Other Monoterpenes

Evidence for de novo synthesis of pheromone components was obtained by showing that labeled acetate and mevalonate were incorporated into ipsdienol by male Ips pini [103,104]. Similarly, labeled acetate and other labeled intermediates were shown to be incorporated into frontalin in a number of Dendroctonus species [105]. Possible precursors to frontalin include 6-methyl-6-hep-ten-2-one, which was incorporated into frontalin by D. ruffipennis [106]. The precursor 6-methyl-6-hepten-2-one also was shown to be converted to bre-vicomin in the bark beetle, Dendroctonus ponderosae [107]. In addition, the expression patterns of HMG-CoA reductase and HMG-CoA synthase are tightly correlated with frontalin production in Dendroctonus jeffreyi [108, 109]. A geranyl diphosphate synthase cDNA from I. pini was also isolated, functionally expressed, and modeled [110]. These data indicate that the de novo isoprenoid biosynthetic pathway is present in bark beetles. A variety of other monoterpene alcohols such as myrcenol, pityol, and sulcitol are probably synthesized through similar pathways [111]... 

Heteropoly acids such as H3PW12O40 (PW) are good catalysts for the hydration of limonene and other monoterpenes. PWs can be used as homogeneous catalysts in solution or supported on, for example, silica or MCM-41 materials. In aqueous acetic acid limonene gives, in the presence of PW, mainly a-terpineol (7) and a-terpinyl acetate (8) [17]. 

This review of the biosynthesis of the bisindole alkaloids of C. roseus is organized along a developing biosynthetic pathway, as far as possible, and relies on the notion that the most sophisticated studies are those utilizing the purified enzyme systems. Biosynthetic studies on the other monoterpene indole alkaloids are not reviewed here. 

Table 6.24, for example, shows one estimate of the annual global emissions of isoprene, other monoterpenes, and VOCs as well as methane (Guenther, 1999). Emissions of isoprene are believed to be about four times those of the other monoterpenes and about equal to all other VOCs. 

The slightly turpentine-like odor and the relatively low solubility of the oil are caused by its high content of a-pinene and other monoterpene hydrocarbons. The main oxygen-containing component is l-terpinen-4-ol [551-556]. 

Turpentine oils extracted from pine resins are now marginal sources of terpenes pinenes, carene and some other monoterpenes are essentially obtained from the paper oils produced in the KRAFT process. Nevertheless this process is based on a treatment of wood chips in sodium sulfide, which leaves significant fractions of sulfur compounds in the paper oils. For the use of terpenes, these sulfur compounds must be eliminated. The process requires ... 

The amount of oil in a sample is determined by Scott oil analysis (AOAC, 1990e). This is a bromination reaction previously used to determine the number of fatty acid double bonds. This titration method quantifies the recoverable oil in fruits and fruit products based on the release of Br2 and the formation of limonene tetrabromide (Braddock, 1999). Figure Gl.5.3 illustrates the chemical reaction for the bromination of limonene. Other monoterpenes (a-pinene and citral) also react however, the method is accurate to within 10 ppm limonene (Scott and Valdhuis, 1966). For this procedure, limonene is co-distilled with isopropanol and titrated with a potassium bromide/bromate solution. 

Actinidine (26) has been isolated from the roots and rhizomes of Valeriana officinalis L.2S Boschniakine (27) has been found in the seeds of Plantago sempervirens its absolute configuration has been established by optical rotatory dispersion comparisons with other monoterpene bases.26 Venoterpine (28) has been found in Striga hermonteca the stereochemistry is as yet uncertain.27... 

Both a- and P-pinenes are popular starting materials for the synthesis of other monoterpene chiral synthons such as carvone, terpineol, and camphor (vide infra). Reactions leading to other monoterpenes are briefly summarized in Figure 5.1. Treatment of a-pinene with lead tetraacetate followed by rearrangement gives trans-verbenyl acetate (7), which is hydrolyzed to yield trans-verbenol (8) 8 Subsequent oxidation of 8 gives verbenone (9), which can be reduced to give cw-verbenol... 

Isomerization of the double bond of geranyl pyrophosphate from to 7 produces neryl pyrophosphate. As shown in Figure 28.3, the carbocation that is formed from neryl pyrophosphate can cyclize to a new carbocation that contains a six-membered ring. Nucleophilic addition of water to this carbocation produces a-terpenol, whereas loss of a proton produces limonene, a monoterpene with a lemonlike odor that occurs in citrus fruits. Further transformations lead to other monoterpenes, such as menthol,... 

Approximately 45 constituents have been determined from fennel seed oil (Fig. 12.1), the main constituents being transanethole (60-65%, but up to 90%), fen-chone (2-20%), estragol (methyl chavicol), limonene, camphene, a-pinene and other monoterpenes, fenchyl alcohol and anisalde-hyde. The major compounds in supercritical... 

