Fermentation Kinetics of Selected Dietary Fibers by Human Small Intestinal Microbiota Depend on the Type of Fiber and Subject

SCOPE

An underexplored topic is the investigation of health effects of dietary fibers via modulation of human small intestine (SI) microbiota. A few previous studies hint at fermentation of some dietary fibers in the distal SI of humans and pigs. Here the potential of human SI microbiota to degrade dietary fibers and produce metabolites in vitro is investigated.

METHODS AND RESULTS

Fructans, galacto-oligosaccharides, lemon pectins, and isomalto/malto-polysaccharides are subjected to in vitro batch fermentations inoculated with ileostomy effluent from five subjects. Fiber degradation products, formation of bacterial metabolites, and microbiota composition are determined over time. Galacto- and fructo-oligosaccharides are rapidly utilized by the SI microbiota of all subjects. At 5h of fermentation, 31%-82% of galacto-oligosaccharides and 29%-89% fructo-oligosaccharides (degree of polymerization DP4-8) are utilized. Breakdown of fructo-oligosaccharides/inulin DP ≥ 10, lemon pectin, and iso-malto/maltopolysaccharides only started after 7h incubation. Degradation of different fibers result in production of mainly acetate, and changed microbiota composition over time.

CONCLUSION

Human SI microbiota have hydrolytic potential for prebiotic galacto- and fructo-oligosaccharides. In contrast, the higher molecular weight fibers inulin, lemon pectin, and iso-malto/maltopolysaccharides show slow fermentation rate. Fiber degradation kinetics and microbiota responses are subject dependent, therefore personalized nutritional fiber based strategies are required.

Effects of Different Sources and Levels of Zinc on Growth Performance, Nutrient Digestibility, and Fur Quality of Growing-Furring Male Mink (Mustela vison)

The objective of this study was to investigate the effects of different sources and levels of zinc (Zn) on growth performance, nutrient digestibility, serum biochemical parameters, and fur quality in growing-furring male mink. Animals in the control group were fed a basal diet with no Zn supplementation. Mink in the other nine treatments were fed the basal diet supplemented with Zn from either grade Zn sulfate (ZnSO₄·7H₂O), Zn glycinate (ZnGly), or Zn pectin oligosaccharides (ZnPOS) at concentrations of either 100, 300, or 900 mg Zn/kg dry matter. One hundred and fifty healthy 15-week-old male mink were randomly allocated to ten dietary treatments (n = 15/group) for a 60-day trial from mid-September to pelting in December. Mink in the Zn-POS groups had higher average daily gain than those in the control group (P < 0.05). Zn source slightly improved the feed/gain (P = 0.097). N retention was increased by Zn addition (P < 0.05). Mink supplemented with dietary Zn had higher (P < 0.05) pancreas Zn level than the control group. Fur length was greater (P < 0.05) in ZnGly and ZnPOS groups compared with the control. In addition, fur length and fur density increased (linear, P < 0.05) with Zn supplementation in the diet. In conclusion, our data show that dietary Zn addition improves growth performance by increasing nitrogen retention and fat digestibility in growing-furring mink and Z-POS is equally bioavailable to mink compared to ZnGly.

Rhamnogalacturonan-I Based Microcapsules for Targeted Drug Release

Drug targeting to the colon via the oral administration route for local treatment of e.g. inflammatory bowel disease and colonic cancer has several advantages such as needle-free administration and low infection risk. A new source for delivery is plant-polysaccharide based delivery platforms such as Rhamnogalacturonan-I (RG-I). In the gastro-intestinal tract the RG-I is only degraded by the action of the colonic microflora. For assessment of potential drug delivery properties, RG-I based microcapsules (~1 μm in diameter) were prepared by an interfacial poly-addition reaction. The cross-linked capsules were loaded with a fluorescent dye (model drug). The capsules showed negligible and very little in vitro release when subjected to media simulating gastric and intestinal fluids, respectively. However, upon exposure to a cocktail of commercial RG-I cleaving enzymes, ~ 9 times higher release was observed, demonstrating that the capsules can be opened by enzymatic degradation. The combined results suggest a potential platform for targeted drug delivery in the terminal gastro-intestinal tract.

