D-limonene oxide

The GC was calibrated using a mixture of known quantities of d-limonene, d-limonene oxide (cis and trans), 2-octanone, and carvone. GC analyses were performed by injecting 1 pi samples with 1 40 split (column flow split flow), into a Hewlett-Packard 5840A GC equipped with a flame ionization detector. A fused silica capillary column 50m x 0.25 mm i.d., coated with OV-101 as a liquid phase was used. Column temperature was programmed from 50-250 C at 10 C/min, and helium was used as the carrier gas. 

Tanabe el al. studied in detail the catalytic action and properties of metal sulfates most of the sulfates showed the maximum acidity and activity by calcination at temperatures below 500°C, with respect to the surface acidity and the acid-catalyzed reaction (118, 119). Other acid-catalyzed reactions were studied with the FeS04 catalyst together with measurement of the surface acidity of the catalyst the substance calcined at 700°C showed the maximum acidity at Ho s 1.5 and proved to be the most active for the polymerization of isobutyl vinyl ether, the isomerization of d-limonene oxide, and the dehydration of 2-propanol (120-122). It is of interest that the catalyst calcined at a slightly higher temperature, 750°C, was completely inactive and zero in acidity in spite of the remarkable activity and acidity when heat treated at 700°C. 

The dermal allergenic potential of D-limonene oxidation products has been studied. Air-exposed d-limonene was a strong sensitizer in guinea-pig studies and oxidation of D-limonene is necessary for its sensitizing potential, producing potent allergens such as limonene oxide and carvone. 

Low levels of D-limonene in the diet have not been reported to cause adverse effects in humans. D-Limonene can be a dermal sensitizer (see above for discussion about D-limonene oxidation products) however, an 8% solution of D-limonene in petrolatum did not cause an allergic skin response in any of 25 volunteers tested. D-limonene is also a recommended quencher in that it can decrease the sensitizing effect of cinnamic aldehyde when used at a 1 1 ratio with cinnamic aldehyde (International Fragrance Association, that is, IFRA, guidelines developed and used by the fragrance and consumer product industries). There is inadequate evidence in humans for the carcinogenicity of D-limonene, and the overall conclusion by experts is that, as discussed above, D-limonene produces renal tubular tumors in male rats by a non-DNA reactive a-2-globulin-asso-ciated response. Therefore, the mechanism by which D-limonene increased the incidence of renal tubular tumors in male rats is not relevant to humans. 

FIGURE 5.1 Structure of d-limonene, oxidated forms and derived methadienes. 

The isomerization of many terpene oxides (see Section 5.4) has been investigated using a wide range of solid acids (and bases). Arata and Tanabe are responsible for much of this work which includes d-limonene oxide [16], 2- and 3-carene oxide [17], and carvomenthene oxide [18]. 

Grosjean D, EL Williams, E Grosjean, JM Andino, JH Seinfeld (1993c) Atmospheric oxidation of biogenic hydrocarbons reaction of ozone with 3-pinene, D-limonene, and rra -caryophyllene. Environ Sci Technol 27 2754-2758. 

Grosjean, D., E. L. Williams, II, E. Grosjean, J. M. Andino, and J. H. Seinfeld, Atmospheric Oxidation of Biogenic Hydrocarbons Reaction of Ozone with /J-Pinene, d-Limonene, and trans-Caryophyllene, Em iron. Sci. Techriol., 27, 2754-2758 (1993a). 

C. Samples were withdrawn every two days from the samples stored at 45 C and every three days from the samples stored at 37 C. Pulled samples were stored in screw cap vials at 0 C until analsis by gas chromatography (GC). The products were monitored for the formation of limonene-1,2-epoxide and L-carvone, both oxidation products of d-limonene (3). 

TERPENELESS OIL. An essential oil from which the teqoene components have been removed by extraction and fractionation, either alone or in combination. The optical activity of the oil is thus reduced. The terpene-less grades are much more highly concentrated than the original oil (15—30 times). Removal of terpenes is necessary to inhibit spoilage, particularly of oils derived from citrus sources. O11 atmospheric oxidation the specific terpenes form compounds that impair the value of the oil for example, d-limonene oxidazes to carvone and y-terpinene to p-cymene. Terpeneless grades of citrus oils are commercially available. 

