Superoxide anion scavenging activity of graft chitosan derivatives

Two kinds of graft chitosan derivatives (CMCTS-g-MAS and HPCTS-g-MAS) were prepared by the graft copolymerization of maleic acid sodium onto etherified chitosans-carboxymethyl chitosan (CMCTS) and hydroxypropyl chitosan (HPCTS), respectively. Superoxide anion scavenging activity of the derivatives was evaluated in a luminal-enhanced autoxidaton of pyrogallol by chemiluminescence techniques. Compared with chitosan, the graft chitosan derivatives have much improved scavenging ability against superoxide anion. They have similar 50% inhibition concentrations (IC₅₀s) as ascorbic acid and superoxide dismutase (SOD). Graft chitosan derivatives with hydroxypropyl groups have relatively higher superoxide anion scavenging ability owing to the incorporation of hydroxyl groups. The graft chitosan derivatives (HPCTS-g-MAS 1, 2, and 3) with different grafting percentages exhibit IC₅₀s values ranging from 243 to 308 μg/mL, which could be related to the contents of active hydroxyl and amino groups in the polymer chains.     

Hydroxyl radicals scavenging activity of N-substituted chitosan and quaternized chitosan

N-substituted chitosan and quaternized chitosan were synthesized and their antioxidant activity against hydroxyl radicals was assessed, respectively. Compared with the antioxidant activity of chitosan, the results indicated that the two kinds of chitosan derivatives had different scavenging ability on hydroxyl radicals, which should be related to the form of amido in the two kinds of chitosan derivatives.     

基于与木糖进行美拉德反应的低聚壳聚糖衍生物的抗氧化性能研究

研究低聚壳聚糖与木糖的美拉德反应,考察了两种体系(低聚壳聚糖与木糖的质量比分别为1∶1和1∶3)反应过程中pH、吸光度及荧光值的变化,醇沉法提取4 h和8 h的低聚壳聚糖美拉德反应衍生物,分别为CX11-4、CX13-4、CX11-8和CX13-8。对衍生物进行红外表征和分子量测定,并研究其对羟基自由基.OH和DPPH的清除能力以及还原能力。结果显示:壳聚糖衍生物的抗氧化能力都明显优于低聚壳聚糖,抗氧化活性顺序为CX13-4>CX11-4,CX11-8>CX13-8。可见,壳聚糖美拉德衍生物的抗氧化活性不仅与反应物的比例有关,还与反应的时间有关。     

Water-soluble chitosan derivatives as a BACE1 inhibitor

BACE1 (the beta-site APP-cleaving enzyme) inhibitory activities of water-soluble chitosan derivatives substituted with aminoethyl, dimethylaminoethyl and diethylaminoethyl groups were investigated. AE-chitosan (90%) prepared from 90% deacetylated chitosan showed the strongest BACE1 inhibitory activity than those of other derivatives. The inhibitory pattern was found to be non-competitive by Dixon plot, and the value of the inhibition constant (K(i)) was 85 microg/mL.     

Synthesis and antifungal properties of sulfanilamide derivatives of chitosan

Sulfanilamide derivatives of chitosan (2-(4-acetamido-2-sulfanimide)-chitosan (HSACS, LSACS), 2-(4-acetamido-2-sulfanimide)-6-sulfo-chitosan (HSACSS, LSACSS) and 2-(4-acetamido-2-sulfanimide)-6-carboxymethyl-chitosan (HSACMCS, LSACMCS)) were prepared using different molecular weights of chitosan (CS), carboxymethyl chitosan (CMCS) and chitosan sulfates (CSS) reacted with 4-acetamidobenzene sulfonyl chloride in dimethylsulfoxide solution. The structures of the derivatives were characterized by FT-IR spectroscopy and elemental analysis, which showed that the substitution degree of sulfanilamide group of HSACS, HSACSS, HSACMCS, LSACS, LSACSS and LSACMCS were 0.623, 0.492, 0.515, 0.576, 0.463 and 0.477, respectively. The solubility of the derivatives (pH<7.5) was higher than that of chitosan (pH<6.5). The antifungal activities of the derivatives against Aiternaria solani and Phomopsis asparagi were evaluated based on the method of Jasso et al. in the experiment. The results indicated that all the prepared sulfanilamide derivatives had a significant inhibiting effect on the investigated fungi in the polymer concentration range from 50 to 500 microg mL(-1). The antifungal activities of the derivatives increased with increasing the molecular weight, concentration or the substitution degree. The sulfanilamide derivatives of CS, CMCS and CSS show stronger antifungal activities than CS, CMCS and CSS.     

