Antibacterial activity of the lichens<i>Usnea Florida</i>and<i>Flavoparmelia caperata</i>(Parmeliaceae)

Abstract

Acetone extracts of the two common epiphytes lichens <i>Usnea florida</i> and <i>Flavoparmelia caperata</i> have been evaluated for their antimicrobial activities against <i>Staphylococcus aureus</i>, <i>Candida albicans</i> and <i>Aspergillus brasiliensis</i>. The dibenzofuran derivative (+)-usnic acid (<b>1</b>) was the main metabolite in these two species. Thamnolic (<b>5</b>), evernic (<b>6</b>), physodic (<b>7</b>) and 3-hydroxyphysodic acids (<b>8</b>) were isolated from <i>U. florida</i>, as well as 5,7-dihydroxy-6-methylphtalide (<b>2</b>) which was newly identified in this <i>Genus</i>. Protocetraric (<b>3</b>) and caperatic acids (<b>4</b>) and ergosterol peroxide (<b>9</b>) are usually biosynthezised by <i>F. caperata</i>. Antibacterial activity was determined for the four main compounds against <i>Staphylococcus aureus</i> using bioautography and broth dilution method. Minimal inhibitory concentrations of usnic acid, caperatic acid and protocetraric acid were comprised between 7.25 and 12.5 µg/mL.