Antibacterial activity of various compounds were tested in vitro. 2, 5-Dimethyl-4'-hydroxydiphenyl ether and some lichen components such as anziaic acid, microphyllic acid, protocetraric acid, α-collatolic acid, collatolon, rangiformic acid, l-protolichesterinic acid, and sphaerophorol, were able to inhibit the growth of Micrococcus pyogenes var. aureus in 80, 000 dilutions, and anziaic acid, microphyllic acid, protocetraric acid, α-collatolic acid, collatolon, rangiformic acid, β-collatolic acid, and stictinic acid, all lichen substances, were also able to inhibit the growth of Escherichia coli communior in 80, 000 dilutions. Anziaic acid, microphyllic acid, protocetraric acid, α-collatolic acid, sphae-rophorol, divaricatic acid, and sphaerophorin, the lichen substances, and 2, 5-dimethyl-3-hydroxydiphenyl ether, and 3, 7-dihydroxy-1, 9-dimethyldibenzofuran were able to inhibit the growth of Bacillus subtilis in 80, 000 or more dilutions. Of these compounds, anziaic acid, microphyllic acid, protocetraric acid, and α-collatolic acid were all effective against the three kinds of microorganisms tested, in 80, 000 dilutions.
