15 according to Eq. (1) and it was found to be around 975 M−1. In addition, the value is between 100 and 10,000 M−1, which is typical to many CD–drug complexes ,  and . TGA curves from Fig. 15 and Table 4 are describing weight losses of the pure components (propiconazole nitrate (NO3PCZ) and β-cyclodextrin (β-CD)) and of their inclusion complex obtained by the freeze-drying method. Pure NO3PCZ has a first stage of decomposition between 132 and 166 °C, reaching a weight
loss of 16.50%, and this step is attributed to the degradation of the triazolic ring . After Roxadustat order that at 250 °C, the weight loss is increasing rapidly reaching 95% at 320 °C. β-CD loses selleck water in the 50–104 °C interval and starts degrading at about 260 °C. It can be seen from Fig. 16 and Table 4 that the thermostability of the guest molecule was increased, from 132 to 152 °C, due to its inclusion in the cavity of cyclodextrin . In conclusion, TGA analysis indicated inclusion complex formation at the triazolic ring by increasing the thermostability of the triazole ring of drug from 132 to 152 °C after complexation. DSC reveals some information on solid state interactions between drug and cyclodextrin. The DSC curves of the pure NO3PCZ and of the physical mixture (3.5/3.5 w/w) (non-complexed components) exhibit two melting peaks of
different intensities at 126 and 137 °C, due to the fact that the drug has a minor and a major isomer  and  (Fig. 16). The loss of crystallized water from β-CD exhibits a broad endothermic peak, both in pure β-CD and physical mixture, around 110 °C. Analyzing the DSC curve of the inclusion complex it can be observed that the two endothermic peaks of drug occur in a single broad peak at 140 °C, with a small intensity, which can be attributed
to the formation of a new solid phase. DSC curves indicated an inclusion process by the presence of a much smaller and flat melting peak in the curve of the complex, compared to those of pure propiconazole nitrate  and . Preliminary comparative data on antifungal activity of PCZ, NO3PCZ and β-CD–NO3PCZ complex molecules are presented in Table 5. Overall, the antifungal activity of NO3PCZ and β-CD–NO3PCZ was exhibited at very Thalidomide low concentrations of the active substance, the values of MIC50 and MIC90 being 0.0156 and 0.0312 mg/L, respectively. Both forms of the drug showed comparable potent in vitro activity against Candida albicans strains (p>0.05) and this fact indicates a good availability of the drug in aqueous medium by incorporating the drug into CD cavity. Also, the data showed in Table 5 demonstrated that PCZ alone presented higher MICs than its derivatives (NO3PCZ), this fact indicating a limited antifungal effect of this parental triazole molecule.