Enhanced antifungal and antioxidant activities of new chitosan derivatives modified with Schiff base bearing benzenoid/heterocyclic moieties

New gel from a water-soluble Carboxymethyl chitosan-Cinnamaldehyde Schiff base derivative as an effective preservative against soft rot in ginger

Ginger, valued for its culinary and medicinal properties, suffers substantial production loss-up to 90 %-due to fungal soft rot. To combat this, we have developed an environmentally sustainable antifungal polysaccharide gel derived from a water-soluble Schiff base of O-carboxymethyl chitosan (CMC) and cinnamaldehyde (CIN). Terpene incorporation was confirmed via various characterization techniques, including Fourier transform infrared (FT-IR), pH-dependent release, solubility, thermogravimetric analysis, and UV-vis spectra. Results showed successful grafting of CIN onto the polysaccharide, at a CIN:CMC ratio of 120 mg/g. In vitro evaluation demonstrated significant antifungal activity against F. oxysporum, with a MIC value of 159.25 μg/mL. Application of the CMC=CIN gel to ginger rhizomes inhibited spore germination in all evaluated wounds, enhancing gloss and appearance. These findings validate the efficacy of this novel, environmentally friendly gel in preventing ginger loss caused by fungal infections.

Herbal materials used as soil amendments alleviate root rot of Panax ginseng

Root rot is a serious soil-borne fungal disease that seriously affects the yield and quality of Panxa ginseng. To develop a sustainable strategy for alleviating ginseng root rot, an herb-based soil amendment is suggested in this study. Mixed powers of medicinal herbs (MP) and corn stalks (CS) were used as soil amendments, respectively, along with a control group (CK) without treatment. The application of MP and CS led to significant relief from ginseng root rot. The disease index (%) represents both the incidence rate and symptom severity of the disease. The disease index of the MP and CS group was 18.52% and 25.93%, respectively, lower than that of CK (40.74%). Correspondingly, three soil enzyme activities improved; the antifungal components in the soil increased; and the relative abundances of root rot pathogens decreased in response to MP Soil enzyme activities were negatively correlated with disease grades. MP group also led to possible interactive changes in the communities of soil fungi and chemical components. In conclusion, our results suggest that the use of herb-based soil amendments has significant potential as an ecological and effective approach to controlling root rot disease of ginseng by the changing rhizosphere fungal community and soil compositions.

Synthesis, characterization and antifungal activity of imidazole chitosan derivatives

Five novel imidazole-functionalized chitosan derivatives 3a-3e were synthesized via addition reactions of chitosan with imidazole derivatives. The partial incorporation of imidazole moiety in chitosan were confirmed by FTIR, UV, 1H NMR, XRD, SEM and GPC. Meanwhile, the antifungal activity against three common plant pathogenic fungi: Phytophthora nicotianae (P. nicotianae), Fusarium graminearum (F. graminearum) and Rhizoctonia solani (R. solani), was assayed in vitro at 0.5 and 1.0 mg/mL by hyphal measurement, and the introduction of imidazole group can influence the antifungal activity. At 0.5 mg/mL, 3e inhibited P. nicotianae growth by 42 % and had an inhibitory index against R. solani of 50 %. Derivative 3e was more effective than unmodified chitosan whose antifungal index was 17 % against P. nicotianae and 22 % against R. solani. To our surprise, at 1.0 mg/mL, the inhibition rate of 3e against R. solani can reach 99 %, while the inhibition rate of chitosan is only 38 %. These results indicated that some imidazole chitosan derivatives with enhanced antifungal activities could serve as potential biomaterial for antifungal application.

Synthesis and characterization of novel carboxymethyl inulin derivatives bearing cationic Schiff bases with antioxidant potential

This study aimed to enhance the antioxidant activity of carboxymethyl inulin (CMI) by chemical modification. Therefore, a series of cationic Schiff bases bearing heteroatoms were synthesized and incorporated into CMI via ion exchange reactions, ultimately preparing 10 novel CMI derivatives (CMID). Their structures were confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. The radical scavenging activities and reducing power of inulin, CMI, and CMID were studied. The results revealed a significant enhancement in antioxidant activity upon the introduction of cationic Schiff bases into CMI. Compared to commercially available antioxidant Vc, CMID demonstrated a broader range of antioxidant activities across the four antioxidant systems analyzed in this research. In particular, CMID containing quinoline (6QSCMI) exhibited the strongest hydroxyl radical scavenging activity, with a scavenging rate of 93.60 % at 1.6 mg mL-1. The CMID bearing imidazole (2MSCMI) was able to scavenge 100 % of the DPPH radical at 1.60 mg mL-1. Furthermore, cytotoxicity experiments showed that the products had good biocompatibility. These results are helpful for evaluating the feasibility of exploiting these products in the food, biomedical, and cosmetics industries.

