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Based on the scaffolds widely used in drug design, a series of novel tryptophan derivatives containing azepine and acylhydrazone moieties have been designed, synthesized, characterized, and evaluated for their biological activities. The bioassay results showed that the target compounds possessed moderate to good antiviral activities against the tobacco mosaic virus (TMV), among which compounds 5c, 6a, 6h, 6t, 6v, and 6y exhibited higher inactivation, curative, and protection activities in vivo than that of ribavirin (40 ± 1, 37 ± 1, 39 ± 2% at 500 mg/L). Especially, 6y showed comparable activities to that of ningnanmycin (57 ± 2, 55 ± 3, 58 ± 1% at 500 mg/L). Meanwhile, we were pleased to find that almost all these derivatives showed good larvicidal activities against Plutella xylostella. Meanwhile, these derivatives also showed a broad spectrum of fungicidal activities. [ABSTRACT FROM AUTHOR]

In this study, a series of chitosan derivatives bearing active halogenated aromatic imines were successfully synthesized via Schiff bases with the high degrees of substitution. Detailed structural characterization was carried out using Fourier transform infrared (FTIR) spectroscopy, solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis. Besides, the antifungal activity against three common plant pathogenic fungi, including Botrytis cinerea , Fusarium oxysporum f. sp. cucumerinum , and Fusarium oxysporum f. sp. niveum , was investigated using in vitro hyphal measurements. The results showed that double Schiff bases of chitosan derivatives exhibited enhanced antifungal activity compared with chitosan, especially at 1.0 mg/mL. The double Schiff bases of chitosan bearing halogeno-benzenes showed >95% inhibitory indices at 1.0 mg/mL against Botrytis cinereal since halogens had the stronger electron-withdrawing property. The higher degree of substitution was another positive effect to improve the antifungal activity. This study provides a practical strategy to synthesize new double Schiff bases of chitosan derivatives bearing halogeno-benzenes, which could be developed into stronger antifungal agents. • Chitosan derivatives bearing active halogenated aromatic imines were synthesized. • Detailed structural characterization of chitosan derivatives was carried out. • Chitosan derivatives had superior antifungal activity compared with chitosan. • Electron absorption capacity and DS were key factors affecting the antifungal activity. [ABSTRACT FROM AUTHOR]

As one of the most promising biopolymers for a variety of potential applications, chitosan has attracted much attention because of its unique biological, chemical, and physical properties. The functionalization of chitosan has been adopted to synthesize novel chitosan derivatives with improved water-solubility and excellent biological activities. In this paper, chitosan was functionalized with a triphenylphosphonium group by means of the copper (I) catalyzed azide-alkyne "click" reaction and has been investigated as potential polymer for agricultural antifungal biomaterial. The influence of chemical modification on the structural characteristics and water-solubility of chitosan was investigated by FTIR spectroscopy, 1H NMR spectroscopy, elemental analysis, and UV–vis spectrum. Furthermore, the antifungal property of target chitosan derivative against four plant threatening fungal pathogens was evaluated and in vitro investigation demonstrated that triphenylphosphonium salt incorporated chitosan backbone had excellent antifungal property compared with chitosan and intermediate chitosan derivative. Notably, target chitosan derivative displayed relatively strongest antifungal effect with over 80% inhibitory index against Botrytis cinerea at 1.0 mg/mL. The results of a detailed antifungal study indicated that cationic chitosan derivative bearing 1,2,3-triazole and triphenylphosphonium moieties provided a promising platform for preparation of novel cationic antifungal biomaterials in the field of agriculture. [ABSTRACT FROM AUTHOR]

Eight novel chitosan derivatives bearing urea groups are designed and synthesized. Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectrometer, and elemental analysis are performed to confirm the structural characteristics of chitosan derivatives. The antioxidant activities, including superoxide radicals' scavenging activity, 1,1‐diphenyl‐2‐picrylhydrazyl radicals' scavenging activity, and hydroxyl radical' scavenging activity, of the derivatives are explored within different concentrations in the reaction system. In vitro fungicidal activity of these compounds is further tested against Fusarium oxysporum f. sp. niveum, Phomopsis asparagus, F. oxysporum f. sp. cucumebrium Owen, and Botrytis cinerea, respectively, particularly compounds exhibit significant control effect at 1.0 mg mL−1. The experimental results indicate that the products bearing urea groups show enhanced antifungal property and antioxidant activity compared with pristine chitosan. Meanwhile, their bioactivities follow some regularity on the whole, that is, they are related to the electron‐withdrawing property of the different substituted groups of urea. Derivatives with stronger electron‐withdrawing property will have higher biological activities. L929 cells are used to carry out cytotoxicity test of chitosan and chitosan derivatives by Cell Counting Kit‐8 assay. The results indicate that some of the samples show low cytotoxicity. This research will be helpful to broaden the application of chitosan in materials. [ABSTRACT FROM AUTHOR]

