Menthofuran Menthone

Fig. 2 Fluorescence scan of a chromatogram of peppermint oil menthol (1), cineole (2), menthone (3), menthyl acetate (4), menthofuran/terpenes (5).

The oil of Mentha piperita (peppermint) contains cineol, limonene, menthofuran, menthol, and menthone. It has been used as a carminative and antispasmodic for esophageal spasm and irritable bowel syndrome (10). 

Composition 30-55% (-)-menthol, 14-32% (-)-menthone, 1.5-10% (-i-)-iso menthone, 2.8-10% menthyl acetate, 3.5-14% 1,8-cineole, 1-9% menthofuran, up to 4% pule-gone [220], as well as 3-octanol, trans-sabinene hydrate, piperitone, viridrflorol, mono- and sesquiterpene hydrocarbons. For further constituents see [221, 222, 223[. On the differentiation between peppermint oils and the detection of dementholised commint oil as a major adulterant see the results of Lawrence et al. [224], The ratio of 1,8-cineole limonene (min. 2) was even implemented in the European Pharmacopoeia. The latter also limits the isopulegol content for Mentha piperita oil to 0.2%. 

Composition 70-80 % (-)-menthol. The commercially available oils are dementholised and again rectified, contain mainly menthol (33 6%), menthone (18-32%), isomenthone (8-14%) and menthyl esters, and are employed for diluting the more expensive piperita oils. The composition of the unrectrfied oil is similar to that of piperita oil, whereas (E)-sabinene hydrate, viridiflorol and menthofuran are only present in traces. Isopulegol occurs up to 3%. 

Related studies record the change in monoterpene corporation during maturation of Sequoia spp.949 and the similar variations of menthol and its p-glucoside in Mentha.950 Hybridization experiments have shown that the occurrence of 60—90% pulegone in certain strains of Mentha spp. resulted from the lack of the genes necessary to reduce this ketone to menthone or to oxidize it to menthofuran.951 A detailed genetic analysis of menthone-isomenthone production in Mentha spp. has also been described.952... 

Lane 1 menthol, menthone lane 2 menthyl acetate, menthofuran lanes 3- 8 peppermint oils from different manufacturers... 

As in commint oil, the main component of peppermint oil is (-)-menthol (34— 46%) it also contains (-)-menthone (15-27%) and (-)-menthyl acetate (2.5-7 %). However, peppermint oil, unlike cornmint oil, has a higher content of (+)-menthofuran [17957-94-7] (0.5-6%). These data refer to oils of US type oils of other origins (China, India) may have slightly different compositions [628-6331]. 

Plants especially from the Lamiaceae family can inhibit the growth of several weeds by releasing phytotoxic monoterpenes (a-pinene, P pinene, camphene, limonene, a-phellandrene, p-cymene, 1,8-cineole, borneol, pulegone, and camphor) (Angelini et al., 2003). The herbicide effect of 1,4-cineole and 1,8-cineole is also described by Dayan et al. (2012). Plants that are exposed to essential oils often metabolize them, and when citral was added geraniol, nerol and their acids appeared. When citronellal metabolization was tested, citronellol and citronellic acid were formed, and with pulegone (iso)-menthone, isopulegol and menthofuran were found (Dudai et al., 2000). 

Fig. 97. Use of TLC in following the biosynthesis of terpenes in Mentha piperita [43]. Peppermint plants were grown in an atmosphere of COg and radioactive pulegone isolated from the essential oil of these plants, using preparative TLC. This compound was incubated with sections of young leaves from peppermint plant shoots. The autoradiograph of a chromatogram demonstrates formation of menthone (b) and menthofuran (a) from pulegone (c) in this leaf tiussue...

Presumably the most studied essential oil plant is peppermint (Mentha x piperita L.). Already in the 1950s Lemli (1955) stated that the proportion of menthol to menthone in peppermint leaves changes in the course of the development toward higher menthol contents. Lawrence (2007) has just recently shown that from immature plants via mature to senescent plants the content of menthol increases (34.8-39.9 8.2%) and correspondingly the menthone content decreases dramatically (26.8-17.4-4.7%). At the same time, also an increase of menthyl acetate from 8.5% to 23.3% of the oil could be observed. At full flowering, the peppermint herb oil contains only 36.8% menthol but 21.8% menthone, 7.7% menthofuran, and almost 3% pulegone due to the fact that the flower oils are richer in... 

Mentha piperita (-)-Menthol, (-)-menthone, (-)-menthyl acetate, (+)-menthofuran, a-pinene, a-phellandrene. 

Peppermint yields 0.1-1.0% (usually 0.3-0.4%) of volatile oil that is composed mainly of menthol (29 8%), menthone (20-31%), and menthyl acetate (ca. 310%), with smaller amounts of menthofuran (1-7%) and limonene. Other constituents present in... 

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