Rapid and simple isolation of zingiberene from ginger essential oil

Article abstract of DOI:10.1021/np9800699

A sesquiterpene-enriched fraction of ginger oil was treated with the dienophile 4-phenyl-1,2,4-triazoline-3,5-dione (2), which selectively formed a Diels-Alder adduct with the sesquiterpene hydrocarbon zingiberene (1). The adduct was purified by flash chr

Full text of DOI:10.1021/np9800699

J . Nat. Prod. 1998, 61, 1025-1026
1025
Ra p id a n d Sim p le Isola tion of Zin giber en e fr om Gin ger Essen tia l Oil
J ocelyn G. Millar*
Department of Entomology, University of California, Riverside, California 92521
Received March 4, 1998
A sesquiterpene-enriched fraction of ginger oil was treated with the dienophile 4-phenyl-1,2,4-
triazoline-3,5-dione (2), which selectively formed a Diels-Alder adduct with the sesquiterpene
hydrocarbon zingiberene (1). The adduct was purified by flash chromatography, then hydrolyzed
to return zingiberene in good yield and >99% purity.
Sch em e 1
The sesquiterpene hydrocarbon zingiberene (1) [5-(1,5-
dimethyl-4-hexenyl)-2-methyl-1,3-cyclohexadiene] has
been shown to have a considerable spectrum of biological
activity. For example, recent studies have determined
its antiviral,1 antiulcer,2 and antifertility3 effects. Fur-
thermore, it has been widely used in cosmetics and
fragrances.4 Zingiberene is a major component of com-
mercially available oil derived from rhizomes of the
ginger plant Zingiber officinale Roscoe (Musales: Zin-
giberaceae), but obtaining pure 1 from the mixture of
sesquiterpenes in the oil can be problematic. For
example, recent publications have described the isola-
tion of zingiberene of low purity5 or in low yield1 only
after several tedious sequential purification steps.
In connection with the identification of sex pheromone
components of the stinkbug Thyanta pallidovirens Stål
(Hemiptera: Pentatomidae), the males of which produce
several sesquiterpene hydrocarbons,6 we required 100-
mg amounts of zingiberene of high purity for laboratory
and field bioassays. A search of the literature revealed
that zingiberene is generally isolated from essential oils
in preparative scale by fractional distillation to produce
a fraction enriched in sesquiterpenes, followed by one
or more liquid chromatographic steps. However, zin-
giberene has been selectively removed from ginger oil
by the formation of Diels-Alder adducts with maleic
anhydride or other powerful dienophiles during the
isolation of other sesquiterpene components of ginger
oil, such as R-curcumene and sesquiphellandrene.7 It
occurred to us that this strategy of selective removal
could be used to obtain zingiberene of high purity by
choosing a dienophile that would produce an adduct
amenable to controlled degradation, to return the parent
diene. 4-Phenyl-1,2,4-triazoline-3,5-dione (PTAD) (2),
which was developed as a protecting group for endocyclic
1,3-dienes in the B-ring of steroids,8,9 appeared to be a
likely dienophile candidate. In particular, PTAD reacts
with 1,3-dienes essentially instantaneously at room
temperature to form the Diels-Alder adducts. Fur-
thermore, the resulting adducts are reported to be
readily degraded to the parent dienes by either base
hydrolysis or reduction with LiAlH4.8,9
acted zingiberene or excess PTAD were readily removed
by chromatography. Thus, after concentration, the
mixture was purified by flash chromatography on Si gel
to remove the other unreacted hydrocarbons, yielding
the pure adduct 3 as a colorless gum. Base hydrolysis
of 3, followed by extraction of the recovered zingiberene
into hexanes and Kugelrohr distillation, produced 1 in
>99% purity by GC (Scheme 1).
Thus, the method is amenable to the rapid and
straightforward preparative scale isolation of zingib-
erene from ginger oil, without the use of specialized
equipment such as spinning band distillation columns
or silica LC columns impregnated with AgNO3. Fur-
thermore, the method should be equally applicable to
the isolation of related compounds containing endocyclic
1,3-diene moieties, such as 7-epizingiberene5 or the
monoterpene R-phellandrene.
Exp er im en ta l Section
Flash chromatography was carried out with 0.04-
0.063-mm Si gel (Aldrich Chemical Co., Milwaukee, WI).
1H and 13C NMR spectra were recorded in CDCl3 at 300
and 75 MHz, respectively, using a General Electric QE
300 instrument. GC-MS analyses (EI, 70 eV) were
performed on a Hewlett-Packard 5890 gas chromato-
graph interfaced to an Hewlett-Packard 5970B mass
selective detector. A DB-5 column was used (30 m ×
0.25 mm, J &W Scientific, Folsom, CA; temperature
program, 50 °C/0 min, 10°/min-250 °C). HREIMS were
obtained with a VG7070 instrument.
In our hands, a solution of PTAD in THF was added
dropwise to a ginger oil sesquiterpene fraction in THF
until the pink color of unreacted PTAD persisted. The
amount of PTAD added was not critical, because unre-
Ginger oil (Spectrum Chemical Co., Gardena, CA) was
Kugelrohr distilled at 0.1 mmHg. The first fraction
(oven temperature <60 °C) containing monoterpenoids
was discarded. A second fraction (oven temperature
* To whom correspondence should be addressed. Tel.: 909 787 5821.
Fax: 909 787 3086. E-mail: jocelyn.millar@ucr.edu.
S0163-3864(98)00069-X CCC: $15.00
© 1998 American Chemical Society and American Society of Pharmacognosy
Published on Web 07/11/1998

