Studies of the structure, reactivity, cytotoxicity and antimicrobial activity of picolinic acid-derived herbicides

Chlorinated derivatives of picolinic acid are a group of chemical compounds commonly used as a component of plant protection products (herbicides) applied against weeds. This study examined the structural properties, microbiological activity, and cytotoxicity of picolinic acid and its four derivatives: clopyralid, aminopyralid, picloram, and triclopyr. Structural analysis was performed using spectroscopic methods: FTIR, Raman, and UV-VIS spectroscopy. The research was supported by theoretical calculations using quantum chemistry methods. The calculations of electronic charge distribution, electrostatic potential maps, HOMO and LUMO frontier orbital energies, and global reactivity descriptors were performed to characterize the electronic properties and relative reactivity of the studied compounds. Microbiological activity was tested against soil bacterial strains (Arthrobacter psychrolactophilus ATCC 700733, Bacillus megatherium ATCC 14581, Pseudomonas aeruginosa ATCC 15442, and Serratia liquefaciens ATCC 27592). Cytotoxicity studies were performed on normal human fibroblasts (BJ, ATCC CRL-2522), colorectal adenocarcinoma cells (Caco-2, ATCC HTB-37) and immortalized human keratinocytes (HaCaT, Cytion 300493). Tests were also conducted to assess the herbicides' susceptibility to thermal decomposition and to analyse thermal decomposition products. TG/FTIR analyses were used for this purpose.