Effects of pectin supplementation on the fermentation patterns of different structural carbohydrates in rats

SCOPE

We aimed to investigate and compare the effects of four types of pectins on dietary fiber (DF) fermentation, microbiota composition, and short chain fatty acid (SCFA) production throughout the large intestine in rats.

METHODS AND RESULTS

Male Wistar rats were given diets supplemented with or without 3% structurally different pectins for 7 weeks. Different fermentation patterns of pectins and different location of fermentation of pectin and diet arabinoxylans (AXs) in the large intestine were observed. During cecal fermentation, sugar beet pectin significantly stimulated Lactobacillus (p < 0.01) and Lachnospiraceae (p < 0.05). The stimulating effects of sugar beet pectin on these two groups of microbes are stronger than both other pectins. In the cecum, low-methyl esterified citrus pectin and complex soy pectin increased (p < 0.05) the production of total SCFAs, propionate and butyrate, whereas high-methyl esterified pectin and sugar beet pectin did not. The fermentation patterns of cereal AXs in the cecum were significantly different upon supplementation of different pectins. These differences, however, became smaller in the colon due to an enhanced fermentation of the remaining DFs.

CONCLUSION

Dietary supplementation of pectin is a potential strategy to modulate the location of fermentation of DFs, and consequently microbiota composition and SCFA production for health-promoting effects.

[Effectiveness of use in preventive nutrition the food ptoducts with contents of pectin and vitamins]

Daily inclusion in the diet of Pskov GRES workers the drinks or kissels containing 2 g pectin per daily serving (cup) during 6 months was accompanied by a statistically significant decline of their supply with vitamins C, B2, A and beta-carotene. This is reflected both in reducing the average vitamin concentration in blood serum and in the increase of the quota of people with deficiency of several vitamins. Additional inclusion of 13 vitamins in these drinks and kissels, in a dose about 80% of the RDA, has prevented the deterioration of vitamin status.

Role of the Ca-pectates on the accumulation of heavy metals in the root apoplasm

In order to better understand the processes that regulate the accumulation in the apoplasm of heavy metals and their mobilization by the plant metabolites it is essential to study the mechanisms that regulate the interactions between metal ions and pectins. In such a context, the sorption of Cd(II), Zn(II), Cu(II) and Pb(II) from single and multi-metal solutions, by a Ca-polygalacturonate gel with a degree of esterification of 18.0 (PGAM(1)) and 65.5% (PGAM(2)) was studied in the 3.0-6.0 pH range in the presence of CaCl(2) 2.5mM. The sorption of Cr(III) from single metal solution was also considered. The results show that the amount of each metal ion sorbed increases with increasing the initial metal ion concentration and pH. The data from the single metal solution tests show that at pH 6.0 the affinity of the metal ions towards the PGAM(1) matrix follows the order: Cr(III)>Cu(II)≅Pb(II)≫Zn(II)≅Cd(II). The simultaneous sorption of the bivalent metal ions by the PGAM(1) gels indicates that Pb(II) is selectively sorbed. The FT-IR spectra show that the carboxylate groups are mainly responsible for the metal ion coordination. The ability of PGAM(2) to accumulate Cr(III), Cu(II), and Pb(II) was lower than that found in the PGAM(1) systems whereas the sorption of Zn(II) and Cd(II) was negligible.

Pectin-cysteine conjugate: synthesis and in-vitro evaluation of its potential for drug delivery

This study was aimed at improving certain properties of pectin by introduction of thiol moieties on the polymer. Thiolated pectin was synthesized by covalent attachment of cysteine. Pectin-cysteine conjugate was evaluated for its ability to be degraded by pectinolytic enzyme. The toxicity profile of the thiolated polymer in Caco-2-cells, its permeation enhancing effect and its mucoadhesive and swelling properties were studied. Moreover insulin-loaded hydrogel beads of the new polymer were examined for their stability in simulated gastrointestinal conditions and their drug release profile. The new polymer displayed 892.27 ± 68.68 μmol thiol groups immobilized per g polymer, and proved to have retained its biodegradability, upon addition of Pectinex Ultra SPL in-vitro, determined by viscosity measurements and titration method. Pectin-cysteine showed no severe toxicity in Caco-2 cells, as tested by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Moreover, the synthesized polymer exhibited a relative permeation enhancement ratio of 1.61 for sodium fluorescein, compared to unmodified pectin. Pectin-cysteine conjugate exhibited approximately 5-fold increased in in-vitro adhesion duration and significantly improved cohesive properties. Zinc pectin-cysteine beads showed improved stability in simulated gastrointestinal media; however, insulin release from these beads followed the same profile as unmodified zinc pectinate beads. Due to favourable safety and biodegradability profile, and improved cohesive and permeation-enhancing properties, pectin-cysteine might be a promising excipient in various transmucosal drug delivery systems.

