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PubMed2000

Evidence for covalent binding between copper ions and cyclodextrin cavity: a vibrational circular dichroism study.

Vibrational absorption and circular dichroism (VCD) spectra were obtained for parent cyclodextrins, hydroxyl deuterated alpha-cyclodextrin, cyclodextrin-copper complexes, and for the cyclodextrin inclusion complexes with Methyl Orange, methyloxirane, 1-propanol, and substituted cyclohexanones, in the solution phase. Changes in the VCD spectra, reflecting perturbations of cyclodextrin cavity, were found in the case of an inclusion complex with Methyl Orange, but for the remaining inclusion complexes measurable changes in VCD were not found. Significant changes observed in the VCD spectra of cyclodextrin-copper complexes suggest that the covalent binding of copper ions to the hydroxyl groups of cyclodextrin is involved.

1-Propanol↗
PubMed2001

Cyclodextrins in topical drug formulations: theory and practice.

Cyclodextrins are cyclic oligosaccharides with a hydrophilic outer surface and a somewhat lipophilic central cavity. Cyclodextrins are able to form water-soluble inclusion complexes with many lipophilic water-insoluble drugs. In aqueous solutions drug molecules located in the central cavity are in a dynamic equilibrium with free drug molecules. Furthermore, lipophilic molecules in the aqueous complexation media will compete with each other for a space in the cavity. Due to their size and hydrophilicity only insignificant amounts of cyclodextrins and drug/cyclodextrin complexes are able to penetrate into lipophilic biological barriers, such as intact skin. In general, cyclodextrins enhance topical drug delivery by increasing the drug availability at the barrier surface. At the surface the drug molecules partition from the cyclodextrin cavity into the lipophilic barrier. Thus, drug delivery from aqueous cyclodextrin solutions is both diffusion controlled and membrane controlled. It appears that cyclodextrins can only enhance topical drug delivery in the presence of water.

Administration, Topical↗
PubMed2002

Cyclodextrins and drug permeability through semi-permeable cellophane membranes.

Determinations of drug fluxes through semi-permeable cellophane membranes are used to evaluate cyclodextrin complexes and cyclodextrin containing drug formulations. In the present study we investigated how the cyclodextrin concentration, the membrane thickness and the molecular weight cut off (MWCO) of the membrane influence drug fluxes. The cyclodextrin used was 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) and the sample drug was hydrocortisone. The MWCO of the membranes ranged from 500 to 14,000 and the HPbetaCD concentration ranged from 0 to 25% (w/v). The hydrocortisone flux from saturated solutions through the MWCO 500 membrane was unaffected by the cyclodextrin concentration. When MWCO of the membrane was greater than the molecular weight of the complex the flux from solutions saturated with hydrocortisone increased with increasing HPbetaCD concentration. This increase showed negative deviation from linearity. When the flux was corrected for the viscosity increase with increasing HPbetaCD concentration then the flux pattern could be described on the basis of Fick's first law and Stokes-Einstein equation. However, the flux did not correlate with the viscosity when it was increased by adding polymer to the saturated drug solutions. It was shown that the observed flux pattern was consistent with self-association of cyclodextrin complexes in the aqueous donor phase.

Chromatography, High Pressure Liquid↗
PubMed2002

Voltammetric studies of the interaction of lumazine with cyclodextrins and DNA.

The interaction of lumazine, an antibacterial drug, with alpha-, beta-cyclodextrins and DNA in aqueous solution was studied by differential pulse stripping voltammetry and cyclic voltammetry as well as UV-vis spectroscopy. The electrochemical and absorption spectral data indicated a 1:1 complex formation of lumazine with alpha-, beta-cyclodextrins and DNA. The nature of the process, taking place at the hanging mercury drop electrode, was clarified. It was found that the complexation of lumazine molecules enhances the stacking interactions which might facilitate the formation of a perpendicularly stacked layer of lumazine-alpha-cyclodextrin complex on the electrode surface. Based on the variations in the current or absorbance, the formation constants and consequently, the Gibbs energy of these complexes were determined. The small size cavity of alpha-cyclodextrin was found to have a greater affinity for lumazine than the beta-cyclodextrin. Moreover, the interactions of lumazine-alpha-cyclodextrin or lumazine-beta-cyclodextrin inclusion complex with DNA have been investigated by means of voltammetry. The results suggest that lumazine displayed high affinity for DNA and the inclusion complex decomposed when it binds to DNA.

