Usnic Acid, Metabolite from Neuropogon Sp., An Antarctic Lichen Isolation, Structure Elucidation and Biological Activity

ABSTRACT

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.