Antibacterial activity of usnic acid from Usnea longissima Ach

Isolation and identification of secondary metabolite from n-hexane fraction of lichen Usnea longissima Ach. and its bioactivity as antibacterial have been carried out. The isolation of chemical compounds was performed by using Gravity Column Chromatography (GCC), solvent systems as mobile phase (n-hexane, ethyl acetate), and Thin Layer Chromatography (TLC). The form of isolated compound was yellow needle crystals. The result of 1D-NMR (¹H and ¹³C-NMR) data showed that the isolated compound was usnic acid. Antibacterial bioactivity testing was conducted by using the paper disk diffusion method indicated that the usnic acid compound was actively inhibited the growth of E. coli (ATCC35218) and S. aureus (ATCC25923) at the concentrations of 500mg/mL and 1000mg/mL with inhibition zone between 12mm and 17mm. In addition, S. typhi (YCTC) was only inhibited at the concentration of 1000mg/mL with inhibition zone of 14mm.