Preparation and antimicrobial activity of hydroxypropyl chitosan

Water-soluble hydroxypropyl chitosan (HPCS) derivatives with different degrees of substitution (DS) and weight-average molecular weight (Mw) were synthesized from chitosan and propylene epoxide under basic conditions. Their structure was characterized by IR spectroscopy, NMR spectroscopy, and elemental analysis, which showed that both the OH groups at C-6 and C-3 and the NH2 group of chitosan were alkylated. The DS value of HPCS ranged from 1.5 to 3.1 and the Mw was between 2.1x10(4) and 9.2x10(4). In vitro antimicrobial activities of the HPCS derivatives were evaluated by the Kirby-Bauer disc diffusion method and the macrotube dilution broth method. The HPCS derivatives exhibited no inhibitory effect on two bacterial strains (Escherichia coli and Staphylococcus aureus); however, some inhibitory effect was found against four of the six pathogenic fruit fungi investigated. Some derivatives (HPCS1, HPCS2, HPCS3, HPCS3-1, and HPCS4) were effective against C. diplodiella and F. oxysporum. HPCS3-1 is the most effective one with MIC values of 5.0, 0.31, 0.31, and 0.16mg/mL against A. mali, C. diplodiella, F. oxysporum, and P. piricola, respectively. Antifungal effects were also observed for HPCS2 and HPCS3-1 against A. mali, as well as HPCS3 and HPCS3-1 against P. piricola. The results suggest that relatively lower DS and higher Mw value enhances the antifungal activity of HPCS derivatives.     

Wound healing potential of chitosan and N-sulfosuccinoyl chitosan derivatives

Comparative study of chitosan wound healing properties and its synthesized derivatives in MC-100 gel was carried out using the model of experimental full thickness skin wounds. It was determined that N-sulfosuccinoyl chitosan derivatives added into the gel in a concentration of 0.05% possess the higher wound healing activity in comparison with other chitosan derivatives and decrease the half-healing period of wounds 2–3 times in comparison with the control.     

Studies on chitosan: 2. Solution stability and reactivity of partially N-acetylated chitosan derivatives in aqueous media

The stability of the solutions of partially N-acetylated chitosans was studied by two methods: (1) 1% solutions of the chitosan derivatives in 0.1 M aqueous acetic acid were added dropwise to buffer solutions with pH from 8.6 to 12 and to a 0.1 M NaOH solution; (2) to each 0.5% solution of the derivatives in 0.1 M acetic acid was added the desired amount of a 1 M NaOH solution. The stability data obtained were summarized with respect to the degree of N-acetylation. It was found that the solutions of the derivatives with more than 50% acetyl content were stable even in alkaline conditions and the gelation and precipitation of the solutions did not occur. The reactivity of the derivatives with the degree of N-acetylation of more than 50% was studied using methyl 4-azidobenzoimidate (MABI) and ethylene glycol diglycidyl ether in homogeneous states. It was found that MABI reacted with amino groups of the chitosans only at neutral pH and glycidyl groups reacted at neutral and alkaline pH. It seems that these unique properties of chitosans with a degree of N-acetylation of more than 50% will enable us to prepare new chitosan derivatives.     

Synthesis of organosoluble chitosan derivatives with polyphenolic side chains

A one-pot synthesis was used to produce chitosan derivatives with polyphenolic side chains via a regioselective phenolic coupling reaction. Under Mannich reaction conditions, treatment of chitosan with formaldehyde and methyl 2,4-dihydroxybenzoate gave N-(2,6-dihydroxy-3-methoxycarbonylphenyl)methylated chitosan in good yield (87%). Formation of a CC bond occurred regioselectively at the C(3) position of methyl 2,4-dihydroxybenzoate. Chitosan derivatives having various phenolic compounds as a side chain were easily synthesized in a similar manner. The chitosan derivatives showed good biodegradability and improved their solubility in methanol (9.8mgmL(-1)) and 2-methoxyethanol (> 10mgmL(-1)). The UV protection provided by the derivatives with phenolic benzophenone side chain was evaluated using UV spectra of polyethylene terephthalate and poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) films coated with the derivatives and the derivatives absorbed effectively in the UV-A region (<60%). Self-aggregation of the chitosan derivatives with the phenolic side chain was observed by using a fluorescent probe in aqueous solution.     

