Talat Baran

Synthesis and characterization of water soluble O-carboxymethyl chitosan Schiff bases and Cu(II) complexes.

In this study, mono-imine was synthesized (3a and 4a) via a condensation reaction between 2,4-pentadion and aminobenzoic acid (meta or para) in alcohol (1:1). The second-imine (CS-3a and CS-4a) was obtained as a result of the reaction of the free oxo groups of mono-imine (3a and 4a) with the amino groups on the chitosan (CS). Their structures were characterized with FTIR and (13)C CP-MAS. Then, the water soluble forms of CS-3a and CS-4a were obtained through oxidation of the hydroxide groups on the chitosan to carboxymethyl groups using monochloracetic acid ([O-CMCS-3a] · 2H2O and [O-CMCS-4a] · 2H2O). Thus, the solubility problem of chitosan in an aqueous media was overcome and Cu(II) complexes could be synthesized more easily. Characterization of the synthesized O-carboxymethyl chitosan Schiff base derivatives and their metal complexes, [O-CMCS-3a-Cu(OAc)2] · 2H2O and [O-CMCS-4a-Cu(OAc)2] · 2H2O, was conducted using FTIR, UV-Vis, TG/DTA, XRD, SEM, elemental analysis, conductivities and magnetic susceptibility measurements.

Physicochemical comparison of chitin and chitosan obtained from larvae and adult Colorado potato beetle (Leptinotarsa decemlineata)

Chitins and chitosans obtained from larva and adult Colorado potato beetles (Leptinotarsa decemlineata) were physico-chemically characterized and differences between adults and larvae were identified. The dry weight chitin contents of the adult Colorado potato beetles and larvae were determined as 20% and 7%, respectively. The chitin produced chitosan yields of 72% from the adult Colorado potato beetles and 67% from the larvae. FTIR analysis showed that the isolated chitins were in the alpha form. Crystalline index values, determined by XRD, were 72% for larvae and 76% for adults. The degradation temperatures of the isolated chitin structures were measured by TGA, and this showed that the chitin from adult Colorado potato beetles had a more stable structure than that from the larvae. The surface morphologies of the isolated chitin and chitosan structures were analysed with SEM and it was revealed that these structures consisted of nanofibres. According to elemental analysis, the purity of chitin and chitosan from adults was greater than that from the larvae. The results of molecular analysis showed that the chitosans from adults (2.722 kDa) and larvae (2.676 kDa) of the Colorado potato beetle have low molecular weights. Antimicrobial and antioxidant activities of both adult and larval chitosans were determined. The adult potato beetle is more appropriate than the larvae as an alternative chitin source because of the fact that its dry weight chitin content, chitosan yield and purity of chitin are higher than those from the larvae, and its antimicrobial and antioxidant activities are also higher than those from the larvae.

New Chitin, Chitosan, and O-Carboxymethyl Chitosan Sources from Resting Eggs of Daphnia longispina (Crustacea); with Physicochemical Characterization, and Antimicrobial and Antioxidant Activities

The paper describes the isolation and characterization of chitin and chitosan from Daphnia longispina resting eggs harvested from a reservoir. Resting eggs are fertilized eggs that are encased in chitinous shells called ‘ephippia’ and which ensure the survival of the Daphnia population in adverse conditions. The chitin-content of D. longispina resting eggs was found to be 23 ∼ 25% and the chitosan (having a 70 ∼ 75% deacetylation degree) yield of the chitin was 76 ∼ 77%. This high chitin-content indicates that D. longispina resting eggs can be exploited as a chitin source. The structure and thermal properties of chitin, extracted from D. longispina resting eggs, were characterized by employing Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. The crystallinity of the chitin was found to be very low (48%). Physicochemicallycharacterized chitosan and the produced O-carboxymethyl chitosan were tested for their antimicrobial and antioxidant activity. It has been observed that chitosan displays antimicrobial activity against all pathogenic bacteria, whereas O-carboxymethyl chitosan only exhibits inhibition activity against L. garvieae, L. Monocytogenes ATCC 7644, Y. enterocolitica NCTC 11175 and S. aureus ATCC 25923. In a free radical scavenging activity assay, the IC50 values of chitosan, O-carboxymethyl chitosan and butylated hydroxytoluene were found to be 23.01, 56.43 and 0.05, respectively. The ferric-reducing power of O-carboxymethyl chitosan (EC50 = 8.30) indicated higher activity than chitosan (EC50 = 10.12).

A physicochemical characterization of fully acetylated chitin structure isolated from two spider species: With new surface morphology

Spiders are a huge group which includes more than 44,000 species. But there has been no study of the chitin structure of spiders. In this study we physicochemically characterized chitin structure of two common spider species (Geolycosa vultuosa and Hogna radiata). Chitin content was determined as 8-8.5% for G. vultuosa and 6.5-7% for H. radiata. FTIR, TGA and XRD results showed that the chitin structures are in α-form. Environmental scanning electron microscopy (ESEM) revealed that the surface morphology of each species is different. Chitin yielded from G. vultuosa has two different pore structures. The type one pore is rarely sequenced and its size ranges between 190 and 240 nm, while the type two pore is tightly sequenced and its size ranges between 11 and 32 nm. There is no information in previous studies about the chitin structure with two different pore morphologies. A new chitin surface morphology has been determined in G. vultuosa. The chitin isolated from H. radiata, has classic morphology: nanofibre structures (10-17 nm) and 195-260 nm sized pores. Acetylation degree of the chitin samples was calculated as 97% for G. vultuosa and 99% for H. radiata in accordance with elemental analysis results.