• Five novel urea-functionalized chitosan derivatives were synthesized. • Chitosan derivatives bearing urea groups had better bioactivity than chitosan. • Urea groups had a positive effect on biological activity. • The electronegativity of urea groups could affect the biological rule of products. • Chitosan derivatives bearing urea groups showed relatively low cytotoxicity. In the current study, five novel urea-functionalized chitosan derivatives were synthesized via condensation reactions of chloroacetyl chitosan (CTCS) with urea groups bearing nitrogen-containing heterocycles. In order to identify the structure characteristics of chitosan derivatives, FT-IR, 1H NMR spectroscopy, and elemental analysis were carried out. The antifungal activity of the derivatives against four species of phytopathogen (Fusarium oxysporum f. sp. niveum , Phomopsis asparagus , Fusarium oxysporum f. sp. cucumebrium Owen, and Botrytis cinerea) was evaluated. Furthermore, the antioxidant activity of chitosan derivatives was tested by hydroxyl-radical scavenging and superoxide-radical scavenging assays. The results indicated that chitosan derivatives bearing urea groups displayed superior bioactivity compared with chitosan. Besides, L929 cells were adopted for cytotoxicity test of chitosan and synthesized samples by CCK-8 assay and all samples showed decreased cytotoxicity. These results suggested that the novel urea-functionalized chitosan derivatives could be an ideal biomaterial for antifungal and antioxidant applications. [ABSTRACT FROM AUTHOR]

Abstract In this work, quaternary ammonium group was introduced into chitosan backbone by cuprous-catalyzed azide-alkyne cycloaddition (CuAAC) to synthesize the cationic chitosan derivative bearing 1,2,3-triazole. The products were identified structurally by FTIR, 1H NMR spectroscopy, XRD, and elemental analysis. The water solubility of chitosan derivatives at different pH values was determined by a turbidity measurement. The antifungal properties of cationic chitosan derivatives against Botryis cinerea , Phomopsis asparagi , Fusarium oxysporum f. sp. niveum, and Fusarium oxysporum f. sp. cucumerium were evaluated using the radial growth assay. Besides, the antioxidant activities of them were also tested by superoxide-radical scavenging and reducing power assays. Compared to chitosan, cationic chitosan derivative bearing 1,2,3-triazole showed the good water solubility especially at alkaline condition, excellent antifungal action with over 70% inhibitory indices against tested fungi at 1.0 mg/mL, and enhanced antioxidant activity with complete scavenging efficiency against superoxide-radical at 1.6 mg/mL because of the introduction of 1,2,3-triazole and quaternary ammonium moieties. These excellent biological properties present a promising prospect for this chitosan derivative in antifungal and antioxidant biomaterials. [ABSTRACT FROM AUTHOR]

Chemical modification of chitosan is one of effective methods to improve the biological activity of chitosan. In this paper, aminoethyl chitosan quaternary ammonium salts, including N‐trimetyl quaternary ammonium salt chitosan (TMC), 6‐O‐(aminoethyl)‐2‐trimethyl quaternary ammonium chitosan derivative (ONC), and 6‐N‐(aminoethyl)‐2‐trimethyl quaternary ammonium chitosan derivative (NNC), are successfully designed, synthesized, and characterized by FT‐IR, 1H NMR, and elemental analyses. Moreover, three kinds of antifungal activities, including B. cinerea Pers., Gibberella zea, and P. asparagi, are all tested by hyphal measurement in vitro. The results show that all chitosan derivatives have better antifungal activities than chitosan. And the antifungal activity decrease in the order: NNC>ONC >TMC>chitosan at 1.0 mg mL−1. Furthermore, the inhibitory indices of NNC and ONC against three kinds of phytopathogens are higher than 75% at 1.0 mg mL−1. Especially, the inhibitory index of NNC against B. cinerea Pers. attain even 90% at 1.0 mg mL−1. These data demonstrate that the aminated chitoan derivative could remarkably improve the antifungal activity of chitosan. On the one hand, the higher positive charge would interact with the anionic components to damage the cell wall. On the other hand, based on the “permeability” point, the aminoethyl as lipophilic group might pass the oil film into the cell. [ABSTRACT FROM AUTHOR]