Two novel ternary albendazole-cyclodextrin-polymer systems: dissolution, bioavailability and efficacy against Taenia crassiceps cysts

The effect of two water-soluble polymers: pectin and polyvinylpyrrolidone in combination with beta-cyclodextrin, on the dissolution, bioavailability and cysticidal efficacy of albendazole was evaluated using a commercial suspension as reference product. The dissolution of the albendazole-beta-cyclodextrin-pectin formulation was slow and incomplete (44.7%). No statistical differences in C(max) and AUC were found between this formulation and the reference. Also its cysticidal efficacy (33%) was similar to the reference (38%). The albendazole-beta-cyclodextrin-polyvinylpyrrolidone formulation exhibited the highest dissolution rate (78.5%) and its bioavailability was also significantly increased (2.3-fold). In addition, the cysticidal activity of this formulation (83%) was greater than a commercial suspension. Our results suggest that the ternary system of albendazole-beta-cyclodextrin-polyvinylpyrrolidone could be a potential alternative for the treatment of systemic helmintic diseases and it is worth to continue its preclinical evaluation.

[Preparation and lymphatic targeting research of targeting antitumor drug: pectin-adriamycin conjugates]

Pectin, a polysaccharide extracted from the cell wall of plants, was used as the drug carrier to synthesize the pectin-adriamycin conjugates (P(A)n). The structure of the conjugates was confirmed by UV and IR. The degree of esterification (DE) of the pectin was assessed, and it was found that DE significantly influenced the carboxy group contents, inherent viscosity and galacturonic acid contents of the pectin. The results of drug release test in vitro showed that the conjugate was stable in normal saline, but was gradually enzymolyzed to release the adriamycin in blood plasma and in lymph nodes. The results of lymphatic targeting study of P(A), demonstrated that the modification of DE or drug coupling capacity of pectin significantly influenced the lymphatic targeting characteristics of P (A)n. The adriamycin concentration of lymph nodes was 208 times higher than that of plasma after local injection of the P(A)n, of which the adriamycin content was 27.9% and the pectin was deesterificated 120 minutes by the use of hypothermy alkaline deesterification method.

Calcium Pectinate Capsules for Colon-Specific Drug Delivery

The calcium pectinate (CaP) capsule, a novel, colon-specific delivery system, was designed and developed using 5-fluorouracil (5-FU) as a model drug. Technically, CaP capsules were prepared by dipping a glass or stainless steel rod successively into pectin and calcium chloride solutions, followed by subsequent air-drying and coating. In vitro studies showed that the release of 5-FU from CaP capsules markedly increased in the presence of rat cecal contents, and the release characteristic was mainly associated with some capsule parameters such as calcium content, shell thickness, and coat amount. Gamma scintigraphic studies demonstrated that CaP capsules could pass through the stomach and small intestine intact and could release drug in colon. The 5-FU releasing characteristics acquired both from in vitro biomimic dissolution experiments and from healthy volunteers indicated that the newly developed CaP capsule possessed the ideal colon-specific drug delivery characteristic.

[Effect of acid suppression therapy for eradicating Helicobacter pylori infection on bismuth absorption from colloidal bismuth pectin]

OBJECTIVE

To investigate whether acid suppression therapy influences the absorption of bismuth from colloidal bismuth pectin (CBP).

METHODS

48 male SD rats were randomly divided into five groups to be administer with different medicines once a day for 14 days: group A1 (administered with CBP only and killed on the cessation day of administration), group B1 (administered with CBP only and killed 8 weeks after the cessation of administration), group A2 [administered with CBP + amoxicillin (AMO) + metronidazole (MTR) + losec and killed on the cessation day of administration], group B2 (administered with CBP + AMO + MTR + losec and killed 8 weeks after the cessation of administration), and control group (administered with distilled water). The kidney issue sections were counterstained after AMG development. The bismuth deposited in tissues was observed by microscopy. The gray level of kidney tissue sections were measured and compared through image processing program. The deposition of bismuth and the degrees of cell organ's impairment were observed by electron microscopy. By using electron probe microanalysis bismuth was identified from the chemical elements in the specimens.

