Info

0-tr<

trc

tr1

Notes t — tentative identification; tr = traces; a <3-3-carene + 1,4-dneole; b limonene + 1,8-cineoie; c myrcene + octanal; d "-terpinene + octanol; e terpinolene + nonanal; f /3-pinene + sabinene; g limonene + 4-phellandrene + 1,8-cineole; h 3-bisabolene + (E,E)-a-farnesene; i geranial-r perilla aldehyde; j 2,3-dimethyl-3-(4-methyl-3-pentenyl)-2 norbor-nanoi; k neryl acetate + nnknown hydrocarbon.

Appendix to Table 13.5

1 Haro and Faas (1985). Mexico; one sample type A and one type B; column chromatography on silica-gel impregnated with 0.79b of Carbowax 1540; GC on capillary column coated with SE-30; relative percentage of peak areas. Haro and Faas also found ¿¡-sesquiphellandrene (1.55% in type A and 1.89% in type B), tridecanal (0.01 % in type A).

2 Clark and Chamblee (1992). Absolute w%, Clark and Chamblee also found J-copaene1 (0.33%' in type A and 0.30% in type B), heptanal (0.02% in type A), octanol + 1,4-cmeole (0.02%' in type A).

3 Dugo P. etal. (1997). Four samples type A and one sample type B; GC on capillary columns coated with SE-52 and DB-5; GC/MS; relative percentage of peak areas. Dugo etal. also found exo-fenchol (tr—0.02% in type A and tr in type B), probably a misidentification of endo-fenchol.

4 Dugo etal. (1999). One sample; GC on capillary columns coated with SE-52 and DB-5; GC/MS with interactive use of linear retention indices. Dugo etal. also found o-elemene (0.08%), endo-fenchol (0.01%), ¡3-bisabolol (0.01%), selm-1 l-en^-Q-of (0.01%), w-sesquisabinene hydrate (0.03%), spathulenol (0.02%9, /raHJ-pinocarvyl acetate (0.01%), «j-limonene oxide (0.01%), and trace amounts of allo-ocimene®, (E)-~,-bisabolene, (Z)-";.-bisabolene, a-santalene, m-piperitol, (E,Z)-farnesol, decyl acetate, /nwu-limonene oxide, caryophyllene oxide.

The results reported in the table, even if based to a limited number of papers, provide a good description of the real composition of cold-pressed Key lime oil. The results obtained by the different authors are in good agreement. The apparent different values reported by Clark and Chamblee (1992) compared to those obtained by the other authors, particularly for what concerns limonene, are due to the quantification method used. Clark and Chamblee, in fact, reported their values as absolute w per cent, while other authors expressed their results as relative per cent of the peak areas, not adjusted. It should also be noticed that /3-sesquiphellandrene identified by Haro and Faas (1985) could have been a misidentification of (E,E)-a-farnesene.

The comparison between lime oil type A and type B shows that these two cold pressed oils do not present substantial composition differences.

In addition to the systemic studies on the composition of industrially processed Key lime oil whole volatile fraction, in literature are found papers on some peculiar aspects on the composition of this oil.

McHale (1980) reported the following information on the quantitative composition of the volatile fraction of ecuelled lime oil:

monoterpene hydrocarbons

74.9%

myrcene

1.2%

limonene

41.8%

(3-phellandrene

0.6%

Q-pinene

2.9%

/3-pinene

17.8%

sabinene

3.1%

7-terpinene

7.2%

terpinolene

0.4%

sesquiterpene hydrocarbons

3.7%

tow-ct-bergamotene

0.6%

/3-bisabolene 1.0%

caryophyllene* 0.5%

/3-sesquiphellandrene 1.0%

geranial + neral 6.2%

a-terpineol 0.3% other alcohols (fenchol*, linalool, terpininen-4-ol) 0.3%

geranyl acetate + neryl acetate 0.5%

McHale (1980) also reported the presence of camphene, ^-cymene, isoterpinolene, a-terpinene, <5-elemene, a- and /3-humulene. In the same paper McHale also assessed the similarity of the /3-sesquiphellandrene structure with that of (E,E)-a:-farnesene (isolated and identified by Moshonas and Shaw (1980) in distilled lime oil and in Valencia sweet orange oil), showing how these molecules could not be unequivocally distinguished by IR spectroscopy.

Chamblee etal. (1985) after pre-fractionating the oil by normal phase HPLC, analysed the fractions obtained by HRGC-MS. The components identified for the first time in Key lime oil, were the following: farnesal*, 3-hexanone, 6~methyl-5-hepten-2-one, piperitone, cis- and trans-carveol, citronellol,^-cymen-8-ol, 7-isogeraniol, isopiperitenol,^-menth-3-en-l-ol, myrtenol, trans-pinocarveol, sabinol, /3-terpineol*, a-bisabolol, a-cadinol, 1,3- and 2,3-dimethyl-3(4-methyl-3-pentenyl)-2-norbornanol, famesol*, verbenol, dodecyl acetate.

Clark etal. (1987) using HPLC isolated from Key lime oil the sesquiterpene hydrocarbon germacrene B, and confirmed the structure by GC/MS, IR and NMR. The germacrene B is very important to the fresh lime character of the oil.

Mondello etal. (1995b) using an on-line coupled HPLC-HRGC/MS system, identified in Key lime oil the following components listed in decreasing amount order: /3-bisabolene, /ww-a-bergamotene, /3-caryophyllene, germacrene B, ¿-elemene, germacrene D, iif-Q-bergamotene, /3-elemene, (Z)-/3-farnesene, a-humulene, a-selinene, ,5-santalene, (Z)- and (E)-7-bisabolene, (E)-epi-a-selinene.

Chamblee etal. (1997) by using cryofocusing GC/FT-IR confirmed the presence of germacrene B and germacrene D in Key lime oil, and identified for the first time the presence of (Z)-a-bisabolene.

Industrial cold-pressed Persian lime oil (Citrus latifolia Tan.)

In Table 13-6 are summarised the literature data relative to the composition of the volatile fraction of cold-pressed Persian lime oil.

Table 13.6 Percentage composition of the volatile fraction of cold-pressed Persian lime oil

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