Lipoxygenase alcohols

The lipase-catalyzed fatty acid ester hydrolysis and the lipoxygenation of free polyunsaturated fatty acids are involved in the same lipid degradation pathway. They are respectively the first and second reaction in the lipoxygenase pathway (Fig. 3) [87-91]. The pathway produces volatile products of considerable importance in food technology including Cg[92, 93] or Cg- 94—96 aldehydes and alcohols from polyunsaturated fatty... 

Scheme 7.2 Pathway for the enzymatic degradation of linoleic acid and linolenic acid via the lipoxygenase (LOX) pathway to Ce key aroma compounds in fruits and vegetables responsible for green notes. HPL hydroperoxide lyase, ADH alcohol dehydrogenase...

Melons stored at low temperatures showed different relative amounts of volatiles recovered by solvent extraction [34]. Some of the C9 unsaturated esters and alcohols presumably originated as a result of lipoxygenase activity. The previous results together with some investigations of the C9 unsaturated esters and alcohols suggested that the activity of lipoxygenase on melons seems to be dependent on cultivar, age, storage conditions, and sample location [65]. 

Hexenol ( leaf alcohol ) Linolenic acid Soy lipoxygenase + plant hydroperoxide lyase + baker s yeast 4 g kg 5-101 year (also by isolation from plant oils) Addition of baker s yeast to obtain the alcohol without yeast the aldehyde is the major product [60, 66]... 

Srinivasulu, S. and Rao, A.G.A. 1995. Structure and kinetic thermal stability studies of the interaction of monohydric alcohols with lipoxygenase 1 from soybeans (Glycine max). J. Agric. Food Chem. 43 562-567. ... 

Another application of lipoxygenase (183) is the hydroxylation of unsaturated alcohols (116) via their adipate monoesters (117) where Ris (CH2)4CH3, CH2CH(CH3)2, CH2C6Hb, (CH2)3C6H5, or (CH2)3C(0)CH3. 

Chkaiban, L., Botondi, R., Bellincontro, A., De Santis, D., Kefalas, P., and Mencarelli, F. (2007). Influence of postharvest water stress on lipoxygenase and alcohol dehydrogenase activities, and on the composition of some volatile compounds of Gewiirtztraminer grapes dehydrated under controlled and uncontrolled thermohygrometric conditions. Aust. J. Grape Wine Res. 13,142-149. 

FIGURE 7.6 Short-chain aldehydes and alcohols produced from the degradation of fatty acids in grapes via the lipoxygenase (LOX)/hydroperoxide lyase (HPL) pathway during the prefermentative stages of vinification (adapted from Camara, 2004). 

Soybean lipoxygenase can produce vanillin from esters of coniferyl alcohol (Markus et al., 1992). 

Lipoxygenases play an important role in determining oil quality. The aromas typical of olive oil are due to complex mixtures of volatile compounds those especially abundant are saturated and unsaturated six carbon atom aldehydes, alcohols, and the esters of alcohols, the cited aldehydes and alcohols having sensory properties responsible for the so-called green odour (Hatanaka, 1996). 

The volatile fraction of good quality oils is mainly formed by compounds produced enzymatically from polyunsaturated fatty acids through the lipoxygenase (LOX) pathway. Aldehydes (C6), alcohols (C6) and their corresponding esters are the most abundant products (Figure 2.7). 

This group of compounds is formed from the lipid fraction of the juice, through the sequential action of several enzymes. In Fig. 4.2. the mechanism described by Crouzet (1986) for the formation of cis-3- and tran5 -2-hexanal and their corresponding alcohol is shown. Linolenic acid is a common constituent of grape juice. Through the action of a lipoxygenase enzyme, linolenic acid is transformed... 

Linoleic acid is probably the best substrate for assay. It is readily dispersed at alkaline pH, and at acid or neutral pH it is no more difficult to suspend than the methyl ester or the glyceride. Although some species of lipoxygenase show more favorable action with esters than others, we know of no instance where such enzymes do not also act well on linoleic acid. The poor water solubility of linoleic acid and its changing dissociation in the pH range of interest are a disadvantage and usually require emulsifiers. The sulfate ester of linoleyl alcohol, which does not possess this disadvantage, has been proposed by Allen (108) and appears to be a welcome improvement. 

Scheme 5 Generation of 16- and 9-HPOTEs from linolenic acid by different lipoxygenases. They are reduced to corresponding alcohols.

The formation of Cg aldehyde and alcohols in plant tissues is related to cell destruction. Disruption of intact cells during crushing and milling results in the release of lipid-degrading en2ymes, lipoxygenases and fatty acid hydroperoxide lyase, which cleave the fatty acid moiety to Cg... 

The overall modest yields achieved in these syntheses have recently been markedly improved by the use of the solid-phase copolymer of 4-vinylpyridine (P4-VP) (112) in the formation of the starting di-ynic esters. For example, when a suspension of P4-VP polymer in dichloromethane was stirred with the acid chloride from (1011 and then the propargyl alcohol (114), the ester (1151 was obtained excellent yield. By heating in xylene, (1151 underwent intramolecular cyclization to yield justicidin E(1041 and taiwanin C(1051 as the major products in addition, the isomers helioxanthin (1081 and retrohelioxanthin (1161 could also be isolated (Scheme 22) (113). Increased interest in these four lactone products has resulted from an assay which indicates 5-lipoxygenase inhibitory activity (114). 

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