Lipids biological oxidation

XOR is a cytoplasmic enzyme and a ready source of electrons for transfer to molecular oxygen to form reactive oxygen species such as superoxide and peroxide. It is therefore thought to be involved in free radical-generated tissue injury and has been implicated in the pathogenesis of ischemia-reperfusion damage. Moreover, it has recently been implicated in the production of peroxynitrite (89), and carbonate radical anion (92), both potent biological oxidants. Its exact role in lipid peroxidation, inflammation, and infection needs... 

HDL HDL promote the cholesterol efflux from arterial. In addition, HDL protect LDL from oxidation and induction of subsequent cytotoxicity (Von Eckardstein et al., 2001 Kwiterovich, 1998 Berliner and Heinecke, 1996). This effect is apparently due to the presence of 2 enzymes (paraoxonase and PAF-acetylhydrolase bound to HDL) which may hydrolyse the oxidized lipids of LDL, thus blocking the subsequent biological responses (Hajjar and Haberland, 1997). Moreover, HDL could reduce hydroperoxides to their corresponding hydroxides, or extract oxidized lipids from oxidized LDL (Bonnefont-Rousselot et al., 1999). HDL inhibit oxidized LDL cytotoxicity (Hessler et al., 1979), through inhibition of oxT, DT. -induced stress and calcium rise. HDL act as an anti-oxidant lowering the oxidative modification of LDL, and preventing the cells of arterial wall from the deleterious effect of oxidized LDL, but their precise cellular mechanism of protection still remains unknown. 

Tocopherols and tocotrienols are often discussed as compounds with separate biological, vitamin, and antioxidant functions, although in a comprehensive review of Traber and Atkinson (2007) it was concluded that all of the biological activities of tocopherols and tocotrienols can be understood and derived from their antioxidant activity to protect polyunsaturated lipids from oxidation in membranes. 

Because BLM made of pure lipid or oxidized cholesterol In common salt solutions are nonconducting, the physical properties of BLM are with one exception similar to those of a liquid hydrocarbon layer of equivalent th ckness. The Interfaclal tension of BLM Is less than 5 dynes cm, which Is approximately one order of magnitude lower than that of the hydrocarbon/water Interface. This low Interfaclal tension Is due to the presence of polar groups at the Interface. BLM have negligible permeability for Ions and most polar molecules. Permeability to water Is comparable to that of biological membranes. The permeability to water of Chlorophyll BLM, as determined by an osmotic flew method. Is 50 pm s, which Is in-the range of phospholipid BLM but six times larger than that of oxidized cholesterol BLM. 

Free radicals are very important both in food systems and in biological systems. In food, the process of lipid auto-oxidation and development of rancidity involves a free radical chain mechanism proceeding via initiation, propagation, and termination steps. This lipid peroxidation process is responsible for the development of off-flavors and undesirable chemical compounds in food. In vivo, free radical-initiated auto-oxidation of cellular membrane lipids can lead to cellular necrosis and is an... 

Shimasaki, H., Ueta, N., and Shiga, J. 1998. Ceroid accumulation and in vivo lipid peroxidation in human aorta with atherosclerosis, in Biological Oxidants and Antioxidants Molecular Mechanisms and Health Effects, Packer, L. and Ong, A.S.H. Eds., AOCS Press, Champaign, IL, Chapter 26, 228. 

Another Lauraceae is Laurus nobilis (laurel). The EO obtained from the leaves of wild grown shrubs is characterized by a very high content of eugenol. The biological activities, especially the antioxidative properties, of the extract were studied in different in vitro test methods. The scavenging capacity in the DPPH assay yielded an IC50 value of 0.113 mg/mL. Also the P-carotene bleaching test of the nonpolar fractions was able to protect the lipids from oxidation. After an incubation... 

Riboflavin in its coenzyme forms (FMN and FAD) plays key metabolic roles in biological oxidation-reduction reactions involving carbohydrates, amino acids and lipids, and in energy production via the respiratory chain. These coenzymes also act in cellular metabolism of other water-soluble vitamins through the production and activation of folate and pyridoxine (vitamin Bg) to their respective coenzyme forms and in the synthesis of niacin (vitamin B3) from tryptophan. In addition, some neurotransmitters and other amines require FAD for their metabolism. Recently, Chocano-Bedoya et al. (2011) suggested a possible benefit of high intakes of riboflavin (about 2.5 mg/ day) from food sources on the reduction of incidence of premenstrual syndrome. 

The toxic effects of oxygen can be attributed to its free radical activity. Biological oxidations and auto-oxidations can convert molecular oxygen to the free radical form, superoxide anion (O2 ). Other reactive intermediates include hydrogen peroxide (H2O2) and hydroxyl free radical (OH ). When these forms react with lipids, potent lipoperoxides form, which damage cell membranes and other vital cellular and subcel-lular structures [5]. 

Riboflavin, also called vitamin B2, is stmcturally composed of an isoafloxazine ring with a ribityl side chain at the nitrogen at position 10. This vitamin functions metabol-icafly as the essoitial component of two flavin coenzymes, flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), complexed with proteins, which act as intmnediaries in transfers of electrons in biological oxidation-reduction reactions. Both FAD and FMN function as coenzymes for flavoproteins of flavoenzymes. Flavoproteins are essoitial for the metabolism of carbohydrates, amino acids, and lipids and for pyridoxine and folate conversion to their respective coenzyme forms. 

Studies focused on oxidative and thermal behavior of oils have been performed to investigate quality and stability patterns of oils in foods to investigate lipid and biological oxidation in foods [5-9]. Other authors [10] conducted comparative studies on the oxidative stability of linseed oils. 

Peroxide oxidation processes in human organism are one of based phenomena that is responsible for homeostasis. For this reason development and investigation of interaction mechanism between different biomacromolecules and lipids peroxide are important for forming complete picture of functioning of human being as biological system. 

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