Biological activities of novel 2-pyrazolin-5-one derivatives and their toxicity on certain pests infesting field crops in laboratory conditions

Abstract

A variety of highly potent derivatives of 2-pyrazoline-5-one, including chromene-3-carbohydrazide 2, 2-thioxothiazole-5-carbohydrazide 3, 2-oxopyridine-3-carbonitriles (4–6), 3-aryl-2-cyanoacrylohydrazide (7, 8), and 3-amino-5-arylpyrazole-4-carbohydrazide (9, 10), were synthesized as pesticide agents using acetohydrazide 1, a versatile and easily obtainable compound. The compounds structures were entirely ascertained utilizing different spectroscopic methods, including Fourier-transform infrared (FTIR), nuclear magnetic resonance spectroscopy, and analysis of elements. In the laboratory, we assessed the impact of nine 2-pyrazoline-5-one derivatives on the fourth larval stage of the cotton leaf worm (Spodoptera littorals), Monacha obstructa, and Tetranychus urticae adults. We used abamectin as the reference compound. The LC50 values of compound 3 for S. littorals, M. obstructa, and T. urticae are 0.90, 0.70, and 0.52 mg a.i./L, respectively. The LC50 values for the same compound for S. littorals, M. obstructa, and T. urticae are 0.80, 0.60, and 0.45 mg a.i./L, respectively. Therefore, it is a remarkably potent compound. Compound 6 exhibited lower levels of danger, as indicated by LC50 values of 1.94, 1.90, and 1.83 mg a.i./L against the three tested pests. Ten days after treatment, all three pests were moderately toxic to the remaining 2-pyrazolin-5-one derivatives, 1, 2, 4, 5, and 7–10. Conversely, the mortality rate of the tested compounds increased when the treated individuals were exposed to high concentrations. These 2-pyrazolin-5-one derivatives are suggested as suitable alternatives and foundational structures for developing novel insecticides.

Keywords

• Bioactivity
• 2-Pyrazolin-5-one
• Cyanoacetohydrazide
• Spodoptera littorals
• Monacha obstructa
• Tetranychus urticae