Structure–Activity Relationships of Hemocompatible Cationic 6-Azaindole Pyridinium Salts: Antimicrobial and Anticancer Activity

A series of 6-azaindole pyridinium derivatives were synthesized, structurally characterized, and evaluated for their antimicrobial (against Staphylococcus aureus, Escherichia coli, and Candida albicans) and anticancer properties (against NCI 60 panel). Hemocompatibility was evaluated using the hemolytic index, while ADME properties were estimated using in silico methods. Structure–activity relationship analysis indicated that para-substitution of the phenyl ring, particularly with halogen or methoxy groups, influences antimicrobial activity, selectivity toward Gram-positive bacteria, and hemocompatibility. Compounds 2b and 2c showed the most notable antimicrobial effects, including inhibition of microbial adhesion at hemocompatible concentrations. Compound 2b exhibited growth inhibition against cancer cells, showing 57% percent growth inhibition (PGI) against the MDA-MB-468 breast cancer cell line at 10 mM. Overall, these results highlight 6-azaindole pyridinium salts as a promising class of compounds for further investigation.