RESULTS

Under the light microscopy, black-brown granules were discovered in the cell bodies of the proximal convoluted renal tubule. The amounts of bismuth accumulated in kidney of the 2 quadruple therapy groups were much more than those of the 2 single compound therapy groups (all P < 0.05). The amount of bismuth accumulated in kidney on the cessation day of administration was more than that eight weeks later (both P < 0.01). Under electron microscopy, black-brown granules were observed exclusively in the lysosomes of the proximal convoluted renal tubule cell. Electron microscopy found cell impairment in the quadruple therapy groups. Impairment of these cells could be recovered 8 weeks after the cessation of administration.

CONCLUSION

Acid suppression therapy causes an increase of absorption and accumulation of bismuth from CBP in the kidney. Bismuth can be accumulated in the cell bodies of proximal convoluted renal tubule after its absorption. The absorbed bismuth can be discharged out of the body via kidney. Large amounts of bismuth accumulation in kidney can impair the functions of proximal convoluted renal tubule cells.

Emulsion gel beads of calcium pectinate capable of floating on the gastric fluid: effect of some additives, hardening agent or coating on release behavior of metronidazole

Emulsion gel (EMG) beads of calcium pectinate capable of floating in the gastric condition were developed using an emulsion-gelation method and their release properties were investigated. Attempts to modify the drug release were made by applying some additives into the starting solution prior to bead formation, by hardening with glutaraldehyde, and by coating with polymer. The metronidazole-loaded EMG beads were found to float on simulated gastric fluid. Increasing the drug to pectin ratio in the beads slowed the drug release from the conventional and the EMG beads. However, the drug release from these beads was rapid, i.e., about 80% of drug loading released within 20-80 min. The additives (PEG10000, glyceryl monostearate and Eudragit L) had a slight, insignificant, effect on the drug release. Using 2% glutaraldehyde as a hardening agent prolonged the drug release. Coating the beads with Eudragit RL significantly sustained the drug release while the beads remained buoyant. The results suggest that EMG beads are suitable as a carrier for intragastric floating drug delivery and that their release behaviour could be modified by hardening with glutaraldehyde or by coating with Eudragit RL.

[Some interactions of natural and synthetic anionic polymers with biologically active substances]

Anionic polymers are nowadays extensively used in drug form technology, especially in drug delivery and drug targeting. Development of proper drug and macromolecular excipient composition allows controlled drug delivery in the term of the drug concentration in blood or other tissues, and in the term of the action-time. Between anionic polymers most frequently carbopols, eudragits, alginates and pectins are used. Application of anionic polymers in drug form technology is an up to date problem. According to new synthesis methods and new anionic polymers, new drug delivery systems would be researched. Most selective and safe devices should be developed, concerning biodegradation aspects.

N-Trimethyl chitosan chloride as absorption enhancer in oral peptide drug delivery. Development and characterization of minitablet and granule formulations

In this study, minitablet and granule formulations were developed as solid oral dosage forms for the delivery of peptide drugs with the absorption enhancer N-trimethyl chitosan chloride (TMC). Minitablets were deemed suitable as a dosage form due to their ability, as components of multiple unit dosage forms (MUDFs), to disperse from each other, before disintegration, effectively increasing the area in which the polymer can assert its absorption-enhancing effect. The polymer should be released from the dosage forms prior to the release of the peptide, which was, together with achieving maximum release of both ingredients, the main focus of this study. Desmopressin (1-(3-mercaptopropionic acid)-8-D-arginine vasopressin monoacetate (DDAVP) was used as model peptide drug. The optimized minitablet formulation consisted of two types of granules, namely DDAVP and TMC granules. DDAVP granules, containing tetraglycerol pentastearate (TGPS), were specifically aimed at delaying the release of the peptide from the dosage form. Burst release of TMC was attempted with TMC granules. Both these granule types were included in the granule formulation. Release profiles for both the optimized minitablet formulation as well as the granule formulation showed that the release of DDAVP was effectively delayed from the formulation compared to the formulation where no attempt at delaying the release was made. In comparison, more TMC was released, and at a faster rate, from the granule formulation than the optimized minitablet formulations. Both the optimized minitablet formulation and the granule formulation show suitable release profiles for the delivery of peptide drugs with TMC as absorption enhancer in solid oral dosage forms.

