Harnessing chitosan and chitosan phosphate in vitro to combat fungal spoilage in vegetables through molecular docking interaction mechanisms

Chitosan (CH) is a natural, biodegradable polymer derived from chitin. It is known for its broad-spectrum antimicrobial properties. Three fungal pathogens—Mucor circinelloides, Cladosporium herbarum, and Aspergillus niger—were isolated from decayed cucumbers. The CH and chitosan phosphate inhibited fungal growth in a concentration-dependent manner. The chitosan phosphate exhibited superior antifungal activity, achieving up to 84.2% inhibition at 2.75% (w/v). M. circinelloides was more sensitive than C. herbarum and A. niger. The CH was investigated for its antifungal potential via molecular docking against key protein targets from three pathogenic fungi: M. circinelloides (PDB: 6VRX), C. herbarum (PDB: 7KQV), and A. niger (PDB: 1GAL). Using MOE 2019 software, docking scores and interaction profiles were analyzed. Chitosan exhibited the most favorable binding affinity towards M. circinelloides with a docking score of -7.81 kcal/mol, followed by C. herbarum protein (PDB: 7KQV; -6.78 kcal/mol) and A. niger protein (PDB: 1GAL; -6.62 kcal/mol). Hydrogen bonding dominated the interactions, with critical residues including ASP 80 (6VRX), GLU 190 (7KQV), and ASP 416 (1GAL). These results suggest chitosan phosphate’s potential as a broad-spectrum antifungal agent targeting essential fungal enzymes.