E-p-Ocimene

C1 p-Myrcene C2 a-Myrcene C3 (Z)-a-Ocimene C4 (E>a-Ocimene C5 (Z)-p-Ocimene C6 (E)-p-Ocimene... 

Bell pepper Capsicum annuum, Solanaceae), also known as sweet pepper, pepper or capsicum, and chilli pepper (C. frutescens), contains as the key compound 2-isobutyl-3-methoxypyrazine (8-175), which carries the typical sharp spice-like odour of fresh vegetables and has an extremely potent odour. Other major components identified include terpenic hydrocarbons and alcohols, such as (E)-P-ocimene, hmonene and linalool, methyl salicylate, aldehydes (2 ,6Z)-nona-2,4-dienal (as in cucumbers) and (2 ,4 )-deca-2,4-dienal and (Z)-hex-3-en-l-ol produced from unsaturated fatty acids. 

The sensory properties of black pepper oil obtained by steam distillation of ground peppercorns were analysed with the aid of column chromatography, high-resolution GC and GC-MS. A total of 46 compounds were identified, including (EJ-p-ocimene, 8-guaiene, (Z)(E)-farnesol, 8-cadinol and guaiol, which are reported for the first time as volatile compounds of the essential oil. Sabinene and terpinen-4-ol appeared to be the most important contributors among the volatile compounds to the characteristic odour of black pepper oil (Pino et al., 1990). 

Monoterpenic hydrocarbons found in foods are hnear (acychc), monocyclic, bicyclic and tricyclic compounds. Linear monoterpenes are mainly present in fruits and essential oils. Examples of common hydrocarbons are myrcene (fl-myrcene, 8-1) and ocimene (P-ocimene, 8-1), which occurs in two stereoisomers, as traws-isomer (E)-ocimene and as cis-isomer (Z)-ocimene. 

Among the leafy spices, 45 aroma volatiles of desert parsley have been identified, with the major constituents as myristicin, apiole, /3-phellandrene, p-mentha-1,3,8-triene and 4-isopropenyl-l-methylbenzene (MacLeod eta/., 1985). Among these, apiole in particular has a desirable parsley odour character. The leaf stems of celery show three main constituents of volatiles, e.g. apiole (about 23%), 3-butylphthalide (about 22%) and sedanolide (about 24%). The last two possess a strong characteristic celery aroma (MacLeod et al., 1988). Limonene (40.5%), P-selinene (16.3%), cis-ocimene (12.5%) and P-caryophyllene (10.5%) are some of the volatile oil constituents present in celery leaves from Nigeria (Ehiabhi et al., 2003). 

The curry leaf plant is highly valued for its characteristic aroma and medicinal value (Philip, 1981). A number of leaf essential oil constituents and carbazole alkaloids have been extracted from the plant (Mallavarapu et al., 1999). There are a large number of oxygenated mono- and sesquiterpenes present, e.g. c/s-ocimene (34.1%), a-pinene (19.1%), y-terpinene (6.7%) and P-caryophyllene (9.5%), which appear to be responsible for the intense odour associated with the stalk and flower parts of curry leaves (Onayade and Adebajo, 2000). In fresh bay leaves, 1, 8-cineole is the major component, together with a-terpinyl acetate, sabinene, a-pinene, P-pinene, P-elemene, a-terpineol, linalool and eugenol (Kilic et al., 2004). 

The reactions of metal complexes of monoterpenes continue to be actively explored and many specific examples will be found in later sections. Of general interest are the dimerization of 7r-allyl-Pd complexes of a- and p-pinenes and of carvone that are effected by irradiation at 366 nmM and the thermal decompositions of (TC-allyl)nickel halide complexes of, e.g., isoprene (33), to form myrcene.95 Hydrosilylation of 1,3-dienes e.g. isoprene, myrcene, ocimene) was found to be a regiospecific 1,4-addition for Pd complexes but followed the alternative route for Rh compounds a good discussion is appended.96 A series of dimers of isoprene... 

Figure 2. Structures of terpenoids chemically formed from linalool (1 ) at pH 3.5 (cf. Fig.1-4). (2) 2,4(8)-p-menthadiene (3) B-myrcene (4) a-phellandrene (5) cx-terpinene (6) limonene (7) B-phellandrene (8) (Z)-ocimene (9) y-terpinene (10) (E)-ocimene (11) p-cymene (12) terpinolene (13) (E,Z)-alloocimene (14) (E,E)-alloocimene (15) a-terpineol (16) 3,7-dimethyl-l-oct-ene-3,7-diol (17) 1,8-cineole (18) 2,2,6-trimethyl-2-vinyl-te-trahydropyran.

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