Abstract
The activities of 15 nitrofuran compounds against E. coli were tested with the aid of serial dilution method and turbidity method using meat extract medium and, as a result, some of them were found to possess stronger activity than nitrofuran compounds available commercially. The correlation between the in vitro activity and chemical structure was similar as that showed by other authors in the past.
The absorption, excretion, and stability in the gastrointestinal organs were tested by using the turbidimetric assay method reported previously.
Most compounds tested were not detectable in serum following the intravenous administration of 200 or 500mcg/kg. into rabbit. Among these, furazolidone was found to be a compound showing the highest serum concentration of 1 mcg/ml after 5 minutes of administration. The serum concentrations following oral administration of 100mg/kg to rabbits varied from none with acid amide type compounds, to 0.5-1mcg/ml with furazolidone of aminooxazolidone type compounds, to about 2mcg/ml with NF-17 of oxim type compounds, and up to 3-4mcg/ml with furaltadone of morpholinomethyloxazolidone type compounds.
The urine concentrations following oral administration of 100mg/kg to rabbit were determined on 3 compounds. Only furaltadone showed urine concentration of about 50 mcg/ml after 4 and 6 hours of administration and about 0.14 per cent of the administered dose was recovered in the urine collected for a 6 hour period.
The stability of nitrofuran compounds in the saline suspensions of the rabbit gastrointestinal organs varied considerably according to the type of chemical structure and the organs used. In general, oxim type compounds were relatively unstable in the stomach while acid amide type compounds were highly, unstable in the intestine. Besides, it has been found that nitrofuran compounds in the same type showed a tendency to become unstable in the intestine according as the conjugated double bond of side chain increased in number.
It has been noted that there was a close correlation between the concentrations in blood, urine, and gastrointestinal tracts after oral administration and the stability in the saline suspensions of gastrointestinal organs, that is, it is needless to say that one of the most important conditions in which nitrofuran compounds display their systemic antimicrobial activities after oral administration is that nitrofuran compounds must be stable in the gastrointestinal tracts.
