalysed degradation of polyunsaturated fatty acids is supposed to be a major cause of undesirable off-flavour development in legumes. In the present study, a photometric LOX assay including adequate sample workup was adapted to lupin seeds, kernels and flakes, respectively. Optimum reaction conditions were at pH 7.5 using a phosphate buffer concentration of 150 mmol l(-1) without the addition of sodium chloride. The LOX activities of different lupin species and varieties were compared. Significant variations among the species and varieties ranging from 50 to 1004 units mg(-1) protein were determined, being significantly lower than soybean LOX activity. Hulling and flaking of the seeds resulted in a 15% increase of LOX activity. In contrast to soy and other legumes, LOX from lupin only converted free fatty acids, whereas trilinolein and β-carotene were not oxidised. Consequently, according to the established classification, lupin LOX activity may be assigned to the LOX type-1, which, to the best of our knowledge, was demonstrated for the first time.

Topics: beta Carotene; Fatty Acids, Unsaturated; Glycine max; Hydrogen-Ion Concentration; Lipoxygenase; Lupinus; Seeds; Triglycerides

Primary radicals were generated by UV photolysis of samples of trilinolein, at 77 K and under a controlled atmosphere. The resulting EPR spectra clearly show that the amount of radicals is dependent on the purity of the lipid, the exposure to visible light in the presence of a photosensitizer and oxygen, and, finally, the presence of an antioxidant. These solid state EPR experiments indicate that if all of the elements for the production of singlet oxygen (Rose Bengal, molecular oxygen, and visible light) are not present, primary radicals are practically not generated. They also point out the various steps of the oxidation mechanism: formation of singlet oxygen, which reacts with the lipid to form a hydroperoxide; and photolytic formation of the hydroxyl radical, which reacts with the frozen lipid to generate primary lipidic radicals. This constitutes a new method for investigating lipid oxidation and studying the influence of photosensitizers and molecules that are likely to react with singlet oxygen.

Topics: beta Carotene; Electron Spin Resonance Spectroscopy; Hydroxyl Radical; Lipid Peroxides; Oxygen; Photochemistry; Photolysis; Singlet Oxygen; Triglycerides; Ultraviolet Rays