1) Several 4-hydroxycoumarins having acyl-groups in 3-position were tested as to their antibacterial properties against nine bacteria in several cultivating media in vitro.
The length of the acyl-side chains was found to be an important factor for the activity. 3-
n-Decanoyl derivative was found to be the most active compound. It could prevent the growth of
Staph. aureus in a dilution of 1:64000000 in Knight's medium.
2) Some 3-alkyl-4-hydroxycoumarins and 6-methyl-4-hydroxy-3-octanoylpyrone-2 were tested as to their activities in order to compare them with the above mentioned compounds.
Both the former, which lacks the tricarbonylmethane group, and the latter, which lacks benzene ring were less active compared with the corresponding 3-acyl derivatives.
3) The most active compound, 3-
n-decanoyl-4-hydroxycoumarin was tested as to its toxicity in mice.
4) 3-Acyl-4-hydroxycoumarins were tested as to a number of properties, which are commonly positive for detergents, such as surface activity and heamolytic power, but these tests were found to be negative.
5) The low antibacterial activities of 3-acyl-4-hydroxycoumarins when tested in serum broth may be due to the serum albumin present, which was found to antagonise the activity, while egg albumin was inert.
6) The influences of copper or cobalt ions, and cysteine, on the antibacterial activities of these 3-acyl derivatives were tested. No remarkable effects of these substances were found.
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