Carotenoids carotenoid-derived volatiles

Monoterpene aldehydes, isophorone and isophorone-related compounds have been also found in saffron. Zarghami and Heinz [3] have identified six new isophorone-related compounds listed in Table 1 from ether extracts of saffron by IR, NMR, UV and MS. In the same table are listed the most common volatiles of saffon. The structures of carotenoid derived volatiles found by various researchers are shown below (scheme 3). 

In the natural world, carotenoid oxidation products are important mediators presenting different properties. Volatile carotenoid-derived compounds such as noriso-prenoids are well known for their aroma properties. Examples include the cyclic norisoprenoid P-ionone and the non-cyclic pseudoionone or Neral. Carotenoid oxidation products are also important bioactive mediators for plant development, the best-known example being abscisic acid. Apo-carotenoids act as visual and volatile signals to attract pollination and seed dispersal agents in the same way as carotenoids do, but they are also plant defense factors and signaling molecules for the regulation of plant architecture. 

Tobacco, unlike most other commodities, is not produced as a food crop, but it is used for manufacture of smoking materials and other products. The essential oils in tobacco are important for impact and balance in smoking (11). Smoking pleasure is derived from a balance of nicotine and volatile components. Tobacco chemists and flavorists are certain that carotenoid derivatives contribute to smoke flavor and aroma (5) Over a hundred compounds related to carotenoids have been isolated from tobacco and tobacco smoke. 

Another important class of volatile compounds originating from terpenoids are the cleavage products of carotenoids which have carbon skeletons ranging from C8 to Cl 8 (Fig. 2) [9, 75]. Many of these volatile carotenoid derivatives are key aroma constituents of finits and flowers due to their extremely low aroma thresholds. For example, P-damascenone, found in numerous fruits, has a floral/finity odor with an aroma threshold of a few parts per trillion, making it one of the most potent odorants known... 

Pure essential oils are mixtures of more than 200 components, normally mixtures of terpenes or phenyl-propanic derivatives, in which the chemical and structural differences between compounds are minimal. They can be essentially classified into two groups A volatile fraction, constituting 90-95% of the oil in weight, containing the monoterpene and sesquiterpene hydrocarbons, as well as their oxygenated derivatives along with aliphatic aldehydes, alcohols, and esters and a nonvolatile residue that comprises 1-10% of the oil, containing hydrocarbons, fatty acids, sterols, carotenoids, waxes, and flavonoids. 

In an acid medium, several not very odoriferous oxygenated Ci3-norisoprenoids undergo chemical modifications that may result in the formation of odoriferous /i-damascenone (Skouroumounis et al., 1992 Winterhalter, 1993) (Figure 7.5). Certain non-megastigmane Ci3-norisoprenoids, in particular TDN, are also derived from megastigmanes by chemical modifications in an acid medium (Winterhalter, 1993). However, Ci3-norisoprenoids are mainly present in grapes in the form of non-volatile precursors (carotenoids and gluco-sides). 

Some natural complex matrices do not need sample preparation prior to GC analysis, for example, essential oils. The latter generally contain only volatile components, since their preparation is performed by SD. Citrus oils, extracted by cold-pressing machines, are an exception, containing more than 200 volatile and nonvolatile components. The volatile fraction represents 90-99% of the entire oil, and is represented by mono- and sesquiterpene hydrocarbons and their oxygenated derivatives, along with aliphatic aldehydes, alcohols, and esters the nonvolatile fraction, constituting 1-10% of the oil, is represented mainly by hydrocarbons, fatty acids, sterols, carotenoids, waxes, and oxygen heterocyclic compounds (coumarins, psoralens, and polymethoxylated flavones—PMFs) [92]. 

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