As an abundant and renewable polysaccharide, chitosan has been drawing broad attention due to its natural properties. For the further utilization of chitosan, chemical modification can be applied in improving its water solubility and the bioactivities. In this study, four chitosan derivatives were synthesized by the reaction of chloracetyl chitosan derivative with quaternary ammonium salt (CTCS) and urea groups bearing 4-amino-pyridine, including BCTCS, 2CBCTCS, 3CBCTCS, and 4CBCTCS. The structure characteristics of synthesized products were established based on FT-IR spectroscopy, 1 H NMR, and elemental analysis. Their antifungal activities against Fusarium oxysporum f. sp. niveum, Phomopsis asparagus , Fusarium oxysporum f. sp. cucumebrium Owen, and Botrytis cinerea were estimated by hyphal measurement in vitro. Generally, the inhibition ratio of most products was higher than 80% at 1.0 mg/mL. Their inhibitory activity decreased roughly in the order: 4CBCTCS > 3CBCTCS > 2CBCTCS > BCTCS > CTCS > chitosan, resulted from the different degrees of substitution of the effectively active groups–urea groups. Meanwhile, the effects on beneficial soil microbes, including Bacillus cereus , Bacillus subtilis, and Sinorhizobium saheli LMG7837, of these synthesized chitosan derivatives were evaluated by disk diffusion method. The results showed that these substances do not inhibit the growth of beneficial bacteria and some of them could be employed as green antifungal biomaterials. [ABSTRACT FROM AUTHOR]

Two novel chitosan derivatives modified with quaternary phosphonium salts were successfully synthesized, including tricyclohexylphosphonium acetyl chitosan chloride (TCPACSC) and triphenylphosphonium acetyl chitosan chloride (TPPACSC), and characterized by FTIR, 1 H NMR, and 13 C NMR spectra. The degree of substitution was also calculated by elemental analysis results. Their antifungal activities against Colletotrichum lagenarium , Watermelon fusarium , and Fusarium oxysporum were investigated in vitro using the radial growth assay, minimal inhibitory concentration, and minimum bactericidal concentration assay. The fungicidal assessment revealed that the synthesized chitosan derivatives had superior antifungal activity compared with chitosan. Especially, TPPACSC exhibited the best antifungal property with inhibitory indices of over 75% at 1.0 mg/mL. The results obviously showed that quaternary phosphonium groups could effectively enhance antifungal activity of the synthesized chitosan derivatives. Meanwhile, it was also found that their antifungal activity was influenced by electron-withdrawing ability of the quaternary phosphonium salts. The synthetic strategy described here could be utilized for the development of chitosan as antifungal biomaterials. [ABSTRACT FROM AUTHOR]

1,2,3-Triazolium-functionalized starch derivative was obtained by straightforward quaternization of the synthesized starch derivative bearing 1,2,3-triazole with benzyl bromide by combining the robust attributes of cuprous-catalyzed azide-alkyne cycloaddition. These novel starch derivatives were characterized by FTIR, UV–vis, 1 H NMR, 13 C NMR, and elemental analysis. Their antifungal activities against Colletotrichum lagenarium , Watermelon fusarium , and Phomopsis asparagi were investigated by hypha measurement in vitro . The fungicidal assessment revealed that compared with starch and starch derivative bearing 1,2,3-triazole with inhibitory indices of below 15% at 1.0 mg/mL, 1,2,3-triazolium-functionalized starch derivative had superior antifungal activity with inhibitory rates of over 60%. Especially, the best inhibitory index of 1,2,3-triazolium-functionalized starch derivative against Colletotrichum lagenarium attained 90% above at 1.0 mg/mL. The results obviously showed that quaternization of 1,2,3-triazole with benzyl bromide could effectively enhance antifungal activity of the synthesized starch derivatives. The synthetic strategy described here could be utilized for the development of starch as novel antifungal biomaterial. [ABSTRACT FROM AUTHOR]

