Search

The kinetics of amylose leaching in hot, excess water from native, oxidized-by-potassium permanganate and heat-treated potato starch at temperatures of 62–90 °C was investigated in isothermal conditions. For the first time, it was proposed to describe the kinetic data by the Kroger–Ziegler equation. It was found that for native starch in the range of 62–70 °C, the activation energy of the amylose leaching process is 192.3 kJ/mol, and at a temperature of 80–90 °C, it decreases to 22 kJ/mol. Similar patterns were established for modified starches. In the kinetic mode, the activation energy was 102.5 kJ/mol for oxidized starch and 44.7 and 82.5 kJ/mol for heat-treated starches at a temperature of 135 °C for 2.5 and 5 h. In the diffusion mode, it was: 18.7 kJ/mol for oxidized and 16.2 and 18.9 kJ/mol for heat-treated starches for 2.5 and 5 h, respectively. It is shown that the consideration of amylose leaching as a heterogeneous pseudochemical process makes it possible to explain the change in the activation energy with increasing temperature by the transition of the leaching process from the kinetic to the diffusion mode. As such a pseudochemical process, it is proposed to consider the breaking of multiple hydrogen bonds between amylose macromolecules. The change in the activation energies of amylose extraction from modified starches is explained by the change in the degree of amylose polymerization. Thin-layer chromatography was used to compare the molecular weight distributions of the resulting modified amylose samples. FTIR spectroscopy and thermal methods of analysis were used to study the transformations of starch during heat treatment.

This report presents a new modification of the isoniazid (INH) structure linked with different anilines via a carbonyl group obtained by two synthetic procedures and with N-substituted 5-(pyridine-4-yl)-1,3,4-oxadiazole-2-amines prepared by their cyclisation. All synthesised derivatives were characterised by IR, NMR, MS and elemental analyses and were evaluated in vitro for their antimycobacterial activity against Mycobacterium tuberculosis H$_{37}$Rv, Mycobacterium avium 330/88, Mycobacterium kansasii 235/80 and one clinical isolated strain of M. kansasii 6509/96. 2-Isonicotinoyl-N-(4- octylphenyl)hydrazinecarboxamide displayed an in vitro efficacy comparable to that of INH for M. tuberculosis with minimum inhibitory concentrations (MICs) of 1–2 μM. Among the halogenated derivatives, the best anti-tuberculosis activity was found for 2-isonicotinoyl-N-(2,4,6-trichlorophenyl)hydrazinecarboxamide (MIC = 4 μM). In silico modelling on the enoyl-acyl carrier protein reductase InhA confirmed that longer alkyl substituents are advantageous for the interactions and affinity to InhA. Most of the hydrazinecarboxamides, especially those derived from 4-alkylanilines, exhibited significant activity against INH-resistant nontuberculous mycobacteria.