Studies on Insecticidal Activity of Some Hydroxytriazene Derivatives

Nine hydroxytriazenes have been synthesized and screened for their insecticidal activity against one day old Drosophila melanogaster Meig (Fruit fly). Out of all the nine compounds screened, 3-hydroxy-3-n-propyl-1-mchlorophenyltriazene is the most active having LC50 values 0.9847 ppm. The least active compound is 3-hydroxy -3-n-propyl-1-p-methylphenyltriazene, whose values are 16.52 ppm. In general, the LC50 values range from 3.92 to 5.52 ppm.


Introduction
Hdroxytriazenes have been extensively used as analytical reagents [1][2] .Recently, they have also been screened for their biological activity including insecticidal activity in our laboratories [3][4][5][6][7][8] .In the present investigation, nine hydroxytriazenes have been synthesized and screened for their insecticidal activity against one day old males of fruit fly (Drosophila melanogaster Meig).

Synthesis of hydroxytriazenes
All the nine hydroxytriazenes have been synthesized by the method as reported in the literature [9][10][11][12][13][14] .The method involves preparation of aryl or alkyl hydroxylamine, aryldiazonium salts and coupling them at the temperature between 0-5ºC.The compounds so prepared were crystallized and their compositions were verified by elemental analysis, melting point determinations and I.R. studies.

Details of culture
In wide mouth bottles at a temperature of 27±1 0 C Drosophila melanogaster Meig were reared on the agar medium described by Lewis 15 .For preparing the medium, maize flour (150 g), jaggary (130 g), agar-agar (20 g), yeast (22 g), distilled water (1500 mL) and propionic acid (1 mL) were mixed and heated for 10 to 15 min.The flasks were allowed to cool.In each flask about 10-20 insects of D. melanogaster were released and it was covered immediately by muslin cloth.The newly emerged one day old male flies were used for investigation.

Toxicity studies
Micro bioassay was done using one day old male Drosophila melanogaster Meig by residue film method 16 .

Preparation of stock solution
A stock solution of 1000 ppm of each hydroxytriazenes was prepared in ethanol and acetone.Solutions of lower concentration were prepared by proper dilution of stock solution with the solvent.

Procedure
Residue film of one mL of the solution of each hydroxytriazene was prepared on Petri dish (10 cm diameter) by spreading 0.5 mL of the solution on each of the two parts of the Petri dish.The solution in both the parts of Petri dish was swirled gently in order to coat the entire surface.Thereafter, 20 one day old male insects were released in Petri dish and exposed for 24 h.The insects were anaesthetized by keeping them in deep freeze for about three minutes in order to make them inactive for about one minute.Each such treatment was replicated thrice.To record the natural mortality a control in three replication was also run by side.The mortality was taken after 24 h moribund insects were also counted as dead.

Results and Discussion
For the estimation of LC 50 values a method of probit analysis has been applied which involves changing of observed percent mortality to corrected percent mortality.For sake of brevity all the table and data of regression equation have not been incorporated.The concentration range used for test compound was 100 ppm and 500 ppm depending up on the response in individual concentration.Table 1 show LC 50 values and relative toxicity of hydroxytriazenes against one day old male D. melanogaster Meig Table 1.LC 50 values and relative toxicity of hydroxytriazenes against D. melanogaster Meig.

S.No.
Name LC 50 for HT* ppm  In the residual film method the probable mechanism of action of hydroxytriazenes might be as contact poison.Slight activity may be due to vaporization of the compounds in the closed Petri dish.
The contact poison either directly penetrates through body integument or may cause oxidation suffocating the insects.Thus it is certain that hydroxytriazene can be useful as insecticidal compounds if explored further.