Algorithms↗
PubMed2002

Cyclodextrin complexation: influence on the solubility, stability, and cytotoxicity of camptothecin, an antineoplastic agent.

The solubility of camptothecin (CPT), a highly potent antineoplastic agent, as a function of different concentrations of cyclodextrins (alpha-cyclodextrin, alpha-CD; beta-cyclodextrin, beta-CD; and gamma-cyclodextrin, gamma-CD; hydroxypropyl-beta-cyclodextrin, HP-beta-CD; and randomly substituted dimethyl-beta-cyclodextrin, RDM-beta-CD, and dimethyl-gamma-cyclodextrin, RDM-beta-CD) in 0.02 N HCl solution at 25 degrees C was investigated. The results showed a linear increase in the solubility of CPT with increasing concentration of CDs. The apparent stability constants (K(c)) for the CPT complexes with alpha-CD, beta-CD, gamma-CD, HP-beta-CD, RDM-beta-CD, and RDM-gamma-CD were 188, 266, 73, 160, 910, and 40.6 M(-1), respectively, suggesting that RDM-beta-CD afforded the most stable complex. At a 25% w/v concentration of RDM-beta-CD, the solubility of CPT was 228.45 +/- 8.45 microg/ml, about 171 times higher than that in 0.02 N HCl. The stability of CPT in pH 7.4 buffer at 25 degrees C also increased linearly with an increase in the concentration of RDM-beta-CD. The observed pseudo-first-order hydrolysis rate constants (k(obs)) for the free and complexed CPT were 11.8 x 10(-3) and 1.18 x 10(-3) min(-1), corresponding to an increase in half-life of CPT from 58.7 to 587.3 min, respectively. The preliminary cytotoxicity study against the human-derived myeloid THP-1 leukemia cell line showed RDM-beta-CD/CPT and HP-beta-CD/CPT complexes to be about two-fold more active than free CPT. In conclusion, the results showed that CDs, in general, and RDM-beta-CD, in particular, are effective complexing agents and can be used to improve the solubility and stability of CPT. The increase in cytotoxicity of CPT in the presence of CD is likely due to an increase in its stability.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Study on the interaction of methylene blue with cyclodextrin derivatives by absorption and fluorescence spectroscopy.

The ability of beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and carboxymethyl-beta-cyclodextrin (CM-beta-CD) to break the aggregate of the methylene blue (MB) and to form 1:1 inclusion complexes has been studied by absorption and fluorescence spectroscopy. Experimental conditions including concentrations of various cyclodextrins (beta-CD, HP-beta-CD and CM-beta-CD) and media acidity were investigated for the inclusion formation in detail. The formation constants are calculated by using steady-state fluorimetry, from which the inclusion capacity of different cyclodextrins (CDs) is compared. The results suggest that the charged beta-cyclodextrin (CM-beta-CD) is more suitable for inclusion of the cationic dye MB than the neutral beta-cyclodextrins (beta-CD, HP-beta-CD) at pH>5. A mechanism is proposed which is consistent with the stronger binding of MB with CM-beta-CD compared with the other CDs at pH>5.

Cyclodextrins↗
PubMed2005

Effect of beta-cyclodextrin in improving the correlation between lycopene concentration and ORAC values.

Lycopene, a lipophilic antioxidant, plays a crucial role in biological systems. It may play an important role in human biological systems by providing protection against cardiovascular disease and some cancers and by boosting the immune system. The oxygen radical absorbance capacity (ORAC) has been validated as an index of antioxidant activity for many hydrophilic antioxidants but not for lycopene. This study validates the ORAC assay for different concentrations of lycopene in the presence of beta-cyclodextrin, a water-solubility enhancer. Lyc-O-Mato 6% extract was used as a source of lycopene for these experiments. Lycopene was extracted according to a standard spectrophotometric assay procedure in the presence of beta-cyclodextrin at concentrations of 0, 0.4, 0.8, and 1.6%, and the antioxidant activity of lycopene was measured with the ORAC assay. Experiments were conducted in quadruplicate and statistical pooled correlations analyzed. Statistical analysis showed a very high correlation (R2 = 0.99) between ORAC and ascorbic acid concentrations, validating this method. Lycopene concentration correlated poorly with ORAC (R2 = 0.33) in the absence of beta-cyclodextrin. Correlations improved with increasing levels of beta-cyclodextrin (R2 = 0.58 and 0.91 for 0.4 and 0.8% beta-cyclodextrin, respectively). A very high beta-cyclodextrin concentration (1.6%) decreased the correlation between ORAC and lycopene concentration. Inclusion of beta-cyclodextrin in the ORAC assay improves correlation between ORAC and lycopene concentration, thus expanding the scope of the ORAC assay to include an additional fat-soluble antioxidant.

