Synthesis and antioxidant property of novel 1,2,3-triazole-linked starch derivatives via ‘click chemistry’

Mothana R, M. Noman O, Eto B, Chigr F, Chigr M. Synthesis and In Silico Analysis of New Polyheterocyclic Molecules Derived from [1,4]-Benzoxazin-3-one and Their Inhibitory Effect against Pancreatic α-Amylase and Intestinal α-Glucosidase

This study focuses on synthesizing a new series of isoxazolinyl-1,2,3-triazolyl-[1,4]-benzoxazin-3-one derivatives 5a-5o. The synthesis method involves a double 1,3-dipolar cycloaddition reaction following a "click chemistry" approach, starting from the respective [1,4]-benzoxazin-3-ones. Additionally, the study aims to evaluate the antidiabetic potential of these newly synthesized compounds through in silico methods. This synthesis approach allows for the combination of three heterocyclic components: [1,4]-benzoxazin-3-one, 1,2,3-triazole, and isoxazoline, known for their diverse biological activities. The synthesis procedure involved a two-step process. Firstly, a 1,3-dipolar cycloaddition reaction was performed involving the propargylic moiety linked to the [1,4]-benzoxazin-3-one and the allylic azide. Secondly, a second cycloaddition reaction was conducted using the product from the first step, containing the allylic part and an oxime. The synthesized compounds were thoroughly characterized using spectroscopic methods, including 1H NMR, 13C NMR, DEPT-135, and IR. This molecular docking method revealed a promising antidiabetic potential of the synthesized compounds, particularly against two key diabetes-related enzymes: pancreatic α-amylase, with the two synthetic molecules 5a and 5o showing the highest affinity values of 9.2 and 9.1 kcal/mol, respectively, and intestinal α-glucosidase, with the two synthetic molecules 5n and 5e showing the highest affinity values of -9.9 and -9.6 kcal/mol, respectively. Indeed, the synthesized compounds have shown significant potential as antidiabetic agents, as indicated by molecular docking studies against the enzymes α-amylase and α-glucosidase. Additionally, ADME analyses have revealed that all the synthetic compounds examined in our study demonstrate high intestinal absorption, meet Lipinski's criteria, and fall within the required range for oral bioavailability, indicating their potential suitability for oral drug development.

Triazoles in Medicinal Chemistry: Physicochemical Properties, Bioisosterism, and Application

Triazole demonstrates distinctive physicochemical properties, characterized by weak basicity, various dipole moments, and significant dual hydrogen bond acceptor and donor capabilities. These features are poised to play a pivotal role in drug-target interactions. The inherent polarity of triazole contributes to its lower logP, suggesting the potential improvement in water solubility. The metabolic stability of triazole adds additional value to drug discovery. Moreover, the metal-binding capacity of the nitrogen atom lone pair electrons of triazole has broad applications in the development of metal chelators and antifungal agents. This Perspective aims to underscore the unique physicochemical attributes of triazole and its application. A comparative analysis involving triazole isomers and other heterocycles provides guiding insights for the subsequent design of triazoles, with the hope of offering valuable considerations for designing other heterocycles in medicinal chemistry.

Efficient synthesis of 3-alkyl-2-(-1H-1,2,3-triazolyl)methyl)thio)-2,3-dihydroquinazolin-4(1H)-one derivative via multistep synthesis approach by novel Cu@Py-Oxa@SPION catalyst

In this pared, an efficient method is introduced for the synthesis of 3-alkyl-2-(((4-(2-oxopropyl)-1H-1,2,3-triazol-1-yl)alkyl)thio)-2,3-dihydroquinazolin-4(1H)-one derivatives. These novel products have both 1,2,3-triazole and quinazolinone in their structures. For the synthesis of these products, a novel catalyst is designed, synthesized, and characterized by the immobilization of copper onto modified magnetic iron oxide. The catalyst (denoted: Cu@Py-Oxa@SPION) was characterized by several characterization techniques. In this regard, 16 3-alkyl-2-(((4-(2-oxopropyl)-1H-1,2,3-triazol-1-yl)alkyl)thio)-2,3-dihydroquinazolin-4(1H)-one derivatives were synthesized in high isolated yields (77-86%). As an advantage, the catalyst is highly recoverable and its activity has not decreased after 7 sequential runs. The method is very efficient for the synthesis of the products in high isolated yields under mild reaction conditions in a green solvent. The scope of the method is broad and several examples were successfully synthesized using starting materials with different functional groups.

