Reactive oxygen species scavenging activity of aminoderivatized chitosan with different degree of deacetylation

Chitosans with different degree of deacetylation were prepared from crab shell chitin in the presence of alkali. Aminoderivatized chitosan derivatives were prepared in addition of amino functional groups at a hydroxyl site in the chitosan backbone. Six kinds of aminoderivatized chitosan such as aminoethyl-chitosan (AEC90), dimethylaminoethyl-chitosan (DMAEC90), and diethylaminoethyl-chitosan (DEAEC90), which were prepared from 90% deacetylated chitosan, and AEC50, DMAEC50 and DEAEC50, which were prepared from 50% deacetylated chitosan, were prepared and their reactive oxygen species (ROS) scavenging activities were investigated against hydroxyl radical, superoxide anion radical and hydrogen peroxide. The electron spin resonance (ESR) spectrum revealed that AEC90 showed the highest scavenging effects against hydroxyl and superoxide anion radical, the effects were 91.67% and 65.34% at 0.25 and 5 mg/mL, respectively. For hydrogen peroxide scavenging effect, DEAEC90 exhibited the strongest activity. These results suggest that the scavenging effect depends on their degree of deacetylation and substituted group.     

Cytotoxic activities of water-soluble chitosan derivatives with different degree of deacetylation

Chitosans with different degree of deacetylation (DD) (90% and 50% deacetylated chitosan) were prepared by N-deacetylation followed by grafted onto chitosan to form water-soluble aminoethyl-chitosan (AE-chitosan), and dimetylaminoethyl-chitosan (DMAE-chitosan), diethylaminoethyl-chitosan (DEAE-chitosan). In the present study, cytotoxic activities of the chitosan derivatives were evaluated using three tumor cell lines and two normal cell lines, and structure-activity relationship was suggested. The cytotoxic activity was dependent on their DD and substituted group.     

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.     

Cytotoxic and antibacterial activity of 2-oxopurine derivatives

Initial screening of the cytotoxic and antibacterial properties of 6-substituted 2-oxopurines and dihydro-2-oxopurines revealed that several compounds exhibited cytotoxicity against K-562 cells in the same range as the well known antileukemic drug 6-mercaptopurine. Most compounds were also tested for inhibitory effect on a Gram-positive bacterium, Lactobacillus casei, as well as the mycobacterium Mycobacterium tuberculosis. Generally the 2-oxopurines exhibited low antibacterial effect.     

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.     

Antibacterial and antiproliferative activity of cationic fullerene derivatives

We examined the antibacterial and antiproliferative activities of alkylated C₆₀-bis(N,N-dimethylpyrrolidinium iodide) derivatives. The fullerene derivatives inhibited bacteria and cancer cell growth effectively. However, the fullerene derivatives with a long alkyl chain did not show antibacterial activity.     

Biocidal activity of some Mannich base cationic derivatives

A novel series of cationic surfactants was prepared based on Mannich base (produced from the condensation of piperidine and/or morpholine as secondary amine and paraformaldehyde in the presence of 8-hydroxyquinoline). The chemical structures of the synthesized cationic surfactants were confirmed using elemental analyses, FTIR spectroscopy and 1H NMR. Surface activities of the prepared surfactants were measured including: surface tension (gamma), critical micelle concentration (CMC), effectiveness (pi(CMC)), efficiency (Pc20), maximum surface excess (Gamma(max)), minimum surface area (A(min)), interfacial tension (gamma(IT)), emulsification power and foaming power at 25 degrees C. The structural influences on their surface activities and adsorption free energy were discussed. The synthesized cationic surfactants were evaluated for their biocidal activity towards Gram +ve bacteria (Staph. Cocu., Bacillus), Gram -ve bacteria (Salmonella, E. coli), fungi (A. terrus., A. flav.) and yeast (Candida) at 1.0, 2.5 and 5.0mg/mL, respectively. The target compounds showed good inhibition towards Gram +ve bacteria, Gram -ve bacteria and yeast. Meanwhile, excellent fungicidal results were obtained against the various types of fungi under investigation.     

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.     

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.     

Antibacterial activity of aminoderivatized chitosans against methicillin-resistant Staphylococcus aureus (MRSA)

This work describes the anti-MRSA activity of aminoderivatized chitosans. Two kinds of aminoethyl-chitosans (AEC), AEC90 and AEC50, having degrees of deacetylation of 90% and 50%, respectively, exhibited the strongest anti-MRSA activities by presenting MICs of 16–64 μg/mL against two standard strains and twelve clinical isolates. The bactericidal activity, thermal and pH stability, and cell membrane integrity effects of AEC90 and AEC50 are also discussed.     

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.     

Preparation and antimicrobial activity of some carboxymethyl chitosan acyl thiourea derivatives

Acetyl, chloroacetyl and benzoyl thiourea derivatives of carboxymethyl chitosan (ATUCMCS, CATUCMCS, and BZTUCMCS) with comparable grafting degree were synthesized and their structures were characterized by FTIR spectroscopy and elemental analyses. The antimicrobial behaviors of CMCS and its derivatives against three types of bacteria [Bacillis subtilis (B. subtilis), Staphylococous aureus (S. aureus) and Escherichia coli (E. coli)] and three crop-threatening pathogenic fungi [Aspergillus fumigate (A. fumigate), Geotrichum candidum (G. candidum) and Candida albicans (C. albicans)] were investigated. The results indicated that the antibacterial and the antifungal activities of the acyl thiourea derivatives are much higher than that of the parent CMCS. The acyl thiourea derivatives were more potent in case of Gram-positive bacteria than Gram-negative bacteria. This is illustrated for example by the values of minimum inhibitory concentration (MIC) of the ATUCMCS, CATUCMCS and BZTUCMCS against B. subtilis were 3.9, 15.6 and 62.5, respectively, while the MIC values of these derivatives against E. coli were 62.5, 125 and 500. Moreover, the antifungal activity of the CATUCMCS is higher than that of the acetyl and benzoyl thiourea derivatives. This may be due to the presence of chlorine atom.     