Preparation and characterisation of biodegradable pollen–chitosan microcapsules and its application in heavy metal removal

Biosorbents have been widely used in heavy metal removal. New resources should be exploited to develop more efficient biosorbents. This study reports the preparation of three novel chitosan microcapsules from pollens of three common, wind-pollinated plants (Acer negundo, Cupressus sempervirens and Populus nigra). The microcapsules were characterized (Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and elemental analysis) and used in removal of heavy metal ions: Cd(II), Cr(III), Cu(II), Ni(II) and Zn(II). Their sorption capacities were compared to those of cross-linked chitosan beads without pollen grains. C. sempervirens-chitosan microcapsules exhibited better performance (Cd(II): 65.98; Cu(II): 67.10 and Zn(II): 49.55 mg g(-1)) than the other microcapsules and the cross-linked beads. A. negundo-chitosan microcapsules were more efficient in Cr(III) (70.40 mg g(-1)) removal. P. nigra-chitosan microcapsules were found to be less efficient. Chitosan-pollen microcapsules (except P. nigra-chitosan microcapsules) can be used in heavy metal removal.

Chitin extraction and characterization from Daphnia magna resting eggs.

New application areas for chitin and its derivatives have been extensively investigated and there is a solid, growing demand for new chitin sources. In this present study, chitin content of Daphnia magna resting egg (18-21%) was determined for the first time. FTIR, elemental analysis, TGA, XRD and SEM studies revealed the structural and thermal properties of extracted α-chitin. This study suggests that D. magna resting eggs can be exploited as an attractive alternative chitin source.

Cu(II) and Pd(II) complexes of water soluble O-carboxymethyl chitosan Schiff bases: Synthesis, characterization.

This study reports the synthesis of two new water soluble O-carboxymethyl chitosan Schiff bases (OCMCS-5 and OCMCS-6a) and their Cu(II) and Pd(II) complexes. Characterizations of these complexes were carried out with FTIR, elemental analysis, (13)C CPMAS, UV-vis, magnetic moment and molar conductivity techniques. The degrees of substitution (DS) for OCMCS-5a and OCMCS-6a were determined to be 0.48 and 0.44 in elemental analysis. The solubility test revealed that OCMCS-5a and OCMCS-6a dissolved thoroughly in water. The surface morphologies of chitosan (CS), OCMCS-5a, OCMCS-6a and their complexes were studied with SEM-EDAX. Thermal stability of the synthesized compounds was evaluated by TG/DTG and their crystallinity values were investigated with powder X-ray diffraction. Cu(II) and Pd(II) contents of the complexes were estimated with ICP-OES. The characterization studies demonstrated that the thermal stability and crystallinity values of the OCMCS-5a and OCMCS-6a were lower than those of CS.

Comparison of chitin structures isolated from seven Orthoptera species.

Differences in the physichochemical properties of the chitin structure of the exoskeleton of seven species from four genera were investigated in this study. The same method was used to isolate the chitin structure of the seven species. The physicochemical properties of the isolated chitins were revealed by ESEM, FTIR, TGA and XRD analyses. The FTIR, TGA and XRD results from the chitin samples were similar. The surface morphologies of the chitins were investigated by ESEM and interesting results were noted. While the surface morphologies of the chitins isolated from two species within the same genus were quite different, the surface morphologies of chitins isolated from species belonging to different genera showed similarity. It was determined that the dry weight chitin contents of the grasshopper species varied between 5.3% and 8.9%. The results of molecular analysis showed that the chitins from seven Orthoptera species (between 5.2 and 6.8 kDa) have low molecular weights. Considering that these invasive and harmful species are killed with insecticides and go to waste in large amounts, this study suggests that they should be collected and evaluated as an alternative chitin source.

Synthesis, characterization, and catalytic activity in Suzuki coupling and catalase-like reactions of new chitosan supported Pd catalyst.

The aim of this study is to analyze the synthesis of a new chitosan supported Pd catalyst and examination of its catalytic activity in: Pd catalyst was synthesized using chitosan as a biomaterial and characterized with FTIR, TG/DTG, XRD, (1)H NMR, (13)C NMR, SEM-EDAX, ICP-OES, Uv-vis spectroscopies, and magnetic moment, along with molar conductivity analysis. Biomaterial supported Pd catalyst indicated high activity and long life time as well as excellent turnover number (TON) and turnover frequency (TOF) values in Suzuki reaction. Biomaterial supported Pd catalyst catalyzed H2O2 decomposition reaction with considerable high activity using comparatively small loading catalyst (10mg). Redox potential of biomaterial supported Pd catalyst was still high without negligible loss (13% decrease) after 10 cycles in reusability tests. As a consequence, eco-friendly biomaterial supported Pd catalyst has superior properties such as high thermal stability, long life time, easy removal from reaction mixture and durability to air, moisture and high temperature.

Description of a new surface morphology for chitin extracted from wings of cockroach (Periplaneta americana)

In this study a new morphology of chitin, which could find wide applications in the fields of medicine, pharmacy, agriculture, food and textiles, has been described. The chitin was isolated from the wings of Periplaneta americana employing a conventional method. Considering chitin isolation studies conducted previously, chitin has three surface morphologies, which are (1) hard and rough surface without pores or nanofibers, (2) surface solely composed of nanofibers and (3) surfaces with both pores and nanofibers. In this study, the surface of the chitin, examined with environmental scanning electron microscopy (ESEM), only has oval nanopores (230-510 nm) without nanofibers, and this is different from the above mentioned surface morphologies. The nanopores are not distributed on the chitin surface randomly. Typically, there is a pore in the center that is surrounded by six or seven other pores in an ordered manner. Structures similar to cell walls exist between the pores. Chitin with the new surface morphology was characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), X-ray diffraction (XRD) and elemental analysis.