Disintegrating pellets from a water-insoluble pectin derivative produced by extrusion/spheronisation

Pectinic acid (PA) and microcrystalline cellulose (MCC) as extrusion aiding excipients have been compared. Three different drugs were selected as models: Riboflavin with a very low water solubility, paracetamol and theophylline as drugs with high water-solubility. The drug load was varied from 1 to 80% wt. The low-soluble pectin derivative, PA (degree of methoxylation <10%) was found to be well suited as an extrusion aiding excipient in pellet preparation by extrusion/spheronisation. The substance has a high drug loading capacity and produces disintegrating pellets that are well suited for fast delivery of drugs with a low water-solubility. The pellets are also mechanically stable. Compared to MCC, PA was found to require less water for pellet formation and was more sensitive against changes in the water content. In order to achieve optimal shape of the pellets, spheronisation was carried out at 45 degrees C. PA is more sensitive to type and amount of drug and is, consequently, not as universally applicable as the conventionally used microcrystalline cellulose. The great advantage of pectinic acid is, however, the disintegrating properties of the pellets after only a short time of exposure to liquid.

The formation and permeability of drugs across free pectin and chitosan films prepared by a spraying method

This study has investigated the permeation of drugs through free films made of pectin and chitosan. The background for this study is the intended use of the films as coating material in a colon-specific drug delivery device. The factors that varied when making the films were the pectin source and grade of the pectin, degree of deacetylation of the chitosan and ratio between pectin and chitosan. The permeability of the model drug in 0.1 M HCl was low with an average drug release of 1.3 x 10(-3)%/cm. The films containing high content of chitosan showed exponential kinetics while the films containing high content of pectin showed 0-order kinetics. The release of drug in phosphate buffer pH 6.8 showed 0-order kinetics. The lowest permeability was obtained for a film consisting of a high content of pectin to chitosan, chitosan with a high degree of deacetylation and non-amidated low methoxylated citrus pectin. The permeation of paracetamol for this combination was 9.4 x 10(3)%/cm. This film combination had a combined diffusion of only 0.046%/cm after 1 h in 0.1 M HCl and 4 h in phosphate buffer pH 6.8.

Composite film-coated tablets intended for colon-specific delivery of 5-aminosalicylic acid: using deesterified pectin

Combinations of Eudragit RS and deesterified pectin, polygalacturonic acid (PGA), or its potassium and sodium salts, when applied as a film coat, has a potential value as a colon-specific delivery system. Dispersions of PGA in Eudragit RS were used as the film former for coating of 5-aminosalicylic acid (5-ASA) tablet cores. Drug release behavior was assessed, in vitro, under simulating conditions in term of pH and time to in vivo during their transit to the colon. Negligible drug release occurred during first 5 hr where the coated tablets were in the stomach and small intestine. After that, the pectinolytic enzymes were added into the pH 6.8 medium to simulate the in vivo condition where there is the digestion of bacteria in the colon. The release of 5-ASA from the coated tablets occurred linearly as a function of time. Drug release depended on the composition of the mixed film, as well as the ratio of Eudragit RS to PGA or its salts. The highest drug release from the coated tablets of about 40% was obtained when the ratio of Eudragit RS to potassium salt of PGA was 2.5 to 1. Drug release profiles seemed to conform to the mechanism involving the osmotically driven release and formation of channels in the film caused by dissolution of PGA salts. Channel formation was, in most cases, activated by the presence of pectinolytic enzymes, showing that the PGA in the mixed film was subjected to enzymic breakdown. In conclusion, PGA could be used as an additive in Eudragit RS films to control the release of colonic delivery system.

