Hydrocarbons

Monoterpenesa

Tricyclene (or a-thujene) 0.1 tr*

Camphene 5.6 1.7

Sabinene 0.1 tr

Myrcene 1.1 0.5

a-Phellandrene 0.2 0.2

8-3-Carene tr tr p-Cymene 0.1 tr

1,8-Cineole (4.5 %) + limonene + ß-phellandrene 10.5 4.5

7-Terpinene tr tr Terpinolene (+ linalool) 1.4 0.7 Sesquiterpenesb

8-Elemene (+ neryl acetate) 0.05 tr a-Copaene 0.3 0.35 ß-Elemene 0.1 0.2 ß-Caryophyllene tr 0.1 a-Bergamotene 0.3 0.35 (E)-ß-Farnesene 0.3 0.3 allo-Aromadendrene 0.2 0.3 ar-Curcumene 4.2 3.1 Germacrene D 1.05 1.6 a-Zingiberene 12.2 28.1 ß-Bisabolene 5.6 8.4 7-Cadinene 0.4 0.7 ß-Sesquiphellandrene 6.45 10.6 ALCOHOLc

Monoterpenes

Linalool tr tr

(Z)-Sabinene hydrate 0.2 0.1

(E)-Sabinene hydrate 0.1 tr

Isoborneol 0.1 tr

Borneol 2.2 1.6

Terpinen-4-ol 0.2 0.1

a-Terpineol 1.1 0.8

Citronellol 0.7 0.45

Geraniol 0.8 0.5 Sesquiterpenes

Elemol 0.2 0.3

Nerolidol 0.1 0.7

Viridiflorol 0.3 0.4

ß-Eudesmol tr tr

(£,£)-Farnesol 0.3 0.4 CARBONYL COMPOUNDS AND ESTERSd

6-Methyl-5-heptenone 0.2 0.1

Camphor 0.2 0.1

Citronellal 0.3 0.15

Geranial 15.0 9

Bornyl acetate 0.4 0.3

Citronellyl acetate 0.1 0.1

Neryl acetate tr tr

Geranyl acetate 0.4 0.5

aTotal monoterpene hydrocarbons 16.4 3.7

bTotal sesquiterpene hydrocarbons 30.15 51.6

cAlcohol 6.9 5.95

dCarbonyl compounds and esters 25.9 16.05

Total 79.35 77.3

*tr: traces

These results showed a usual percentage of a-zingiberene for the essential oil obtained from dried rhizomes (28%) and a high content in neral and geranial as in Australian and Japanese oils. These percentages are higher in oils obtained from fresh rhizomes. The rhizomes of ginger were also examined for their oil and moisture contents by Dambatta et al. (1988). Some characteristics of the oil, such as acid value, the saponification index, and the iodine value, showed slight variations from the values reported for ginger oils obtained in other countries. GC/MS analysis of the oil revealed the presence of many components including camphene, myrcene, a-phellandrene, a-copaene, a-farnesene, (3-caryophyllene, a-zingiberene, and germacrene, all being well-known components in ginger oils. The next year, Onyenekwe and Hashimoto (1999) studied the composition of the Nigerian essential oil obtained from dried rhizomes. The hydrodistilled oil (2.4%) consisted of 64.4% carbonyl compounds, 5.6% alcohols, 2.4% monoterpene hydrocarbons, and 1.6% esters. The main components were: a-zingiberene (29.5%), and ses-quiphellandrene (18.4%). Besides the usual compounds, they also identified: 2,6-dimethyl hepten-1-ol, a-gurjunene, linalool oxide, isovaleraldehyde, 2-pentanone, a-cadinol, a-and

7-calacorenes, eremophyllene, 7-muurolol, a-himachalene, a-cubebene, acetic acid, pinanol, a-santalene, geranyl propionate, geranic acid, (£,£^-a-farnesene, and N-meth-ylpyrrole. The identification of this latter heterocyclic compound is of interest.

Afzal et al. (2001) reported retention indices both on polar and nonpolar columns, as well as the percentages of 29 volatile compounds identified in a Nigerian ginger oil. These results are given in Table 3.21 and compared with those reported by Akhila and Tewari (1984).

Table 3.21 Gas chromatography analysis of ginger oils from Nigeria*

Table 3.21 Gas chromatography analysis of ginger oils from Nigeria*

Compounds

a

b

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