摘要：Lichen metabolites have multiple functions in nature and these include several biological activities against pathogens and multi-drug resistant bacteria. This study shows the antibacterial properties of 18 Usnea species collected from five provinces in the northern part of Luzon, Philippines. A total of 41 lichen specimens were extracted using acetone to a final concentration of 10 mg/ml. The crude extracts were initially subjected to TLC. Interestingly, 17 different lichen metabolites were identified. The 41 crude lichen extracts were then tested against Staphylococcus aureus and Bacillus subtilis using paper-disk diffusion assay, most of which were found to be more active against the latter test organism. In addition, 28 of the 41 lichen extracts were also tested against Mycobacterium phlei . Interestingly, most of the samples exhibited much greater activities than that of the antibiotics used as indicated by the zones of inhibition. Moreover, 15 crude extracts showing distinct spots in their TLC profiles were tested against Nocardia asteroides using TLC-bioautography. Results showed that usnic acid, norstictic acid, and salazinic acid were the bioactive lichen metabolites
关键词：acid-fast bacilli – gram-positive bacteria – lichen acids – paper disk diffusion assay – TLC bioautography