In this study, three series of chitosan derivatives bearing imidazole rings, including the Schiff‐bases of chitosan, N‐substituted chitosan, and quaternized chitosan are designed and synthesized. The structures of these chitosan derivatives are verified by FT‐IR and 1H NMR, and their antioxidant, antibacterial, and antifungal activities are tested. The Schiff‐bases of chitosan and N‐substituted chitosan have similar biological properties compared with chitosan. Derivatives 2IMTMC, 4IMTMC, MIMTMC, and BIMTMC exhibit significant antioxidant ability and antifungal activity, especially derivative BIMTMC. All the quaternized chitosan remarkably inhibits Escherichia coli, Staphylococcus aureus, and Vibrio harvey, especially derivative BIMTMC, whose minimum inhibitory concentration values are 0.03125, 0.0625, and 0.03125 mg mL−1, respectively. The results indicated that quaternized chitosan are synergistic with imidazole groups and have the better antioxidant, antifungal, and antibacterial properties than chitosan, which can be used as drug materials for antioxididant and antimicrobial purposes. [ABSTRACT FROM AUTHOR]

• Chitosan derivatives bearing benzenoid / heterocyclic moieties were synthesized. • The structure was confirmed by means of FTIR, 1H NMR, and elemental analysis. • Chitosan derivatives showed significant improvement in antioxidant activity. • The introduction of halogenated benzene is more effective on antifungal activities. In this paper, several novel chitosan derivatives bearing benzenoid / heterocyclic moieties were synthesized via introducing aminobenzene and heterocyclic compounds onto carboxymethyl chitosan. The specific structures of chitosan derivatives were confirmed by FTIR, 1H NMR, and elemental analysis. Meanwhile, the antioxidant efficiencies of chitosan derivatives were assayed in vitro. In particular, all chitosan derivatives showed significant improvement in superoxide-radical scavenging activity and DPPH radical scavenging activity. Their antifungal activities against two plant pathogenic fungi (Colletotrichum lagenarium and Phomopsis asparagi) were estimated in vitro by hyphal measurement, and all products exhibited excellent antifungal activity. Besides, the cytotoxicity of them was also measured by CCK-8 in vitro on L929 cells, and all samples showed low cytotoxicity. The good biocompatibility and enhanced biological activity of new synthetic chitosan derivatives might be obvious advantages, while applied in wide range of applications as antifungal agents or antioxidants in food, medicine, cosmetics, and other fields. [ABSTRACT FROM AUTHOR]

• 2-urea-COS derivatives and 2,6-diurea-COS derivatives were synthesized. • Synthesized COS derivatives showed improved bioactivity over pristine COS. • The conjunct mode of urea groups was key factor affecting bioactivity. • The order of bioactivity was related to electron-withdrawing ability of urea groups. • Most COS derivatives bearing urea groups exhibited relatively low cytotoxicity. In this study, 2-urea-chitosan oligosaccharide derivatives (2-urea-COS derivatives) and 2,6-diurea-chitosan oligosaccharide derivatives (2,6-diurea-COS derivatives) were successfully designed and synthesized via intermediate 2-methoxyformylated chitosan oligosaccharide. All samples were characterized and compared based on FT-IR, 1H NMR spectroscopy, and elemental analysis. The antifungal effects of COS derivatives were tested against Fusarium oxysporum f. sp. niveum , Phomopsis asparagus , and Botrytis cinereal. Their antioxidant properties, including superoxide radicals' scavenging activity, hydroxyl radicals' scavenging activity, and DPPH radicals' scavenging activity were also explored within different concentrations. COS derivatives bearing urea groups showed improved bioactivity compared with pristine COS and 2,6-diurea-COS derivatives had a higher biological activity than 2-urea-COS derivatives in tested concentrations. Additionally, L929 cells were used to carry out cytotoxicity test of COS and COS derivatives by CCK-8 assay. The results indicated that some of samples showed low cytotoxicity. These findings offered a suggestion that COS derivatives bearing urea groups are promising biological materials. [ABSTRACT FROM AUTHOR]

