Hexane, 1-hydroperoxy

Free soybean lipoxygenase 9-Hydroperoxy-acid from y-linolenic acid Hexane-borate buffer pH 6.5(1/1) High production only in presence of anionic surfactants 23... 

Boonprab K, Matsui K, Akakabe Y, YotsukuraN, Kajiwara T (2003) Hydroperoxy-arachidonic acid mediated n-hexanal and (Z)-3- and (E)-2-nonenal formation in Laminaria angustata. Phytochemistry 63 669-678... 

Di (hydroperoxydimethyl)-hexane see 2,5-Bis (hydroperoxy-2,5-dimethyl)-hexane 2 B144... 

Benzolation of 2,5-bis(hydroperoxy-2,5-dimethyl) -hexane yielded the Dibenzoate, C22H2606, fine pltlts(from MeOH), mp 117°, exploding when heated in a flame. Also, there was prepd the Di-p -nitrobenzoate, C22H24N20 0, It yel Ifts, mp 150°, exploding on heating in a flame(Ref 2)... 

T etrame thy I tetramethylene-dihyd roper oxide. See under 2,5-Bis(hydroperoxy-2,5 -dime thyl)) -hexane in Vol 2, B144-R... 

Linoleic acid has two non-conjugated double bonds and consequently the theoretical number of hydroperoxides is higher. The main hydroperoxy-octadienoic acids are 9-HPOD, lO-HPOD, 12-HPOD and 13-HPOD (cf. Fig. 3.29). Further reaction produces among others the odorant aldehydes hexanal (35), 2( )-heptanal (36), 2( )-octenal (37), 2(Z)-octenal (38), 2( )-nonenal (39), 3(Z)-nonenal (40), 2,4( , )-decadienal (41) and 2,4( , Z)-decadienal (42). The potent odorant 41 (odour threshold 0.2 mg/kg... 

Figure 3.6 Oxidative breakdown of hydroperoxy cyclic peroxides of linoleate leading to pentane and hexanal. Reproduced from Min, D. B., Lee, S. H. and Lee, E. C., Singlet oxygen oxidation of vegetable oils, in Flavor Chemistry of Lipid Foods (eds D. B. Min and J. H.

Although LOX from tomato fruits forms predominantly 9-hydroperoxides from linoleic and linolenic acids (Matthew et al., 1977), the cleavage enzyme from tomato does not attack these positional isomers but, rather, is specific for the 13-hydroperoxy isomers, producing hexanal or c/5-3-hexanal, respectively (Galliard and Matthew, 1977). Thus one can rationalize the formation of both Cg and C9 volatiles aldehydes in cucumber extracts with less specificity of LOX and cleavage enzymes and the absence of C9 volatiles in tomato with the substrate specificity of the cleavage enzyme. 

The hydroperoxy epidioxides formed from photosensitized oxidized methyl linoleate are important precursors of volatile compounds, which are similar to those formed from the corresponding monohydroperoxides. Thus, 13-hydroperoxy-10,12-epidioxy-tra 5 -8-enoic acid produces hexanal and methyl lO-oxo-8-decenoate as major volatiles (Figure 4.24). The 9-hydroperoxy-10,12-epidioxy-rrans-13-enoic acid produces 2-heptenal and methyl 9-oxononanoate. Other minor volatile products include two volatiles common to those formed from the monohydroperoxides, pentane and methyl octanoate, and two that are unique, 2-heptanone and 3-octene-2-one. The hydroperoxy epidioxides formed from autoxidized methyl linolenate produce the volatiles expected from the cleavage reactions of linolenate hydroperoxides, and significant amounts of the unique compound 3,5-octadiene-2-one. This vinyl ketone has a low threshold value or minimum detectable level, and may contribute to the flavor impact of fats containing oxidized linolenate (Chapter 5). 

Figure 6.6. Normal phase HPLC isomers of hydroperoxy epidioxide isomers from autoxidized linolenate on microporous 10 jum silica Partisil 10 column, 0.3% ethanol in hexane (v/v) as eluting solvent, variable wavelength detector at 212 nm. From Frankel et al (1981). Courtesy of the American Oil Chemists Society.

The 9- and 13-hydroperoxides of methyl linoleate were separated on a silica column (Z = 205 nm) using a 99.5/0.5 hexane/IPA mobile phase [691]. For the systems that contained vitamin E, only the two peaks were obtained (all the same isomer). However, when the oxidation product was generated without vitamin E present, the appearance of cis-tmns and truns-tmns isomers occurred. Complete resolution of all isomers was not achieved. In all cases elution was complete in 10 min. Similarly, the peroxidation products of linoleic acid, 9- and 13-hydroperoxy-linoleic acids, were separated on a silica column (2 = 234 nm) using a 98/1.9/0.1 hexane/ethanol/acetic acid mobile phase [692]. Elution was complete in < 11 min. The peaks were incompletely resolved. The stock solutions were 4mM. 

Oxygenation by SLO-1 is inhibited by various additives. Some of the reasons are (1) the reduction of active iron from the ferric form to the ferrous form, e,g, by N-alkylhydroxylamine [268], phenyldiazene [269], 2-benzyl-1-naphthol [270], diaryl-N-hydroxyurea [271] (2) oxidation of residues, e.g, methionine residues, by hexanal phenylhydrozone [272] (3) coordination to the active site, e.g. catechol [273], cysteine [274], hydroperoxy acids [275], chelating reagents [276], and Pt complex [277] (4) reaction with the active site, e.g. 12-iodo-ci5-9-octadecenoic acid [278]. In addition, it is reported that leukotriene A4, the electrophilic product of 5-lipoxygenases, irreversibly inactivates the enzyme [279]. 

Many species of plants have hydroperoxide lyase enzymes that cleave fatty acid hydroperoxides into two fragments (11,12). If the substrate is a 13-hydroperoxy fatty acid, then the products are 12-oxo-cls-9-dodecenoic acid and either hexanal or cls-3-hexenal, depending on whether the hydroperoxide was derived from linoleic or linolenic acid, respectively (Fig. 2). 

Hydroperoxy- 5Z,8Z,llZ,13E)-eicosatetraenoic acid (1 -HP0-arachidonic acid) 0 (Hexanal)... 

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