Improvement of antifungal activity of carboxin by inclusion complexation with cucurbit[8]uril

Interaction between cucurbit8]uril (Q8]) with a fungicide, carboxin in aqueous solution, was investigated by ¹H-NMR, electronic absorption spectroscopy, and fluorescence spectroscopy. Spectroscopy analysis established a basic interaction model which formed an inclusion complex with a host:guest ratio of 1:1. ¹H-NMR showed that Q8] encapsulated the phenyl ring into its cavity and the rest of the guest molecule stayed outside the host. Comparative in vitro evaluations of the growth inhibitory effects of the inclusion complex solution toward Rhizoctonia solani demonstrated appreciable improvements in the antifungal activity of carboxin through the addition of Q8]. In comparison with the positive control, improvement was evaluated in terms of area covered by the mycelia of R. solani and their growth inhibition rate. Inclusion complexation of carboxin with Q8] suggests a potential means for production of an environmentally friendly carboxin-based fungicide to counteract R. solani.