Release of albumin from chitosan-coated pectin beads in vitro

The release behavior of albumin from chitosan-coated pectin beads in vitro was investigated. The factors, such as concentration of CaCl(2), molecular weight of chitosan, pH of chitosan solution, and pH of release medium, which can have a significant effect on the release behavior from the beads, were discussed in this study. The loading efficiency (LE) of albumin showed maximum value when the concentration of CaCl(2) and the weight ratio of pectin to albumin were 2 wt.% and 2, respectively. The release of albumin from pectin beads could be retarded by coating with chitosan at various pH medium. The increase of the concentration of CaCl(2) induced the decrease of albumin release for uncoated-pectin beads, but not much difference of release for coated-pectin ones. The higher molecular weight of chitosan showed less albumin release than the lower one. The release of albumin from the chitosan-coated pectin beads was dependent on pH of coating solution and release medium, which might affect the degree of swelling of pectin beads.

Formulation and roentgenographic studies of naproxen-pectin-based matrix tablets for colon drug delivery

A study has been carried out to assess the potential use of pectin in combination with two added hydrocolloids, i.e., hydroxy-propyl-methyl cellulose and hydroxyethyl cellulose in varied concentrations and coated with ethyl cellulose and cellulose acetate phthalate. The results of in vitro drug release showed that the matrix tablets prepared with pectin, hydroxy ethyl cellulose (20 percent) when coated with ethyl cellulose and cellulose acetate phthalate were found to be 63.0 percent, 8.4 percent, and 4.5 percent, respectively, in after eight hours during drug release study period. These results were confirmed with the results of roentgenographic studies in nine healthy human volunteers to find the shape and integrity of the dosage form. The X-ray photographs revealed that the enteric-coated tablet was visible only up to 5.5 hours and at the end of eighth hour, the photograph has not shown any presence of tablet indicating the loss of shape and size by the microflora present in the colon region. So, the results of in vitro and roentgenographic studies revealed that pectin, hydroxy ethyl cellulose (20 percent) base coated with ethyl cellulose and cellulose acetate phthalate was found to be a promising carrier for naproxen to colon.

Electrosorption of pectin onto casein micelles

Pectin, a polysaccharide derived from plant cells of fruit, is commonly used as stabilizer in acidified milk drinks. To gain a better understanding of the way that pectin stabilizes these drinks, we studied the adsorption and layer thickness of pectin on casein micelles in skim milk dispersions. Dynamic light scattering was used to measure the layer thickness of adsorbed pectin onto casein micelles in situ during acidification. The results indicate that the adsorption of pectin onto casein micelles is multilayered and takes place at and below pH 5.0. Renneting, i.e., cleaving-off kappa-casein from the casein micelles, did not alter the adsorption pH. It did, however, show that pectin arrests the rennet-induced flocculation of casein micelles below pH 5.0. From the findings we concluded the attachment of pectin onto casein micelles is driven by electrosorption. Adsorption measurements confirmed the multilayered nature of the adsorption of pectin onto casein micelles. Both the adsorbed amount and the layer thickness increased with decreasing pH in the relevant range 3.5-5.0. The phase behavior of a casein micelles/pectin mixture was determined and could be explained in terms of thermodynamic incompatibility being relevant above pH 5.0 and adsorption, leading to either stabilization and bridging, being relevant below pH 5.0. The results confirm that electrosorption is the driving force for the adsorption of pectin onto casein micelles.

In vitro evaluation of pectin-HPMC compression coated 5-aminosalicylic acid tablets for colonic delivery

In this study, we report pectin-HPMC compression coated core tablets of 5-aminosalicylic acid (5-ASA) for colonic delivery. Each 100 mg core tablet contained 5-ASA and was compression coated at 20 kN or 30 kN using 100% pectin, 80% pectin-20% HPMC, or 60% pectin-40% HPMC, at two different coat weights as 400 or 500 mg. Drug dissolution/system erosion/degradation studies were carried out in pH 1.2 and 6.8 buffers using a pectinolytic enzyme. The system was designed based on the gastrointestinal transit time concept, under the assumption of colon arrival times of 6 h. It was found that pectin alone was not sufficient to protect the core tablets and HPMC addition was required to control the solubility of pectin. The optimum HPMC concentration was 20% and such system would protect the cores up to 6 h that corresponded to 25-35% erosion and after that under the influence of pectinase the system would degrade faster and delivering 5-ASA to the colon. The pectin-HPMC envelope was found to be a promising drug delivery system for those drugs to be delivered to the colon.