Preparation of N-vanillyl chitosan and 4-hydroxybenzyl chitosan and their physico-mechanical, optical, barrier, and antimicrobial properties

Chitosan derivatives such as N-vanillyl chitosan and 4-hydroxybenzyl chitosan were prepared by reacting chitosan with 4-hydroxy-3-methoxybenzaldehyde (vanillin) and 4-hydroxybenzaldehyde. Amino groups on chitosan reacts with these aldehydes to form a Schiff base intermediate, which is later on converted into N-alkyl chitosans by reduction with sodium cyanoborohydride. The chemical reaction was monitored by ¹H NMR spectroscopy and the absence of aldehydic proton at 9.83 ppm in NMR spectra was observed for both the modified chitosan derivatives confirming the reaction. Modified chitosan films were later prepared by solution casting method and their physico-mechanical, barrier, optical and thermal properties were studied. The results clearly indicated significant change in tensile strength, water vapour transmission rate, and haze properties of modified chitosans. Modified chitosan films were also studied for their antimicrobial activity against Aspergillus flavus. The results showed a marked reduction of aflatoxins produced by the fungus in the presence of the N-vanillyl chitosan and 4-hydroxybenzyl chitosan film discs to 98.9% and non-detectable levels, respectively.     

Synthesis of novel quaternary chitosan derivatives via N-Chloroacyl-6-O-triphenylmethylchitosans

Various quaternary chitosan derivative structures were synthesized by reacting N-chloroacyl-6-O-triphenylmethylchitosans with tertiary amines. Full substitutions were obtained from the quaternization reactions and the obtained water-soluble quaternary chitosan derivatives were thoroughly characterized with (1)H NMR, (13)C NMR, (1)H-(13)C HSQC NMR, and FT-IR.     

Synthesis and characterization of water-soluble glucosyloxyethyl acrylate modified chitosan

A novel water-soluble chitosan derivative, glucosyloxyethyl acrylated chitosan was successfully synthesized by Michael addition reaction of chitosan with glucosyloxyethyl acrylate (GEA), and the obtained glyco-chitosan derivative was characterized by FT-IR, (1)H NMR, elemental analysis, XRD, TG, DSC and SEM. The FT-IR and (1)H NMR results showed that GEA residues were grafted onto the amino group of chitosan. The degree of substitution (DS) was calculated by elemental analysis. XRD data revealed that the introduced saccharide moieties decreased the crystalline structure of chitosan. TG and DSC results demonstrated that the glucosyloxyethyl acrylated chitosan was less thermal stable than chitosan. This efficient synthetic method provided an approach of preparing water-soluble glyco-chitosan derivatives. The obtained derivatives would show stronger specific affinity of lectin than chitosan thus would have potential applications in biomaterials.     

The preparation and antioxidant activity of the sulfanilamide derivatives of chitosan and chitosan sulfates

Chitosan (CS) and chitosan sulfates (CSS) with different molecular weight (Mw) were reacted with 4-acetamidobenzene sulfonyl chloride to obtain sulfanilamide derivatives of chitosan and chitosan sulfates (LSACS, HSACS, LSACSS, HSACSS). The preparation conditions such as different reaction time, temperature, solvent, and the molar ratio of reaction materials are discussed in this paper. Their structures were characterized by FTIR spectroscopy and elemental analyses. The antioxidant activities of the derivatives were investigated employing various established in vitro systems, such as hydroxyl-radical ((*)OH) superoxide anion (O2(*-)) scavenging and reducing power. All kinds of the compounds (HCS, LCS, HCSS, LCSS, HSACS, LSACS, HSACSS, LSACSS) showed stronger scavenging activity on hydroxyl radical than ascorbic acid (Vc). The inhibitory activities of the derivatives toward superoxide radical by the PMS-NADH system were obvious. The experiment showed that the superoxide radical scavenging effect of sulfanilamide derivatives of chitosan and chitosan sulfates was stronger than that of original CS and CSS. All of the derivatives were efficient in the reducing power. The results indicated that the sulfanilamide group were grafted on CS and CSS increased the reducing power of them obviously.     

Synthesis and fungicidal activity of new N,O-acyl chitosan derivatives

Novel N,O-acyl chitosan (NOAC) derivatives were synthesized to examine their fungicidal activity against the gray mould fungus Botrytis cinerea (Leotiales: Sclerotiniaceae) and the rice leaf blast fungus Pyricularia oryzae (Teleomorph: Magnaporth grisea). The fungicidal activity was evaluated by the radial growth bioassay. NOAC derivatives were more active against the two plant pathogens than chitosan itself, and the effect was concentration dependent. Against B. cinerea, 4-chlorobutyryl chitosan (EC50=0.043%), decanoyl chitosan (EC50=0.044%), cinnamoyl chitosan (EC50=0.045%), and p-methoxybenzoyl chitosan (EC50=0.050%) were the most active (12-13-fold more active than chitosan). (Un)-substituted benzoyl chitosan derivatives were more active against B. cinerea than most of these with N,O-alkyl derivatives. Against P. oryzae chitosan derivatives with lauroyl, methoxy acetyl, methacryloyl and decanoyl were the most active.     