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.

Polysaccharides and lipoproteins as reactants for the synthesis of pharmaceutically important scaffolds: A review

The growing number of diseases in the past decade has once again highlighted the need for extensive research on the development of novel drugs. There has been a major expansion in the number of people suffering from malignant diseases and types of life-threatening microbial infections. The high mortality rates caused by such infections, their associated toxicity, and a growing number of microbes with acquired resistance necessitate the need to further explore and develop the synthesis of pharmaceutically important scaffolds. Chemical entities derived from biological macromolecules like carbohydrates and lipids have been explored and observed to be effective agents in the treatment of microbial infections and diseases. These biological macromolecules offer a variety of chemical properties that have been exploited for the synthesis of pharmaceutically relevant scaffolds. All biological macromolecules are long chains of similar atomic groups which are connected by covalent bonds. By altering the attached groups, the physical and chemical properties can be altered and molded as per the clinical applications and needs, this ring them potential candidates for drug synthesis. The present review establishes the role and significance of biological macromolecules by articulating various reactions and pathways reported in the literature.

Preparation and characterization of PVA/arginine chitosan/ZnO NPs composite films

In this study, arginineated chitosan (ACS) was used as a soft brain membrane and chelating agent to synthesize ACS-ZnO NPs, and then ACS and ACS-ZnO NPs were added to a polyvinyl alcohol (PVA) matrix as an antimicrobial agent to form films by casting. The formation and structural morphology of ACS and ACS-ZnO NPs were investigated by applying FTIR, ¹H NMR, XRD, EDS, SEM, and TEM techniques, and ACS has shown better water solubility. The cytotoxicity experiments of ACS and ACS-ZnO NPs on A549 cells showed that both had good cytocompatibility. The incorporation of ACS and ACS-ZnO NPs improves the composite film's mechanical properties, water barrier, and oxygen barrier and exhibits excellent antibacterial activities against S. aureus and E. coli. More importantly, in addition to extending the shelf life of cherry tomatoes, the composite film is also biodegradable to some degree. Therefore, polyvinyl alcohol films based on ACS and ACS-ZnO NPs added as antimicrobial agents have great potential for food packaging applications.

Biomass-derived isosorbide-based thermoresponsive hydrogel for drug delivery

Herein, we describe the design and synthesis of a new variety of bio-based hydrogel films using a Cu(I)-catalyzed photo-click reaction. These films exhibited thermal-triggered swelling-deswelling and were constructed by crosslinking a triazide derivative of glycerol ethoxylate and dialkyne structures derived from isosorbide, a well-known plant-based platform molecule. The success of the click reaction was corroborated through infrared spectroscopy (FTIR) and the smooth surface of the obtained films was confirmed by scanning electron microscopy (SEM). The thermal characterization was carried out in terms of thermogravimetry (TGA) and differential scanning calorimetry (DSC), from which the decomposition onset and glass transition temperatures were determined, respectively. Additionally, mechanical properties of the samples were estimated by stress-strain experiments. Then, their swelling and deswelling properties were systematically examined in PBS buffer, revealing a thermoresponsive behavior that was successfully tested in the release of the anticancer drug doxorubicin. We also confirmed the non-cytotoxicity of these materials, which is a fundamental aspect for their potential use as drug carriers or tissue engineering matrices.

Organoselenium-chitosan derivative: Synthesis via "click" reaction, characterization and antioxidant activity

The derivatization of chitosan (CS) is widely exploited to endow this polysaccharide with enhanced physicochemical and biological properties. Beyond the synthetic route, the nature of the compounds used to functionalize the CS-derivatives exerts a pivotal role in their final properties. Making use of a simple "click" reaction, we synthesized for the first time an organoselenium-CS derivative through a 1,2,3-triazole formation. The product (CS-TSe) was characterized in detail by FTIR, NMR (¹H, ¹³C, and ⁷⁷Se) and UV-Vis techniques, and SEM microscopy. The antioxidant activity of CS-TSe was examined by ABTS⁺ and DPPH (free radical-scavenging) assays. Experimentally, it was demonstrated that CS-TSe has superior antioxidant activity compared with raw CS and "free" organoselenium compound, suggesting a benign and synergistic effect due to the derivatization. In short, the antioxidant property of CS-TSe combined with the other attractive properties of CS and selenium could be useful in the formulation of advanced materials for biomedical and packaging applications.

