Cucumber alcohols

SYNS CUCUMBER alcohol FEMA No. 2780 NONADIENOL 2-crans-6-cis-NONADlEN-l-OL VIOLET LEAF ALCOHOL... 

Synonyms Cucumber alcohol (2E,6Z)-Nona-2,6-dien-1-ol (E,Z)-2,6-Nonadien-1-ol trans-2,cis-6-Nonadien-1-ol Violet leaf alcohol... 

Cucumber cotyledons were inoculated with purified tobacco mosaic virus (TMV) 20 to 24 hours before vacuum infiltration with different concentrations of crude water extracts of plant leaves (4). After 7 days, inoculated leaves were harvested and stored 24 hours in the dark in a moist chamber to remove excess starch. Starch lesions were counted after clearing with alcohol and staining with an iodine-potassium iodide-lactic acid mixture. The inhibitory effects of various extracts were demonstrated by comparing lesion counts of treated cotyledons to counts on control cotyledons. 

The fruit of the cucumber plant Cucumis sativus) is mainly eaten raw or as pickle. Approximately 30 volatile compounds have been detected in the volatile fraction of cucumber, with aliphatic alcohols and carbonyl compounds being most abundant [35]. Fresh cucumber flavour develops as a result of enzymatic degradation of linoleic and linolenic acid rapidly after the tissue is disrupted (Scheme 7.2), by which ( ,Z)-2,6-nonadienal and ( )-2-nonenal mainly are formed [184]. ( ,Z)-2,6-Nonadienal is the main flavour volatile of cucumber fruit, with ( )-2-nonenal as the second most important compound (Table 7.7) [185, 186]. 

RF McFeeters. Single-injection HPLC analysis of acids, sugars, and alcohols in cucumber fermentations. J Agric Food Chem 41(9) 1439-1443, 1993. 

The blossoms of Cucurbitaceae are well known to be highly attractive to many species of Diabrotica beetles. However, the volatile compounds that act as attractants differ in different Diabrotica species. Cinnamaldehyde strongly attracts the spotted cucumber beetle, Diabrotica undecimpunctata hoivardi, whereas 4-methoxycinnamaldehyde is a specific attractant for the western corn rootworm, Diabrotica virgifera virgifera.51 The northern corn rootworm, Diabrotica barberi, and Diabrotica cristata are attracted to eugenol, cinnamyl alcohol, and 2-(4-methoxyphenyl)ethanol. Volatiles of maize, one of the host plants, also attract D. v. virgifera... 

Leaves skeletonized. Cause Leaf-feeding beetles. Japanese beetles are prime suspects here, although other beetles, such as spotted cucumber beetles and rose chafers, may also attack. Handpick or spray with a solution of 1 tablespoon 70 percent isopropyl alcohol to 1 pint prepared pyrethrin mixture. Repeat every 3-5 days until beetles are gone. 

Compound identifications were based on comparison of mass spectral data and co-chromatography of plant components with standards as reported (8,9). A sample of 3,6-nonadien-l-ol was isolated from melon (10) whereas 8,11—heptadecadienal and 8,11,14-heptadecatrienal were obtained from cucumber fruit (11). Of primary interest in the present study is the identification of Cg aldehydes and alcohols including nonanal and nonanol which are effective promotors of wheat rust spore germination. The unsaturated Cg compounds have not been evaluated for activity but their close structural relationships to nonanal and nonanol make them candidates for germination promotors. 

The relative ratios of alcohols and carbonyls for the six-, eight- and nine-carbon volatiles in fish (23-24) and oysters (26) parallel those encountered in cucumber fruits (37) and mushrooms (27, 56) if the two systems are combined. Therefore, the use of plant-based enzyme systems for the controlled generation of fresh seafood flavors and aromas has been under consideration in our laboratory as a means to overcome some of the self-inactivating problems associated with fish lipoxygenases. 

The process of making dill pickles does not differ much from that of making sauerkraut as far as the fermentation is concerned. The sugars of the cucumbers diffuse out of the cut cucumbers into the liquor and are fermented by lactic acid bacteria and alcoholic yeasts. As in sauerkraut, B. coli communis and allied bacteria are active fermenters producing hydrogen and carbon dioxide. Oidium lactic finally grows on the surface of the liquor and reduces the acidity. 

The surprising feature of this fruit is the quantity of six-carbon alcohols and aldehydes. Taken as a group, these conpounds constitute over 70% of the total volatiles. We had fully expected to find a variety of nine-carbon compounds in our essence and we specifically looked for them since they are the major volatiles in other Cucurbitaceae. For exanple, nonanal, 2-nonenal, 6-nonenal and 2,6-nonadienal are some of the major components of cucumber ( ) and 6-nonenol is the major compound in frozen muskmelon ( ). None of these compounds were found if present, they are below the 1% level. 

The enzymic formation of aldehydes, ketones, alcohols, and oxoacids (from linoleic and linolenic acids) on disruption of plant tissues is an important biosynthetic pathway by which fruit and vegetable volatiles are formed. Some examples are (E)-2-hexenal ("leaf aldehyde") and ( )-3-hexenol ("leaf alcohol") in tea (E)-2-hexenal in apples (E,Z)-2,6-nonadienal ("violet Teaf aldehyde") and (E)-2-nonenal in cucumber ( Z)-5-nonenal in musk melon (Z,Z) -3,6-nonadienol in water melon, and 1-octen-3-ol ("mushroom alcohol") in certain edible mushrooms and Fungi. The enzyme system is highly substrate specific to a (Z,Z)-1,4-pentadiene system (like lipoxygenase) splitting the >C = C< double bond at the W - 6 and/or W - 9 position. Therefore linoleic-, linolenic-, and arachidonic acids are natural substrates. It seems to be a common principle in leaves, fruits, vegetables, and basidiomycetes. 

Experiments I to III were carried out under comparable conditions (250 g cucumbers, phosphatebuffer pH 6.8, 40 s homogenization, addition of 100 mg precursors, volatiles were enriched by extraction / or distillation-extraction and determined by GC-MS). It can be seen that linolenic acid is transformed into hexanal, ( )-3-nonenal, pentylfuran, and (E)-2-nonenal in the 40 s trial I and I (I = extraction I = distillation-extraction). During 120 s homogenization the labile intermediate (Z)-3-nonenal decreased from 0.23 mg to 0.02 mg and all carbonyls are reduced to some extent to the corresponding alcohols. 

Chemical examination of the sea cucumber Holothuria leucospilota led to the isolation of a phytosphingosine-type glucocerebroside (40) with a 2-hydroxylated fatty acid of 22 carbons and an anteiso type side chain in the base moiety (Fig. 12) [55]. The absolute configuration of the branched methyl group was determined by release of a C13 fragment of the native cere-broside and further reduction to 10-methyl dodecanol. The absolute configuration of the natural alcohol was elucidated by comparison with synthetic optically active 10-methyl dodecanol synthesized from 1,4-butanediol [56]. 

If the fermented fruit and vegetables are to be distributed unpasteurized, it is essential that all fermentable carbohydrates have been metabolized. Otherwise, a secondary fermentation may occur caused by yeasts and resulting in gaseous spoilage, brine turbidity and probably an alcoholic fermentation. In the case of cucumbers, secondary fermentation may cause bloater formation (Daeschel Fleming, 1984). 

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