Zwitterion modified chitosan as a high-performance corrosion inhibitor for mild steel in hydrochloric acid solution

Herein, a novel chitosan Schiff base (CS-FGA) as a sustainable corrosion inhibitor has been successfully synthesized via a simple amidation reaction by using an imidazolium zwitterion and chitosan (CS). The corrosion inhibition property of CS-FGA for mild steel (MS) in a 1.0 M HCl solution was studied by various electrochemical tests and physical characterization methods. The findings indicate that the maximum inhibition efficiency of CS-FGA as a mixed-type inhibitor for MS in 1.0 M HCl solution with 400 mg L-1 reaches 97.6 %, much much higher than the CS and the recently reported chitosan-based inhibitors. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) results reveal that the CS-FGA molecules firmly adsorb on the MS surface to form a protective layer. The adsorption of CS-FGA on the MS surface belongs to the Langmuir adsorption isotherm containing both the physisorption and chemisorption. According to the X-ray photoelectron spectroscopy (XPS) and UV-vis spectrum, FeN bonds presented on the MS surface further prove the chemisorption between CS-FGA and Fe to generate the stable protective layer. Additionally, theoretical calculations from quantum chemical calculation (DFT) and molecular simulations (MD) were performed to reveal the inhibition mechanism of CS-FGA.

Review on chitosan-based antibacterial hydrogels: Preparation, mechanisms, and applications

Chitosan (CS) is known for its remarkable properties, such as good biocompatibility, biodegradability, and renewability, in addition to its antibacterial and biological activities. However, as CS is insoluble in water, it displays limited antibacterial performance under neutral and physiological conditions. A viable solution to this problem is grafting chemically modified groups onto the CS framework, thereby increasing its solubility and enhancing its antibacterial effect. Herein, the antibacterial action mechanism of CS and its derivatives is reviewed, confirming the prevalent use of composite materials comprising CS and its derivatives as an antibacterial agent. Generally, the antimicrobial ability of CS-based biomaterials can be enhanced by incorporating supplementary polymers and antimicrobial agents. Research on CS-based composite biomaterials is ongoing and numerous types of biomaterials have been reported, including inorganic nanoparticles, antibacterial agents, and CS derivatives. The development of these composite materials has considerably expanded the application of CS-based antibacterial materials. This study reviews the latest progress in research regarding CS-based composite hydrogels for wound repair, tissue engineering, drug release, water purification, and three-dimensional printing applications. Finally, the summary and future outlook of CS-based antibacterial hydrogels are presented in anticipation of a broader range of applications of CS-based antibacterial hydrogels.

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

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-2H-chromen-2-one (M2), 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde (M3), and 4-oxo-4H-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-4H-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.

Strategies for the Preparation of Chitosan Derivatives for Antimicrobial, Drug Delivery, and Agricultural Applications: A Review

Chitosan has received much attention for its role in designing and developing novel derivatives as well as its applications across a broad spectrum of biological and physiological activities, owing to its desirable characteristics such as being biodegradable, being a biopolymer, and its overall eco-friendliness. The main objective of this review is to explore the recent chemical modifications of chitosan that have been achieved through various synthetic methods. These chitosan derivatives are categorized based on their synthetic pathways or the presence of common functional groups, which include alkylated, acylated, Schiff base, quaternary ammonia, guanidine, and heterocyclic rings. We have also described the recent applications of chitosan and its derivatives, along with nanomaterials, their mechanisms, and prospective challenges, especially in areas such as antimicrobial activities, targeted drug delivery for various diseases, and plant agricultural domains. The accumulation of these recent findings has the potential to offer insight not only into innovative approaches for the preparation of chitosan derivatives but also into their diverse applications. These insights may spark novel ideas for drug development or drug carriers, particularly in the antimicrobial, medicinal, and plant agricultural fields.

Water-soluble fluorine-functionalized chitooligosaccharide derivatives: Synthesis, characterization and antimicrobial activity