Chitosan is an active biopolymer, and the combination of it with other active groups can be a valuable method to improve the potential application of the resultant derivatives in food, cosmetics, packaging materials, and other industries. In this paper, a series of N,N,N-trimethyl-O-(ureidopyridinium)acetyl chitosan derivatives were synthesized. The combination of chitosan with ureidopyridinium group and quaternary ammonium group made it achieve developed water solubility and biological properties. The structures of chitosan and chitosan derivatives were confirmed by FTIR, 1H NMR spectra, and elemental analysis. The prepared chitosan derivatives were evaluated for antioxidant property by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability, hydroxyl radical scavenging ability, and superoxide radical scavenging ability. The results revealed that the synthesized chitosan derivatives exhibited improved antioxidant activity compared with chitosan. The chitosan derivatives were also investigated for antifungal activity against Phomopsis asparagus as well as Botrytis cinerea, and they showed a significant inhibitory effect on the selected phytopathogen. Meanwhile, CCK-8 assay was used to test the cytotoxicity of chitosan derivatives, and the results showed that most derivatives had low toxicity. These data suggested to develop analogs of chitosan derivatives containing ureidopyridinium group and quaternary ammonium group, which will provide a new kind of promising biomaterials having decreased cytotoxicity as well as excellent antioxidant and antimicrobial activity. [ABSTRACT FROM AUTHOR]

In this paper, we report chemical modifications of inulin by seven kinds of aromatic Schiff bases, which are different from their substituent groups. The obtained inulin derivatives were confirmed by FTIR, 1H NMR, and 13C NMR. Then, we studied their antifungal activity against four kinds of plant pathogens involving Botrytis cinerea, Fusarium oxysporum f. sp. cucumerium Owen, Fusarium oxysporum f. sp. niveum, and Phomopsis asparagi by the mycelium growth rate method. The results revealed that all inulin derivatives were endowed with significant antifungal activity compared to inulin. Among them, 6-amino-(N-4-chlorobenzylidene)-6-deoxy-3,4-di-O-acetyl inulin (4CBSAIL) and 6-amino-(N-3,4-dichlorobenzylidene)-6-deoxy-3,4-di-O-acetyl inulin (3,4DCBSAIL), which were synthesized from p-chlorobenzaldehyde and 3,4-dichlorobenzaldehyde, could completely inhibit the growth of the test fungi at 1.0 mg/mL. The inhibitory indices of the inulin derivatives were related to the type, position, and number of substituent groups (halogens) on the Schiff bases. The results confirmed that it was feasible to chemically modify inulin with Schiff bases to confer high antifungal activity to inulin. The products described in this paper have great potential as alternatives to some harmful pesticides used for plant disease control. [ABSTRACT FROM AUTHOR]

The toxicity concerns associated with chemical fungicides currently on the market have resulted in an increased demand for alternative ecofriendly fungicides. As a biodegradable and biocompatible dietary fiber, inulin shows potential as such a compound, given its lack of toxicity. In the current study, seven novel inulin derivatives with promising antifungal activity (BUCAIL, 2CBUCAIL, 3CBUCAIL, 4CBUCAIL, 3,4CBUCAIL, 2FBUCAIL, and 2BBUCAIL) are synthesized via condensation reactions of chloroacetyl inulin (CAIL) with urea groups bearing 4‐amino‐pyridine. Their structures are confirmed using FT‐IR, 1H NMR, 13C NMR, and elemental analysis. Their antifungal activity against three kinds of phytopathogen (Fusarium oxysporum f. sp. niveum, Phomopsis asparagus, and Fusarium oxysporum f. sp. cucumebrium Owen) is evaluated using the mycelial growth rate in vitro at concentrations of 0.10, 0.25, 0.50, 0.75, and 1.0 mg mL−1. Results reveal that all seven inulin derivatives show improved antifungal properties compared with unmodified inulin, and two obvious inhibition rules are found: 3,4CBUCAIL > 4CBUCAIL > 3CBUCAIL > 2CBUCAIL > BUCAIL > CAIL > inulin and 2FBUCAIL > 2CBUCAIL > 2BBUCAIL > BUCAIL > CAIL > inulin. Thus, the introduction of urea groups into inulin derivatives could be key to increasing the antifungal activity of such compounds. In the current study, seven novel inulin derivatives containing urea groups are designed and successfully synthesized. All of the inulin derivatives exhibit higher antifungal activity compared with inulin. The results suggest that the introduction of urea groups into inulin derivatives is key to increasing the antifungal activity of such compounds. [ABSTRACT FROM AUTHOR]