In summary, Foeniculum is stated to have three species, F. vulgare (fennel), F. azoricum Mill. (Florence fennel) and F. dulce (sweet fennel). Fennel is widely cultivated, both in its native habitat and elsewhere, for its edible, strongly flavoured leaves and seeds. The flavour is similar to, but milder than, that of anise and star anise. Anethole and fenchone are the major constituents of the solvent extract of seed phenols, free fatty acids, carbohydrates, proteins, vitamins and minerals have been reported in varying proportions. In the mature fruit, up to 95% of the essential oil is located in the fruit, greater amounts being found in the fully ripe fruit. Approximately 45 constituents have been determined from fennel seed oil, the main constituents being frans-anethole, fenchone, estragol (methyl chavicol), limonene, camphene, a-pinene and other monoterpenes, fenchyl alcohol and... 

Increasing the rate of nitrogen fertilizer application affected the relative proportions of some of the essential oil components (Martin et al., 1985). At higher N rates, limonene and other monoterpene concentrations decreased to very low values, while those of sedanolide and phthalides increased to above 75% (D Antuono et al., 2002). 

The essential oil is a pale yellowish green with a sweet, sharp refreshing citrus odour. Its chemical composition is very high in the monoterpene limonene (85-98%) with other monoterpenes P-myrcene (1.2-1.7%),... 

The two C5 pyrophosphates are converted to geranyl pyrophosphate, a C o monoterpene. Geranyl pyrophosphate is the starting material for all other monoterpenes. 

Terpenic compounds are resorbed from the digestive tract and sue situated in the hepatie tissues. Thanks to their ability to dissolve fats, they prevent the formation of cholesterol gathering inside the liver and they also recover proper colloidal state to the bile. Terpenes also enhance the bile content in the hepatic cells and in the liver tracts. Terpenic hydrocarbons dilating the smooth muscles [78, 79] make the hepatic tracts more distended both inside and outside. It has been pointed out that the terpenes contained in Rowachol dissolve bile stones [87-89]. The meehanism of terpenes activity has not as yet been completely explained. It was explained that menthol and other monoterpenes inhibit the activity of the lecithin-cholesterol acyltransferase in the human serum [90]. They also lower the activity of the hepatic S-3-hydroxy-3-methylglutaryl-CoA reductase, which is responsible for the physiological inhibition of cholesterol synthesis in the liver [82, 91, 92]. 

Composition Pinocamphone and iso-pinocamphone (together 40-70%), p-pinene and other monoterpene hydrocarbons, myrtenyl methyl ether, pinocarvone, P-bourbonene, p-caryophyllene, alloaromadendrene, germacrene D, spathulenol, elemol and others. The ISO standard for the essential oil obtained from the leaves is temporarily under... 

Composition p-Mentha-l,3,8-triene is the main constituent, which also constitutes the major aroma carrier 195]. Also other monoterpene hydrocarbons, such as p-phellandrene and l-methyl-4-isopropenylbenzene (a-p-dimethylstyrene), are reported to contribute to the overall flavour profile [196]. Further constituents are a- and p-pinene, myrcene, terpinolene, myristicin, apiol and phthalides. The composition varies significantly based on origin and time of harvest [197, 198[. In some herb oils the occurrence of Diels-Alder adducts between p-mentha-l,3,8-triene, myrcene or itself (molecular weights of 268 and 270) can be observed in considerable amounts (up to 10%) [199, 200[. 

The biosyntheses of other monoterpene hydrocarbons, such as those of sabinene, and (-t-)-car-3-ene, are considered to involve the cyclization of such cyclohexenyl homoallyl cations to three-membered ring derivatives. ... 

Qccurance and Identification. An early report of cotton volatile composition by Minyard et al. (44) involved steam distillation of large quantities of leaves and flowers. Major compounds identified included the monoterpenes a-pinene, B-pinene, myrcene, trans-B-ocimene, and limonene ( 4). Several other monoterpene hydrocarbons were also present in low concentration. Since that report, many other terpenes have been identified in cotton essential oil steam distillates and solvent extracts. These compounds include cyclic hydrocarbons such as bisabolene, caryophyllene, copaene and humulene (45-47), the cyclic epoxide caryophyllene oxide (45), cyclic alcohols such as bisabolol, spathulenol, and the aromatic compound... 

Secologanin (1) of Fig. (1) is the most important representative of the iridoids (la), a special type of cyclopentanoid monoterpenes. (1) belongs the subclass of secoiridoids (lb), in which the bond C-7-C-8 is cleaved [1]. The number of known iridoids is more than 650 [2], The biosynthesis of iridoids like that of other monoterpenes starts from two C5 units (lc) whose precursor was considered to be mevalolactone [3], However, recently it was proved that the biosynthesis of some classes of terpenoids [4,5], and specially of secologanin [6] runned from 1-deoxy-D-xylulose-5-phosphate as an alternative or even main route. 

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