Preparation, stabilization, and bioefficacy of beta-cyclodextrin inclusion compounds of chloramidophos

Cyclodextrins are common compounds capable of forming inclusion complexes with a variety of pesticides to improve their solubility, bioavailability, and stability. In this study, chloramidophos (CP) was inclusion-complexed with beta-cyclodextrin (beta-CD) by a kneading method in an attempt to gain a more stable but equally effecacious formulation compared with CP alone. A 1:1 CP-beta-CD complex with an inclusion constant of 203.0 M(-1) was determined to exist by UV spectrophotometry. The structural identification, thermal stability, and biological assays of the CP-beta-CD complex were then carried out with a product with the maximum guest loading efficiency. The data measured by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD), where the endothermic peaks of beta-CD, the FT-IR bands, and the XRD peaks were generally changed, deduced the formation of complex. Results of the thermal stability assay showed that the degradation rate of CP in 14-day incubation was slowed by a factor of 3.6 when it was complexed with beta-CD. Then, activity and toxicity of CP influenced by the encapsulated process of beta-CD were evaluated by an in vitro acetylcholinesterase (AChE) inhibition assay and an acute aquatic toxicity assay, respectively. No significant differences were found in both the two biological assays by a t-test. This indicated that the encapsulation process greatly improved the thermal stability of the pesticide with no adverse effects on bioefficacy compared to that of CP. There is a promising outlook for CP-beta-CD to be produced as the active ingredient of various formulation additives of CP for its continued application.