Page 7 - Volume 4, Issue 2, July 2011

1

Laboratory of Agricultural Entomology, Department

of Entomology and Agricultural Zoology, Benaki Phy-

topathological Institute, 8 St. Delta Str., GR-145 61 Ki-

fissia (Athens), Greece

2

Laboratory of Chemistry & Biochemistry, Department

of Agricultural Development, Democritus University

of Thrace, 193 Pantazidou Str., GR-682 00 Orestiada,

Greece

3

Chemistry Laboratories, Agricultural University of

Athens, 75 Iera Odos Str., GR-118 55 Athens, Greece

Corresponding author:

kimparis@agro.duth.gr

Hellenic Plant Protection Journal

4:

35-43, 2011

Larvicidal evaluation of three

Mentha

species essential oils and

their isolated major components against the West Nile virus

mosquito

A. Michaelakis

1

, D. Papachristos

1

, A. Kimbaris

2

and M. Polissiou

3

Summary

The larvicidal activity of essential oils derived from three different

Mentha

species (Lami-

aceae) as well as their major aroma

p

-menthane type components were evaluated against

Culex pipi-

ens

(Diptera: Culicidae). Therefore, pulegone, piperitenone, piperitone, carvone, menthone and men-

thol were isolated using column chromatography. The LC

50

values revealed that

M. pulegium

and

M. pi-

perita

oils were the most toxic (46.97 and 40.28 mgl

-1

respectively) and pulegone was the most effec-

tive (27.23 mgl

-1

) among the major ingredients. The activity of all essential oils is in agreement with the

proportion/toxicity rate of their individual major components, apart from the case of

M. piperita

where

the LC

50

values of its major ingredients menthone and menthol stand higher than 100 mgl

-1

. For the

isolated molecules, studies on structure activity relationships revealed that the location of C-C double

bond and the presence of the isopropylidene group might be key factors.

Additional keywords: Culex pipiens,

essential oil, larvicidal activity, major components isolation,

Mentha

species

Introduction

Control of mosquitoes is crucial due to the

fact that they are vectors of many virus-

es.

Culex pipiens

serves as both an enzoot-

ic and an epidemic (i.e. “bridge”) vector of

West Nile Virus (WNV) to humans, is a wide

spread insect pest with medical importance.

According to Bakonyi et al. (4) WNV emerged

in several European countries within the last

50 years. Outbreaks of WNV encephalitis in

humans and horses were reported. Recent-

ly, new WNV strains were isolated in Central

Europe from mosquito vectors and from en-

cephalitic cases of vertebrate host (18). Dur-

ing the last decade cases are also reported

from Russia, Israel, Turkey and other Med-

iterranean countries (10). During summer

of 2010, hundreds of people were seriously

affected from WNV and more than 30 died

in Northern Greece (18). Currently specific

treatment and vaccines are not available for

the protection of horses or humans and only

mosquito control measures could reduce the

risk of the development of serious diseas-

es (6). Therefore the use of improved mos-

quito control measures is strongly empha-

sized. According to Floore (11) the success

of mosquito control relies on product effica-

cy and tools that are environmentally friend-

ly. Shaalan et al. (21) stated that “.. the failure

to discover a significant new class of insecti-

cides has led many researchers back to bio-

discovery studies…”. Plant derived pesticides

are biodegradable and may be the future ar-

senal against mosquitoes but there are many

topics that need more investigation.

Previous investigations have indicated

that various

Mentha

spp. plant extracts dis-

played larvicidal effect on

Cx. pipiens

,

Cx.

quinquefasciatus

,

Aedes aegypti, Anopheles

stephensi

and

An. tesselatus

(2, 3, 19, 20, 22, 23).

Furthermore, pure substances (thymol, men-

thone, menthol and pulegone) and menthol

derivatives have been tested against mosqui-