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  • Articles  (192)
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  • Articles  (192)
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  • 1
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    Synthesis and Antimicrobial Activity of N-(6-Carboxyl Cyclohex-3-ene Carbonyl) Chitosan with Different Degrees of Substitution (2018)
    Hindawi
    Details
    Publication Date: 2018-03-06
    Description: Five products of -(6-carboxyl cyclohex-3-ene carbonyl) chitosan as antimicrobial agents were prepared by reaction of chitosan with tetrahydrophthalic anhydride (THPA) at different degrees of substitution (DS). The antimicrobial activity was evaluated against four plant bacteria and eight fungi. The results proved that the inhibitory property and water solubility of the synthesized chitosan derivatives, with increase of the DS, exhibited a remarkable improvement over chitosan. The product with a DS of 0.40 was the most active one with MIC of 510, 735, 240, and 385 mg/L against Erwinia carotovora, Ralstonia solanacearum, Rhodococcus fascians, and Rhizobium radiobacter, respectively, and also in mycelial growth inhibition against Alternaria alternata (EC50 = 683 mg/L), Botrytis cinerea (EC50 = 774 mg/L), Botryodiplodia theobromae (EC50 = 501 mg/L), Fusarium oxysporum (EC50 = 500 mg/L), F. solani (EC50 = 260 mg/L), Penicillium digitatum (EC50 = 417 mg/L), Phytophthora infestans (EC50 = 298 mg/L), and Sclerotinia sclerotiorum (EC50 = 763 mg/L). These compounds based on a biodegradable and biocompatible chitosan could be used as potentially antimicrobial agents in crop protection instead of hazardous synthetic pesticides.
    Print ISSN: 1687-9341
    Electronic ISSN: 1687-935X
    Topics: Chemistry and Pharmacology
    Published by Hindawi
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  • 2
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    Biosynthesis and Biological Activity of Carbasugars (2016)
    Hindawi
    Details
    Publication Date: 2016-08-01
    Description: The first synthesis of carbasugars, compounds in which the ring oxygen of a monosaccharide had been replaced by a methylene moiety, was described in 1966 by Professor G. E. McCasland’s group. Seven years later, the first true natural carbasugar (5a-carba-R-D-galactopyranose) was isolated from a fermentation broth of Streptomyces sp. MA-4145. In the following decades, the chemistry and biology of carbasugars have been extensively studied. Most of these compounds show interesting biological properties, especially enzymatic inhibitory activities, and, in consequence, an important number of analogues have also been prepared in the search for improved biological activities. The aim of this review is to give coverage on the progress made in two important aspects of these compounds: the elucidation of their biosynthesis and the consideration of their biological properties, including the extensively studied carbapyranoses as well as the much less studied carbafuranoses.
    Print ISSN: 1687-9341
    Electronic ISSN: 1687-935X
    Topics: Chemistry and Pharmacology
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  • 3
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    Dissolution of (1-3),(1-4)-β-Glucans in Pressurized Hot Water: Quantitative Assessment of the Degradation and the Effective Extraction (2016)
    Hindawi
    Details
    Publication Date: 2016-05-18
    Description: The purpose of this work was to study the behavior of (1-3)(1-4)-β-D-glucan in pressurized hot water. For this purpose, solid β-glucan (450 kDa) was put in water and heated at different temperatures (120, 150, and 170°C) for different times (5 to 360 minutes). At 120°C it was found that the highest soluble β-glucan concentration was measured after 60 minutes; at 150 and 170°C optimal times were 45 and 20 minutes, respectively. The maximum amount of β-glucan dissolved in each of the optimal conditions was 1.5, 2.2, and 2.0 g/L, respectively. Under those conditions an important reduction was observed in the molecular weight: at 120°C and 60 min it was 63 kDa; at 150°C and 45 min it was reduced down to 8 kDa; and at 170°C and 20 min it was only 7 kDa. Besides this reduction in the MW some hydrolysis products, such as glucose and HMF, were observed. These results revealed the convenience of using PHW to dissolve β-glucans since the operation times, compared to the conventional process (55°C, 3 h), were reduced despite the fact that the MW was significantly reduced once the β-glucan was dissolved; therefore, PHW can be used to extract β-glucans from barley under controlled conditions in order to prevent severe degradation.
