In a bid to discovering novel antibiotics to combat growing trend of multi-drug resistance strains of Salmonella typhi, 48 new pyridine derivatives with significant inhibitory activities against the aforementioned bacterium were subjected to molecular docking against DNA gyrase protease of the bacterium, drug likeness evaluation and pharmacokinetics profiling. All the 48 leads displayed better binding affinity values when compared with Amoxicillin, Ciprofloxacin, Ceftriaxone, Ampicillin, and chloramphenicol, the standard antibiotics used herein for quality assurance. Furthermore, the majority of the compounds were, however, screened out due to their poor pharmacokinetics profiles and drug-likeness. Only five compounds emerged as the most promising leads and they include C4 with binding affinity of -8.0 kcal/mol, C8 (-8.6 kcal/mol), C9 (-8.1 kcal/mol), C26 (-8.3 kcal/mol), and C27 (-8.0 kcal/mol). These compounds not only displayed better binding affinity when compared with the reference antibiotics but also exhibit different modes of interactions with the target protease of the bacterium making them more potent and drug like. Toxicity evaluation of the leads also revealed that the compounds are neither tumorigenic nor mutagenic. In view of the excellent binding affinity, high pharmacokinetics profile and positive drug-likeness of the novel ligands, we recommend these promising compounds for in vitro and in vivo studies in order to discover novel antibiotics that could curb the dangerous trend of multiple drug resistance by Salmonella typhi.

Natural organic pigments such as carotenoids, betalains, anthocyanins, and carminic acid are notably found as safer food preservatives compared to other harmful synthetic chemicals. Due to glycosylation and acylation, betalains exhibit a broad-spectrum antimicrobial functionality with protection against degenerative diseases. Thus, betalains have been investigated as a potential bacterial inhibitor for food preservative applications. Initially, 36 betalain derivatives have been taken for primary screening using molecular docking. Afterward, the top ten ligands are taken for further study and analysis. The results of Prediction of Activity Spectrum of Substances (PASS) assured the antibacterial capabilities of betalains, and Lipinski's rule-of-five ensures the acceptability of the selected ligands as antibacterial inhibitors. The bacterial pathogens, such as C. botulinum (3FIE), E. coli (2ZWK), and S. typhi (3UU2) are selected for molecular docking by these betalain pigments. Furthermore, ADMET investigations and QSAR studies are performed to check insights into the bacterial inhibition process. Most active and common binding sides were observed at GLY159, ASN165, and SER166 for C. botulinum, at ASP8, LYS40, and TRP50 for E. coli; and at ARG37, GLN5, and ARG74 for S. typhi. The present study clearly shows an excellent insight towards the invention of plant-based new organic inhibitors to face the challenges of bacterial-resistant common food preservatives.