Citral monoterpene

Figures 1 and 2 show the capillary gas chromatographic analyses of the hydrocarbon and the oxygenated hydrocarbon fractions. In the hydrocarbon fraction, 13 selected monoterpene compounds and sesquiterpene compounds were compared. In the oxygenated hydrocarbon fraction, 22 volatile components, which include aliphatic aldehydes, 2-alkanones, citral, monoterpene alcohols and sesquiterpene alcohols, were compared.

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. 

Lemon peel oil is much more valuable than its juice therefore, extensive research efforts have been expended to determine its natural composition as a way to detect adulteration as well as to determine quality factors [6, 31, 32]. However, a few studies on lemon juice volatiles can be found [33-35]. Lemon oils are notable for possessing relatively low levels of limonene (more than 70%) and relatively high levels of a-pinene (1-2%), -pinene (6-13%), sabinene (1-2%) and y-terpinene (8-10%) [32]. The relatively high concentration of -pinene is thought to instil the green peely odour of lemon oil. The concentrations of aliphatic and monoterpenic aldehydes, (especially citral) as well as those of esters and alcohols are critical components in the perceived quality of the oil. As lemon oil is unstable, quality can deteriorate with improper storage, resulting in... 

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. 

Fig. 8 Monoterpene ketones carvone, geranial, neral, and citronellal together geranial and neral make up citral...

Stingless bees lay chemical trails with mandibular gland constituents which have been identified as normal aliphatic alcohols or monoterpene aldehydes. Trigona spinipes generates a trail with a mixture of 2-heptanol, 2-undecanol, and 2-tridecanol, and it has been possible to successfully lay artificial trails with these alcohols (136). Trail following in workers of Trigona subterranea is released by citral (130), the stereoisomers of which are also utilized as alarm pheromones and defensive compounds. Such pheromonal parsimony appears to be especially typical of eusocial bees and ants. 

The essential oil is a pale yellow with a light, bitter-sweet floral odour. The absolute is darker and more viscous with an odour closer to the original flower. The main chemical components of the essential oil are the alcohol lin-alool (30-37%), the ester linalyl acetate (6-17%) and monoterpenes limonene (12-18%) and [3-pinene (12-15%). Also present geraniol (2-3%), nerol (1-3%), nerolidol (3-6%), citral and jasmone. Both the plant and the essential oil have many established uses. The essential oil is considered to be one of the most effective as a sedative, carmative and antidepressant and often used to treat insomnia. It is also claimed to be relaxant for smooth muscle (internal, involuntary muscles) especially those of the gut. Suitable for all skin types, both the essential oil and hydrolat are versatile materials for the aromatherapist. Considered safe as it is nonirritant and non-sensitizing and an example of a non-phototoxic citrus essential oil. 

Examples of monoterpenes include the linear aldehyde citral, which is found in many essential oils, and the (cis) alcohol geraniol, a major component of oil of geranium. Cyclic monoterpenes include limonene, menthol, pinene, camphor, and carvone, major components of lemon oil, mint oil, turpentine, camphor oil, and caraway oil, respectively. Sesquiterpenes include farnesol, a component of rose oil, and bisabolene, a component of Bisabol myrrh. The diterpenes include phytol, a component of chlorophyll, and vita-... 

Non-cyclic monoterpenes are unsaturated, pleasant-smelling, C]q aliphatic compounds including aldehydes such as citronellal and citral (lemon-scented) the sweet-rose... 

Citral A (Geranial) Citral B(Neral) = trans- cis-3,7-Dimethyl-2,6-octadienal) (monoterpene) Myrcia acris (bay oil) (Myrtaceae), Citrus Andropogon citratus (lemon grass oil) (Poaceae), Rosa spp. (rose oil) (Rosaceae), Citrus lirrwn (lemon peel), C. sinensis (orange) (Rutaceae) [flower], Verbena triphylla (verbena) (Verbenaceae) [antiseptic]... 

D-Bornyl acetate (= Borneol acetate) (monoterpene) Cardenolides (triterpene glycosides aglycones) see Table 4.1 for cardenolide Na+, K+-ATPase inhibitors Citral (= mixture of a-Citral (Geranial) (3-Citral (Neral) = trans-St av-3,7-Dimethyl-2,6-octadienal) (monoterpene) Citronellal (= 3,7-Dimethyloct-6-enal) (monoterpene) a-Farnesene (sesquiterpene)... 

Routes to furan monoterpenes from other monoterpenoids are well known, and the photooxygenation route from myrcene (7) to perillene (849) was discussed in Vol. 4 (p. 561). Using the aldehyde 863 led, by the same route ( 62, then ferrous ion) to perillenal (846). The simplest reported preparation of perillene (849) from a dimethyloctane monoterpenoid precursor is certainly the autoxidation of citral enol acetates (864), yielding 11% of a mixture of perillene (849) and rose furan (848) after passing air through a chloroform solution for 24 hours. 

The substances of different classes of organic compounds - monoterpene hydrocarbons, alcohols, esters, aldehydes, aldehyde-alcohols and phenols were selected as antioxidants. The next substances have been investigated lemonene ( Lluch , Spain), linalool ( Moellhausen , Italy), octyl acetate ( Ventos , Spain), anise aldehyde ( Lluch , Spain), vanillin ( Dinos , China) and eugenol ( Ventos , Spain). All compounds, including test-substance - citral ( Moellhausen , Italy), were characterized by gas chromatography. 

Solution (a) Monoterpenes are compounds which have the general formula of CioHie They can be found in essential oils, resins, and many other natural substances. They are usually made up of isoprene units (2-methyl-l,3-butadiene), joined in a head-to-tail manner. This information tells one that citral has at least one olefinic bond. 

N,H-D1ethylgeranylamine is a key intermediate for the synthesis of industrially important acyclic monoterpenes such as geranyl acetate, linalooi, 8 citral and citronellal... 

In the presence of oxygen, ketyl radicals and those derived from their hydrogen donors are converted to peroxy radicals. Figure 6.15 shows an example of an aldehyde photolyzed in ethanol. These peroxy radicals are often quite susceptible to loss of HOO and subsequent production of hydrogen peroxide (see Equations 4.10 and 4.23 in the Oxidation chapter). Citral (25), a naturally occurring monoterpene aldehyde that is abundant in Citrus species and other plants, has been shown to be phototoxic, perhaps by this mechanism (Asthana et al., 1992). 

Monoterpenes 2 Pinene, nerol, citral, camphor, menthol, limonene, borneol... 

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