Ascorbic Acid↗
PubMed2003

Synthesis of phosphoryl-tethered beta-cyclodextrins and their molecular and chiral recognition thermodynamics.

Two novel phosphoryl-bridged bis- and tris(beta-cyclodextrin)s of different tether lengths, i.e., bis[m-(N-(6-cyclodextryl)-2-aminoethylaminosulfonyl)phenyl]-m-(chlorosulfonyl)phenylphosphine oxide (5) and tris[m-(N-(6-cyclodextryl)-8-amino-3,6-diazaoctylaminosulfonyl)phenyl]phosphine oxide (6), have been synthesized by reactions of 6-oligo(ethylenediamino)-6-deoxy-beta-cyclodextrins with tris[m-(chlorosulfonyl)phenyl]phosphine oxide. The complex stability constants (K(S)), standard molar enthalpy (Delta H degrees ), and entropy changes (Delta S degrees ) were determined at 25 degrees C for the inclusion complexation of phosphoryl-modified bis- and tris-cyclodextrins (5 and 6, respectively), mono[6-O-(ethoxyhydroxyphosphoryl)]-beta-cyclodextrin (2), mono[6-O-(diethylamino-ethoxyphosphoryl)]-beta-cyclodextrin (3), and mono[6-O-(diphenoxyphosphoryl)]-beta-cyclodextrin (4) with representative alicyclic and N-Cbz-D/L-alanine guests in 0.1 M phosphate buffer solution at pH 7.2 by means of titration microcalorimetry. The thermodynamic parameters obtained indicate that the charge-dipole interaction between the phosphoryl moiety and the negatively charged guests, as well as the conformational difference of modified beta-cyclodextrins in aqueous solution, significantly contribute to the inclusion complexation and the enhanced chiral discrimination. The interactions and binding modes between the hosts and chiral guests were further studied by two-dimensional NMR spectroscopy to elucidate the influence of the structural features of hosts on their increased chiral recognition ability and to establish the correlation between the conformation of the resulting complexes and the thermodynamic parameters obtained.

Alanine↗
PubMed1996

Pharmaceutical applications of cyclodextrins. 1. Drug solubilization and stabilization.

Cyclodextrins are cyclic oligosaccharides which have recently been recognized as useful pharmaceutical excipients. The molecular structure of these glucose derivatives, which approximates a truncated cone or torus, generates a hydrophilic exterior surface and a nonpolar cavity interior. As such, cyclodextrins can interact with appropriately sized molecules to result in the formation of inclusion complexes. These noncovalent complexes offer a variety of physicochemical advantages over the unmanipulated drugs including the possibility for increased water solubility and solution stability. Further, chemical modification to the parent cyclodextrin can result in an increase in the extent of drug complexation and interaction. In this short review, the effects of substitution on various cyclodextrin properties and the forces involved in the drug-cyclodextrin complex formation are discussed. Some general observations are made predicting drug solubilization by cyclodextrins. In addition, methods which are useful in the optimization of complexation efficacy are reviewed. Finally, the stabilizing/destabilizing effects of cyclodextrins on chemically labile drugs are evaluated.

Carbohydrate Sequence↗
PubMed1996

Pharmaceutical applications of cyclodextrins. 2. In vivo drug delivery.

