Info

0.02c

0.02e

tr

Notes t = tentative; tt = traces; * correct isomer not characterised; a 3-pinene + sabinene; b limonene+/>-cymene +

¡3-phellandrene; c citronellal + octyl acetate; d geraniol + linalyl acetate; e «j-limonene oxide + iraKr-limonene oxide;

Appendix to Table 13-3

1 Wilson and Shaw (1980),

2 Wilson etal. (1981). USA; One sample from Duncan and Marsh grapefruit; GC on capillary column coated with Carbovax 20 M; W%.

3 Cappello etal. (1981). Argentina; 2 samples; GC on capillary column coated with UCON LB 550 X; relative percentage of peak areas. Cappello et al. also found 6-methyl-5-hepten-2-one (0.07%).

4 Koketsu etal. (1983). Brazil; FMC; 3 samples; GC on packed columns of Carbowax 20 M and of SE-30 and on capillary column coated with Carbowax 20 M; retention times and Kovats indices; relative percentage of peak areas. Koketsu etal. also found nonanol (0.09-0.18%) and methyl N-methyl anthranilate (tr).

5 Myers (1988). USA. Myers also found trace amounts of (E)-2-hexenal, (Z)-3-hexenol, ethyl butyrate.

6 Inoma etal. (1989). One commercial sample; GC on capillary columns coated with OV-lOl and Carbowax 20 M; GC/MS; relative percentage of peak areas. Inoma etal. also found cis-carveol (0.12%), limonene oxide* (0.28%), limonene dioxide (0.18%), and trace amounts of /«»j-hexenylbutyrate.

7 Haubruge etal. (1989). One commercial sample; GC on capillary column coated with CP-TM-WAX 52 CB; GC/MS; relative percentage of peak areas.

8 Boelens (1991). Israel, white (a) and pink (b); GC; relative percentage of peak areas. Boelens also found mentha-l,8(9)-dien-10-yl acetate (0.01%-tr), and trace amounts of (E,E)-2,4-decadienal, (E,Z)-2,4-decadienal, a-sinensal, perillene.

9 Dugo etal. (1999). Italy; 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 (Z)-S-ocimene (0.01%), bicyclogermacrene (0.03%), germacrene D (0.06%), hexadecanal (0.01%), «4-sabinene hydrate (0.01%), «j-/?-terpineol (0.01%), (E,E)-farnesol (0.01%), (E,Z)-farnesol (0.01%), caryophyllene oxide (0.03%), and trace amounts of tetradecanal, germacrene D-4-olc, (E)-nerolidol, trans-carvyl acetate1.

The apparent differences among the quantitative data reported by Wilson and Shaw (1980), by Wilson etal. (1981), by Myers (1988), and those reported by other authors, particularly evident for limonene, are due to the different expression of the quantitative results: the data in rows 1, 2 and 5 are expressed as w per cent of the whole oil, all the others are calculated as relative per cent of peak area obtained by GC analysis of the volatile fraction. The high content of non-volatile residue of grapefruit oil, about 7 per cent, determines these high differences among the data reported in the rable.

However, among the results reported in the table, some are not in agreement with all the others: the content of myrcene of 3-67 per cent, reported by Wilson and Shaw (1980) and by Wilson etal. (1981), appears to be high. This value is out of range not only for grapefruit oil, but also for any other cold-pressed citrus peel essential oil. This value could be explained by a possible co-elution of myrcene with another component during the GC analysis performed by these authors. The values reported by Inoma etal. for carvone (0.21 per cent), dt-carveol (0.12 per cent) and irawj-carveol (0.24 per cent) are also high.

In addition to the data reported in Table 13-3, in literature other researches on particular aspects of the composition of this oil can be found.

Wilson and Shaw (1984) proposed a GC method on a DB-5 capillary column for the separation of carbonyl compounds (aldehydes and ketones) in various US citrus oils. From the analysis of two samples of Florida grapefruit essential oils they reported rhe following results:

The data obtained by GC are in agreement with those obtained by the same authors using the method approved by the United States Pharmacopoeia (USP, 1965): 1.55 per cent and 1.46 per cent respectively for the two samples.

In an industrial grapefruit oil produced in Sicily, Mondello etal. (1995b) identified, by on-line HPLC-HRGC/MS, the following sesquiterpene hydrocarbons, listed in decreasing amount order: /3-caryophyllene, a-copaene, /3-cubebene, ¿-cadinene, germacrene D, o-humulene, (Z)-/3-farnesene, (E,E)-a-farnesene':, a-muurolenet. The presence of a-copaene, /3-cubebene, and germacrene D in grapefruit oil from Florida has been confirmed by Chamblee etal. (1997), using a GC/FT-IR. In this work has also been reported the presence in grapefruit oil, of ct-cubebene, bicyclogermacrene and germacrene B.

decanal dodecanal nonanal octanal citronellal geranial neral perilla aldehyde

,3-sinensal nootkatone

Schulz etal, (1992) proposed a HPLC method for the quantitative determination of nootkatone and the oxygen heterocyclic compounds in grapefruit oil. Three industrial cold-pressed essential oils, produced in Florida (USA), in Italy and in Argentina, were reported to contain the following amounts of nootkatone: 0.7 per cent, 0.2 per cent and 0.6 per cent respectively.

Laboratory extracted oik

In addition to the research carried on industrial grapefruit oils, a literature review has found different papers on the composition of laboratory extracted grapefruit oils, from different geographic origins. Kekelidze etal. (1985) reported for 2 different cul-tivars of grapefruit, Duncan and Marsh, cultivated in Georgia (ex USSR), the following composition:

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