13C-CP/MAS NMR studies of the cyclomalto-oligosaccharide (cyclodextrin) hydrates

Heyes, Stephen J.; Clayden, Nigel J.; Dobson, Christopher M.

doi:10.1016/s0008-6215(00)90916-9

Cited by 75 publications

(63 citation statements)

References 39 publications

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“…As estruturas obtidas apresentaram-se na forma de hidratos α-CD.6H 2 O, β-CD.15H 2 O e γ-CD.18H 2 O, contendo 2, 10 e 12 moléculas de água no interior da cavidade das respectivas CD's. Segundo Connors 15 , a α-CD é geralmente encontrada na forma hexa-hidratada 16 , a β-CD existe usualmente na forma undecahidratada 17 ou dodeca-hidratada 18 , dependendo da umidade relativa, e a γ-CD é, em algumas situações, encontrada como sendo octahidratada, podendo ser cristalizada com 7 a 18 moléculas de água 19 . As estruturas cristalográficas das CD's e as moléculas de água presentes nessas estruturas foram obtidas sem os átomos de hidrogê-nio.…”

Section: Metodologia De Cálculounclassified

Análise estrutural de ciclodextrinas: um estudo comparativo entre métodos teóricos clássicos e quânticos

Britto¹,

Nascimento²,

Santos³

2004

Quím. Nova

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Recebido em 3/9/03; aceito em 23/3/04; publicado na web em 27/07/04 STRUCTURAL ANALYSIS OF CYCLODEXTRINS: A COMPARATIVE STUDY OF CLASSICAL AND QUANTUM MECHANICAL METHODS. In the present work, we analyzed the accuracy of distinct theoretical methods to reproduce the solid state structures of cyclodextrins. The α, β and γ-cyclodextrins (CD) were considered and also their hydrates with included water molecules: α-CD.2H 2 O, β-CD.10H 2 O and γ-CD.12H 2 O. The geometries were fully optimized using Molecular Mechanics (MM2), semiempirical (AM1 and PM3) and ab initio (HF/3-21G) methods and quantitatively compared with experimental data from X ray diffraction. The results obtained from the classical MM2 method were in best agreement with the experiment. The semiempirical and ab initio structures were also in satisfactory accordance with the experimental data. In general, the PM3 method was found to be more suitable than the AM1 to describe the CD geometries, mainly when the intramolecular hydrogen bonds are considered.Keywords: cyclodextrin; quantum-mechanical calculation; molecular mechanics. INTRODUÇÃOCiclodextrinas (CD's) são oligossacarídeos cíclicos formados por moléculas de D-glicose unidas através de ligações glicosídicas α(1-4) (Figura 1a), obtidas a partir da degradação enzimática do amido 1 . As CD's mais conhecidas são as α, β e γ-ciclodextrinas, constituídas por 6, 7 e 8 unidades de glicose, respectivamente, que adotam a conformação de cadeira. Do ponto de vista estrutural, as CD's apresentam-se na forma de "cones truncados" com o lado mais largo formado pelas hidroxilas secundárias em C-2 e C-3 e a face mais estreita constituída pelas hidroxilas primárias ligadas em C-6 (Figura 1b). A dimensão da cavidade é determinada pelo número de unidades de glicose constituintes da CD. Os átomos de oxigênio envolvidos nas ligações glicosídicas (em C-1 e C-4) e os átomos de hidrogênio ligados em C-3 e C-5 determinam o caráter hidrofóbico do interior da cavidade das CD's (Figura 1b). A presença das hidroxilas livres na parte externa das CD's confere a essas moléculas um caráter hidrofílico. Esse arranjo estrutural das moléculas de glicose nas CD's possibilita a utilização desses compostos como hospedeiros na formação de complexos de inclusão. A presença de uma cavidade hidrofóbica e de grupos hidroxilas livres na parte externa da molécula permite a "dissolução" em meio aquoso de compostos (hóspedes) de baixa solubilidade. Esse aspecto molecular tem possibilitado a utilização de ciclodextrinas em diferentes áreas da ciência e tecnologia, sendo o principal domínio de aplicação a indústria farmacêutica, em função da possibilidade de obtenção de novos fármacos com propriedades físicas e químicas diferentes e o mesmo princípio ativo.Apesar do grande número de trabalhos desenvolvidos na linha de pesquisa de compostos de inclusão com CD's, a caracterização dos complexos constitui ainda hoje uma etapa delicada no processo de síntese. A fraca interação entre hóspede e hospedeiro representa uma característica intrínseca do sistema...

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Section: Metodologia De Cálculounclassified

Análise estrutural de ciclodextrinas: um estudo comparativo entre métodos teóricos clássicos e quânticos

Britto¹,

Nascimento²,

Santos³

2004

Quím. Nova

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“…Gidley and Bociek (1988), Heyes et al (1992) and , while the NMR spectrum of amorphous α-CD looks similar to that of amorphous starch prepared by ethanol precipitation of gelatinized maize starch (Gidley and Bociek, 1988). Moreover, the results of NMR measurement also indicated that there was no trace of degradation of CD powder which could have been caused by the relatively high temperature conditions of spray drying.…”

Section: Nmr Spectroscopymentioning

confidence: 57%

“…(1,4) linkages, those of C 6 are associated with hydrogen bonding interactions , while the C 2-3-5 resonances overlapped and could not be individually assigned (Heyes et al, 1992).…”

