Synthesis of acyl thiourea derivatives of chitosan and their antimicrobial activities in vitro

Three different acyl thiourea derivatives of chitosan (CS) were synthesized and their structures were characterized by FT-IR spectroscopy and elemental analysis. The antimicrobial behaviors of CS and its derivatives against four species of bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Sarcina) and four crop-threatening pathogenic fungi (Alternaria solani, Fusarium oxysporum f. sp. vasinfectum, Colletotrichum gloeosporioides (Penz.) Saec, and Phyllisticta zingiberi) were investigated. The results indicated that the antimicrobial activities of the acyl thiourea derivatives are much better than that of the parent CS. The minimum value of MIC and MBC of the derivatives against E. coli was 15.62 and 62.49 μg/mL, respectively. All of the acyl thiourea derivatives had a significant inhibitory effect on the fungi in concentrations of 50–500 μg/mL; the maximum inhibitory index was 66.67%. The antifungal activities of the chloracetyl thiourea derivatives of CS are noticeably higher than the acetyl and benzoyl thiourea derivatives. The degree of grafting of the acyl thiourea group in the derivatives was related to antifungal activity; higher substitution resulted in stronger antifungal activity.[1]


Anion binding with urea and thiourea derivatives

The importance of anion receptors is a reflection of the ubiquitousness of anions, their functions in biological and industrial processes, as well as their behaviour as pollutants. In the immense field of anion receptor chemistry which has expanded greatly in the past few decades, one of the most prominent binding sites is (thio)urea. The simple synthesis of diverse (thio)urea derivatives, their possibility to form two H-bonds with anions and a promising selectivity with anions of complementary geometry are factors that gave rise to a plethora of studies reporting new organic molecules with different properties and applicability. This review includes the most important examples of (thio)urea receptors from the very beginning, until present. Many authors have used (thio)urea moieties in the computer-aided design of anion sensors, which was then followed by their synthesis, and utilization in the photophysical characterization of host–guest systems, and studies in the transport of ions and ion pairs through membranes. These endeavours led to their successful utilization in the fields of crystal engineering and development of functional materials. Characterization of supramolecular systems and investigations of the complexation thermodynamics has been conducted by use of different analytical and physico-chemical methods. Consequently, it is highly beneficial to summarize all aspects of anion recognition by (thio)ureas within one review article. This critical review containing 386 references classifies (thio)urea derivatives, published from 1990 to 2015, with respect to the complexity of the receptors and the number of urea groups in the molecule.[2]


Synthesis, characterization and biological evaluation of some thiourea derivatives bearing benzothiazole moiety as potential antimicrobial and anticancer agents

Five series of thiourea derivatives bearing benzothiazole moiety (20 compounds) were efficiently synthesized and evaluated for antimicrobial and anticancer activities. The results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms and showed higher activity against fungi than bacteria. Compounds 1b, 2b, 3b, 4b and 5b exhibited the greatest antimicrobial activity. Preliminary study of the structure–activity relationship revealed that electronic factors in benzothiazole rings had a great effect on the antimicrobial activity of these compounds. In preliminary MTT cytotoxicity studies, the thiourea derivatives (2d, 5c and 5d) were found most potent. In MCF-7 and HeLa cells, the IC50 values were observed in the range of 18–26 μM and 38–46 μM, respectively.[3]

Protection of Metal Surfaces from Microbial Colonization

This review discusses some aspects relating to the microbial interaction to metal surfaces. Most of the previous studies assumed that this process results in increased corrosion rates (MIC), however more recently it has been reported that many bacterial species can reduce corrosion rates of different metals and alloys in many corrosive environments by changing drastically the electrochemical conditions at the metal-solution interface. These changes ranged from acceleration of corrosion to corrosion inhibition. Microorganisms can contribute to corrosion inhibition by different means such as neutralizing the action of corrosive substances, formation of protective films on a metal surface and finally through the induction of a decrease in the medium corrosiveness. The mechanism of corrosion protection seems to be different for different bacteria since it has been found that the corrosion potential Ecorr became more negative in the presence of Shewanella ana and algae, but more positive in the presence of Bacillus subtilis. We previously described the efficient effect of the prepared 1,3-Bis-(4-amino-benzoyl) thiourea (AB-T) compound on corrosion inhibition of carbon steel in 0.5 M hydrochloric acid solution using different concentrations and different methods. In addition, results obtained indicated that AB-T was found to possess an anti-microbial activity against Gram-positive bacteria (Bacillus mycoides), Gram-negative bacteria (Escherichia coli) and non-filamentous fungi (Candida albicans).[4]


The Antibacterial Activity of 2-aminoindanbiguanide Chloride and Acetate Salts against Resistant Gram-negative Bacilli

Antiseptics and disinfectants are important substances for medical care. However, the needs for new antiseptics have increased in the last few years, due to multi-drug resistant pathogens. In this study we aimed to evaluate, the efficacy of 2-aminoindanbiguanide chloride (2-AIB.HCI) and 2-aminoindanbiguanideacetate (2-AIB.HOAc) salts that were synthesized against multi-drug resistant Gram-negative bacilli (MDR-GNB) (Acinetobacter spp, Escherichia coli and Klebsiella pneumoniae). According to our resultsat70 mg/mL concentrations of 2-AIB.HCI and 2-AIB.HOAc salts have been confirmed to be effective against hospital infection causing MDR-GNB. It was shown that 2-AIB.HCI and 2-AIB.HOAc salts have antibacterial efficacy against MDR-GNB.[5]

Reference

[1] Zhong, Z., Xing, R., Liu, S., Wang, L., Cai, S. and Li, P., 2008. Synthesis of acyl thiourea derivatives of chitosan and their antimicrobial activities in vitro. Carbohydrate research, 343(3), pp.566-570.

[2] Bregović, V.B., Basarić, N. and Mlinarić-Majerski, K., 2015. Anion binding with urea and thiourea derivatives. Coordination Chemistry Reviews, 295, pp.80-124.

[3] Saeed, S., Rashid, N., Jones, P.G., Ali, M. and Hussain, R., 2010. Synthesis, characterization and biological evaluation of some thiourea derivatives bearing benzothiazole moiety as potential antimicrobial and anticancer agents. European journal of medicinal chemistry, 45(4), pp.1323-1331.

[4] Mansour, R. and Elshafei, A.M., 2017. Protection of Metal Surfaces from Microbial Colonization. Annual Research & Review in Biology, pp.1-8.

[5] Genç, H. and Karabay, O., 2014. The antibacterial activity of 2-aminoindanbiguanide chloride and acetate salts against resistant gram-negative bacilli. Annual Research & Review in Biology, pp.1353-1360.