Assessment of lichen metabolites as possible natural antioxidant and antimicrobial agents

Background: Lichens are known to produce diverse secondary metabolites with significant pharmacological properties, including antioxidant and antimicrobial activities. However, studies on lichens from the Similipal Biosphere Reserve remain limited. Objective: The present study aimed to evaluate the phytochemical profile, antioxidant potential, and antimicrobial activity of four predominant lichen species from the Similipal Biosphere Reserve. Materials and Methods: Four lichens Arthonia polymorpha (OQ845612), Harpothellon rubrocincta (OQ832495), Parmelia saxatilis (OQ825976), and Parmotrema reticulatum (OQ832494) were collected and identified using both morphological and molecular (18S rRNA, 28S rRNA, 5.8S rRNA, 1.5S rRNA, and ITS regions) approaches. The antioxidant activity was determined using radical scavenging assays (DPPH and ABTS) and enzymatic assays (SOD and CAT). Antimicrobial activity was evaluated using antibacterial assays and determination of minimum inhibitory concentration (MIC) values. GC-MS analysis was performed to identify bioactive secondary metabolites. Results: All lichen methanolic extracts exhibited promising radical scavenging activity in both DPPH and ABTS assays. Enzymatic antioxidant analysis revealed multiple isoforms of SOD (cytosolic and mitochondrial) and significant CAT activity. Antibacterial assays demonstrated that methanol and acetone extract of P. reticulatum and P. saxatilis had strong bactericidal effects, with notable MIC values against pathogenic bacteria. GC-MS profiling identified several bioactive compounds including polyphenols, hydroquinones, coumarins, alkaloids, flavonoids, arenes, meta-divarinol, benzoquinones, terpenes, azaarenes, and aromatic ethers, particularly in P. saxatilis and P. reticulatum. These compounds are associated with antioxidant, antibacterial, and cytotoxic activities. Conclusion: This study highlights the pharmacological significance of secondary metabolites present in lichens from the Similipal Biosphere Reserve. The findings demonstrate their potential as valuable bioresources for future therapeutic applications.