Synthesis and antioxidant activity of the inulin derivative bearing 1,2,3-triazole and diphenyl phosphate

In this paper, the inulin derivative (3) bearing 1,2,3-triazole and diphenyl phosphate was successfully synthesized by CuAAC Click chemistry. Detailed structural characterization was determined using FTIR spectroscopy, ¹H NMR spectroscopy, ¹³C NMR spectroscopy, and elemental analysis. The antioxidant activities against hydroxyl radicals, superoxide radicals, and DPPH radicals were estimated in vitro respectively. The results showed that the antioxidant activity of the inulin derivative (3) was significantly enhanced compared with inulin. The inulin derivative (3) exhibited stronger radical scavenging abilities, especially against hydroxyl radicals and superoxide radicals. The scavenging values of the inulin derivative (3) were 98.2% and 95.4% at 1.6 mg/mL against hydroxyl radicals and superoxide radicals respectively. Besides, the scavenging value of the inulin derivative (3) increased by about 40% to scavenge DPPH radicals at 1.6 mg/mL than inulin. The results showed that the inulin derivative (3) bearing 1,2,3-triazole and diphenyl phosphate exhibited tremendously enhanced antioxidant activity compared with inulin. The synthetic strategy might provide an effective way to prepare novel inulin antioxidant biomaterials.

Antioxidant Activity of 1,2,4-Triazole and Its Derivatives: A Mini Review

The information about the presence of free radicals in biological materials was given for the first time about 70 years ago. Since then, numerous scientific studies have been conducted and the science of free radicals was born. Today we know that free radicals are by-products of enzymatic reactions occurring in the organism. They are produced during endogenous processes such as: cell respiration, phagocytosis, biosynthesis, catalysis, and biotransformation. They can also be produced by exogenous processes (radiation, sunlight, heavy metals, bacteria, fungi, protozoa and viruses). The overproduction of free radicals affects the aging processes, oxidative stress (OS) and takes part in the pathogenesis of various diseases. Among them are cancer, rheumatoid arthritis, neurodegenerative diseases: Alzheimer and Parkinson, pulmonary diseases, atherosclerosis and DNA damage. Compounds with antioxidant activity are very important nowadays because they allow organisms to keep a balance between the production of free radicals and the speed of their neutralization in the body. Next to the natural antioxidants (flavonoids, carotenoids, vitamins, etc.), synthetic ones are also of great importance. Among synthetic compounds with antioxidant activity are 1,2,4-triazoles and its derivatives. 1,2,4-Triazoles are heterocyclic compounds with three nitrogen atoms. Due to a broad spectrum of biological activities, these derivatives have been of interest to scientists for many years. Some of them are also used as drugs. The finding of new synthetic compounds with antioxidant features in the triazole group has become important problem of medicinal chemistry.

New synthetic chitosan derivatives bearing benzenoid/heterocyclic moieties with enhanced antioxidant and 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.

Synthesis, characterization, and the antioxidant activity of the acetylated chitosan derivatives containing sulfonium salts

In this study, a new class of chitosan derivatives possessing sulfonium salts was synthesized, and characterized by FT-IR, ¹H NMR, ¹³C NMR, and elemental analyses. IR spectra, ¹H NMR and ¹³C NMR of the structural units of these polymers validated the designed chitosan derivatives were successfully synthesized. In addition, the antioxidant potential of chitosan and chitosan derivatives was assessed in vitro, screened by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, hydroxyl radical scavenging, and superoxide radical scavenging, respectively. Results revealed that designed chitosan derivatives could effectively scavenge DPPH radical, hydroxyl radical, and superoxide radical with inhibition rate of more than 90% at 1.6 mg/mL, higher than chitosan. Moreover, in the cytotoxicity assay, no cytotoxicity was observed for the L929 cells with chitosan and its derivatives at all the testing concentrations. These results indicated that the acetylated chitosan derivatives containing sulfonium salts may be a promising natural antioxidant for the pharmaceutics, food, cosmetics and agriculture management.