Solubilization of rhamnogalacturonan I galactosyltransfrases from membranes of a flax cell suspension

Galactosyltransferases (GalTs), capable of transferring a galactosyl residue from UDP-galactose (UDP-Gal) to polysaccharide acceptor, were solubilized from flax (Linum usitatissimum L.) membranes using 0.5% CHAPS. The observed requirement for a rhamnogalacturonan I (RG-I) exogenous substrate to stimulate the solubilized GalT activity provided the first evidence for the presence of RG-I GalT activities in flax cells. An assay to measure specifically the products of this RG-I GalT activity was designed, based on size-exclusion chromatography. Labelled products were characterized as an RG-I polymer by using purified RG-I hydrolase or lyase. At pH 8 and in the presence of 5 mM CaCl2, beta-D-galactosyl residues were specifically transferred onto RG-I branches of short beta-(1 --> 4)-D-galactan side chains. These side chains were liable to hydrolysis by beta-galactosidase and endo-beta-(1 --> 4)-D-galactanase. The RG-I GalT had a temperature optimum of 30 degrees C. an apparent Km for UDP-Gal and exogenous RG-I substrate of 460 +/- 40 microM and 1.1 +/- 0.1 mg ml(-1) respectively, and a Vmax of 3.0 +/- 0.5 pkat mg(-1) protein.

Natural gums and modified natural gums as sustained-release carriers

Although natural gums and their derivatives are used widely in pharmaceutical dosage forms, their use as biodegradable polymeric materials to deliver bioactive agents has been hampered by the synthetic materials. These natural polysaccharides do hold advantages over the synthetic polymers, generally because they are nontoxic, less expensive, and freely available. Natural gums can also be modified to have tailor-made materials for drug delivery systems and thus can compete with the synthetic biodegradable excipients available in the market. In this review, recent developments in the area of natural gums and their derivatives as carriers in the sustained release of drugs are explored.

Oral mucosal bioadhesive tablets of pectin and HPMC: in vitro and in vivo evaluation

The potential of tablets containing 1:4, 1:1 and 4:1 weight ratios of pectin and hydroxypropyl methylcellulose (HPMC) for the sustained release of diltiazem by sublingual administration has been investigated. Measurements of maximum adhesive force to rat peritoneal membrane indicated a satisfactory bioadhesive strength. An in vitro sustained release of diltiazem over 5 h was achieved with bilayer tablets composed of a drug-free ethylcellulose layer in addition to the pectin/HPMC layer containing drug. Plasma concentration-time curves obtained following sublingual administration to rabbits of single and bilayer tablets with 1:1 weight ratios of pectin and HPMC showed evidence of sustained release of diltiazem. Bioavailability of diltiazem was 2.5 times that achieved by oral administration for single layer tablets and 1.8 times for the bilayered tablets.

Development of pectin matrix tablets for colonic delivery of model drug ropivacaine

The objective of this work was to develop pectin-based matrix tablets for colonic delivery of the model drug ropivacaine, with the future perspective of radiolabelling the system by neutron activation technique for a gamma-scintigraphic study. The aim was to investigate some formulation factors that could reduce the release of the drug in the simulated gastric and intestinal fluids, increase the release in the simulated cecal fluid (with pectinolytic enzymes) and improve the poor compactibility of pectins. For dissolution studies, the flow-through apparatus with sequential dissolution liquids simulating the mouth-to-colon conditions was used. The effect of two pectin types, the incorporation of ethylcellulose as a dry matrix-additive and water or ethanol as granulation liquids were investigated in a study designed as a D-optimal mixture. Amidated pectin (Am.P) produced harder tablets than the calcium salt of pectin (Ca.P) and was more susceptible to enzymatic degradation. Addition of ethylcellulose increased the tablet strength and the dissolution rate. Furthermore, directly compressed Am.P tablets were produced by addition of coarse or micronised qualities of ethylcellulose. The latter improved the crushing strength markedly imposing a marginal release-reducing effect. Coating this formulation with Eudragit((R)) L 100 reduced the release in the simulated upper GI conditions without interference with the subsequent enzymatic activity.