Section: Nmr Spectroscopymentioning

confidence: 92%

“…The changes in the structure resulted in an alteration of the chemical shift of the peaks. These differences are due to the conformation of crystalline α-CD being less symmetrical than that of amorphous α-CD (Lu et al, 2000), or due to changes in intramolecular torsion angles and intermolecular effects (Heyes et al, 1992). C NMR spectra of spray-dried amorphous and crystalline α-CD powders.…”

Section: Nmr Spectroscopymentioning

confidence: 99%

“…The responses of a spin ½ nucleus to external magnetic fields provide an insight of bond angles, internuclear distances and orientation of nuclei (Aslimovska, 2007). The changes in the chemical shift and peaks on the NMR spectra of ICs are the results of conformational and local magnetic environmental effects caused by guest molecules (Heyes et al, 1992). These differences, as compared to the NMR spectra of uncomplexed CD, are evidence to confirm the IC formation (Francisco et al, 2012).…”

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confidence: 99%

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Studies of the encapsulation and release of carbon dioxide from amorphous and crystalline alpha-cyclodextrin powders and its application in food systems

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Carbon dioxide gas has been widely used in food production. Nevertheless, the conventional ways to utilize CO 2 gas have limitations in terms of safety, convenience, handling and storage. To offer a safe and convenient approach to use CO 2 gas, the production of food-grade CO 2 powder in which CO 2 release can be controlled was investigated. Conventionally, such gas powder has been produced via molecular encapsulation, accomplished by compression of the gas into either a solution of alpha-cyclodextrin (-CD) or crystalline -CD in a solid state. However, shortcomings (low yield or stability of the complex) of these techniques have prevented their actual application.In this project, an innovative method to produce CO 2 --CD complex powder with high yield and stability was investigated using amorphous spray-dried α-CD powder followed by crystallization of the complex. Due to a lack of understanding of amorphous α-CD powder properties and the complexities of conventional methods to quantify CO 2 in solid systems, the project commenced with the characterization of α-CD powders and the development of a simple system to determine the amount of encapsulated CO 2 .The study of the structure of α-CD powders revealed that spray drying of α-CD solution resulted in a completely amorphous powder (T g  83 o C). The differences in molecular structure between crystalline and amorphous α-CDs were illustrated by the analytical results of SEM, X-ray, FTIR, DSC, TGA and 13 C-NMR. The study of moisture sorption showed that an amorphous α-CD powder adsorbed more water than its crystalline counterpart at the same a w but it crystallized as it was equilibrated at higher than 65% RH (>13.70g moisture/100 g of dry solids).A simple system to quantify the CO 2 in the complex through measuring the amount of CO 2 released from the complex into an air-tight chamber headspace by using an infra-red CO 2 probe was designed and tested. The concentrations measured using this new system and conventional acidbase titration were insignificantly different (p > 0.05). This was also validated by the gas chromatography method.A study of solid encapsulation of crystalline (9.84% MC, w.b.) and amorphous (5.58% MC, w.b.) α-CD powders at 0.4-1.6 MPa for 0-96 h showed that amorphous α-CD encapsulated a much larger quantity of CO 2 than the crystalline form at low pressure and short time (p < 0.05). An increase in pressure and prolongation of the time increased encapsulation capacity (EC) of α-CD, especially for the crystalline form. The highest EC of crystalline α-CD was 1.45 mol CO 2 /mol α-CD, which was markedly higher than that of amorphous α-CD (0.98 mol CO 2 /mol α-CD). Solid encapsulation did iii not affect the structure of amorphous α-CD, but slightly altered the structure of crystalline α-CD.Peak representing the encapsulated CO 2 in the complex was clearly observed on the FTIR (2334 cm -1 ) and NMR (125.3 ppm) spectra. However, the complexes were not stable enough for actual application, especially those produced from amorphous α-CD.To impr...

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Solid-state NMR characterization of cyclomaltoheptaose (?-cyclodextrin) polymers using high-resolution magic angle spinning with gradients

Crini

Bourdonneau

Martel

et al. 2000

J. Appl. Polym. Sci.

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Solid-state nuclear magnetic resonance (NMR) techniques were used to characterize cyclomaltoheptaose (␤-cyclodextrin, ␤-CD) polymers. These insoluble materials have been investigated by cross-polarization magic angle spinning with dipolar decoupling (CP/MAS), magic angle spinning without dipolar decoupling (MAS), and high-resolution magic angle spinning with gradients (HRMAS). These NMR spectra allow the assignment of the principal 1 H and 13 C signals. The presence of two distinct components (cross-linked ␤-CD and polymerized epichlorohydrin) in the materials was clearly demonstrated. These polymers were used as sorbents and the resulting NMR spectra are presented and discussed.

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13C-CP/MAS NMR studies of the cyclomalto-oligosaccharide (cyclodextrin) hydrates

Cited by 75 publications

References 39 publications

Análise estrutural de ciclodextrinas: um estudo comparativo entre métodos teóricos clássicos e quânticos

Análise estrutural de ciclodextrinas: um estudo comparativo entre métodos teóricos clássicos e quânticos

Studies of the encapsulation and release of carbon dioxide from amorphous and crystalline alpha-cyclodextrin powders and its application in food systems

Solid-state NMR characterization of cyclomaltoheptaose (?-cyclodextrin) polymers using high-resolution magic angle spinning with gradients

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