The objective of this Review is to summarize and critique recent findings and applications of both unmodified and modified cyclodextrins for in vivo drug delivery. This review focuses on the use of cyclodextrins for parenteral, oral, ophthalmic, and nasal drug delivery. Other routes including dermal, rectal, and pulmonary delivery are also briefly addressed. This Review primarily focuses on newer findings concerning cyclodextrin derivatives which are likely to receive regulatory acceptance due to improved aqueous solubility and safety profiles as compared to the unmodified cyclodextrins. Many of the applications reviewed involve the use of hydroxypropyl-beta-cyclodextrins (HP-beta-CDs) and sulfobutylether-beta-cyclodextrins (SBE-beta-CDs) which show promise of greater safety while maintaining the ability to form inclusion complexes. The advantages and limitations of HP-beta-CD, SBE-beta-CD, and other cyclodextrins are addressed.

Animals↗
PubMed1999

Interaction between surface active drug (FK906:rennin inhibitor) and cyclodextrins in aqueous solution.

The aggregation behavior of FK906, which is a peptide like hypertensive agent, in aqueous solution was studied by static light scattering, 1H-nuclear magnetic resonance (NMR), and surface tension. These experiments showed a clear critical micelle concentration (cmc) at around 6.3 x 10(-3) to 1.3 x 10(-2) M of FK906 aqueous solution. The result of 1H NMR experiments revealed that FK906 aggregates primarily by hydrophobic interactions involving the benzyl moiety. The Debye plots from light-scattering studies showed that the apparent molecular weight of aggregated FK906 molecule is 1670 which corresponds to 2-3 molecules of FK906. The effect of alpha- and beta-cyclodextrins on the surface tension of FK906 aqueous solution was investigated. It appeared that the addition of alpha-cyclodextrin showed very small shift of cmc, but that of beta-cyclodextrin shifted the cmc to much higher concentration. The investigation on the surface tension of FK906 aqueous solution in the presence of beta-cyclodextrin indicated that FK906 forms a 1:1 complex with beta-cyclodextrin. On the basis of these experiments, it appears that beta-cyclodextrin has an ability to change the surface active property of FK906 in its aqueous solution. Therefore, it is expected that the addition of beta-cyclodextrin to FK906 aqueous solution may prevent the adsorption onto container walls and/or reduce the local irritancy.

Antihypertensive Agents↗
PubMed2005

Cyclodextrins as carriers for cinchona alkaloids: a pH-responsive selective binding system.

A series of cyclodextrin-cinchona alkaloid inclusion complexes were prepared from beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and four cinchona alkaloids in ca. 90% yields, and their inclusion complexation behavior was investigated at pH 7.2 and 1.5 by means of fluorescence, UV/Vis and 2D NMR spectroscopy. The results showed that the cinchona alkaloids can be efficiently encapsulated in the cyclodextrin cavity in an acidic environment and sufficiently released in a neutral environment, which makes these cyclodextrin derivatives the potential carriers for cinchona alkaloids. The binding ability and molecular selectivity of cyclodextrins toward cinchona alkaloids were discussed from the viewpoint of the size-fit concept and multiple recognition mechanism between host and guest.

Binding Sites↗
PubMed2005

Influence of supplemental high molecular weight pullulan or gamma-cyclodextrin on ileal and total tract nutrient digestibility, fecal characteristics, and microbial populations in the dog.

This study was conducted to determine if supplemental pullulan and gamma-cyclodextrin affect canine nutrient digestibility, microbial populations, and fecal characteristics. Ileal cannulated dogs were fed a commercial diet, and treatments were administered daily in a 5 x 5 Latin square design: (i) no supplement; (ii) 2 g pullulan; (iii) 4 g pullulan; (iv) 2 g gamma-cyclodextrin; (v) 4 g gamma-cyclodextrin. Ileal and fecal samples were collected the last 4 d of each 14-d period. Increasing pullulan tended (p < 0.10) to linearly increase ileal bifidobacteria and lactobacilli and quadratically increase fecal lactobacilli. A similar response was noted in ileal bifidobacteria and lactobacilli with gamma-cyclodextrin. Gamma-Cyclodextrin resulted in a quadratic decrease (p < 0.05) in fecal Clostridium perfringens. Increasing pullulan linearly increased (p < 0.05) fecal score, while gamma-cyclodextrin resulted in a linear decrease (p < 0.05). Pullulan and gamma-cyclodextrin supplementation may have beneficial effects on the microbial ecology of dogs.

