Conjugate diene

The double bonds in a conjugated diene are hydroborated separately, that is, there is no 1,4 addition. However, it is not easy to hydroborate just one of a conjugated system, since conjugated double bonds are less reactive than isolated ones. Thexylborane °(48) is particularly useful for achieving the cyclic hydroboration of dienes, conjugated or nonconjugated, as in the formation of 53." ... 

The work of Sharp and his many co-workers at Edinburgh cannot be underestimated. In a more recent communication they have extended the scope of his cyclisation of diene-conjugated nitrile ylides to triene homologues <96CC2739>. Thus cyclisation of the triene 21 afforded the cyclopropa[c]isoquinoline 22, which on heating gave a mixture of 23 and 24. The isomeric triene 25 also gave 24 as the sole product (Scheme 4). In this instance the intermediate cyclopropane could not be isolated. 

Second-derivative spectrophotometry has been used to monitor the time-dependent production of cis,tmns-(Xmax 242 nm) and trans, tram- (Xmax 232 nm) diene conjugates of microsomal PUFAs following the exposure of rats to carbon tetrachloride (CCU) (Corongui et al., 1986). These signals have been postulated to be derived from mixtures of peroxidized substrates. Previous studies using chemical model systems have established that autoxidation of linolenic or arachidonic acid results in the production of cis, trans- and tmns, trawr-conjugated diene... 

Shaw, S., Rubin, K.P. and Lieber, C.S. (1983). Depressed hepatic glutathione and increased diene conjugation in alcoholic liver disease. Dig. Dis. Sci. 28, 585-587. 

Speisky, H., Bunou, D., Orrego, H. and Israel, Y. (1985). Lack of changes in diene conjugate levels following ethanol-induced glutathione depletion or hepatic necrosis. Res. Commun. Chem. Pathol. Pharmacol. 48, 77-90. 

TBA, thiobarbituric acid reactivity DCs, diene conjugates MA, microangiopathy LP, lipid peroxides DM, diabetic patients C, controls HDL, high-density lipoprotein. 

Collier, A., Jackson, M., Dawkes, R.M., Bell, D. and Clarke, B.F. (1988). Reduced free radical activity detected by decreased diene conjugates in insulin-dependent diabetic patients. Diabetic Med. 5, 747-749. 

Thompson, S. and Smith, M.T. (1985). Measurement of the diene conjugated from of linoleic acid in plasma by high performance liquid chromatography. A questionable non-invasive assay of free radical activity. Chem. Biol. Interactions 55, 357-366. 

Oxidative stress Lipid oxidation Oxygen absorption Manometric, polarographic Diene conjugation HPLC, spectrophotometry (234 nm) Lipid hydroperoxides HPLC, GC-MS, chemiluminescence, spectrophotometry Iodine liberation Titration Thiocyanate Spectrophotometry (500 nm) Hydrocarbons GC Cytotoxic aldehydes LPO-586, HPLC, GC, GC-MS Hexanal and related end products Sensory, physicochemical, Cu(II) induction method, GC TBARS Spectrophotometry (532-535 nm), HPLC Rancimat Conductivity F2-iP GC/MS, HPLC/MS, immunoassays... 

Lipid peroxidation is probably the most studied oxidative process in biological systems. At present, Medline cites about 30,000 publications on lipid peroxidation, but the total number of studies must be much more because Medline does not include publications before 1970. Most of the earlier studies are in vitro studies, in which lipid peroxidation is carried out in lipid suspensions, cellular organelles (mitochondria and microsomes), or cells and initiated by simple chemical free radical-produced systems (the Fenton reaction, ferrous ions + ascorbate, carbon tetrachloride, etc). In these in vitro experiments reaction products (mainly, malon-dialdehyde (MDA), lipid hydroperoxides, and diene conjugates) were analyzed by physicochemical methods (optical spectroscopy and later on, HPLC and EPR spectroscopies). These studies gave the important information concerning the mechanism of lipid peroxidation, the structures of reaction products, etc. 

