Lijie Wei

Synthesis, characterization, and antifungal property of chitosan ammonium salts with halogens.

In this study, a group of novel water soluble chitosan ammonium salts with halogens were successfully synthesized, including chitosan-bromoacetate (CSB), chitosan-chloroacetate (CSC), chitosan-dichloroacetate (CSDC), chitosan-trichloroacetate (CSTC), and chitosan-trifluoroacetate (CSTF), and their antifungal activities against three kinds of phytopathogens were comparatively estimated by hypha measurement in vitro, respectively. The fungicidal assessment revealed that the synthesized chitosan derivatives had higher antifungal activity than chitosan. Especially, the inhibitory indices of CSTC and CSTF against three kinds of phytopathogens were higher than 70% at 1.0mg/mL. Generally, the antifungal activity decreased in the order: CSTF>CSTC>CSDC>CSC>CSB>chitosan. Apparently, the order of antifungal activity was consistent with the electronegativity of different substituted groups with halogens. The substituted groups with stronger electronegativity could augment the positive charge densities of cationic amino groups by drawing more electrons from the cationic amino groups of chitosan ammonium salts, which demonstrated that the protonation of amino groups was significant for the antifungal activity of chitosan derivatives.

Synthesis, Characterization, and the Antioxidant Activity of Double Quaternized Chitosan Derivatives

With the specialty of improving the water solubility of chitosan, quaternary ammonium salts have broadened the application of this polysaccharide in food, medicine and pesticides. To identify the effect of quaternary ammonium salts’ quantity, single quaternized chitosan N-phenmethyl-N,N-dimethyl chitosan (PDCS), double quaternized chitosan N-(1-pyridylmethyl-2-ylmethyl)-N,N-dimethyl chitosan (MP2MDCS), N-(1-pyridylmethyl-3-ylmethyl)-N,N-dimethyl chitosan (MP3MDCS), and N-(1-pyridylmethyl-4-ylmethyl)-N,N-dimethyl chitosan (MP4MDCS) were designed and synthesized successfully through chemical modification of chitosan. Besides, three kinds of antioxidant activities, including hydroxyl radicals, superoxide radicals, and 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radicals were tested in vitro. As shown in this paper, the scavenging ability was ranking in order of MP3MDC > MP4MDCS > MP2MDCS > PDCS > chitosan at 1.6 mg/mL in all assays. All double quaternary ammonium salts were better than chitosan or the single quaternary ammonium salt. In addition, MP3MDCS could scavenge hydroxyl radicals totally at 1.6 mg/mL. MP2MDCS and MP4MDCS with more than 90% scavenging indices both had great scavenging ability on hydroxyl radicals or DPPH radicals. Furthermore, these data demonstrated that the increasing number of the positive charge would improve the antioxidant property of chitosan derivatives, and the N-pyridinium position would influence the scavenging radical ability.

Novel cationic chitosan derivative bearing 1,2,3-triazolium and pyridinium: Synthesis, characterization, and antifungal property

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, 1H 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 1.0mg/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.

Design, synthesis of novel chitosan derivatives bearing quaternary phosphonium salts and evaluation of antifungal activity

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, 1H NMR, and 13C 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 1.0mg/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.

Synthesis, characterization, and antifungal evaluation of novel 1,2,3-triazolium-functionalized starch derivative

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, 1H NMR, 13C 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 1.0mg/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 1.0mg/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.

The evaluation of antioxidant and antifungal properties of 6-amino-6-deoxychitosan in vitro

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 1.6mg/mL, respectively. Moreover, inhibition of lipid peroxidation was 57% at 0.1mg/mL. And the reducing power of NCS was 0.68 at 0.8mg/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 0.5mg/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.

