Background: The prevalence of morbidity and mortality due to infections from parasitic
worms and protozoa is on rise especially in third world countries. The situation is further worsened
by drug resistant microbial pathogens.
Objectives: The antimicrobial and anthelmintic activities associated with substituted furfuraldehyde
and 1,8-naphthyridine nucleus of nalidixic acid prompted us to synthesize some new quinolone
Schiff bases with an aim to obtain potent antibacterial and anthelmintic agents with improved safety
Methods: A new series of 1,8 naphthyridine based Schiff bases were designed and synthesized by
the reaction of Nalidixic acid methyl ester 1 with hydrazine hydrate in anhydrous condition which
yielded 1-ethyl-1,4-dihydro-7-methyl-4-oxo-1,8-naphthyridine-3-carbohydrazide 2. The compound
2 was further treated with several furfural aldehydes to furnish the desired Schiff bases (3a-k).
The in vitro antibacterial activity of Schiff bases was investigated against four Gram positive and
four Gram negative bacterial strains. The newly prepared Schiff bases were also tested for their
anthelmintic activity against Pheritima posthuma and Perionyx excavatus.
Results: Chemical structures and identity of the prepared compounds were confirmed by their
spectral data. Overall, Schiff bases (3a-k) showed good antimicrobial activity and interestingly five
compounds exhibited more potent inhibitory effect than the standard drug Ampicillin against
S. aureus, B. cereus, E. faecalis, S. epidermidis, E. coli, S. typhi and S. dysenteriae. Schiff bases
also exhibited significant anthelmintic activity as indicated by their mean paralyses time (min) of
7.07-16.49, and 11.23- 20.46 min against Perionyx excavatus and Pheritima posthuma in comparison
to the 8.23 and 12.58 min shown by standard drug- Albendazole.
Conclusion: It could be proposed that substitution of aromatic ring at C-5 of furfuryl heterocyclic
ring in the Schiff bases produce compounds with promising antibacterial and anthelmintic actions.