Possible reaction pathways of the lincomycin molecule according to the DFT calculation method

Human- used antibiotics are eliminated from the body with little or no transformation at all. Traces of eliminated antibiotics enter the receiving environment directly since they cannot be treated in prevalent wastewater treat­ment facilities. Thus, wastewaters containing traces of antibiotics have to be treated accordingly. Lincomycin is subsequently isolated from Streptomyces lincolnensis . Lincomycin and its derivatives are antibiotics exhibiting bio­log­ical activity against Gram-positive bacteria, and are natural antibiotics in the environment as pollutants. This study aims to predict the degradation mech­anism of lincomycin molecule in the gaseous phase and aqueous media. Pro­bable reaction path of lincomycin molecule with OH radicals was analyzed. Optimized geometry was calculated via Gauss View 5. Subsequently, the low­est energy status was determined through geometric optimization via Gaussian 09 program. Aiming to determine the intermediates in photocatalytic degrad­ation mechanism of lincomycin, geometric optimization of the molecule was realized through DFT method. Activation energy for the probable reaction path was calculated, and their most stable state from the thermodynamic perspective determined for the gaseous phase and aqueous media. Impact of water solvent was investigated using the conductor-like screening solvation model (COSMO). The predicted mechanism was confirmed by comparison with experimental results on simple structures reported in literature.