2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
Table I
Concentration of dichlone used in MIC testing
Dilution 1 Dilutions 2 Dilutions 3
0.001 μg ml –1 0.125 μg ml –1 16.0 μg ml –1
0.002 μg ml –1 0.25 μg ml –1 32.0 μg ml –1
0.004 μg ml –1 0.5 μg ml –1 64.0 μg ml –1
0.008 μg ml –1 1.0 μg ml –1 128.0 μg ml –1
0.016 μg ml –1 2.0 μg ml –1 256.0 μg ml –1
0.032 μg ml –1 4.0 μg ml –1
0.064 μg ml –1 8.0 μg ml –1
HPLC technique: for the identification of 2,3-dichloronaphtoquinone
in the samples a 1 mg ml –1 solution was prepared
in acetonitrile and 10 μl injected into the HPLC system.
The sample was injected three times.
Mobile phase was 60 % acetonitrile with 40 % water.
Chromatograms were registered at 254 nm.
Results
Antimicrobial susceptibility testing results show that the
dichlone have no antimicrobial activity on Gram-negative
bacteria Enterobacter aerogenes; in the same time the growth
of Gram-positive coccus Enterococcus faecalis (both strains)
was completly inhibited, as in Table II.
Table II
Dichlone’s MIC on Enterococcus faecalis strains
Strain MIC [μg ml –1 ]
E. faecalis – ATCC 29212 0.5
E. faecalis – ATCC 19433 0.5
As we mentioned in introduction, dichlone’s grade of
remanence, in the inoculated culture mediums for MIC was
determined by HPLC. The chromatograms of the mentioned
naphtoquinone obtained at the most effective chromatographic
conditions are shown in Figs. 2. and 3.
The height and area of PDA signal (254 nm) for this
naphtoquinone confirmed the calculated value for MIC.
Fig. 2. hPLC chromatogram for dichlone’s MIC (e. faecalis
– ATCC 29212)
s480
Fig. 3. hPLC chromatogram for dichlone’s MIC (E. faecalis
– ATCC 19433)
Conclusions
The results of this study show that dichlone has no antimicrobial
activity on Gram-negative germs (Enterobacter
aerogenes). In the mean time, dichlone’s MIC on Gram-positive
germs (Enterococcus faecalis – both strains) it was at
0.5 μg ml –1 in liquid culture media (M-H broth). This concentration
was confirmed by HPLC determination.
This work has been supported by Romanian Ministry
of Education and Research, National Authority for Scientific
Research, National Centre for Programmes Management
on Project No. 1885 NANOQMED: “Obtaining and characterization
of new targeted-nanodrugs with naphtoquinonic
active substance”.
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