Synthesis and Antioxidant Activity of Cationic 1,2,3-Triazole Functionalized Starch Derivatives

In this study, starch was chemically modified to improve its antioxidant activity. Five novel cationic 1,2,3-triazole functionalized starch derivatives were synthesized by using "click" reaction and N-alkylation. A convenient method for pre-azidation of starch was developed. The structures of the derivatives were analyzed using FTIR and 1H NMR. The radicals scavenging abilities of the derivatives against hydroxyl radicals, DPPH radicals, and superoxide radicals were tested in vitro in order to evaluate their antioxidant activity. Results revealed that all the cationic starch derivatives (2a-2e), as well as the precursor starch derivatives (1a-1e), had significantly improved antioxidant activity compared to native starch. In particular, the scavenging ability of the derivatives against superoxide radicals was extremely strong. The improved antioxidant activity benefited from the enhanced solubility and the added positive charges. The biocompatibility of the cationic derivatives was confirmed by the low hemolytic rate (<2%). The obtained derivatives in this study have great potential as antioxidant materials that can be applied in the fields of food and biomedicine.

Copper(i)-catalysed azide–alkyne cycloaddition and antiproliferative activity of mono- and bis-1,2,3-triazole derivatives

A series of mono- and bis-1,2,3-triazole derivatives were prepared via the copper(i)-catalysed azide–alkyne cycloaddition between substituted aromatic derivatives, comprising one or two terminal alkyne groups and a selection of aromatic azides.

Preparation, characterization and antibacterial properties of 6-deoxy-6-arginine modified chitosan

In this study, 6-deoxy-6-arginine modified chitosan (DAC), was synthesized and characterized by Fourier Transform Infrared Spectroscopy (FTIR), ¹H and ¹³C nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and elemental analysis. The arginine was grafted onto C6 groups of chitosan. Antibacterial activity of DAC against gram-negative bacteria Escherichia coli (E. coli) and gram-positive bacteria Staphylococcus aureus (S. aureus) were investigated at concentration between 0.02 mg/mL and 10 mg/mL. Cell viability assessment was estimated in vitro with Caco-2 and L929 cells. Water solubility of DAC at different pH was also evaluated. The results showed that the minimum inhibitory concentration (MICs) of DAC against S. aureus and E. coli were 0.078 mg/mL and 0.312 mg/mL, respectively. The minimum bactericidal concentration (MBC) against S. aureus and E. coli was 0.625 mg/mL. The cytotoxicity of chitosan and DAC was not significantly different. It demonstrated that DAC might be a potential safe antibacterial agent.

Exploring the Chemistry and Therapeutic Potential of Triazoles: A Comprehensive Literature Review

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Triazole is a valuable platform in medicinal chemistry, possessing assorted pharmacological properties, which could play a major role in the common mechanisms associated with various disorders like cancer, infections, inflammation, convulsions, oxidative stress and neurodegeneration. Structural modification of this scaffold could be helpful in the generation of new therapeutically useful agents. Although research endeavors are moving towards the growth of synthetic analogs of triazole, there is still a lot of scope to achieve drug discovery break-through in this area. Upcoming therapeutic prospective of this moiety has captured the attention of medicinal chemists to synthesize novel triazole derivatives. The authors amalgamated the chemistry, synthetic strategies and detailed pharmacological activities of the triazole nucleus in the present review. Information regarding the marketed triazole derivatives has also been incorporated. The objective of the review is to provide insights to designing and synthesizing novel triazole derivatives with advanced and unexplored pharmacological implications.

Synthesis of Multicompartment Nanoparticles of ABC Miktoarm Star Polymers by Seeded RAFT Dispersion Polymerization

Polymeric multicompartment nanoparticles (MCNs) of μ-ABC miktoarm star polymers composed of poly(N,N-dimethylacrylamide) (PDMA), poly(butyl methacrylate) (PBMA), and polystyrene (PS) were synthesized by Cu(I)-catalyzed click reaction and seeded RAFT dispersion polymerization. The synthesized MCNs have a solvophobic PBMA core with separate segregated PS microdomains and a solvophilic PDMA corona. The size and/or morphology of MCNs are correlative to the length of PDMA, PBMA, and PS segments. Ascribed to the characteristic structure, MCNs of μ-DBS can decrease interfacial tension in n-hexane/water, which is much superior to linear diblock copolymer nanoassemblies.

