Antibiotic Activity of Lichens

Abstract

-Water extracts were made after grinding moistened fresh lichens. Their antibiotic property was tested by the cylinder plate procedure. Chloroform, ether and alcohol extracts of selected spp. were distilled, taken up in aqueous phosphate buffer and tested in cup plates. Of extracts of 42 spp. of lichens, 27 spp. were found active against Staphylococcus aureus or Bacillus subtilis, 4 spp. inhibited Proteus vulgaris or Alcaligenes fecalis, but none showed antagonism for Escherichia coli. Differences in the effects of the extracts from different spp. of lichens on different bacteria (including some gram-negative bacteria) suggest that > 1 antibiotic compound is involved. It is unknown whether these should be attributed to the algal or fungal member of the complex and whether the responsible substances are lichen acids or unidentified substances perhaps like those known lichen compounds with structural features in common with the antibacterial extracts from molds.