Umar Ali, Maimuna Usman B, and Abdussalam Abubakar S

Keywords: Antimicrobial, Cytotoxicity, Chitosan, Complexes, Schiff base

Abstract 

Chitosan was prepared from Schistocerca gregaria (desert grasshopper) and chemically modified with different aldehydes and their metal (II) complexes were prepared. The chitosan Schiff bases and their metal complexes were characterized on the basis of physicochemical properties, FT-IR and SEM. Chitosan and its derivatives were evaluated for their in vitro antimicrobial activity against two Gram positive bacteria (Escheria coli and Salmonella typhii), one gram negative (Staphylococcus aureus) and three fungi (Aspergillus niger, Aspergillus flavus, Tricodma spp) by MIC and MBC/MFC method. The chitosan Schiff bases have a melting point range of 235-252⁰C, decomposing temperature of the chitosan metal complexes 278291⁰C. Magnetic moment of the complexes suggested the paramagnetic nature of the complexes, also molar conductivity obtained revealed the non-electrolytic nature of the complexes. The infrared bands at 3257 cm^-1, 1622 cm^-1 and 1626 cm^-1, 1603 cm^-1, and 1611 cm^-1 confirmed the chitosan, chitosan Schiff bases and its co-ordination with the metal ions via the azomethane nitrogen respectively. The results revealed that chitosan Schiff bases and their complexes have higher antifungal/antibacterial activities than the non-modified chitosan, which are in the order of chitosan metal complexes >chitosan Schiff bases>non modified chitosan. Cytotoxicity test in vivo was also carried out for the samples and results revealed that chitosan non modified sample was the most active against the brine shrimps at all concentrations 10µg/ml,100 µg/ml,1000 µg/ml compared to chitosan Schiff bases and chitosan metal complexes.