New chitosan derivatives with potential antimicrobial activity

A series of four water-soluble chitosan derivatives differing in molecular mass, hydrophobicity, and charge was synthesized and tested for the intensity of their effects on Gram-negative and Gram-positive bacteria. It was shown that the tested compounds allowed the penetration of ethidium bromide into the bacteria, which showed increased permeability of their cell walls under the effect of chitosans. The tolerance to various chitosan derivatives differed in Gram-negative and Gram-positive bacteria. The Gram-negative bacteria were the most responsive to high-molecular chitosan and the Gram-positive ones, to N-,O-carboxypropylchitosan, whereas high-molecular chitosan had little effect. Research on the correlation between the structure and activity of the studied compounds revealed that depolymerization of chitosan reduced, and introduction of hydrophobic substantives in chitosan molecule significantly enhanced its permeability effect on bacterial cell walls. The obtained results provide a basis for the construction of new chitosan derivatives with antimicrobial activities.     

Galactosylated derivatives of low-molecular-weight chitosan: production and properties

Chitosan, a binary heteropolysaccharide consisting of 2-acetamide-2-deoxy-beta-D-glucopyranose and 2-amino-2-deoxy-beta-D-glucopyranose residues linked in different proportions via beta-glycosidic bonds. The presence of a primary amino group in the chitosan structure allows for the synthesis of various derivatives. The procedure of obtaining activated N-hydroxysuccinimide esters with the use of lactobionic acid was applied to obtain galactosylated derivatives of low-molecular-weight chitosan with a substitution degree varying from 8 to 23%. The properties of these derivatives (viscosity, solubility, and biodegradability) were studied. These derivatives are well soluble at pH values greater than the acidity constant of amino groups of chitosan (6.5). Broadening the pH range towards increase and the presence of galactose residues allows these derivatives to be used in working with biological objects.     

Synthesize and characterization of organic-soluble acylated chitosan

Acylated chitosan was synthesized by reaction of chitosan and stearoyl chloride. The chemical structures and physical properties of the prepared compounds were confirmed by Fourier transform infrared (FT-IR), ¹H Nuclear Magnetic Resonance (¹H NMR) spectroscopy, X-ray diffraction (XRD) and Thermogravimetric (TG) techniques. The degree of substitution (DS) was calculated by ¹H NMR and ranged from 1.8 to 3.8. The synthesized compounds exhibited an excellent solubility in organic solvents. XRD analysis showed that they had high crystalline structure. TG results demonstrated that thermal stability of the prepared compounds was lower than that of chitosan, the weight loss decreased with increase of DS. This procedure could be a facile method to prepare organic-soluble chitosan derivatives.     

Antioxidant activity of water-soluble chitosan derivatives.

Water-soluble chitosan derivatives were prepared by graft copolymerization of maleic acid sodium onto hydroxypropyl chitosan and carboxymethyl chitosan sodium. Their scavenging activities against hydroxyl radical *OH were investigated by chemiluminescence technique. They exhibit IC(50) values ranging from 246 to 498 microg/mL, which should be attributed to their different contents of hydroxyl and amino groups and different substituting groups.     

Modification of chitosan to improve its hypocholesterolemic capacity.

Cholestyramine is the most widely used bile acid sequestrant in the treatment of hypercholesterolemia. However, cholestyramine has unpleasant side effects as a consequence of its hydrophobic backbone. Therefore, high-capacity bile acid sequestering biopolymers with cationic chitosan derivatives were developed, because electrostatic interactions are important for binding with bile acid anions. Dialkylaminoalkylation and reductive amination of chitosan were done to add dialkylaminoalkyl and an additional free amino group at a hydroxyl site in the chitosan backbone respectively and the amino-derivatized chitosan derivatives were quaternized with methyl iodide to produce a cationic polyelectrolyte. The in vitro bile acid binding capacity of the chitosan derivatives in aqueous NaCl was measured by reversed-phase HPLC. The binding capacities of sodium glycocholate (a major bile acid) to chitosan, DEAE-chitosan, quaternized DEAE-chitosan, and cholestyramine were 1.42, 3.12, 4.06, and 2.78 mmol/g resin, respectively. With quaternized DEAE-chitosan, the bile acid binding capacity increased approximately 50% over that of cholestyramine. The bile acid binding capacity of dialkylaminoalkyl chitosan derivatives increased with the number of carbons in the alkyl groups, indicating that hydrophobic interaction is a secondary factor for the sequestration of bile acids.     

Cytotoxic activity of aminoderivatized cationic chitosan derivatives

Chitosan derivatives were prepared by dialkylaminoalkylation and reductive amination followed by quaternization. In this study, the cytotoxic activity of the chitosan derivatives was investigated and a relationship between structure and activity is suggested. The cationic chitosan derivatives elicited dose-dependent inhibitory effects on the proliferation of tumor cell lines.