The Effectiveness of Organotin (IV) Benzylisopropyldithiocarbamate Compounds as Insecticide Against Aedes aegypti Linn. (Diptera:Culicidae) in Laboratory

: The widespread use of insecticides has resulted in insecticide resistance of vectors of dengue as well as polluting the environment. Organotin (IV) compounds have the potential to be developed as the insecticides to overcome the existing problem. The aim of this study was to examine the insecticidal effects which is larvicidal and adulticidal effects of organotin (IV) benzylisopropyldithiocarbamate compounds against Aedes aegypti Linn. in laboratory. Larvicidal bioassay test of a series of three organotin (IV) benzylisopropyldithiocarbamate compounds on third instar larvae of Aedes aegypti had been carried out. The study found that compound B showed the best larvicidal effect with the LC and LC values of 0.004 ppm 50 90 and 0.007 ppm, respectively. The compound C also displayed good larvicidal effect with the LC and LC 50 90 values of 0.029 ppm and 0.108 ppm, respectively. While, compound 1 showed the least larvicidal effect with the LC and LC values of 0.404 ppm and 0.749 ppm, respectively. Further testing was conducted on compound 50 90 B on adults of Aedes ageypti female to investigate its adulticidal property. The result showed that compound B displayed good adulticidal activity with LC dan LC of 4.277 ppm and 27.653 ppm, respectively. 50 90 In conclusion, compound B is the most effective compound among three organotin(IV) benzylisopropyldithiocarbamate compounds tested against the dengue vector Aedes aegypti and has potential to be explored as an insecticide to control the spread of dengue fever.


INTRODUCTION
effective method of controlling the spread of the disease Dengue fever is a mosquito-borne disease that reduce the Aedes population and as the result incidence threatens international public health. The disease is found of dengue fever can be reduced [6]. in many tropical and subtropical countries throughout the Unfortunately, the uncontrolled use of insecticide world, especially in urban areas and semi urban [1].
has resulted in problems of insecticide resistance [7]. Dengue fever is caused by dengue virus. There are four In addition, the effect of degradation of a toxic dengue viruses serotype known as DEN-1, DEN-2, DEN-3 insecticide metabolites in the environment leading to and DEN-4 [2]. Aedes aegypti and Aedes albopictus is the environmental pollution such as pollution of surface main vector of this disease, but the Aedes aegypti is the water and ground water [8] as well as negative effects most efficient vector of dengue fever since it live in the on non-target organisms, including human [9]. house and surrounding houses [3].
Recognizing this problem, scientists seek new Until now no vaccine is completely appropriate to be alternatives in the production of environmentally given to society for the prevention of further spread of friendly insecticide and at the same time preventing dengue fever [4]. Thus, vector control is the most resistance in the vector.
[5] and chemical insecticide is a method that is believed to Wide application of organotin(IV) compounds in the Female mosquitoes were periodically blood-fed on industry [10] and its potential in biological activity has restrained guinea pigs to obtain protein used principally attracted researchers to conduct studies on this for egg production. Under these conditions, the full compound [11]. Among the biological activities of development from egg to adult lasted about 3-4 weeks. organotin(IV) compound are this compounds have been Batches of 2-5 day-old healthy female mosquitoes were identified as a potential antiviral agent [12], antineoplastic used in the adulticidal bioassay. agents, antituberculosis [13][14][15][16], antibacterial agent [17], anticancer agent [18] and so on.
Preparation of the Organotin(iv) Benzyl-Use of organotin(IV) compounds in the field isopropyldithiocarbamate Stock Solutions: Stock of entomology are also now getting attention [19].
s o l u t i o n s o f t h e o r g a n o t i n ( I V ) Several studied showed organotin(IV) compounds were benzylisopropyldithiocarbamate were prepared in either effective against some pests like Periplanata Americana, 95% ethanol, dimethyl sulfoxide (DMSO) or acetone Musca domestica, Spodoptera litura and Tetranychus depending on the solubility of the compound at urticae [19] and a few species of larvae and adult concentration 100 parts per million (ppm). The dissolution mosquitoes like Aedes aegypti and Aenopheles stephensi of the organotin(IV) benzylisopropyldithiocarbamate in [20][21][22][23]. Group and the nature of organic group that the organic media was to facilitate the dispersion of the bound to tin atom, such as the monoalkyl, dialkyl and compounds in water. The acetone and DMSO was trphenyl is basic factors determining the biological spectrograde quality while the 95% ethanol was reagent activity [10,18,24].
grade. Until now there has been report of Ae. aegypti resistance to organotin(IV) compound and reported that Larvicidal Bioassay Testing: The larvicidal bioassay this compound will be degrade to non-toxic inorganic testing was followed the method from Basu Baul et al. compound in environment [25,26].
(2010) [23] with slight modification. This testing was In this paper, we report the insecticidal activity performed in 30 ml disposable cup using ten larvae of of three compound of organotin (IV) Ae. aegypti in the 3rd instar stage. Solution of compounds bezylisopropyldithiocarbamate that were dimethyltin (IV) 1-3 were added to 15 ml of distilled water that had been (compound A), dibutyltin(IV) (compound B) and prepared in disposable cup. The Ae. aegypti larvae were triphenyltin(IV) benzylisopropyldithio-carbamate then transferred into the solution and distilled water to (compound C) against Ae. aegypti mosquito in laboratory.
give the desired concentration of solution. The total MATERIALS AND METHODS distilled water and DMSO, but without the organotin(IV)

