Antibacterial activities and chemical characteristics of usnic acid and other secondary metabolites extracted from Flavoparmelia caperata lichen species using methanol as a solvent (LB293)

Abstract

It is known that usnic acid extracted from Icelandic lichens has antimicrobial properties (Ingolfsdottir, 2002). The goal of this project is to investigate the antibacterial activities of the metabolites of the lichen Flavoparmelia caperata found growing in New England. Chemical extractions of lichen metabolites were performed using methanol as a solvent. Following the extraction of the lichen metabolites, their antimicrobial properties were tested using in vitro antimicrobial assays against the Gram positive Staph aureus, and Gram negative E. coli and Ps. aeruginosa. In addition, the antibacterial activities and chemical characteristics of lichens growing in shade were compared to those growing in the sun, based on literature finding that suggest that an increase in usnic acid is influenced by various ecological factors such as light and temperature (Cochietto, 2002). Following extraction, the secondary metabolites of lichens were identified using GC‐MS. Early results indicate that shade‐grown lichens contain larger quantities of usnic acid, and sun‐grown lichens contain smaller quantities of usnic acid in addition to other acids. Moreover, there are some indications that Staph aureus is more sensitive to the sun‐grown lichen. This may be due to the synergic effects of usnic acid and friedelan‐3‐one acid found in the sun‐grown lichen.