Chemical modification is one of the most effective methods to improve the biological activity of chitin. In the current study, we modified C3-OH and C6-OH of chitin (CT) and successfully synthesized 6-amino-chitin (NCT) and 3,6-diamino-chitin (DNCT) through a series of chemical reactions. The structure of NCT and DNCT were characterized by elemental analyses, FT-IR, 13C NMR, XRD, and SEM. The inhibitory effects of CT, NCT, and DNCT against six kinds of phytopathogen (F. oxysporum f. sp. cucumerium, B. cinerea, C. lagenarium, P. asparagi, F. oxysporum f. niveum, and G. zeae) were evaluated using disk diffusion method in vitro. Meanwhile, carbendazim and amphotericin B were used as positive controls. Results revealed that 6-amino-chitin (NCT) and 3,6-diamino-chitin (DNCT) showed improved antifungal properties compared with pristine chitin. Moreover, DNCT exhibited the better antifungal property than NCT. Especially, while the inhibition zone diameters of NCT are ranged from 11.2 to 16.3 mm, DNCT are about 11.4–20.4 mm. These data demonstrated that the introduction of amino group into chitin derivatives could be key to increasing the antifungal activity of such compounds, and the greater the number of amino groups in the chitin derivatives, the better their antifungal activity was. [ABSTRACT FROM AUTHOR]

In this paper, quaternary ammonium salts of chitosan bearing halogenated acetate, including N,N,N-trimethyl chitosan chloroacetate (TMCSC), N,N,N-trimethyl chitosan dichloroacetate (TMCSDC), N,N,N-trimethyl chitosan trichloroacetate (TMCSTC), and N,N,N-trimethyl chitosan trifluoroacetate (TMCSTF), were prepared via N,N,N-trimethyl chitosan iodide (TMCSI). The obtained chitosan derivatives were characterized by FT-IR, 1H NMR spectra, 13C NMR spectra, and elemental analysis. Their antifungal property against Fusarium oxysporum f. sp. cucumebrium Owen (F. oxysporum f. sp. cucumebrium Owen), Botrytis cinerea (B. cinerea), and Phomopsis asparagi (P. asparagi) were evaluated by hyphal measurement method at concentrations ranging from 0.08 mg/mL to 0.8 mg/mL. Meanwhile, two common bacteria, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), were selected as the model Gram-negative and Gram-positive bacteria to evaluate the antibacterial property of the chitosan derivatives by agar well diffusion method. The results showed that TMCSC, TMCSDC, TMCSTC, and TMCSTF had better antifungal and antibacterial activities than chitosan and TMCSI. In particular, a rule showed that the inhibitory activity decreased in the order: TMCSTF > TMCSTC > TMCSDC > TMCSC > TMCSI > chitosan, which was consistent with the electron-withdrawing property of different halogenated acetate. Apparently, the quaternary ammonium salts of chitosan with stronger electron withdrawing ability possessed relatively greater antifungal and antibacterial activities. This experiment provides a potentially feasible method for the further utilization of chitosan in fields of antifungal and antibacterial biomaterials. [ABSTRACT FROM AUTHOR]

We successfully synthesized the water-soluble chitosan derivatives propane sulfonated chitosan (PSCS) and dipropane sulfonated chitosan (DPSCS) in this paper. These derivatives were characterized by FTIR, 1H NMR, and 13C NMR. Moreover, the antioxidant activity of the chitosan derivatives was evaluated by free radical scavenging ability (against DPPH-radical, hydroxyl-radical, and superoxide-radical) and ferric reducing power. Meanwhile, inhibitory effects against two fungi were also tested. Our results suggested antioxidant abilities and antifungal properties were in order of DPSCS > PSCS > CS, which were consistent with the number of propane sulfonated groups. The scavenging activity of DPSCS against superoxide-radical and DPPH-radical were 94.1% and 100% at 1.6 mg/mL, respectively. The inhibitory indices of DPSCS against P. asparagi and F. oxysporum were up to 82.2% and 94% at 1.0 mg/mL, respectively. Obviously, the number of propane sulfonated groups of chitosan derivatives not only contributes to antioxidant activity, but also to antifungal activity. Therefore, DPSCS with more propane sulfonated groups endowed with antioxidant and antifungal activity that can be used as a candidate material in the food and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