    Print ISSN: 1687-9341
    Electronic ISSN: 1687-935X
    Topics: Chemistry and Pharmacology
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  • 4
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    Synthesis and Antimicrobial Activity ofN-(6-Carboxyl Cyclohex-3-ene Carbonyl) Chitosan with Different Degrees of Substitution (2016)
    Hindawi
    Details
    Publication Date: 2016-01-01
    Description: Five products ofN-(6-carboxyl cyclohex-3-ene carbonyl) chitosan as antimicrobial agents were prepared by reaction of chitosan with tetrahydrophthalic anhydride (THPA) at different degrees of substitution (DS). The antimicrobial activity was evaluated against four plant bacteria and eight fungi. The results proved that the inhibitory property and water solubility of the synthesized chitosan derivatives, with increase of the DS, exhibited a remarkable improvement over chitosan. The product with a DS of 0.40 was the most active one with MIC of 510, 735, 240, and 385 mg/L againstErwinia carotovora,Ralstonia solanacearum,Rhodococcus fascians, andRhizobium radiobacter, respectively, and also in mycelial growth inhibition againstAlternaria alternata(EC50= 683 mg/L),Botrytis cinerea(EC50= 774 mg/L),Botryodiplodia theobromae(EC50= 501 mg/L),Fusarium oxysporum(EC50= 500 mg/L),F. solani(EC50= 260 mg/L),Penicillium digitatum(EC50= 417 mg/L),Phytophthora infestans(EC50= 298 mg/L), andSclerotinia sclerotiorum(EC50= 763 mg/L). These compounds based on a biodegradable and biocompatible chitosan could be used as potentially antimicrobial agents in crop protection instead of hazardous synthetic pesticides.
    Print ISSN: 1687-9341
    Electronic ISSN: 1687-935X
    Topics: Chemistry and Pharmacology
    Published by Hindawi
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  • 5
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    Biosynthesis and Biological Activity of Carbasugars (2016)
    Hindawi
    Details
    Publication Date: 2016-01-01
    Description: The first synthesis of carbasugars, compounds in which the ring oxygen of a monosaccharide had been replaced by a methylene moiety, was described in 1966 by Professor G. E. McCasland’s group. Seven years later, the first true natural carbasugar (5a-carba-R-D-galactopyranose) was isolated from a fermentation broth ofStreptomycessp. MA-4145. In the following decades, the chemistry and biology of carbasugars have been extensively studied. Most of these compounds show interesting biological properties, especially enzymatic inhibitory activities, and, in consequence, an important number of analogues have also been prepared in the search for improved biological activities. The aim of this review is to give coverage on the progress made in two important aspects of these compounds: the elucidation of their biosynthesis and the consideration of their biological properties, including the extensively studied carbapyranoses as well as the much less studied carbafuranoses.
    Print ISSN: 1687-9341
    Electronic ISSN: 1687-935X
    Topics: Chemistry and Pharmacology
    Published by Hindawi
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  • 6
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    Unknown
    Dissolution of (1-3),(1-4)-β-Glucans in Pressurized Hot Water: Quantitative Assessment of the Degradation and the Effective Extraction (2016)
    Hindawi
    Details
    Publication Date: 2016-01-01
    Description: The purpose of this work was to study the behavior of (1-3)(1-4)-β-D-glucan in pressurized hot water. For this purpose, solid β-glucan (450 kDa) was put in water and heated at different temperatures (120, 150, and 170°C) for different times (5 to 360 minutes). At 120°C it was found that the highest soluble β-glucan concentration was measured after 60 minutes; at 150 and 170°C optimal times were 45 and 20 minutes, respectively. The maximum amount of β-glucan dissolved in each of the optimal conditions was 1.5, 2.2, and 2.0 g/L, respectively. Under those conditions an important reduction was observed in the molecular weight: at 120°C and 60 min it was 63 kDa; at 150°C and 45 min it was reduced down to 8 kDa; and at 170°C and 20 min it was only 7 kDa. Besides this reduction in the MW some hydrolysis products, such as glucose and HMF, were observed. These results revealed the convenience of using PHW to dissolve β-glucans since the operation times, compared to the conventional process (55°C, 3 h), were reduced despite the fact that the MW was significantly reduced once the β-glucan was dissolved; therefore, PHW can be used to extract β-glucans from barley under controlled conditions in order to prevent severe degradation.
