Antibacterial compounds and other constituents of Evernia divaricata (L.) Ach.

An activity-directed fractionation and purification process was used to isolate the antibacterial compounds from evernia divaricata (l.) ach. six lichen substances were obtained front the active petroleum ether and ethyl acetate fractions antibacterial activity assay showed that (±)-(12 r)-usnic acid (2) and divaric acid (6) strongly inhibited bacterial growth of bacillus subtilis,staphylococcus aureus,escherichia coh and pseudomonas aeruginosa. however,four other compounds of atranorin (1),2,4-di-o-methyldivaric acid (3). divaricatinic acid (4) and 2-o-methyinordivaricatic acid (5) had no apparent antibacterial activities against the four bacteria. compounds 3,4,5 and 6 are reported here for the first time from e. divaricata (l.) ach. furthermore,this is also the first time to report divaric acid exhibits strong anti-bacterial properties.