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medium used in the set-up to monitor biofilm formation. Interestingly, compound A-
14 with a long alkyl chain, does not follow this general trend as no effect on the
growth was observed at 80 µM while the biofilm formation was inhibited at 9 µM.
As depicted in table-3 and figure 1, a similar structure activity relationship was found
for the inhibition of P. aeruginosa biofilm formation at 25°C. Again, introduction of
a short alkyl chain at the N1-position generally results in a decreased activity (except
for compound (A-2), while all the compounds with an intermediate alkyl chain length
show very strong activities. The effect of substitution with a long alkyl chain is in this
case also dependent on the nature of the C5-subsitutent. In the case of compound (A),
substitution with a long alkyl chain results in very active compounds (A-10 to A-14),
The activity of compound (B) is also decreased after introduction of a long N1-alkyl
chain, (compounds B-9 to B-13). Interestingly, growth curve analysis revealed that
these compounds are much less toxic to P. aeruginosa than to S. Typhimurium. Most
compounds show a broad concentration range with only biofilm inhibition and no
effect on the planktonic growth (table -3).
No. Compound
Code
R1
H 2N
N
N
R 1
R2
R 2
S. Typhimurium
IC50
P. aeruginosa
IC50
1 A-1 Me H 431.5 95.1
2 A-2 Et H 206.0 20.6
3 A-3 i-pr H 175.5 4.5
4 A-4 n-Bu H 51.9 2.1
5 A-5 n-Pen H 48.3 2.0
6 A-6 n-Hex H 39.6 19.1
7 A-7 n-Hep H 12.2 6.8
8 A-8 n-Oct H 11.8 18.5
9 A-9 n-Non H 5.9 8.3
10 A-10 n-Dec H 6.1 15.0
11 A-11 n-Und H 7.1 16.2