Page 11 - Volume 4, Issue 2, July 2011
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© Benaki Phytopathological Institute
p
-menthane type compounds against mosquito
39
the most abundant ingredient followed by
isomenthone (13.0%), menthone (4.3%), pi-
peritenone (4.0%), isopulegone (2.9%) and
piperitenone oxide (1.8%). EOpul2 charac-
terized by the dominant occurrence of pi-
peritone (92.6%) and the minor presence of
limonene (2.7%) andmenthone (1.8%). Final-
ly, EOpul3 consisted of piperitone (69.3%),
isomenthone (24.8%), limonene (1.8%) and
menthone (1.6%). Concerning the other two
plants, the major ingredient of EOsp was car-
vone (71.8%) followed by eucalyptol (9.0%)
and
β
-caryophyllene (2.2%) among others,
while EOpip consisted of menthone (39.0%)
and menthol (25.9%) with minor compo-
nents isomenthone (9.9%), eucalyptol (6.9%)
and
β
-caryophyllene (3.5%) among other
less abundant ingredients.
Purity of the isolated major ingredients
The purity of the isolated components
was determined by GC-MS analysis and is
given as follows: pulegone (5.45 g, 99.2% pu-
rity) and piperitenone (0.38 g, 98.6% purity)
from EOpul1, piperitone (8.63 g, 99.5% pu-
rity) from EOpul2, piperitone (6.21 g, 99.4%
purity) and iso-menthone (1.86 g, 98.9% pu-
rity) from EOpul3, carvone (6.05 g, 99.6%
purity) from EOpip and menthone (3.16 g,
99.2% purity) and menthol (2.17 g, 99.0% pu-
rity) from EOsp. Pulegone, piperitenone, pip-
eritone, isomenthone, carvone, menthone
and menthol have been isolated in high pu-
rities and their chemical structures are giv-
en in Figure 1. Although piperitenone does
not constitute a major ingredient, it has also
been isolated due to the fact that it is struc-
turally similar to pulegone and piperitone.
Larvicidal Assays
Essential oils and their major ingredi-
ents were tested for their larvicidal activity
against
Cx. pipiens
3
rd
-4
th
instar larvae. EOpul1
was the most active essential oil as well as its
major component pulegone among the es-
sential oil major ingredients (based on non-
overlapping confidence intervals) (see Table
2
for LC
50
and LC
90
values). The essential oils
EOpul2 and EOsp and their dominated com-
pounds, piperitone and carvone respective-
ly, presented a rather medium activity (Table
2). EOpul3 was the only inactive essential oil
showing no larvicidal effect. The larvicidal
pattern of the EOpip was quite different: LC
values were high and almost the same with
the EOpul1 (LC
50
value 40.28 and 46.97 mgl
-1
Figure 1.
Chemical structures of essential oils’ isolated components.