In this work, a series of water-soluble fluorine-functionalized chitooligosaccharide derivatives were synthesized by conjugating nicotinic acid to chitooligosaccharide via nicotinylation reaction, followed by nucleophilic reaction with ethyl bromide, benzyl bromide and fluorobenzyl bromides. Synthesized derivatives were identified structurally by Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance. In addition, the antibacterial activities of chitooligosaccharide derivatives against several disease-causing bacteria were assessed by the broth dilution method and Kirby-Bauer method, the mycelium growth rate method was used to assessing the antifungal properties of samples against three plant-threatening fungi. Among the chitooligosaccharide derivatives, those containing benzyl or fluorobenzyl exhibited noteworthy antimicrobial activity. Specifically, the chitooligosaccharide derivative containing 2,3,4-trifluorobenzyl displayed remarkable antimicrobial activity, with an inhibition index of 84.35% against Botryis cinerea at a concentration of 1.0 mg/mL. Additionally, its MIC value against Staphylococcus aureus was found to be 0.03125 mg/mL, while the MBC value was determined to be 0.0625 mg/mL. The findings of the study revealed that the incorporation of pyridinium cations and fluorine into the chitooligosaccharide backbone may play a critical role in strengthening its ability to combat harmful microorganisms. Furthermore, the cytotoxicities of chitooligosaccharide derivatives against Huvec cells were evaluated through MTT assay, and all samples were not toxic. As a consequence, the water-soluble fluorine-functionalized chitooligosaccharide derivatives possessed rapid microbicidal properties and good biocompatibility, which provided promising prospects for the development of a more effective and environmentally friendly antimicrobial agent.

Phenolic Acid Functional Quaternized Chitooligosaccharide Derivatives: Preparation, Characterization, Antioxidant, Antibacterial, and Antifungal Activity

As a promising biological material, chitooligosaccharide (COS) has attracted increasing attention because of its unique biological activities. In this study, fourteen novel phenolic acid functional COS derivatives were successfully prepared using two facile methods. The structures of derivatives were characterized by FT-IR and 1H NMR spectra. The in vitro antioxidant activity experiment results demonstrated that the derivatives presented stronger 1,1-Diphenyl-2-picryl-hydrazyl (DPPH), superoxide, hydroxyl radical scavenging activity and reducing power, especially the N,N,N-trimethylated chitooligosaccharide gallic acid salt (GLTMC), gallic acid esterified N,N,N-trimethylated chitooligosaccharide (GL-TMC) and caffeic acid N,N,N-trimethylated chitooligosaccharide (CFTMC) derivatives. Furthermore, the antifungal assay was carried out and the results indicated that the salicylic acid esterified N,N,N-trimethylated chitooligosaccharide (SY-TMC) had much better inhibitory activity against Botrytis cinerea and Fusarium graminearum. Additionally, the results of the bacteriostasis experiment showed that the caffeic acid esterified N,N,N-trimethylated chitooligosaccharide (CF-TMC) had the potential ability to inhibit Escherichia coli and Staphylococcus aureus bacteria. Altogether, this study may provide a neoteric method to produce COS derivatives with significantly increased biological activities, which have potential use in food, medicine, and health care products and other related industries.

Cationic Chitooligosaccharide Derivatives Bearing Pyridinium and Trialkyl Ammonium: Preparation, Characterization and Antimicrobial Activities

In this study, chitooligosaccharide-niacin acid conjugate was designed and synthesized through the reaction of chitooligosaccharide and nicotinic acid with the aid of N,N'-carbonyldiimidazole. Its cationic derivatives were prepared by the further nucleophilic substitution reaction between the chitooligosaccharide-niacin acid conjugate and bromopropyl trialkyl ammonium bromide with different alkyl chain lengths. The specific structural characterization of all derivatives was identified using Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR), and the degree of substitution was obtained using the integral area ratio of the hydrogen signals. Specifically, the antibacterial activities against Escherichia coli, Staphylococcus aureus, Pseudoalteromonas citrea and Vibrio harveyi were evaluated using broth dilution methods. In addition, their antifungal activities, including Botrytis cinerea, Glomerella cingulate and Fusarium oxysporum f. sp. cubense were assayed in vitro using the mycelium growth rate method. Experimental data proved that the samples showed antibacterial activity against four pathogenic bacteria (MIC = 1-0.125 mg/mL, MBC = 8-0.5 mg/mL) and enhanced antifungal activity (50.30-68.48% at 1.0 mg/mL) against Botrytis cinerea. In particular, of all chitooligosaccharide derivatives, the chitooligosaccharide derivative containing pyridinium and tri-n-butylamine showed the strongest antibacterial capacity against all of the test pathogenic bacteria; the MIC against Vibrio harveyi was 0.125 mg/mL and the MBC was 1 mg/mL. The experimental results above showed that the introduction of pyridinium salt and quaternary ammonium salt bearing trialkyl enhanced the antimicrobial activity. In addition, the cytotoxicity against L929 cells of the chitooligosaccharide derivatives was evaluated, and the compounds exhibited slight cytotoxicity. Specifically, the cell viability was greater than 91.80% at all test concentrations. The results suggested that the cationic chitooligosaccharide derivatives bearing pyridinium and trialkyl ammonium possessed better antimicrobial activity than pure chitooligosaccharide, indicating their potential as antimicrobial agents in food, medicine, cosmetics and other fields.