In this work, chitosan derivatives modified with Schiff base bearing benzenoid/heterocyclic moieties were successfully prepared via amidation reaction. Specific structural characterization was implemented using FTIR and 1H NMR, and the DS of chitosan derivatives were quantitatively calculated by ratio of hydrogen proton integral. Meanwhile, the antifungal activity against two common plant pathogenic fungi (Fusarium oxysporum f. sp. cubense and Glomerella cingulata) was assayed in vitro by hyphal measurement, and data proved that the introduction of functional groups including benzene/heterocyclic compounds and Schiff base groups greatly enhanced the antifungal activity. Besides, the antioxidant efficiency was investigated in vitro, and all chitosan derivatives exhibited significantly increased antioxidant activity. Specially, the scavenging effect of 2SATCS was 96.62% at 1.6 mg/mL, which was close to the positive control VC (98.84%). These results indicated that chitosan derivatives with enhanced antifungal and antioxidant activities could serve as potential biomaterial for antifungal and antioxidant applications. [ABSTRACT FROM AUTHOR]

To improve the bioactivity of chitin (CT), novel N‐quaternized (QCT), and N‐diquaternized (DQCT) CT derivatives are synthesized through a series of reactions from CT. The derivatives are characterized using elemental analysis, FTIR, and 13C NMR. In addition, the inhibitory effects of the compounds against three fungi (B. cinerea, F. oxysporum, and P. asparagi) are tested. The inhibitory indices of CT, QCT, and DQCT are 12–15%, 63–73%, and 74–89%, respectively, at 1.0 mg mL−1. The antifungal activities are in the order of DQCT > QCT > CT, which correlated with the number of quaternized groups. Based on these results, it is concluded that the antifungal activity of CT is improved by the introduction of quaternized groups on CT backbone. Novel chitin derivatives containing N‐quaternized chitin and N‐diquaternized chitin are synthesized via sulfonylation, azide, azide reduction, and quaternization. The antifungal activities against three fungi are tested. Compared with chitin with the inhibitory index 12.3–15.0%, the inhibitory indices of N‐quaternized chitin and N‐diquaternized chitin are 63.0–73.4% and 74.4–88.9% at 1.0 mg mL−1, respectively. [ABSTRACT FROM AUTHOR]

Highlights • Chitosan derivatives bearing 6-O-imidazole-based quaternary ammonium salts were successfully synthesized and characterized. • All the chitosan derivatives exhibited enhanced antioxidant activity than chitosan. • All the chitosan derivatives showed stronger antifungal activity than chitosan. • Chitosan derivatives bearing 6- O -imidazole-based quaternary ammonium salts showed relatively low cytotoxicity. Abstract In this paper, a series of 6- O -imidazole-based quaternary ammonium chitosan derivatives via 6- O -chloroacetyl chitosan (CAClC) were successfully designed and synthesized. Detailed structural characterization was carried out by means of FT-IR and 1H NMR spectroscopy, and elemental analysis. Furthermore, the antioxidant property against hydroxyl radicals, superoxide radicals, and DPPH radicals was evaluated in vitro. 2-(N,N,N -trimethyl)-6- O -(2-aminobenzimidazole)acetyl chitosan chloride (2NPhMC) and 2-(N,N,N -trimethyl)-6- O -(1-butylimidazole)acetyl chitosan chloride (NBMC) showed more than 90% scavenging indices at 1.6 mg/mL. Besides, the antifungal activity against Botrytis cinerea and Gibberella zeae was estimated using in vitro MIC and hypha measurements. Most of the quaternized chitosan derivatives especially with the long length alkyl chain and primary amino group showed an inhibitory index of > 85% at 1.0 mg/mL against Botrytis cinerea. Besides, the cytotoxicity of chitosan and all the quaternized chitosan derivatives was evaluated in vitro on HaCaT cells and all the quaternized chitosan derivatives bearing 6- O -imidazole exhibited low cytotoxicity. These results suggested that chitosan derivatives bearing 6- O -imidazole-based quaternary ammonium salts may be used as good biomaterials. [ABSTRACT FROM AUTHOR]