Production of pectinesterase and polygalacturonase by Aspergillus niger in submerged and solid state systems

Production of pectinesterase and polygalacturonase by Aspergillus niger was studied in submerged and solid-state fermentation systems. With pectin as a sole carbon source, pectinesterase and polygalacturonase production were four and six times higher respectively in a solid state system than in a submerged fermentation system and required a shorter time for enzyme production. The addition of glucose increased pectinesterase and polygalacturonase production in the solid state system but in submerged fermentation the production was markedly inhibited. A comparison of enzyme productivities showed that those determined for pectinesterase and polygalacturonase with pectin as a carbon source were three and five times higher by using the solid state rather than the submerged fermentation system. The productivities of the two enzymes were affected by glucose in both fermentation systems. The membranes of cells from the solid state fermentation showed increased levels of C18:1, C16:0 and C18:0 fatty acids. Differences in the regulation of enzyme synthesis by Aspergillus niger depended on the fermentation system, favoring the solid state over the submerged fermentation for pectinase production.

The use of scintigraphy to provide "proof of concept" for novel polysaccharide preparations designed for colonic drug delivery

PURPOSE

The aim of the present study was to provide "proof of concept" data in man for novel polysaccharide preparations designed for colonic drug delivery using gamma scintigraphy.

METHODS

Two placebo calcium pectinate matrix tablet formulations were studied: one contained calcium pectinate and pectin (CaP/P) and was designed to rapidly disintegrate in the ascending colon, the other contained calcium pectinate and guar gum (CaP/GG) and was designed to disintegrate more slowly, releasing its contents throughout the ascending and transverse colon. Both formulations were enteric coated in order to protect them from the stomach. Ten healthy volunteers received either a CaP/P or CaP/GG tablet, in a randomised cross-over study. Transit and disintegration of the radiolabelled formulations was followed by gamma scintigraphy. Rat studies were conducted in order to verify that the expected colonic degradation of the polysaccharide formulations was as a consequence of bacterial enzyme attack.

RESULTS

The in vivo clinical study confirmed the results obtained in the rat and bench in vitro fermentation models; complete tablet disintegration for Formulation CaP/GG appeared to be slower than that of Formulation CaP/P and the time and the location of complete tablet disintegration was more reproducible with Formulation CaP/P compared to Formulation CaP/GG.

CONCLUSIONS

These results provide "proof of concept" data for the use of calcium pectinate preparations for drug delivery to the colon and highlight the value of scintigraphy in focusing the development strategy for colonic targeting preparations.

The effect of some macromolecular ionic complexes on the pharmacokinetics and -dynamics of ocular cyclopentolate in rabbits

The effect of mucoadhesive polymeric vehicles on the mydriatic efficacy, and on the systemic and ocular absorption of cyclopentolate from eyedrops was studied in albino rabbits. Combining cyclopentolate base to polygalacturonic (CY-PGA) or hyaluronic (CY-HA) acid resulted in an increased mydriatic effect when compared with cyclopentolate hydrochloride (CY-HCl). During the first half an hour, the systemic absorption of cyclopentolate was lower after CY-PGA than after CY-HCl. The ocular penetration of cyclopentolate, based on drug concentrations in aqueous humor 30 minutes after the eyedrop instillation, was increased 3 fold when the polygalacturonate complex was used. CY-PGA, as well as other polymeric salts, might offer a possibility to increase the therapeutic index of cyclopentolate.

Comparative bioavailability characteristics of commercial quinidine polygalacturonate and sulfate tablets

This study compared the relative bioavailability characteristics of quinidine polygalacturonate (QP) and quinidine sulfate (QS) after oral administration of commercial tablets and a liquid form prepared from crushed tablets in 13 healthy adult male volunteers. Each subject received the following four single-dose treatments in a randomized, crossover manner with a one-week washout period between treatments: 400 mg QS liquid, two 200-mg QS tablets, 550 mg QP liquid, and two 275-mg QP tablets. All four treatments were equivalent in terms of the dose of quinidine base. Multiple serum samples and two 24-hour urine specimens were collected over 24 and 48 hours, respectively, and assayed for quinidine with a specific HPLC assay method. For the absorption and disposition parameters measured (maximum serum concentration, time to reach maximum concentration, area under the concentration-time curve [0-48 hours], absorption and elimination rate constants, absorption and elimination half-lives, apparent total body clearance, apparent volume of distribution, and dose fraction excreted in the urine) no significant differences were observed for any of the parameters among the four treatments (p greater than 0.05). The results of the present investigation demonstrated that QP and QS produced identical serum quinidine concentration-time curves when given in the form of a tablet or liquid. The clinical implications of these observations with respect to the dosing of QP are discussed.