1,8-Cineole monoterpene

Miyazawa, M., M. Shindo, and T. Shimada, 2001b. Oxidation of 1,8-cineole, monoterpene cychc ether originated from Eucalyptus polybractea, by cytochrome P450 3A enzymes in rat and human hver microsomes. Drug Metab. Dispos., 29 200-205. 

Included in the table are data for L. scoparium obtained from five sites in Australia. The Australian material exhibited a level of a-pinene approaching that of the northern race from New Zealand, but was clearly characterized by the highest level of 1,8-cineole observed in the study, along with the highest value for total monoterpenes and lowest value for total sesquiterpenes. The authors noted the need for further taxonomic study, particularly of the Australian material. 

To identify the volatile components, gas chromatography-mass spectrometry (GC-MS) is still the method of choice. A comparison of the GC fingerprints of B. carter a and B. serrata reveals the different composition of the volatile fractions (Figure 16.1). Common monoterpenes, aliphatic, and aromatic compounds of olibanum are, e g., pinene, limonene, 1,8-cineole, bomyl acetate, and methyleugenol (Figure 16.2). 

Chen F, Ro DK, Petri J, Gershenzon J, Bohhnann J, Pichersky E, Tholl D (2004) Characterization of a root-specific Arabidopsis terpene synthase responsible for the formation of the volatile monoterpene 1,8-cineole. Plant Physiol 135 1956-1966... 

The monoterpene fraction was predominantly made up of 1,8-cineole. The chromene fraction was predominantly made up of encecalin and eupatoriochromene. 

In addition to monoterpene hydrocarbons, this oil contains up to 35% 1,8-cineole. 

Many of the monoterpenes found in essential oils of plants also occur as pheromonal substances in insects (45,57-60) and are often involved in plant-insect interactions. Some compounds found both in plants and insects are the monoterpenes citronellal, cit-ronellol, geraniol, myrcene, citral, 6-phellandrene, limonene, 2-terpinolene, a-pinene, 6-pinene, 1,8-cineole, and verbenone. 

Cineole 42 as well as 1,4-cineole 43 are cyclic ethers (Structure 4.10). All including ascaridol 44 are bicyclic oxygenated monoterpenes. Their formation can be seen in Fig. 4.3. 

Chemical structure-activity relationships suggested that phenolic monoter-penes (thymol, methyleugenol) seemed to be the most active, followed by alcohols (terpineol) and other oxigenated monoterpenes (1,8-cineole) [225, 229, 230]. Within the monoterpenes, -pinene was more active than a-pinene [226], and a-pinene was more active than caryophyllene and myrcene [234]. 

Important aroma compounds of black currant berries have been identified mainly by GC-O techniques by Latrasse et al. [119], Mikkelsen and Poll [115] and Varming et al. [7] and those of black currant nectar and juice by Iversen et al. [113]. The most important volatile compounds for black currant berry and juice aroma include esters such as 2-methylbutyl acetate, methyl butanoate, ethyl butanoate and ethyl hexanoate with fruity and sweet notes, nonanal, /I-damascenone and several monoterpenes (a-pinene, 1,8-cineole, linalool, ter-pinen-4-ol and a-terpineol) as well as aliphatic ketones (e.g. l-octen-3-one) and sulfur compounds such as 4-methoxy-2-methyl-butanethiol (Table 7.3, Figs. 7.3, 7.4, 7.6). 4-Methoxy-2-methylbutanethiol has a characteristic catty note and is very important to blackcurrant flavour [119]. 

Romagni, J. G., Duke, S. O. and Dayan, F. E. 2000. Inhibition of plant asparagine synthetase by monoterpene cineoles. Plant Physiol. 123, 303-313... 

A large number of monoterpenes have been reported to be phytotoxic, and they have been proposed as potential starting structures for herbicides.44 Nevertheless, of the monoterpenes, we only know anything of significance about the mode of action of the cineoles. Early work showed that relataively high concentrations of 1,8-cineole (Fig. 10.1) inhibit mitochondrial respiration of isolated... 