1026 J ournal of Natural Products, 1998, Vol. 61, No. 8
Notes
60-100 °C) consisted almost exclusively of sesquiter-
pene hydrocarbons, including R-curcumene (9.2%), zin-
giberene (46%), sesquiphellandrene (17.4%), and bisab-
olene (10.1%). A portion of the sesquiterpene fraction
(2.0 g, ca. 9.8 mmol of mixed sesquiterpenes) in 20 mL
of dry THF was stirred at room temperature, while
adding PTAD (0.88 g, 5 mmol; Aldrich) in THF (10 mL)
dropwise. The mixture was concentrated and purified
by flash chromatography, eluting with 15% Me2CO in
hexanes. The adduct 3 (1.18 g, ca. 69% yield based on
percentage of zingiberene in the starting material) was
recovered as a colorless gum: 1H NMR (CDCl3, 300
MHz) δ 7.3-7.5 (5H, m, Ph), 5.98 (1H, br d, J ) 5.7 Hz,
H-3), 5.09 (1H, br t, J ) 7 Hz, H-10), 4.97 (1H, dd, J )
5.7, 2.6 Hz, H-4), 4.71 (1H, m, H-6), 2.31 (1H, ddd, J )
13.1, 8.8, 3.5 Hz, H-6), 2.08 (3H, m, H-5, H-9, H-9′), 1.93
(3H, d, J ) 1.6 Hz, H-15), 1.70 (3H, s, H-12), 1.63 (3H,
s, H-13), 1.5 (1H, m, H-8), 1.25 (2H, m, H-6′, H-8′), 1.10
(1H, m, H-7), 0.88 (3H, d, J ) 6.3 Hz, H-14); 13C NMR
(75.48 MHz) δ 156.43, 156.10, 140.83, 131.84, 131.58,
129.04, 128.05, 125.37, 124.07, 120.59, 55.10, 53.60,
41.34, 36.51, 34.30, 28.57, 25.71, 24.88, 19.40, 17.70,
16.31; EIMS m/z 379 [M]+ (92), 268 (6), 241 (100), 204
(28), 178 (33), 119 (63), 91 (27); HREIMS m/z 379.2258
(calcd for C23H29N3O2, 379.2260).
passed through a short column of Si gel (ca. 4 cm × 1.5
cm diam), eluting with hexanes, to remove traces of
aniline. The solution was concentrated, then Kugelrohr
distilled, yielding 143 mg (81%) of zingiberene (1), >
99% pure by GC-MS. The mass spectrum and reten-
tion times exactly matched those of zingiberene in the
crude ginger oil, and the 1H NMR spectrum cor-
responded closely to literature data.5
Ack n ow led gm en t. We thank the California Pista-
chio Commission for financial support of this work, and
the Analytical Services Laboratory, UC Riverside, for
obtaining the HRMS.
Refer en ces a n d Notes
(1) Denyer, C. V.; J ackson, P.; Loakes, D. M. J . Nat. Prod. 1994,
57, 658-662.
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(3) Ni, M.; Chen, Z.; Yan, B. Huadong Huagong Xueyuan Xuebao
1988, 14, 675-679; Chem Abstr. 1989, 111, 195149w.
(4) Handa, K. L.; Sharma, M. L.; Nigam, N. C. Perf. Cosmetics 1963,
44, 233-236.
(5) Breeden, D. C.; Coates, R. M. Tetrahedron 1994, 50, 11123-
11132.
(6) Millar, J . G. Tetrahedron Lett. 1997, 38, 7971-7972.
(7) Connell, D. W.; Sutherland, M. D. Aust. J . Chem. 1965, 19, 283-
288.
(8) Barton, D. H. R.; Shioiri, T.; Widdowson, D. A. J . Chem. Soc.
(C) 1971, 1968-1973.
(9) Barton, D. H. R.; Lusinchi, X.; Ramirez, J . S. Tetrahedron Lett.
1983, 24, 2995-2998.
The adduct 3 (0.33 g, 0.87 mmol) was refluxed under
Ar in 10 mL of 2.1 M KOH in 95% EtOH for 3 h. The
cooled mixture was diluted with H2O and extracted with
hexanes (3 × 25 mL). The hexane extracts were washed
with saturated aqueous NaCl, dried over Na2SO4, and
NP9800699