Rohr, A.C., Wilkins, C.K., Clausen, P.A., Hammer, M., Nielsen, G.D., Wolkoff, P. and Spengler, J.D. (2002) Upper airway and pulmonary effects of oxidation products of (+)-alpha-pinene, d-limonene, and isoprene in balb/c mice. Inhalation Toxicology, 14 (7), 663-84. 

Terpene = p-pinene, carvone, D-limonene, limonene oxide, myrcene... 

GC-MS. The major compounds were found to be trans-linalool oxide and a-terpineol, whereas the dry black pepper oil contained a- and (3-pinenes, d-limonene and (3-caryo-phyllene as major components. When fresh pepper oil was isolated by distillation and analysed by GC and GC-MS, the compounds were found to be of a different nature to that of fresh pepper aromatic compounds (Menon, 2000). 

Tocopherol was effective and ascorbic acid ineffective in the protection of citrus oils evaluated by aroma (13). In a typical study, 5 g of orange oil was oxidized in 75-mL open brown bottles at 45°C and was evaluated by a panel after 6 d, at which time it was ranked as off-odor, "terpeney. The peroxide value of the initial oil was zero the oxidized material had a PV of 100. As a result, days to reach 100 PV was used as an endpoint. Comparative antioxidant effects on a number of citrus oils and on D-limonene [cyclohexene, l-methyl-4-(l-methylethenyl)-(R)-5989-27-5] are presented in Table X. BHA is the most active while AP has no activity alone but does synergize with tocopherol. 

Various chemical processes of limonene, which lead to the obtainment of useful chemicals and some analytical methods, are based on these reactions. Many flavor chemicals are synthesized from limonene by reaction with water, sulfur and halogens, or hydrolysis, hydrogenation, boration, oxidation and epoxide formation (Thomas and Bessiere, 1989). Hydroperoxides have also been studied and isolated because of their effect on off-flavor development in products containing citrus oil flavoring agents (Clark et al., 1981 Schieberle et al., 1987). Hydration of d-limonene produces alpha-terpineol, a compound that gives off an undesirable aroma in citrus-flavored products. It is also possible to produce alpha-terpineol and other useful value-added compounds... 

Comparative studies with acetaminophen indicate that metabolism in the hamster resembles more closely that in man than in mouse. d-Limonene (32) is metabolized in rat, rabbit and hamster preferentially to C-l carboxylic acid derivatives, whereas dog and man largely form the 8,9-diol, and the guinea pig metabolizes 32 by these two pathways to the same extent . Compound 41 is substantially oxidized by rat and guinea pig, but not man, to biphenylacetic acid this possibly explains the ineffectiveness of 41 in rheumatoid arthritis . Sedative-hypnotic 42 is N-hydroxvIated in the cat, a more... 

In another study, Rhodococcus globerulus PWD8 was found to oxidize D-limonene regio- and enantioselectively via (-t-)-trans-carveol to (+)-carvone [192l... 

A rapid loss of d-limonene, from 70 to 40 ppm for orange juice was observed in the 1 liter carton packs during the first days of ambient (25°C) storage (Fig. 4). Similar results were obtained by others (11,12) who claimed absorption by the film as the cause for this phenomenon. Again, the loss may vary between packages as shown in Fig. 5 The loss of d-limonene can be compensated for by increasing the initial d-limonene concentration. However, as d-limonene is a precursor to oxidative reactions of flavour compounds and since some flavour compounds are absorbed selectively at a higher rate, this is not desirable. 

FIGURE 1.10 Effect of water activity on the oxidation rate constant of D-lknonene for carrier matrices of GA-MD. O Limonene oxide, A carvone. (From Soottitantawat, A. et al., J. Agric. Food Ghent., 52, 1269, 2004a. With permission.)... 

LIMONENE or d/-LIMONENE (138-86-3) Forms explosive mixture with air (flash point 109°F/42°C). Unless inhibited, unstable peroxides may be formed in storage, with possible polymerization. Strong oxidizers may cause fire and explosions. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

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