Info

Total 0.8%

26.1%

10.3%

♦According to Pellerin (1991).

**The supercritical CO2 method gives better results than the hexane extraction.

♦According to Pellerin (1991).

**The supercritical CO2 method gives better results than the hexane extraction.

tively. Ginger oleoresins extracted by CO2 were of especially high quality and contained higher amounts of natural gingerols and related compounds.

Gas Chromatography

Both analytical and preparative GC have undergone a considerable development since the discovery by James and Martin in 1952. For about 20 years, stainless steel—packed columns with various polar and nonpolar stationary phases (3 to 15%) on silica gel GC (80 to 100 mesh) were used, which were later replaced by capillary columns (highresolution GC [HRGC]). Ginger oils were first analyzed on packed columns (Jain et al., 1962; Nigam et al., 1964; Connell and Sutherland, 1966; Humphrey, 1970; Harvey, 1981) on, for example, Reoplex 400, silicone nitrile, Apiezon M and L, Carbowax 400 and 20 M, and SE 30. Monoterpenes of ginger oil have been analyzed using Reoplex 400 at 70° C and Carbowax 400 at 144° C as stationary phases (Connell, 1970). Apiezon L and M have been also used at isothermal or programmed temperature. The same authors reported the separation of five sesquiterpenes: ar-curcumene, a-zingiberene, ( — )-P-sesquiphellandrene and trans-P-farnesene on a packed column (6 feet X 1/8 inch i.d.) containing 15% of Apiezon M on silica gel GC (80 to 100 mesh). The pungent constituents of ginger were analyzed as trimethylsilyl derivatives by Harvey (1981) using a 3% silicone SE 30—packed column (100 to 120 mesh), GC Q, programmed from 100 to 300° C at 4° C/min, with nitrogen at 30 mL/min as the carrier gas. Injector (FID) and detector temperature were kept at 300° C. TMS derivatives were used in a combination of chemical reactions (lithium aluminium hydride reduction, deuterium exchange, deuterium exchange reduction, oxidation). Capillary GC chromatogram on Carbowax 20 M of Japanese ginger oil was reported by Masada (1976).

Gas chromatograms of an Indian ginger oil with a high citral content were obtained with DB-1 and DB-Wax capillary columns (Van Beek, 1991). On the nonpolar column (DB-1), a good separation of monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, and oxygenated sesquiterpenes was found. However, limonene, P-phellandrene, and 1,8-cineole overlap. On the polar column (DB-Wax), the three latter compounds were well separated, but oxygenated monoterpene and sesquit-erpene hydrocarbons were poorly separated. Application of GC in the analysis of essential oils was clarified by a commitee (1993). A rapid and simple isolation of a-zingiberene from ginger oil was developed by Millar (1998). A sesquiterpene-enriched fraction was treated with the dienophile 4-phenyl-2,5-oxazolinedione A, which selectively formed a Diels-Alder adduct with zingiberene.

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