In this paper, novel cationic chitosan derivative possessing 1,2,3-triazolium and pyridinium groups was synthesized conveniently via cuprous-catalyzed azide-alkyne cycloaddition (CuAAC) and methylation. FTIR, 1 H NMR, and elemental analysis examined the structural characteristics of the synthesized derivatives. The antifungal efficiencies of chitosan derivatives against three plant-threatening fungi were assayed by hypha measurement in vitro . The determination showed that chitosan derivative bearing 1,2,3-triazolium and pyridinium displayed tremendously enhanced antifungal activity as compared with chitosan and chitosan derivative bearing 1,2,3-triazole and pyridine. Notably, the inhibitory indices of it against Colletotrichum lagenarium attained 98% above at 1.0 mg/mL. The results showed that N -methylation of 1,2,3-triazole and pyridine could effectively enhance antifungal activity of the synthesized chitosan derivatives. Besides, the prepared chitosan derivatives showed non-toxic effect on cucumber seedlings. This synthetic strategy might provide an effective way and notion to prepare novel cationic chitosan antifungal biomaterials. [ABSTRACT FROM AUTHOR]

We synthesized 6-amino-6-deoxychitosan (NCS) through a series of reactions from chitosan (CS). The antioxidant ability of CS and NCS were investigated in vitro , including that of DPPH-radical and hydrogen peroxide, reducing power, chelating abilities and inhibition of lipid peroxidation. As expected, after the introduction of amino groups, antioxidant ability had improved significantly. Especially, scavenging effect against DPPH-radical and hydrogen peroxide of NCS were 97% and 92% at 1.6 mg/mL, respectively. Moreover, inhibition of lipid peroxidation was 57% at 0.1 mg/mL. And the reducing power of NCS was 0.68 at 0.8 mg/mL. Meanwhile, inhibitory effects against four fungi were also tested. Antifungal activity of NCS were better than those of CS and antifungal activity had improved more than 20% at 0.5 mg/mL against these four kinds of plant pathogens. Based on the above results, it was reasonable to speculate that the obtained antioxidant ability and antifungal activity of NCS might benefit from amino groups on chitosan backbone. These in vitro results suggest the possibility that NCS as antioxidant compound could be effectively alleviate oxidative stress and thus inhibit the oxidative mechanisms that lead to degenerative diseases. [ABSTRACT FROM AUTHOR]

Four novel 1,2,3-triazolium-functionalized starch derivatives were synthesized by N -alkylating the precursor starch derivatives with 1,2,3-triazole with iodomethane based on cuprous-catalyzed azide-alkyne cycloaddition (CuAAC). The detailed structural characterization was investigated by means of FTIR, UV-vis, 1 H NMR, and 13 C NMR spectra. The antifungal activities of starch derivatives against Colletotrichum lagenarium , Fusarium oxysporum , and Watermelon fusarium , were then assayed by hypha measurement in vitro . The fungicidal assessment revealed that compared with starch and starch derivatives with 1,2,3-triazole, 1,2,3-triazolium-functionalized starch derivatives displayed tremendously enhanced antifungal activity. Especially, the inhibitory indices of 6-(4-hydroxymethyl-3-methyl-1,2,3-triazolium-1-yl)-6-deoxy starch iodine (2a) with against the tested plant threatening fungi attained 70% above at 1.0 mg/mL. It was also found that their antifungal activity profiles were dependent on the variation in alkyl chain length. As novel 1,2,3-triazolium-functionalized starch derivatives could be prepared efficiently and exhibited superduper antifungal activity, this synthetic strategy might provide an effective way and notion to prepare novel antifungal biomaterials. [ABSTRACT FROM AUTHOR]

In this study, to investigate the influence of glyoxylate bearing Schiff base on bioactivity to chitosan quaternary ammonium salts, different chitosan derivatives were synthesized by ion exchange of glyoxylate bearing Schiff base with chitosan quaternary ammonium salts (TMCI and HACC). For this purpose, glyoxylate was prepared by Schiff base reaction of glyoxylic acid and amino heterocycles and it was further ionization to substitute iodide ions and chloride ions. After structural characterization by FTIR and 1H NMR, the antifungal and antioxidant activities were measured. Results indicated that glyoxylate bearing Schiff base could improve the bioactivity of TMCI and HACC obviously. Specifically, anionic TMCI with Schiff base of amino pyridines possessed best antioxidant activity >92.40% at 1.6 mg/mL against DPPH radicals. Meanwhile, they showed antifungal activity >84.88% at 1.0 mg/mL against G. cingulate. Furthermore, the cytotoxicity was evaluated, and all samples showed good cell viability >80.14% at 1000 μg/mL. [ABSTRACT FROM AUTHOR]