Immunomodulating activity of chitosan derivatives with salicylic acid and its fragments

A study of biological activity of the derivatives of the chitin-chitosan oligomer with salicylic acid and its fragments showed that chitosan salicylate actively protected potato tubers against Phytophthora infestans but sharply inhibited reparation of potato tissues. N-(2-hydroxybenzyl)chitosan exhibited good protective properties but did not influence wound reparation. N-(2-hydroxy-3-methoxybenzyl)-N-pyridoxchitosan, which contained the pyridoxal and 2-hydroxy-3-methoxy fragments, was the most efficient, stimulating both defense against late blight and wound reparation in potato tissues.     

Cytotoxic activities of chitosan nanoparticles and copper-loaded nanoparticles

Chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions and copper ion sorption. In this study, the cytotoxic activities of the chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles was investigated and a relationship between physiochemical properties and activity is suggested. The chitosan nanoparticles and copper(II)-loaded chitosan nanoparticles elicited dose-dependent inhibitory effects on the proliferation of tumor cell lines.     

Synthesis, characterization, and antifungal activity of novel quaternary chitosan derivatives

Three novel quaternary chitosan derivatives were successfully synthesized by reaction of chloracetyl chitosan (CACS) with pyridine (PACS), 4-(5-chloro-2-hydroxybenzylideneamino)-pyridine (CHPACS), and 4-(5-bromo-2-hydroxybenzylideneamino)-pyridine (BHPACS). The chemical structure of the prepared chitosan derivatives was confirmed by Fourier transform infrared (FT-IR) and ¹³C nuclear magnetic resonance (¹³C NMR) and their antifungal activity against Cladosporium cucumerinum, Monilinia fructicola, Colletotrichum lagenarium, and Fusarium oxysporum was assessed. Comparing with the antifungal activity of chitosan, CACS, and PACS, CHPACS and BHPACS exhibited obviously better inhibitory effects, which should be related to the synergistic reaction of chitosan itself with the grafted 2-[4-(5-chloro-2-hydroxybenzylideneamino)-pyridyl]acetyl and 2-[4-(5-bromo-2-hydroxybenzylideneamino)-pyridyl]acetyl.     

Cytotoxic activities of some benzothiazole-piperazine derivatives

Abstract

Synthesis, characterization and cytotoxic activities of ten benzothiazole-piperazine derivatives were reported. In vitro cytotoxic activities of compounds were screened against hepatocellular (HUH-7), breast (MCF-7) and colorectal (HCT-116) cancer cell lines by sulphorhodamine B assay. Based on the GI₅₀ values of the compounds, most of the benzothiazole-piperazine derivatives are active against HUH-7, MCF-7 and HCT-116 cancer cell lines. Compound 1d is highly cytotoxic against all tested cancer cell lines. Further investigation of compound 1d by Hoechst Staining and Fluorescence-Activated Cell Sorting Analysis (FACS) revealed that this compound causes apoptosis by cell cycle arrest at subG₁ phase.     

Cytotoxic halogenoacrylic derivatives of distamycin A

The design, synthesis, in vitro and in vivo activities of a series of halogenoacrylic derivatives of distamycin A are described. The structure-activity relationships indicate a key role of the reactivity of alpha-halogenoacrylic moiety. The reactivity and the putative alkylating mechanism of these compounds are different from those of the nitrogen mustards and possibly based on a Michael type reaction. This supports the hypothesis that these compounds represent a class of minor groove binders mechanistically different from tallimustine.     

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。     

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.     

Cytotoxic activity of orsellinates

The series of 2,4-dihydroxy-6-methylbenzoates 2-10 (methyl to hexyl orsellinates) prepared by alcoholysis of lecanoric acid (1)--a natural product from the lichen Parmotrema tinctorum (Nyl.) Hale - was submitted to the brine shrimp lethality test (BST), which was also performed for 2,4-dihydroxy-6-methylbenzoic acid (11) (orsellinic acid) and the derivative ethyl-2-hydroxy-4-methoxy-6-methylbenzoate (12) (4-methoxy-ethyl orsellinate), in order to detect new substances with probable antineoplasic activity. Results showed that chain elongation--increase in lipophilicity (log P)--causes a rise in the cytotoxic activity of orsellinates. Hexyl orsellinate (7) showed the highest cytotoxic activity (LC50 = 31 microM). A correlation between lipophilicity (log P) and cytotoxic activity (log 1/LC50) is presented. Compounds with ramified chains--iso-propyl, sec-butyl and tert-butyl orsellinates (8-10)--were less active than those with the correspondent linear chain. The activities presented by 4-methoxy-ethyl orsellinate (12) and ethyl orsellinate (3) suggest that the hydroxy group at the C-4 position causes effect in the cytotoxic activity of orsellinates against Artemia salina.