Materials:
Organotin(IV) benzylisopropyl-used as a positive control. Mortalities were recorded at dithiocarbamate compounds (A-C).
24 h of exposure. The moribund and dead larvae in three Larvae and Adults Mosquito: The Aedes aegypti mortality of each concentration. The larvae were mosquito larvae and adult mosquitoes were obtained from considered dead if they showed no sign of swimming the colonies that had been reared continuously for movements even after probing with a needle. generations in a laboratory free of exposure to pathogens and insecticides. They were maintained at 25-30°C and Adulticidal Bioassay Testing: Further testing on the 80-90% relative humidity under a photoperiod of 12:12 h adulticidal activity of the most effective compound in the (light/dark) in t the Insectarium of the Department of larvicidal bioassay testing was conducted on adults of Ae. Biomedical Science, Faculty of Allied Health Sciences, aegypti female. The adulticidal bioassay testing was Universiti Kebangsaan Malaysia. The larvae were fed with performed by topical application of the compound, ground beef liver that have been dried and grind after following slightly modified versions of the WHO standard reaching the 1st instar. The dechlorinated water that protocols - [27]. Adulticidal activity of the compound contains the larvae and the beef liver must be changed was evaluated at four concentrations and 25 females regularly to ensure the water condition is always clean were used for each concentration of the most effective and clear. The adults were reared in cages and was compound.
Non-blood-fed females' mosquitoes provided with 10% sucrose added with multivitamins.
(2-5 days old) were briefly anesthetized with extreme assay volume in each case was 20 ml. Solution containing solution, served as a negative control and temephos was replicates were combined and expresses as a percentage % test mortality -% control mortality % mortality = X 100 100 -% control mortality temperature for 30 seconds and placed on a cold plate.
for these three compounds were less than 1 ppm. The data The selected compound solution (1µl) dissolved in DMSO showed that there were differences in larvicidal effect of was applied onto the upper part of the immobilized compounds which compound B displayed the best mosquito's pronotum using multipette plus (Eppendorf larvicidal effect with the LC and LC values of 0.004 ppm Research, Jerman model no. 4981950). Solution containing and 0.007 ppm, respectively. Compound C showed good distilled water and DMSO, but without the compound larvicidal effect with the LC and LC values of 0.029 ppm solution, served as a negative control and malathion was and 0.108 ppm, respectively while the least larvicidal effect used as a positive control for comparison. Both groups showed by compound A with the LC and LC values of were treated in a similar manner to that treated groups. 0.404 ppm and 0.749 ppm, respectively. From the results, After each test, females were transferred into disposable the order of larvicidal activity based on the organic group cups and 10% sucrose solutions with added multivitamin attached to the tin atom can be observed which on cotton wools were provided.. After application, the compound that attached with dibutyl group (compound females in all groups were maintained at 27±3°C and 80% B) was the most effective larvicide, followed by ± 10% RH in plastic cups. At the end of a 24-hour compound that attached with triphenyl group (compound recovery period, the mosquitoes were considered dead if C) and compound that attached with dimethyl group they showed no sign of movement such as lying on the (compound A) to the tin atom. However, when compared bottom of the plastic cup and not responding to to the LC and LC values of temephos which was gold mechanical stimulation. Three replicates were carried out standard larvicidal testing, only compound B could equal with mosquitoes from different rearing batches and the the effectiveness of temephos as a larvicide agaist Ae. results were pooled.
aegypti mosquito larvae while the effectiveness of Statistical Analysis of Data: Tests with more than 20% mosquito larvae is less than temephos. control mortality were discarded and the repeated.
When compared with other larvicidal activity studies However, if the mortality of control were between 5-20%, of organotin(IV) compounds, these compounds which the observed percentage mortality was corrected by used in this study were among organotin(IV) compounds Abbot's formula [28].
that had good larvicidal effect (reference). The range of metylbutyrate was 0.32 -3.13 ppm [21]. This value larvicide against Ae. aegypti mosquito larvae than these LC and LC with their 95% confidence limits of the compounds. For triphenyltin para-substituted benzoate 50 90 compound was determined using computerized Log probit compound and tricyclohexyltin para-substituted benzoate analysis test [29].
compound, the average of the LC values were 0.62 ppm