Preparation and antioxidant activity of novel chitosan oligosaccharide quinolinyl urea derivatives

In the present study, four new chitosan oligosaccharide derivatives bearing quinolinyl urea groups were synthesized by reaction between 2-methoxyformylated chitosan oligosaccharide and aminoquinoline. The chitosan oligosaccharide derivatives were characterized by Fourier Transform Infrared (FTIR) and 1H Nuclear Magnetic Resonance (1H NMR) spectroscopy. The obtained results confirmed that chitosan oligosaccharide quinolinyl urea derivatives were successfully synthesized. Meanwhile, the antioxidant activities of different chitosan oligosaccharide derivatives were examined in vitro. Experimentally, it was demonstrated that chitosan oligosaccharide quinolinyl urea derivatives had superior antioxidant activity compared with chitosan oligosaccharide and the antioxidant effects were concentration-dependent. Especially, when the concentration was 1.6 mg/mL, their superoxide anion radical scavenging rates could reach to 72.35 ± 0.49%, 100.00 ± 0.21%, 84.63 ± 0.49%, and 87.22 ± 0.32%, respectively. And the hydroxyl radical scavenging rates could reach to 100.00 ± 0.82%, 98.49 ± 4.08%, 100.00 ± 5.76%, and 92.07 ± 5.10%. In addition, the cytotoxic activity of the prepared chitosan derivatives against L929 cells was determined by CCK-8 assay. The cell survival rates were all higher than 90%, which intuitively indicated that the samples had almost no cytotoxicity. The findings indicated that the enhanced antioxidant property and biocompatibility of these chitosan oligosaccharide quinolinyl urea derivatives could enlarge the scope of the application of chitosan oligosaccharide, particularly as an antioxidant in food packaging, biomedical, pharmaceutical, cosmetics industries and other fields.

Preparation of l-Arginine Schiff Bases Modified Chitosan Derivatives and Their Antimicrobial and Antioxidant Properties

We successfully prepared a series of l-arginine Schiff bases acylated chitosan derivatives, aiming to improve the antioxidant activity and antimicrobial activity of chitosan by introducing a furan ring, pyridine ring, and l-arginine structure. The accuracy of the structures of ten compounds was characterized by FT-IR and 1H NMR. In terms of DPPH radical scavenging activity, except for compound CR3PCA, the scavenging rate of other compounds was higher than chitosan, especially CRCF and CRBF had strong scavenging abilities. At the same time, in the superoxide-radical scavenging activity assay, CRCF, CRBF, CR3PCA, CR2C3PCA, and CR2B3PCA were comparable to positive control at 1.60 mg/mL. Simultaneously, CRFF, CRCF, and CRBF had a certain inhibitory effect on Botrytis cinerea. Furthermore, the inhibitory effect of CRFF, CRCF, and CR3PCA on Staphylococcus aureus was very well, close to the positive control at 1.00 mg/mL. CRCF and CR2B3PCA showed better inhibitory effects on Escherichia coli than other compounds. The MTT assay was used to determine the cytotoxicity of the chitosan derivatives, which proved their safety to fibroblast cells. In summary, the study indicated that some of these compounds have the potential for further development and utilization in the preparation of antioxidants and antimicrobial agents.

Chitosan and Chitooligosaccharide: The Promising Non-Plant-Derived Prebiotics with Multiple Biological Activities

Biodegradable chitin is the second-most abundant natural polysaccharide, widely existing in the exoskeletons of crabs, shrimps, insects, and the cell walls of fungi. Chitosan and chitooligosaccharide (COS, also named chitosan oligosaccharide) are the two most important deacetylated derivatives of chitin. Compared with chitin, chitosan and COS not only have more satisfactory physicochemical properties but also exhibit additional biological activities, which cause them to be widely applied in the fields of food, medicine, and agriculture. Additionally, due to their significant ability to improve gut microbiota, chitosan and COS are deemed prospective prebiotics. Here, we introduced the production, physicochemical properties, applications, and pharmacokinetic characteristics of chitosan and COS. Furthermore, we summarized the latest research on their antioxidant, anti-inflammatory, and antimicrobial activities. Research progress on the prebiotic functions of chitosan and COS is particularly reviewed. We creatively analyzed and discussed the mechanisms and correlations underlying these activities of chitosan and COS and their physicochemical properties. Our work enriched people's understanding of these non-plant-derived prebiotics. Based on this review, the future directions of research on chitosan and COS are explored. Collectively, optimizing the production technology of chitin derivatives and enriching understanding of their biological functions will shed more light on their capability to improve human health.