Synthesis, Characterization, and Antioxidant Evaluation of Novel Pyridylurea-Functionalized Chitosan Derivatives

In order to improve the bioactivity of chitosan, we synthesized a novel series of chitosan derivatives: firstly, chitosan was reacted with methylclhlorofonmate obtaining N-methoxyformylated chitosan (1), which was then converted into N-pyridylurea chitosan derivatives (2a-2c) by amine-ester exchange reaction. In addition, N-pyridylurea chitosan derivatives were conducted by reacting with iodomethane to obtain quaternized N-pyridylurea chitosan derivatives (3a-3c). The structural characteristics of as-prepared chitosan derivatives were confirmed by fourier transform infrared (FT-IR), ¹H nuclear magnetic resonance (¹H NMR), elemental analysis, and scanning electron microscope (SEM). Meanwhile, the antioxidant activity of the chitosan derivatives was assessed in vitro. As shown in this paper, the antioxidant activity decreased in the order: c > b > a. Moreover, after the quaternization with iodomethane, quaternized N-pyridylurea chitosan derivatives immediately exhibited enhanced antioxidant capacity compared with N-pyridylurea chitosan derivatives. For example, in 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay, the scavenging activities of 3a-3c were 91.75%, 93.63%, and 97.63% while 2a-2c were 42.32%, 42.97%, and 43.07% at 0.4 mg/mL. L929 cells were also adopted for cytotoxicity test of chitosan and synthesized derivatives by CCK-8 assay and all samples showed decreased cytotoxicity. These results suggested that the novel pyridylurea-functionalized chitosan derivatives could be an ideal biomaterial.

Physical and Antioxidant Properties of Edible Chitosan Ascorbate Films

Chitosan ascorbates with different substitution degrees were synthesized on the basis of salification of chitosan and ascorbic acid at various molar ratios in water and were successfully used to prepare antioxidative films by casting for the first time. Fourier transform infrared and ¹H nuclear magnetic resonance spectra recorded the structural characteristics of all chitosan ascorbates; meanwhile, physicochemical property and antioxidant activity of the produced chitosan ascorbate films were characterized, with chitosan acetate film serving as the control, and these properties were also measured for comparison. The results revealed that salification of chitosan with ascorbic acid not only improved the total color difference, chroma, opacity, capacity for blocking ultraviolet-visible light, and water solubility of chitosan-based films but also decreased water content, swelling degree, and water vapor permeability compared to chitosan acetate film. Also, as was expected, the antioxidant activity assays showed that incorporation of ascorbate into the chitosan matrix effectively enhanced the scavenging activity against the DPPH radical and reducing power. Cs₂Vc₈ and Cs₂Vc₆ especially exhibited the strongest scavenging capacities against the DPPH radical (EC₅₀ < 0.025 mg/mL). These findings offered a suggestion that the prepared chitosan ascorbate films can be applied as novel green oxidation-resistant materials in the food packaging industry.

Significantly enhanced antioxidant activity of chitosan through chemical modification with coumarins

A new class of chitosan derivatives possessing coumarins was synthesized to improve the antioxidant activity of chitosan.

Enhanced antioxidant and antifungal activity of chitosan derivatives bearing 6-O-imidazole-based quaternary ammonium salts

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.

Design, Synthesis and Anticancer Screening of Novel Benzothiazole-Piperazine-1,2,3-Triazole Hybrids

A library of novel regioselective 1,4-di and 1,4,5-trisubstituted-1,2,3-triazole based benzothiazole-piperazine conjugates were designed and synthesized using the click synthesis approach in the presence and absence of the Cu(I) catalyst. Some of these 1,2,3-triazole hybrids possess in their structures different heterocyclic scaffold including 1,2,4-triazole, benzothiazole, isatin and/or benzimidazole. The newly designed 1,2,3-triazole hybrids were assessed for their antiproliferative inhibition potency against four selected human cancer cell lines (MCF7, T47D, HCT116 and Caco2). The majority of the synthesized compounds demonstrated moderate to potent activity against all the cancer cell lines examined. Further, we have established a structure activity relationship with respect to the in silico analysis of ADME (adsorption, distribution, metabolism and excretion) analysis and found good agreement with in vitro activity.

Synthesis, Characterization, and Antifungal Property of Hydroxypropyltrimethyl Ammonium Chitosan Halogenated Acetates

