Synthesis of Schiff Bases Based on Chitosan and Heterocyclic Moiety: Evaluation of Antimicrobial Activity

Abstract

Schiff bases of chitosan (CS) were prepared by reaction of four different heterocyclic compounds, namely, 1,3-dimethyl-2,4,6-trioxohexahydropyrimidine-5-carbaldehyde (M1), 3-acetyl-2 H -chromen-2-one (M2), 5-chloro-3-methyl-1-phenyl-1 H -pyrazole-4-carbaldehyde (M3), and 4-oxo-4 H -chromene-3-carbaldehyde (M4), with CS using thermal and ultrasound approaches. CS Schiff base formation was confirmed by using FT-IR, XRD, and TGA. Characteristic data show that amino groups in chitosan reacted with the functional group in the heterocyclic compound to form the Schiff base. CS Schiff bases show thermal stability more than pure CS. The antimicrobial activity of Schiff bases was tested against +ve Gram bacteria and −ve Gram bacteria. The result shows that Schiff bases prepared by temperature and ultrasound methods possess high antimicrobial activity against +ve Gram bacteria and −ve Gram bacteria; in comparison, Schiff bases produced by the ultrasound method have higher antimicrobial activity. The Schiff base (CSM4U), prepared by the ultrasound method by reaction of CS with 4-oxo-4 H -chromene-3-carbaldehyde, exhibited higher antimicrobial activity than Gentamicin as an antibacterial agent. The inhibition range caused by CSM4U was between 19 and 27 mm. Moreover, CSM4U also acted as an antifungal agent, causing an inhibition zone of 21 mm for both Candida albicans and Candida tropicalis , which was higher than that of Terbinafine.

Modern Rare Earth Imprinted Membranes for the Recovery of Rare Earth Metal Ions from Coal Fly Ash Extracts

“…Th authors intend to use these adsorption materials for further research on hybri Table 8 presents a comparison of the adsorption capacity of our synthesized Nd and YIIPs based on the modified chitosan sorbents with other rare earth ion-imprinted adsorbents. It was found that the synthesized IIPs showed a higher or comparable adsorption capacity compared to most of the examples given in the table, although in the case of [44,45] the obtained adsorption capacities were higher. However, this may be directly related to the different forms of occurrence of the tested sorbents, as well as the different conditions of the adsorption process, such as the pH and temperature.…”

Water-Soluble Quaternary and Protonable Basic Chitotriazolans: Synthesis by Click Chemistry Conversion of Chitosan Azides and Investigation of Antibacterial Activity

“…Consequently, there has been significant interest in the chemical modification of chitosan to obtain more soluble derivatives with enhanced biological properties. Most reported chitosan derivatives have been prepared by reactions with aldehydes and ketones to generate Schiff’s bases [ 5 , 6 , 7 ], acylation [ 8 , 9 ], alkylation [ 10 , 11 , 12 ], the chelation of metals [ 13 , 14 ], sulfonation [ 15 , 16 ], carboxymethylation [ 17 , 18 , 19 ], or free-radical grafting [ 20 ]. However, these standard methods sometimes require harsh conditions that affect the degree of polymerization [ 21 ], and it may be difficult to achieve both selective modification and a high degree of substitution.…”