| From the lichen Neuropogon sp., collected in the region Livingston Island, Antarctica was isolated secondary metabolite, identical to (-) usnic acid(C18H16O7, MW. 344) with antibiotic activity. The structure was settled on the basis of high-resolution electron impact mass spectrometry(HREI-MS) and one and two dimensional NMR spectroscopy(1H, 13C, DEPT, COSY, HSQC and HMBC). The usnic acid was investigated for antimicrobial activity against pathogenic Gram-positive and Gram-negative bacteria as Streptococcus pyogenes 15346, Staphilococcus epidermidis 1093, Bacillus cereus 157, Listeria monocytogenes 981, Yersinia enterocolitica 013, Klebsiella pneumoniae 52145 and Salmonella thyphimurium. |