Animals↗
PubMed2003

The pharmacokinetics and pharmacodynamics of propofol in a modified cyclodextrin formulation (Captisol) versus propofol in a lipid formulation (Diprivan): an electroencephalographic and hemodynamic study in a porcine model.

UNLABELLED: The currently marketed propofol formulation has a number of undesirable properties that are in part a function of the lipid emulsion formulation, including pain on injection, serious allergic reactions, and the support of microbial growth. A modified cyclodextrin-based formulation of propofol (sulfobutyl ether-beta-cyclodextrin) has been developed that may mitigate some of these formulation-dependent problems. However, reformulation may alter propofol's pharmacologic behavior. Our aim in this study was to compare the pharmacokinetics and pharmacodynamics of propofol in the currently marketed lipid-based formulation with those of the novel cyclodextrin formulation. We hypothesized that the pharmacokinetics and pharmacodynamics of the propofol in cyclodextrin would be substantially similar to those of the propofol in lipid. Thirty-two isoflurane-anesthetized animals were instrumented with pulmonary artery, arterial, and IV catheters and were randomly assigned to receive either propofol in lipid or propofol in cyclodextrin by continuous infusion. Arterial blood samples for propofol assay were collected. The processed electroencephalogram, heart rate, mean arterial blood pressure, and cardiac output were measured continuously. The propofol formulations were compared by using model-independent analysis techniques. Combined kinetic/dynamic models were also constructed for simulation purposes. There were no significant differences in the pharmacokinetics or pharmacodynamics of the two propofol formulations. The simulations based on the combined pharmacokinetic/pharmacodynamic models confirmed the substantial similarity of the two formulations. The hypothesis that the propofol-in-cyclodextrin formulation would exhibit pharmacokinetic and pharmacodynamic behavior that was substantially similar to the propofol-in-lipid formulation was confirmed. IMPLICATIONS: A modified cyclodextrin-based formulation of propofol has been developed that may mitigate some of the problems associated with propofol in lipid emulsion. However, reformulation of propofol may change its clinical characteristics. This study in a pig model showed that the novel propofol formulation was substantially similar to the lipid emulsion propofol formulation.

Anesthetics, Intravenous↗
PubMed2004

Synthesis of chitosan microspheres containing pendant cyclodextrin moieties and their interaction with biological active molecules.

A new route to obtain chitosan derivatives containing cyclodextrin moieties as pendant groups was developed. The chitosan microspheres, obtained through crosslinking with glutaraldehyde of an acetic acid solution of chitosan, in an organic suspension medium, were reacted with chloroacyl cyclodextrins in organic basic solvents. The acyl cyclodextrin moieties are linked to the chitosan microspheres through C-N bonds, with the elimination of HCl; higher amounts of acyl cyclodextrin are linked to the microspheres with a smaller crosslinking degree. The chitosan-cyclodextrin conjugates retain higher amounts of bioactive substances (nalidixic acid, piroxicam) or of p-nitrophenol (model substance) than their parent chitosan supports, both by ionic forces and by the formation of inclusion complexes in the cyclodextrin inner cavities. After these preliminary studies, one can appreciate that the cyclodextrin-chitosan conjugates could be used as supports for chromatographic separations or controlled release drug systems.

Chitosan↗
PubMedDate not supplied

Aerosolization potential of cyclodextrins--influence of the operating conditions.

The aim of this work is to characterize the aerosols obtained by jet nebulization with cyclodextrin solutions and to study the influence of operating conditions on nebulization efficiency. Two cyclodextrins, an hydroxypropyl cyclodextrin (Kleptose HP) and a polydisperse methyl beta cyclodextrin (Crysmeb), were tested with 14 nebulizers that differ geometrically. We first determined the physicochemical properties of density, viscosity, and surface tension for the cyclodextrin solutions. Nebulization efficiency was evaluated by measuring droplet size, nebulization rate, quantity of solution nebulized, and nebulization time. We studied the influence of the technological parameters of pressure and nebulizer type and the influence of the formulation on performance efficiency. The use of different nebulizers and different pressure conditions results in variable efficiency. Regardless of the type of nebulizer, an increase in pressure decreases droplet size and increases nebulization rate. The influence of the nebulizer design is considerable. The aqueous cyclodextrin solutions studied can generate aerosols in particle size ranges suitable for pulmonary deposition. Large quantities of aerosol can be nebulized in acceptable nebulization times. The cyclodextrin concentration does not modify nebulization efficiency in the range tested.