Quantitative chromatographic analysis of the composition of distilled essential oil was reported previously by Nigam and Purohit (1960) and by Lawrence (1970). The major constituent of large cardamom essential oil is 1,8-cineole (65-80%), while the content of a-terpenyl acetate is low (traces to 5%). The monoterpene hydrocarbon content is in the range of 5-7%, of which limonene, sabinene, terpinene and pinene are significant components. The terpinols comprise approximately 5-7% of the oil. The high cineole and low terpenyl acetate probably account for the very harsh aroma of this spice in comparison with that of true cardamom (Pruthi, 1993). 

Analysis of the steam-distilled volatile oil of the seeds of the large cardamom grown in Sikkim, India, using GC-MS, identified 25 components, of which 16.3% was monoterpene hydrocarbons and 75.3% was oxygenated monoterpenes, with 1,8-cineole [eucalyptol] (61.3%) being the major component. a-Terpineol, a- and (3-pinene... 

It contains the same aroma compounds as nutmeg but in smaller amounts, mainly monoterpenes (87.5%), monoterpene alcohols (5.5%) and other aromatics (7%). Like nutmeg essential oil, the main constituents of mace essential oil are sabinene, a-pinene, (3-pinene, myrcene, limonene, 1,8-cineole, terpinen-4-ol, myristicin, y-terpinene and safrole. Mace oil is more expensive than nutmeg oil. 

Figure 5.3 shows the typical arrangement of a mass spectrometer. Figure 5.4 shows MS charts for the two monoterpenes [ ]-pinene and limonene, and the oxide 1,8-cineole. 

Figure 5.4 Mass spectra. The monoterpenes -pinene (A) and limonene (B) both have the molecular formula C10H16 and their mass spectra are similar however, the obvious differences at m/z 68 and m/z 93, coupled with accurate and reproducible retention times from GC, enable an identification for each compound. (C) The oxide eucalyptol (1,8-cineole), with molecular formula C H, produces this characteristic pattern when analyzed by mass spectrometry. MS data supplied by Bill Morden of Analytical Intelligence Ltd.

There are a number of allelochemicals among the mono-, sesqui-, and diterpenoids. In particular, plants in arid and semiarid regions produce diverse volatile terpenoids with allelopathic activity.5 Among the volatile monoterpenes, 1,8-cineole (4) and camphor (5) exhibit strong growth inhibitory effects on plants and are considered to be involved in plant competition. 1,4-Cineole (6), a minor isomer of 1,8-cineole, is a potent inhibitor of asparagine synthetase.6 -Menthane-3,8-diols (fir 7 and frw .r8), -menth-2-en-l-ols (cis 9 and trans 10), thymol (11), carvacrol (12), 1,8-cineole, cr-pinene (13), and /3-pinene (14) were isolated as allelopathic monoterpenes from Eucalyptus species.7 Eucalyptus trees also produce allelopathic sesquiterpenes including spathulenol (15), and a-, (3-, and 7-eudesmols (16-18).7... 

Defensive Compounds. Larvae of the weevil Oxyops vitiosa produce a shiny orange secretion that covers their integument and probably acts as deterrent against ants [420]. The composition of the secretion resembles the terpenoid pattern of the host foliage (Melaleuca quinquenervia) from where it is sequestered (concentration about twice that of the host foliage). It contains the sesquiterpene (+)-viridoflorol 230 (Scheme 25), the monoterpene hydrocarbons a-pinene 45, P-pinene 46, limonene 171, a-terpinene 231, and y-terpinene 232 as well as the oxygenated monoterpenesl,8-cineole 58, a-terpineol 233, and terpinen-4-ol 234. 

Mono- and bi-cyclic monoterpenes containing sites of unsaturation tend to be hydroxylated at the allylic position, (more examples of allylic hydroxylation are discussed in Section 1.4.5.2) with regio-isomers occurring if more than one allylic position is accessible. Some illustrative examples of reported hydroxylations are shown in Scheme 10. " The hydroxylation of 1,4-cineole (42) is illustrative of the enantioselectivity that may be achieved in such transformations. Bacillus cereus gives a 1 7 mixture of 2R)-exo- and (25)-e/tdo-monohydroxy-1,4-cineole, both with essentially 100% enantiomeric purity. ... 

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