RESULTS AND DISCUSSION
compound A-C had more potential to be explored as expressed in parts per million and their 95% confidence benzoate compounds. Larvicidal effects of compounds limit for compounds A-C screened against the third instar A-C on Ae. aegypti mosquito larvae also was better than larvae of Ae. aegypti mosquitoes are given in Table 1. triorganotin (IV) complex compound because compound As can be seen from Table 1, compounds A, B and C had A-C have higher LC values [22]. Organic group and the good larvicidal activity on third instar larvae of ligand that attached to tin atom were the main factor that Ae. aegypti mosquitoes because all LC and LC values influence biological activity of organotin(IV) [10,18,24].   However, further study should be conducted to clarify the ACKNOWLEDGEMENT mechanism of toxicity of compound A-C to the Ae. aegypti mosquito larvae.
Adulticidal Bioassay Testing: From the larvicidal bioassay testing, it was showed that compound B performed the best larvicidal activity against third instar Ae. aegypti mosquito larvae compared to compound A and C. Therefore, further study on compound B on adults of Ae. aegypti mosquito was conducted to investigate its adulticidal property by WHO topical application method. The purpose of this method was to determine the intrinsic activity of this compound to a target species to isolate toxicity of from confounding effects resulting from insect behavior [27]. The result of adulticidal bioassay testing was summarized in Table 2 ppm, respectively. Remarkably, the effectiveness of the compound B was comparable to the effectiveness of malathion which was gold standard for mosquito adulticide. The advantages of organotin(IV) compound are it will biodegrade into a non-toxic inorganic compound in environment and there is no reported resistance of this compound towards Ae. aegypti. With these advantages, this organotin(IV) compounds has potentials to be explored as insecticide in the effort to control the widespread of dengue.

CONCLUSION
In conclusion, compound B is the most effective compound among three organotin(IV) compound tested against Ae. aegypti. The larvicidal effect of the compound towards Ae. aegypti mosquito larvae is superior than temephos while its adulticidal effect towards adults of Ae. aegypti mosquito was comparable with malathion. Further study of this compound should be conducted in order to explore its potential as an insecticide to control the dengue vectors in addition to control the spread of dengue.
We would like to thank the Malaysia of Higher Education (MOHE) for the financial support of the FRGS grant (Project code: UKM-NN-06-FRGS0003-2007). Technical support from staffs of Faculty of Allied Health Sciences, Universiti Kebangsaan Malaysia is gratefully acknowledged.