Oxygenated terpenes

Dimerization of Isoprene. Isoprene is becoming an increasingly important raw material for the production of terpenes. For example, myrcene (7) can be produced by the dimerization of isoprene (2-methyl-1,3-butadiene) (42—44) and myrcene is very useful for synthesizing a number of oxygenated terpenes important in the flavor and fragrance industry. 

The severity of these problems is quite sensitive to the nature of the particular organic, as expected, and likely to the particular sampling configuration and conditions as well. For example, Calogirou et al. (1997) showed that saturated oxygenated terpenes adsorbed on Tenax were not affected by the presence of 100 ppb 03 whereas as much as 80-90% of the most reactive, unsaturated compounds reacted. Indeed, no a-terpinene was observed when ozone was present. On the other hand, Koppmann et al. (1995) report no significant interference problems with 03 for the C2-C4 hydrocarbons which were sampled using a heated stainless steel inlet line, which destroys as much as half of the initial ozone, and then cryotrapped. 

Calogirou, A., M. Duane, D. Kotzias, M. Lahaniati, and B. R. Larsen, Polyphenylenesulfide, Noxon, an Ozone Scavenger for the Analysis of Oxygenated Terpenes in Air, Atmos. Environ., 31, 2741-2751 (1997). 

Monocyclic and bicyclic oxygenated terpenes include some familiar and interesting substances such as menthone and menthol from peppermint oil, 1,8-cineole from eucalyptus, and ascaridole, which is a naturally occurring peroxide from chenopodium oil ... 

Higher oxygenated terpenes include the sesquiterpene alcohol, famesol, which has a lily-of-the-valley odor and occurs in ambrette-seed oil. On acid dehydration it gives a-farnesene (Table 30-1) under some conditions, and bis-abolene (a component of oil of bergamot) under others ... 

A number of compounds important to animal physiology have been identified as isoprenoid compounds. Notable examples are vitamin A, retinal (Section 28-7), and squalene (Table 30-1). Also, terpene hydrocarbons and oxygenated terpenes have been isolated from insects and, like famesol, show hormonal and pheromonal activity. As one example, the juvenile hormone isolated from Cecropia silk moths has the structure shown in 3 ... 

Francke W. and Vite J. P. (1983) Oxygenated terpenes in pheromone systems of bark beetles. Z. angew. Entomol. 96, 146-156. 

Renwick J. A. A. (1967) Identification of two oxygenated terpenes from the bark beetles Dendroctonus frontalis and Dendroctonus brevicomis. Contrib. Boyce Thompson Inst, of Plant Res. 23, 355-360. 

The yield and composition of the volatile fraction of the pentane extracts of leaves, stems and seeds of F. vulgare Mill, have been studied by Guillen and Manzanos (1996). The yield obtained from seeds was much higher than that obtained from leaves and stems. The volatile fraction of the pentane extract of the latter two has a higher concentration of terpene hydrocarbons and a smaller concentration of oxygenated terpene hydrocarbons than that of the seeds. Sesquiterpenes and the antioxidant vitamin E have been detected in the leaves and petroselinic acid in the seeds. Saturated aliphatic hydrocarbons with 25 or more carbon atoms have been found in all the plant parts. 

Kubeczka (J58) utilized this general approach to separate a terpene mixture Into oxygenated terpenes, monoterpene hydrocarbons and sesquiterpene hydrocarbons fractions before a final analytical separation. He used a C-18 reverse phase system operated in the semi preparative mode to obtain h1s preliminary separations. The sample fractions were then analyzed by liquid-solid chromatography using deactivated silica gel (4.8% water/n-pentane) at -15 °C. 

Compositions of volatiles in different orange oils are shown in Tables 4 and 5. It is evident that most of the constituents belong to the terpene family and may be arranged into two groups, terpene hydrocarbons (terpenes and sesquiterpenes) and oxygenated terpene products (21). Aside from the volatile components, there are small amounts (2-15%) of nonvolatile residues in citrus peel oils that possess antioxidative property these include coumarins, psoralens, and polymethoxylated flavones (30-34). 

Ethers 2-ethyl-5-hexylthiophene trans-2-nonenal Oxygenated Terpens 3-pentanone... 

Table 2 hRf values of some oxygenated terpenes and other essential oil constituents on silica gel in various eluent systems... 

Today, more than 100 constituents have been identified and the mechanisms for their formation have been explained. The most important classes of volatiles are hydrocarbons, alcohols, aldehydes, esters, phenols, phenol derivatives, oxygenated terpenes and furan derivatives (Boskou 1996, Reiners and Grosch 1998, Morales and Aparicio 1999, Morales and Tsimidou 2000). 

According to Montedoro G. et al [12] and Tiscomia et al [3] different volatile constituents are found in virgin olive oil. They account for approximately 150 compounds of several chemical classes aliphatic and aromatic hydrocarbons, aliphatic alcohols, oxygenated terpens, aldehydes, ethers, ketones, thiophene and furane derivatives, esters (table 1) all these compounds confer on the virgin oil the characteristic aromatic notes. In particular C(> aldehydes and related alcohols (hexanale, cis-3-... 

Bark beetles use oxygenated terpenes as aggregation pheromones. These may be metabolized Irom host compounds, produced de novo following stimulation by host compounds, converted from host compounds by beetle-associated microorganisms, or various combinations thereof. The relevant enzymes, bio-... 

We have incorporated this hypothesis into Fig. 4.14, which is an expanded tritrophic version of Fig. 4.9. The top of this diagram now includes feedback between tunneling, which elicits oxygenated terpene and monoterpene emission and resulting arrival by predators and competitors, and impacts of these predators and competitors on beetle reproduction. Both of these relationships are well supported in the literature. " However, this model also proposes that the spatial and temporal patterns of host availability, in terms of both compromised tree defenses and beetle perception of these alterations, affect natural enemy numbers. Natural enemy populations in turn affect beetle population size, which in turn affects host acceptance behavior (Fig. 4.14 center). 

CDE 2,6-pentyl-3-butyryl-gamma-CD Oxygenated terpenes, alcohols, epoxides... 

CDTA 6-TBDMS-2,3-Acetyl-beta-CD Oxygenated terpenes, aromatics, low volatile... 

While GC-FID is the traditional method for essential oil quantification, GC-MS is the most common analytical method for component identification. However, the wide concentration range of the analytes (from ppb to percentage levels), as well as the presence of numerous isomers (terpenes and oxygenated terpene structures), make qualitative analysis difficult. In addition, the mass spectra of these compoxmds are usually very similar, so peak identification often becomes very difficult and sometimes impossible. 

Essential oils are complex mixtures, constituted by terpenoid hydrocarbons, oxygenated terpenes and sesquiterpenes. They originate from the plant secondary metabohsm and are responsible for their characteristic aroma. 

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