Hydroxypropyltrimethyl ammonium chitosan halogenated acetates were successfully synthesized from six different haloacetic acids and hydroxypropyltrimethyl ammonium chloride chitosan (HACC) with high substitution degree, which are hydroxypropyltrimethyl ammonium chitosan bromacetate (HACBA), hydroxypropyltrimethyl ammonium chitosan chloroacetate (HACCA), hydroxypropyltrimethyl ammonium chitosan dichloroacetate (HACDCA), hydroxypropyltrimethyl ammonium chitosan trichloroacetate (HACTCA), hydroxypropyltrimethyl ammonium chitosan difluoroacetate (HACDFA), and hydroxypropyltrimethyl ammonium chitosan trifluoroacetate (HACTFA). These chitosan derivatives were synthesized by two steps: first, the hydroxypropyltrimethyl ammonium chloride chitosan was synthesized by chitosan and 3-chloro-2-hydroxypropyltrimethyl ammonium chloride. Then, hydroxypropyltrimethyl ammonium chitosan halogenated acetates were synthesized via ion exchange. The structures of chitosan derivatives were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H Nuclear magnetic resonance spectrometer (¹H NMR), 13C Nuclear magnetic resonance spectrometer (13C NMR), and elemental analysis. Their antifungal activities against Colletotrichum lagenarium, Fusarium graminearum, Botrytis cinerea, and Phomopsis asparagi were investigated by hypha measurement in vitro. The results revealed that hydroxypropyltrimethyl ammonium chitosan halogenated acetates had better antifungal activities than chitosan and HACC. In particular, the inhibitory activity decreased in the order: HACTFA > HACDFA > HACTCA > HACDCA > HACCA > HACBA > HACC > chitosan, which was consistent with the electron-withdrawing property of different halogenated acetates. This experiment provides a potential idea for the preparation of new antifungal drugs by chitosan.

Synthesis, characterization, and the antioxidant activity of N,N,N-trimethyl chitosan salts

Chitosan, possessing excellent properties, has been drawing broad attention. For the further utilization of chitosan, chemical modification is performed in improving its water solubility and the bioactivities. In the current study, four N,N,N-trimethyl chitosan salts, including N,N,N-trimethyl chitosan citrate (TMCSCi), N,N,N-trimethyl chitosan acetylsalicylate (TMCSAc), N,N,N-trimethyl chitosan ascorbate (TMCSAs), and N,N,N-trimethyl chitosan gallate (TMCSGa), were prepared via N,N,N-trimethyl chitosan iodide (TMCSI). The as-prepared products were characterized by FT-IR and ¹H NMR. Meanwhile, the degrees of substitution were calculated by elemental analysis results. Furthermore, scavenging activities (against DPPH radicals and superoxide radicals) test and reducing power test were selected to evaluate the antioxidant property of N,N,N-trimethyl chitosan salts in vitro. The results indicated that TMCSAs and TMCSGa displayed excellent activity, probably due to the enhancement of ascorbate and gallate in antioxidant activity. However, because of the weak antioxidant property of citrate and acetylsalicylate, the activity was lower for TMCSCi and TMCSAc. For example, in the DPPH radicals scavenging assay, the scavenging rates of chitosan, TMCSI, TMCSCi, TMCSAc, TMCSAs, and TMCSGa were 25.22, 84.11, 6.90, 2.70, 94.92, and 96.75% at 0.4 mg/mL, respectively. Generally, TMCSAs and TMCSGa could be regarded as a potential source of antioxidants.

Synthesis of Quaternary Ammonium Salts of Chitosan Bearing Halogenated Acetate for Antifungal and Antibacterial Activities

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.

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.

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.

Biologically important hydrazide-containing fused azaisocytosines as antioxidant agents

OBJECTIVES

Two important classes of hydrazide-containing fused azaisocytosines were evaluated as possible antioxidants and characterised by UV spectroscopy.

METHODS

2,2-Diphenyl-1-picrylhydazyl (DPPH), nitric oxide (NO), hydrogen peroxide (H₂O₂) scavenging potencies and reducing power of molecules were evaluated.

RESULTS

The strongest DPPH scavengers were found to be 9, showing the potency superior to that of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) and comparable to that of ascorbic acid (AA), and 6, revealing the antioxidant potency superior to that of BHA, BHT, PG and Trolox. In turn, 3 and 9 were the most promising NO scavengers, exhibiting the potency superior to that of BHA, BHT (3 and 9) and AA (3). The most potent H₂O₂ scavengers proved to be 10 and 9 showing similar or even better neutralising potency than that of Trolox, BHT and BHA. Simultaneously, the majority of hydrazides revealed higher ferric reducing abilities than that of AA and BHT. Some structure-activity relationships were explored. A possible mechanism for the DPPH radical scavenging ability of hydrazide-containing molecules was proposed.

DISCUSSION

Hydrazides 3, 6 and 9 with an antioxidant potential better or comparable to that of the well-known antioxidants are proposed as new antioxidant candidates.