Synthesis, characterization, and antifungal property of starch derivatives modified with quaternary phosphonium salts

Four novel starch derivatives modified with quaternary phosphonium salts were designed and successfully synthesized, including trimethylphosphonium acetyl starch chloride, tributylphosphonium acetyl starch chloride, tricyclohexylphosphonium acetyl starch chloride, triphenylphosphonium acetyl starch chloride, and characterized by FTIR, UV, 1H NMR, 13C NMR, and 31P NMR spectra. Their antifungal activities against four kinds of phytopathogens were evaluated using the radial growth assay and minimum inhibitory concentration procedure. The fungicidal assessment revealed that the synthesized starch derivatives had superior antifungal activity compared with starch. Especially, the inhibitory indices of triphenylphosphonium acetyl starch chloride against these four kinds of plant pathogens were higher than 70% at 1.0mg/mL. The results indicated that quaternary phosphonium groups should be high-efficiency antifungal function groups, and meanwhile longer alkyl chain lengths or the stronger electron-withdrawing groups were responsible for enhanced antifungal versatility and efficacy. The cytotoxicity of starch and starch derivatives bearing quaternary phosphonium salts was evaluated in vitro on HEK-293T cells. As novel quaternary phosphonium 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.

Preparation and Characterization of Quaternized Chitosan Derivatives and Assessment of Their Antioxidant Activity

Chitosan (CS) is an abundant and renewable polysaccharide that is reported to exhibit a great variety of beneficial properties. However, the poor solubility of chitosan in water limits its applications. In this paper, we successfully synthesized single N-quaternized (QCS) and double N-diquaternized (DQCS) chitosan derivatives, and the resulting quaternized materials were water-soluble. The degree of quaternization (DQ) of QCS and DQCS was 0.8 and 1.3, respectively. These derivatives were characterized by FTIR, 1H NMR, 13C NMR, TGA, and SEM. Moreover, the antioxidant activity of the chitosan was evaluated by free radical scavenging ability (against DPPH-radical, hydroxyl-radical, and superoxide-radical) and ferric reducing power. Our results suggested that the antioxidant abilities were in the order of DQCS > QCS > CS, which was consistent with the number of quaternized groups. These data demonstrate that the number of quaternized groups of chitosan derivatives contributes to their antioxidant activity. Therefore, DQCS, with a higher number of quaternized groups and higher positive charge density, is endowed with high antioxidant activity, and can be used as a candidate material in food and pharmaceutical industries.

Antioxidant Activity and Antifungal Activity of Chitosan Derivatives with Propane Sulfonate Groups

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.

Synthesis, Characterization, and Antifungal Activity of Pyridine-Based Triple Quaternized Chitosan Derivatives

In this study, a series of triple quaternized chitosan derivatives, including 6-O-[(2-hydroxy-3-trimethylammonium)propyl]-2-N-(1-pyridylmethyl-2-ylmethyl)-N,N-dimethyl chitosan chloride (7), 6-O-[(2-hydroxy-3-trimethylammonium)propyl]-2-N-(1-pyridylmethyl-3-yl- methyl)-N,N-dimethyl chitosan chloride (8), and 6-O-[(2-hydroxy-3-trimethylammonium)propyl]- 2-N-(1-pyridylmethyl-4-ylmethyl)-N,N-dimethyl chitosan chloride (9) were successfully designed and synthesized via reacting epoxypropyl trimethylammonium chloride with the N-pyridinium double quaternized chitosan derivatives. Detailed structural characterization was carried out using FT-IR and 1H-NMR spectroscopy, and elemental analysis. Besides, the activity of the triple quaternized chitosan derivatives against three common plant pathogenic fungi, Watermelon fusarium, Fusarium oxysporum, and Phomopsis asparagi, was investigated in vitro. The results indicated that the triple quaternized chitosan derivatives had enhanced antifungal activity when compared to double quaternized chitosan derivatives and chitosan, especially at 1.0 mg/mL, which confirmed the theory that the higher density of positive charge contributed to the antifungal activity. Moreover, 8 with an almost 99% inhibitory index showed the better antifungal activity against Watermelon fusarium. Moreover, the cytotoxicity of the products was also evaluated in vitro on 3T3-L1 cells and all the triple quaternized chitosan derivatives exhibited low cytotoxicity. These results suggested that triple quaternized chitosan derivatives may be used as good antifungal biomaterials.