Biological and chemical analysis of five selected lichen species from Sagarmatha National Park of Nepal

Abstract

Lichens are unique organisms consisting of fungi and algae in a symbiotic association. Lichens have been used as medicines for a long time. The purpose of this study was to profile the chemical constituents and biological activities of methanol extract of five lichens; Lobaria japonica, Lobaria retigera, Heterodermia leucomela, Heterodermia speciosa and Ramalina spp. collected from Sagarmatha National Park, Solukhumbu District, Nepal. Total phenolic content was evaluated by Folin Ciocalteu method while total flavonoid content was evaluated by aluminum chloride colorimetric method. Antioxidant activity was evaluated by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay and α-amylase inhibitory activity was evaluated by starch-iodine method. Antibacterial activity was evaluated by agar-well diffusion method. The highest phenolic content was observed in L. retigera and the lowest was in H. speciosa. Similarly, the highest flavonoid content was observed in L. retigera and lowest in Ramalina spp. The highest DPPH radical scavenging activity was shown by L. retigera and lowest by H. speciosa. The methanol extract of L. japonica exhibited the highest α-amylase inhibitory activity. The lichens possessed high antimicrobial properties against E. coli, S. aureus and B. subtilis. Metabolites profiling of selected three lichens species by Gas Chromatography-Mass Spectrometry revealed the presence of atraric acid, methyl haematomate, orcinol and methyl everniate as the major components. Among the five lichens, L. japonica and L. retigera were found to possess potent biological activities as well as higher phenolic and flavonoid contents. These lichens can be further studied and processed for the commercial production of polyphenols.