Complexation of Triclopyr Butoxy Ethyl Ester with β‐Cyclodextrin

β‐cyclodextrin (β‐CD), a macro‐cyclic oligosaccharide exhibits the property of forming inclusion complexes with various molecules. These complexes display some improved properties of starting molecule such as, increase of aqueous solubility, improvement in stability as well as reduction of bad odor and/or toxicity of molecules. The formulation of an inclusion complex of β‐CD as the host molecule and triclopyr butoxy ethyl ester, a selective systemic herbicide, as guest molecule has been studied as an initial step towards the improvement in the conventional herbicide formulations. The interaction of triclopyr butoxy ethyl ester with β‐CD produced the formation of an inclusion complex. Three processing methods (kneading, co‐precipitation and co‐evaporation) were used to prepare solid inclusion complexes. X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and ultra‐violet (UV) spectroscopy techniques were used to study the complexation of this herbicide. The objective of the present work was to study the complexation and enhanced aqueous solubility of triclopyr butoxy ethyl ester. Phase solubility study suggested the existence of a 1:1 complex between herbicide and β‐CD. XRD and DSC analysis indicated the existence of an inclusion complex of herbicide with β‐CD. Dissolution rate study was conducted so as to study dissolution properties of complexes. The dissolution rate of the complexed herbicide in aqueous media was considerably improved as compared with the uncomplexed herbicide. The study also attempts to compare the various methods of complex formation. The best results were obtained when inclusion complexes were prepared by co‐precipitation method. Findings of this paper will allow more rational applications of herbicide with increase in its efficiency.

Keywords:

• β‐cyclodextrin
• inclusion complex
• triclopyr butoxy ethyl ester
• solubility

Acknowledgements

The authors wish to express thanks to Dr. Arun Gurjar for DSC analysis and Mr. Nilesh Kulkarni for XRD analysis from Tata Institute of Fundamental Research (TIFR), Mumbai, India.