To illustrate the importance of vicinal connectivity of conjugating units, we consider two dienes in non-vicinal relationships 1,5-hexadiene, 9, and allene, 10. As shown in Table 3.19, the direct diene conjugations are negligible in both species, on account of spatial separation in 9 and symmetry-imposed orthogonality of the two pi planes in 10. Consistently with the essential absence of conjugation, the unsaturated C—C bonds of 9 and 10 have calculated bond orders characteristic of ethylene or other unconjugated systems and the ficc NLMOs have essentially localized character ... 

Oxygenation of 1,3-dienes. Conjugated dienes can undergo an efficient... 

The content of the products of lipid peroxidation (LPO) was determined after 1 h of incubation of the cells in a buffer A at 37 °C. Aliquot of cell suspension (100 pg protein) was treated with heptane/isopropyl alcohol mixture at the ratio of 1 1. The content of Schiff bases in heptane phase was analyzed on fluorimeter RF-510, Shimadzu (Japan) at iexit = 360 nm and Xgms = 420 nm (Kolesova et al., 1984). The content of diene conjugates was determined by spectrophotometry (Gavrilov et al., 1988) at the wavelength of X = 245 nm using spectrophotometer Scinco (Germany). 

Taking into account that ROS produced by irradiated fullerenes C60 may act only in the radius of their short diffusion existence, one may suppose that cytotoxic effect is determined by the interaction of fullerene C60 with the surface of cells and initiation of chain reactions of free radical peroxidation in membranes. That is why the influence of photoexcited fullerene C60 on the course of LPO process was studied and evaluated by the content of generated primary (diene conjugates) and final (Schiff bases) products. The content of diene conjugates in thymocytes was 17.7 4.2, inEAC cells was 21.1 1.3, andinL1210 was 12.8 3.1 nM/mg protein, and Schiff bases -56 7.9,46.5 4.5, and 36.6 4.6 rel. units/mg protein, respectively, and did not alter during 1 h incubation of the cells. 

In the case of photoexcited fullerenes C60 and fullerene C60-containing composites in incubation medium of thymocytes, the indexes of LPO did not alter compared to the control too (Fig. 6.2A). Upon incubation of EAC cells in the presence of photoexcited samples of fullerenes, the decrease in the content of diene conjugates by 35% in the presence of fullerene C60 and by 20% in the presence of fullerene C60-composite-1 and fullerene C60-composite-2 was observed (Fig. 6.2B). The presence of photoexcited samples of fullerenes in the suspension of L1210 cells influenced LPO indexes only in the presence of fullerene C60-composite-2, when the content of diene conjugates increased by 35% (Fig 6.2C). 

Fig. 6.2 Content of diene conjugates (% from control) in thymocytes (A), EAC (B), and L1210 cells (C) after 1 h of incubation in the presence of photoexcited samples of fullerenes (1 - fullerene C60, 2 - C60-composite-l, 3 - C60-composite-2). P < 0.05 compared to the control...

Simultaneous decrease in the content of diene conjugates and increase in the content of Schiff bases evidence the quick shift of pro-/antioxidant equilibrium, generation of reactive radicals, and damage of cell membranes in EAC cells, because Schiff bases, generated as a consequence of interaction of malonic dialdehyde with aminogroups of phospholipids and proteins, are highly reactive compounds causing polycondensation of molecules and formation of intermolecular bonds. 

It has been shown that the influence of photoexcited fullerene C60 on the processes of free-radical oxidation depends on the type of the cell and on the composition of composite. So, in thymocytes in the presence of photoexcited fullerene C60 as well as fullerene C60-containing composites, the content of primary and final LPO products did not alter compared to the control. In malignant cells the intensification of LPO processes was registered, and its level depends on the type of cells. So, in thymocytes in the presence of photoexcited fullerene C60 in suspension of EAC cells the decrease in the content of diene conjugates simultaneously with the increase in the... 

Gavrilov VB, Gavrilova AR, Khmara NF (1988) Measurement of diene conjugants in the plasma blood by UV absorption of heptane and isopropanole extracts. Russian Faboratomoe Delo. 2 60-63. 

Moody DA. 1992. Effect of phenobarbital treatment on carbon tetrachloride- mediated cytochrome P-450 loss and diene conjugate formation. Toxicol Lett 61 213-224. 

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