Aerosols↗
PubMed2003

Ternary systems of naproxen with hydroxypropyl-beta-cyclodextrin and aminoacids.

The purpose of the present study was to investigate the combined effect of hydroxypropyl-beta-cyclodextrin and different aminoacids (L-lysine, LYS; L-valine, VAL; L-iso-leucine, LEU; and L-arginine, ARG) on the solubility of naproxen, a poorly water-soluble anti-inflammatory drug. Aqueous solubilities of naproxen in binary and ternary systems with hydroxypropyl-beta-cyclodextrin and each aminoacid were determined. The pH was measured in all solubility studies and its role on drug solubility variation was evaluated. Arginine was the most effective aminoacid in improving drug solubility and the only one which showed a synergistic effect when used in combination with hydroxypropyl-beta-cyclodextrin. In contrast, some reduction with respect to the theoretical drug solubility (i.e. the sum of the solubilities in the presence of cyclodextrin and aminoacid separately) was observed in ternary combinations with the other aminoacids. This occurred also in the case of lysine, despite the higher solubility of its ternary system in comparison with the binary cyclodextrin complex at pH 7. Phase-solubility experiments showed that the ternary system with arginine (pH approximately 7) exhibited a stability constant 3.6 times higher and was about 5.5 times more effective in improving drug solubility than the binary complex in buffered (pH approximately 7) aqueous solutions. These results demonstrated that the high increase in the drug solubility shown by ternary systems with arginine was not simply due to a favorable pH change but to multicomponent complex formation. Solid products of naproxen with hydroxypropyl-beta-cyclodextrin, and/or arginine, prepared by different methods, were characterized by Differential Scanning Calorimetry (DSC), Hot Stage Microscopy (HSM) and Scanning Electron Microscopy (SEM).

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2001

Effect of cyclodextrin charge on complexation of neutral and charged substrates: comparison of (SBE)7M-beta-CD to HP-beta-CD.

PURPOSE: To understand the role of charge in substrate/cyclodextrin complexation by comparing the binding of neutral and charged substrates to a neutral cyclodextrin, such as hydroxypropyl beta-CD (HP-beta-CD) with 3.5 degrees of substitution, and an anionically charged cyclodextrin, such as sulfobutyl ether beta-CD ((SBE)7M-beta-CD) with 6.8 degrees of substitution. METHOD: HP-beta-CD and (SBE)7M-beta-CD were evaluated in their ability to form inclusion complexes with neutral compounds, as well as to cationic and anionic substrates in their charged and uncharged forms. The complexation constants (Kc) were determined via a UV spectrophotometric technique, by monitoring the change in substrate absorbance upon incremental addition of a concentrated cyclodextrin solution. The role of electrostatic interaction was probed by observing Kc as a function of solution ionic strength. RESULTS: Neutral molecules displayed a stronger interaction with (SBE)7M-beta-CD compared to HP-beta-CD. In those cases where the guest possessed a charge (positive or negative), HP-beta-CD/substrate complexes exhibited a decrease in complexation strength (2 to 31 times lower) compared to the neutral forms of the same substrate. The same was true (but to a larger extent, 41 times lower) for negatively charged molecules binding to (SBE)7M-beta-CD due to charge-charge repulsion. However, positively charged molecules interacting with the negatively charged (SBE)7M-beta-CD displayed a similar binding capability as their neutral counterpart, due to charge-charge attraction. Further evaluation through manipulation of solution ionic strength revealed strong electrostatic interactions between substrate and cyclodextrin charges. In addition, the studies suggested that on average two sulfonates out of seven may be involved in forming ionic attraction or repulsion effects with the positive charges on prazosin and papaverine, or negative charges of ionized naproxen and warfarin. CONCLUSIONS: Presence of charge on the cyclodextrin structure provides an additional site of interaction compared to neutral cyclodextrins, which may be modified using solution ionic strength.

2-Hydroxypropyl-beta-cyclodextrin↗