Phytochemical Investigation, Antioxidant and Antimicrobial Activities of Some Parmeliaceae Lichens from Western Himalaya

This study aimed to examine the antioxidant and antimicrobial activities and the phytochemical composition of three Parmeliaceae lichens from the western Himalayas. Three lichen species (Everniastrum cirrhatum (Fr.) Hale, Parmotrema reticulatum (Taylor) M. Choisy, and Usnea orientalis Motyka) were analyzed for antimicrobial, antioxidant assay, and chemical analyses using Gas chromatography-mass spectrometry (GC-MS). The chemical constituents were identified, and the percentage of components obtained was calculated. Antimicrobial activity was tested with the agar well diffusion method, and the total antioxidant capacity was measured using the phosphomolybdenum method (Total Antioxidant Capacity – TAC) and the hydrogen peroxide radical scavenging test. GC-MS analysis of methanol extracts from the lichens revealed 57 compounds in all three species. Methanol extracts from these lichens demonstrated strong antimicrobial activity (inhibition zones: 8.6 ± 0.09 to 28.2 ± 0.23 mm) with the highest activity against Salmonella typhi. They also exhibited low minimum inhibitory concentrations (MICs) of 0.125 mg against many microbes. The antioxidant capacity of methanol extracts ranged from 1.256 to 1.991 mg/g ascorbic acid equivalent. Interestingly, the hexane extract of E. cirrhatum showed the highest hydrogen peroxide scavenging activity at 91.13%. This study highlights the antioxidant and antimicrobial properties of these Parmeliaceae lichens, attributed to their diverse secondary metabolites. These findings suggest promising prospects for the development of novel antimicrobial and antioxidant agents from lichen extracts, warranting further exploration in pharmacological and biomedical research.