    Print ISSN: 1687-9341
    Electronic ISSN: 1687-935X
    Topics: Chemistry and Pharmacology
    Published by Hindawi
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  • 7
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    Total Chlorine-Free Bleaching of Populus deltoides Kraft Pulp by Oxone (2015)
    Hindawi
    Details
    Publication Date: 2015-08-13
    Description: Since the bleaching process is one of the most important environmental pollutant stages in the pulp and paper industry, here, the total chlorine-free (TCF) bleaching of poplar kraft pulp by applying Oxone and peroxide under alkaline conditions has been investigated. The pulp samples were bleached in two stages of Oxone () treatment using an A sequence (A: acid pretreatment), and then the treated pulps were bleached by peroxide (P) to achieve target brightness (about 80%). The influence of various reaction parameters such as alkali charge, temperature, reaction time, and bleaching agent dosage was optimized. The final achieved brightness was more than 78%. Accelerated aging experiments showed more stability in brightness for the Oxone treated pulp, because alkali Oxone bleaching stops thermal degradation. Similarly, the AP bleaching sequence was found to be effective in regaining some strength that had been lost during acidification of the pulp. Improvement in pulp strength made with acid treatment was achieved along with significant amount of lignin removal and it demonstrates the feasibility of Oxone in TCF bleaching. Furthermore, other results indicated the feasibility of Oxone bleaching as an environmentally favorable alternative TCF bleaching sequence, compared with elemental chlorine-free bleaching approaches and also other TCF bleaching sequences.
    Print ISSN: 1687-9341
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    Topics: Chemistry and Pharmacology
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  • 8
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    A New Generation of Glycoconjugated Azo Dyes Based on Aminosugars (2015)
    Hindawi
    Details
    Publication Date: 2015-07-30
    Description: The third generation of glycoconjugated azo dyes (GADs) was prepared linking monoazo dyes to 6-amino-6-deoxy-d-galactose or 6′amino-6′-deoxylactose through mixed amido-ester connections. The complementary conjugation reactions were studied using the succinyl derivative of either the acetal protected aminosugar or the azo dye. Target “naturalized” GADs were obtained after acid hydrolysis of the acetal protecting groups present on the sugar moiety.
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    Topics: Chemistry and Pharmacology
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  • 9
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    Physicochemical Properties and Antioxidant Activity of Chitin and Chitosan Prepared from Pacific White Shrimp Waste (2015)
    Hindawi
    Details
    Publication Date: 2015-02-17
    Description: Chitin and chitosan, valuable marine biopolymers, recovered from shrimp waste, are an abundant by-product of the shrimp processing industry in Vietnam, at an estimated 200000 metric tons per year. The obtained chitin and chitosan are characterized by their purity and functional properties. The polymers show good quality with low residual ash and protein content (
    Print ISSN: 1687-9341
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  • 10
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    Total Chlorine-Free Bleaching ofPopulus deltoidesKraft Pulp by Oxone (2015)
    Hindawi
    Details
    Publication Date: 2015-01-01
    Description: Since the bleaching process is one of the most important environmental pollutant stages in the pulp and paper industry, here, the total chlorine-free (TCF) bleaching of poplar kraft pulp by applying Oxone and peroxide under alkaline conditions has been investigated. The pulp samples were bleached in two stages of Oxone (OX) treatment using an AOX1OX2sequence (A: acid pretreatment), and then the treated pulps were bleached by peroxide (P) to achieve target brightness (about 80%). The influence of various reaction parameters such as alkali charge, temperature, reaction time, and bleaching agent dosage was optimized. The final achieved brightness was more than 78%. Accelerated aging experiments showed more stability in brightness for the Oxone treated pulp, because alkali Oxone bleaching stops thermal degradation. Similarly, the AOX1OX2P bleaching sequence was found to be effective in regaining some strength that had been lost during acidification of the pulp. Improvement in pulp strength made with acid treatment was achieved along with significant amount of lignin removal and it demonstrates the feasibility of Oxone in TCF bleaching. Furthermore, other results indicated the feasibility of Oxone bleaching as an environmentally favorable alternative TCF bleaching sequence, compared with elemental chlorine-free bleaching approaches and also other TCF bleaching sequences.
    Print ISSN: 1687-9341
    Electronic ISSN: 1687-935X
    Topics: Chemistry and Pharmacology
    Published by Hindawi
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