Insect antifeedant potent quinoxalines

Some 6-substituted aryl quinoxalines have been prepared and their purities were checked by their physical constants and spectroscopic data reported earlier. The insect antifeedant activities of these quinolones were studied by leaf-discs bio assay method using 4 th instar larvae Achoea Janata L .

The halogen substituted epoxides possess insect antifeedant activity and it was studied by Thirunarayanan [28][29][30]. The insect antifeedant activities of di-imines [31], oxazines [32] and Tröger bases [33] were reported in literature. Recently, Thirunarayanan have evaluated  [34]. Within the above view, there is no report available for the study of insect antifeedant activity of aryl quinoxalines in the past in literature. Therefore, the authors have taken efforts to synthesis the substituted quinoxalines for studying the insect antifeedant activities using leaf-disc bio assay method using 4 th instar larvae Achoea Janata L.

1. Synthesis of substituted quinoxalines
Aryl 5-and 6-substituted quinoxalines were prepared by literature method [35]. The purities of these quinoxalines have been examined by the characterization data reported earlier. The general structure of the 6-substituted quinoxalines is shown in Fig. 1.

1. Insect antifeedant activity
Generally organic compounds which are having carbonyl, unsaturation and halogens they possess insect antifeedant activity. Therefore, the author wishes to examine the insect antifeedant activity of these substituted quinoxalines derivatives and found to be active as insect antifeedants. This test was performed with a 4 th instar larva Achoea janata L against castor semilooper, were reared as described on the leaves of castor, Ricinus communis in the laboratory at the temperature range of 26 °C ±1 °C and a relative humidity of 75-85 %. The leaf -disc bioassay method [12,30,34] was used against the 4 th instar larvae to measure the antifeedant activity. The 4 th instar larvae were selected for testing because the larvae at this stage feed very voraciously.

2. Measurement of insect antifeedant activity of quinoxalines
Castor leaf discs of a diameter of 1.85 cm were punched and intact with the petioles. All synthesized quinoxalines were dissolved in acetone at a concentration of 200 ppm dipped International Letters of Chemistry, Physics and Astronomy Vol. 41 83 for 5 minutes. The leaf discs were air-dried and placed in one liter beaker containing little water in order to facilitate translocation of water. Therefore, the leaf discs remain fresh throughout the duration of the rest, 4 th instar larvae of the test insect, which had been preserved on the leaf discs of all quinoxalines and allowed to feed on them for 24 h. The areas of the leaf disc consumed were measured by leafdisc bio assay method [12,30,34]. The observed antifeedant activity of 5-and 6-substituted quinoxalines derivatives was presented in Table 1.  The results of the antifeedant activity of substituted quinoxalines are presented in Table  1 reveals that compounds 3, 5 and 6 were found to reflect satisfactory antifeedant. This test is performed with the insects which ate only two-leaf disc soaked under the solution of this compound.
Compound 6 showed enough antifeedant activity but lesser than 5. Further compound 5 was subjected to measure the antifeedant activity at different 50, 100, 150 ppm concentrations and the observation reveals that as the concentrations decreased, the activity also decreased. It is observed from the results in Table 2 and that the 5 6-chloro-2,3-diphenylquinoxaline showed an appreciable antifeedant activity at 150 ppm concentration.

CONCLUSIONS
A series of 5,6-substituted 2,3-diphenyl quinoxaline derivatives have been synthesized and examined their purities with their physical constants and spectroscopic data reported in earlier. The insect antifeedant activities of quinoxalines have been evaluated using leaf-disc bioassay method. The quinoxaline 5 6-chloro-2,3-diphenylquinoxaline showed an appreciable antifeedant activity.