Multifaceted approach of GC-MS, pharmacokinetics, and molecular docking for questing novel antibacterials: Profiling Parmotrema perlatum extract, targeting Acinetobacter baumannii and Klebsiella pneumoniae of ESKAPE Group

Parmotrema perlatum (Black Stone Flower-Dagad Phool) belongs to the family Parmeliaceae has been proven to have antibacterial and antifungal activity against several Multi Drug Resistant strains. In this study, the antimicrobial profile of Parmotrema perlatum extract has been evaluated against multidrug-resistant pathogens-Acinetobacter baumannii and Klebsiella pneumoniae. This is done using standard in vitro assays, which reveal that the lichen has a significant ability to inhibit bacterial growth. Fourier Transform Infrared Spectroscopy analysis revealed a distinctive band absorption peak at 3235.80 cm^-1, indicating the free hydroxyl phenolic group (OH) stretching. Other band peaks at 1000, 1062, 1106, 1163, 1201.7, 1263.8, and 1317.13 cm^-1 are due to the vibration of the (C-O) polyol stretching group (hydroxyl flavonoids), indicating the abundance of phenolic and flavonoid compounds, which could be the key components responsible for antimicrobial activity against Acinetobacter baumannii and Klebsiella pneumoniae. The Gas Chromatography-Mass Spectrometry analysis revealed the presence of 20 bioactive molecules out of which, predominantly three molecules were identified to have pharmacological antibacterial activities. The pharmacokinetics of the identified compounds were evaluated using pkCSM and SwissADME, ensuring their potential as drug-like candidates. Molecular docking studies were used to predict the binding affinity of the identified compounds to Penicillin-Binding Protein-2 of A. baumannii and KPC-2 (Carbapenemase) of K. pneumoniae.