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More pronounced than in Indian oil

*Akhila and Tewari, (1984)

aThe aroma character impacts are a-zingiberene, P-zingiberene, geranial, geraniol, and gingerone, while contributors are gingerols, borneol, linalool, 1,8-cineole, isoborneol, camphene, and 4-terpineol.

*Akhila and Tewari, (1984)

aThe aroma character impacts are a-zingiberene, P-zingiberene, geranial, geraniol, and gingerone, while contributors are gingerols, borneol, linalool, 1,8-cineole, isoborneol, camphene, and 4-terpineol.

The composition and organoleptic properties of a ginger extract from the Polish Institute of Fermentation Industry were compared with those of two foreign extracts (see Table 3.24) (Kostrzewa and Karwowska, 1976). The Polish extract contained 26.0% essential oil compared to 25.3% and 20.6% for the other extracts. Levels of a-zingiberene and zingiberol in the oil and the total gingerols and shogaols were 52.0%, 16.0%, 31.1%, and 20.0%, respectively, in the Polish extract against 47.2 to 45.3%, 13.6 to 11.6%, 24.8 to 20.8%, and 14.8 to 11.2%, respectively, for the two foreign extracts. The organoleptic characteristics of the Polish extract were found to be similar to one of the foreign oils, and they were different from the other foreign extract.

Ginger oil obtained by hydrodistillation of the rhizomes of the common ginger grown in Mauritius was investigated by GC and GC/MS (Gurib-Fakim et al. 2002). The oil was characterized by the presence of geranial (16.3%), neral (10%), a-zingiberene (9.5%), P-sesquiphellandrene (6.3%), and ar-curcumene (5.1%). The oil from Mauritius is similar to those containing high amounts of neral and geranial and a low content of a-zingiberene.

Van Beek (1990) analyzed by GC, on two columns at different polarity, 48 ginger oils from nine countries. The sesquiterpe fractions of these oils were qualitatively fingerprint identical in spite of the differences in the growing, storage, drying, and extraction conditions. There were only quantitative differences in composition.Vahira-Lechat et al. (1996) studied a steam-distilled essential oil from Tahiti. They found: a-zingiberene + (E,E)-a-farnesene (3.3 to 7.8%), P-bisabolene (7.9 to 8.8%), P-sesquiphellandrene (7.1 to 8%), ar-curcumene (0.4 to 3.6%), neral (5.4 to 6.7%), and geranial (8.9 to 18.1%) as the major compounds. These results showed a low percentage of a-zingiberene and a high content of neral and geranial. A low content of ar-curcumene seems to indicate no rearrangement of P-bisabolene. The oil is rather similar to that of Mauritius island.

Wild Ginger (Z. zerumbet Smith) Essential Oils

Wild ginger is a perennial root herb that grows in subtropical climates such as India, Southeast countries, South Pacific islands, and Okinawa. It has been used locally for gardening and folk medicines. Since the first report on the essential oil of Indian wild ginger by Nigam and Levi (1963), essential oils have been widely studied for their medicinal properties due to their high content of zerumbone. The oil originating from Fiji, said to have medicinal properties, differs from the cultivated variety in India in its zerumbone content, which is much higher (57.7%) as compared to 37.5% (Duve, 1980). Steam distillation of the local variety yielded 0.3% of clear oil, which compared favorably with that of the cultivated variety overseas.

Chemical investigation of the aerial parts (stems, leaves, and flowers) of wild ginger (Z. zerumbet) of Vietnamese origin was subjected to GC and GC/MS analyses (Dung et al., 1995). About 40 compounds have been identified in the stem and leaf oils, accounting for more than 83 ± 1% of the oils. The major compounds appeared to be (Z)-nerolidol (16.8 and 22.3%), P-caryophyllene (10.4 and 11.2%), zerumbone (21.3 and 2.4%), and trans-phytol (7.0 and 12.6%), respectively. Predominant minor constituents included P-pinene (5.4 and 5.2%), a-humulene (2.5 and 2.9%), caryophyllene oxide (1.1 and 5.5%), and linalool (1.1 and 2.4%). The volatile flower oil was found to contain more than 60 compounds with 45 compounds making up to 85% of the oil. (Z)-nerolidol (36.3%) and P-caryophyllene (13.2%) were the major constituents.

GC/MS analysis of the essential oil obtained from dried rhizomes of wild ginger from India resulted in the identification of 36 compounds. Curzerenone (14.4%), zerumbone (12.6%), camphor (12.8%), isoborneol (8.9%), and1,8-cineole (7.1%) were found as the major components. GC, GC/MS, IR, and 1H-NMR analyses showed that the main constituents found in the hydrodistilled oil from Z. spectabile Valet, were terpinen-4-ol (23.7 percent), labda-8(17),12-diene-15,16-dial (24.3%), a-terpineol (13.1%), and P-pinene (10.3%) (Sirat and Leh, 2001).

Zerumbone isolated from wild ginger has been claimed to be a potent inhibitor of 12-D-O-tetradecanoylphorbol-13 acetate, which induced Epstein-Barr virus activation (Murakami et al., 1999). Its IC50 value (inhibitory concentration of 50 percent) (0.14 fxM) is noticeably lower than those of the antitumor promoters these workers have hitherto obtained. 8-Hydroxy-a-humulene was markedly active (IC50 = 0.95 ^M). Zerumbone is easily obtained from Japanese wild ginger and is a useful and reproducible natural product. It possess a strong suppression of an antiproliferative activity in vitro against cultured tumor cells of mouse t-lymphoma cells, EL4 at a concentration of 100 mg.L-1 (Sawada and Hosokawa, 2002). They also described the synthesis of a woody fragrance by simple hydrogenation of zerumbone, which has a great potential for the preparation of useful compounds (Sawada et al., 2002). Zerumbone derivatives arising from a fragmentation process of zerumbone dibromide were found to be selective inhibitors of the growth of gram-positive bacteria (Kitayama et al., 2001).

Diterpenoids

Besides the usual mono- and sesquiterpene derivatives several diterpenoids, (24 to 26), have been identified in ginger rhizomes (Lee et al., 1982; Kano et al., 1990; Kikuzaki and Nakatani, 1996). The galanolactone (27), a furan diterpene, has been isolated from the Japanese ginger "Kinoki" by Kano et al. (1990), but was not found in ginger from China and India. The 8P-17-epoxy-12-ene-15,16-dicarboxaldehyde isolated from ginger reduces plasma cholesterol concentrations in hypocholesterolemia induced in mice (Tanabe et al., 1993). Labdane-type diterpenes from ginger oleoresin are reported in Figure 3.4, according to Kikuzaki and Nakatani (1996).

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