Carvacrol carvone

Studies on the house fly, Muaca domeatica, revealed the considerable acute larvicidal activity of several terpenoids, especially carvacrol and d-limonene (19). Several metamorphosis inhibition effects were also observed, including inhibition of pupal ecdysis, uneclosed pupae, and deformed adults. Numerous compounds exhibited potency in these developmental mortalities camphene, carvacrol, carvone, cineole, citral, citronellal, citronellol, eugenol, farnesol, geraniol, limonene, linalool, B-phellandrene, and a-pinene. Egg hatch was also inhibited by exposure to the terpenoids the most effective ovicidal compounds were carvacrol, citronellal and B-phellandrene, with no acutely toxic effects noted to the embryos, but rather show inhibition of development of the embryo and inability to eclose from the egg... 

Phytochemistry Fruits contain 3-7 % essential oil, 14-22 % fatty oil, and tannins. The essential oil contains limonene, carvacrol, carvone, and other compounds. The flavonoids quercetin, camphorol, isorhamnetin and polyenes were isolated from the aboveground parts and flowers that were collected during the flowering stage (Khalmatov et al. 1984 Turova and Sapozhnikova 1984 lacobellis et al. 2005). 

Carvacrol, carvone, cinnamaldehyde, cinnamon oil, clove bud oil, eugenol, and oregano oil have resulted in a 30%-50% reduction in ammonia N concentration in diluted ruminal uid with a 50 50 forage concentrate diet during the 24 h incubation (Busquet et al., 2006). 

Phenylpropanol Naphthalene Isosafrole Safrole Anethole Carvacrol Carvone Thymol Carvenone Pulegone a-Terpineol Menthol n-Decyl alcohol... 

Heating carvone wilh aqueous sulfuric acid converts it into carvacrol. Propose a mechanism for the isomerization. 

P-Kne = P-Knene Limon = limonene Menth = menthone Puleg = pulegone Carvo = carvone Thym = thymol Carva = carvacrol. 

Heating of carvone in water at 210 °C for 10 min afforded 8-hydroxy-p-menth-6-en-2-one, the equilibrium position favoring the starting material by a factor of 4 1. The hydroxymenthenone, although in equilibrium with the starting material, also underwent elimination of water and isomerization to carvacrol, giving a 1 1 1 mixture of these three substances at 230 °C after 10 min. At 250 °C, for 10 min, carvone isomerized to carvacrol almost quantitatively (Scheme 2.11) [47]. 

By a traditional method, a- and /i-iononcs can be converted to ionene, catalyzed by HI along with small amounts of phosphorus. A cleaner cydization occurred by heating /i-ionone in water at 250 °C in the MBR [50]. In the workup the usual exhaustive washing procedures were unnecessary. Similarly, as mentioned above, carvacrol was prepared almost quantitatively, by isoaromatization of carvone in water at 250 °C for 10 min [47]. A conventional, literature method utilized acidic conditions, took a longer time and proceeded in lower conversion. The above examples show that elevated temperatures under neutral pH conditions can offer advantages over acidic (or basic) reagents at lower temperatures. 

Other reactions shown to occur at the same rate under the two heating methods include the acid-catalyzed isomerization of carvone 40 to carvacrol 41 [33], and ene reactions involving carbonyl enophiles (Scheme 4.21) [32], The former reaction was performed in a mixture of chlorobenzene (slightly polar) and dioxane (nonpolar) and in the latter reaction a large excess of 1-decene was used and so the reaction was effectively performed in a solution of low polarity. 

Ionene, a commercial fragrance, has been prepared traditionally by treatment of a- and /3-iononcs with hydriodic acid containing phosphorus or by distillative heating in the presence of 0.5% iodine. In an unoptimized demonstration, cyclization occurred more cleanly and simply by MBR with /3-ionone in water at 250 °C (Scheme 19) [83]. Work-up also was facilitated, as the need for removal of catalyst or the formation and separation of bi-products was avoided. At elevated temperature, the addition of water to olefins can occur readily, without adding catalyst. (S)-(+)-carvone in water for 10 min at 180 °C afforded optically pure 8-hydroxy-p-6-mcnlhcn-2-one as an intermediate toward carvacrol [84], Addition of water across the 8,9-double bond of carvone occurred regioselectively, by Markovnikov addition. Carvacrol itself was obtained almost quantitatively from carvone at 250 °C after 10 min (Scheme 19) [84]. 

Carveol (5) is one of the minor components responsible for the odour of spearmint, and is easily prepared by reduction of carvone. Isopulegol (6) is prepared from citronellal, as discussed in the section on menthol below, and is a precursor to other materials in the group. The phenols carvacrol (7) and thymol (8) are important in some herbal odour types, but the major use for thymol is as a precursor for menthol q.v. Piperitone (9) and pulegone (10) are strong minty odorants, the latter being the major component of pennyroyal oil. 1,8-Cineole (11) is the major component of such eucalyptus oils as Eucalyptus globulus. These oils are inexpensive and so there is no need to prepare cineole synthetically. Menthofuran (12) is an important minor component of mint oils and can be prepared from pulegone. 

It has been confirmed that selenium dioxide oxidation of car-3-ene gives 42% of the interesting oxabicyclic diene (288)/ together with some carvone, carvacrol, and a,p-dimethylstyrene. 

Properties. The carvones are colorless to slightly yellow liquids. (-l-)-Carvone has a herbaceous odor reminiscent of caraway and dill seeds, whereas (-)-carvone has a herbaceous odor reminiscent of spearmint. Depending on the reaction conditions, hydrogenation of carvone yields either carveols or dihydrocarvone, which are also used as flavor compounds. When treated with strong acids, carvone isomerizes to carvacrol. 

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