Biomedical subjects

Marshall L Fishman

Publications and source records attributed to Marshall L Fishman.

12 recordsLinked to original sources

PubMed2006

The effect of modified citrus pectin on urinary excretion of toxic elements.

This study was undertaken to evaluate the effect of modified citrus pectin (MCP) on the urinary excretion of toxic elements in healthy individuals. MCP is a reduced molecular weight pectin (weight-average molar mass = 15,400) that is mostly linear homogalacturonan with a 3.8% degree of esterification and approximately 10% rhamnogalacturonan II based on the presence of 2-keto-3-deoxy-octonic acid. Subjects ingested 15 g of MCP (PectaSol, EcoNugenics Inc., Santa Rosa, California 95407) each day for 5 days and 20 g on day 6. Twenty-four hour urine samples were collected on day 1 and day 6 for comparison with baseline. The urine samples were analysed for toxic and essential elements. In the first 24 h of MCP administration the urinary excretion of arsenic increased significantly (130%, p < 0.05). On day 6, urinary excretion was increased significantly for cadmium (150%, p < 0.05). In addition, lead showed a dramatic increase in excretion (560%, p < 0.08). This pilot trial provides the first evidence that oral administration of MCP increases significantly the urinary excretion of toxic metals in subjects with a 'normal' body load of metals. It is suggested that systemic chelation of toxic metals by MCP may in part be attributable to the presence of rhamnogalacturonan II, which has been shown previously to chelate metals.

Adult↗

PubMed2005

Biodegradable composites from sugar beet pulp and poly(lactic acid).

Sugar beet pulp and poly(lactic acid) (PLA) composites were prepared by compression-heating. The resultant thermoplastics had a lower density, but they had tensile strength similar to that of pure PLA specimens as well as the same geometric properties. Tensile properties depended on the initial water content of sugar beet pulp and the process by which composites were manufactured. In comparison with sugar beet pulp, the composite showed improved water resistance. This can be attributed to the hydrophobic character of PLA and pulp-matrix interactions. The composite thermoplastics showed suitable properties for potential use as lightweight construction materials.

Beta vulgaris↗

PubMed2005

Interaction of various pectin formulations with porcine colonic tissues.

Pectins of low and high degrees of esterification, as well as pectin derivatives carrying primary amines, were investigate for gel forming ability with mucosal tissues. The combination of scanning electronic microscopy and small deformation dynamic mechanical studies revealed that pectins with higher net electrical charges are more bioadhesive than the less charged ones. Both the negatively charged pectin formulation, P-25, and the positively charged formulation, P-N, were able to synergize with the mucus to produce rheologically strengthened gels. The highly esterified pectin, P-94, also synergized with the mucosal glycoproteins to form a gel structure via coil entanglements. The ex vivo studies further confirmed the microstructures of mucus gel networks with adsorbed pectins. When incubated with porcine intestinal mucus membrane, P-94 gels were found generally bound to the lumen area, P-25 gels were able to penetrate deeply near the wall area, P-N gels interacted with mucins via electrostatic bonding and dispersed into the whole area from the lumen to the wall. Hence, both P-N and P-94, by enhancing the protective barrier properties of mucus systems, may be useful alternatives for the treatment of mucus related irritation and infection. In drug-delivery systems, P-N and P-25 would deliver incorporated drugs mainly by pectin dissolution, while a diffusion mechanism would release drugs from P-94 gels.

Animals↗

PubMed2005

Isolation, characterization, and pectin-modifying properties of a thermally tolerant pectin methylesterase from Citrus sinensis var. Valencia.

The thermally tolerant pectin methylesterase (TT-PME) was isolated as a monocomponent enzyme from sweet orange fruit (Citrus sinensis var. Valencia). It was also isolated from flower and vegetative tissue. The apparent molecular weight of fruit TT-PME was 40800 by SDS-PAGE and the isoelectric point estimated as pI 9.31 by IEF-PAGE. MALDI-TOF MS identified no tryptic-peptide ions from TT-PME characteristic of previously described citrus PMEs. TT-PME did not absolutely require supplemented salt for activity, but salt activation and pH-dependent activity patterns were intermediate to those of thermolabile PMEs. Treatment of non-calcium-sensitive pectin with TT-PME (reducing the degree of methylesterification by 6%) increased the calcium-sensitive pectin ratio from 0.01 to 0.90, indicating a blockwise mode of action. TT-PME produced a significantly lower end-point degree of methylesterification at pH 7.5 than at pH 4.5. Extensive de-esterification with TT-PME did not reduce the pectin molecular weight or z-average radius of gyration, as determined by HPSEC.

Carboxylic Ester Hydrolases↗

PubMed2003

Monovalent salt-induced gelation of enzymatically deesterified pectin.

Pectin gels were induced by monovalent salts (0.2 M) concurrently with deesterification of high methoxy pectin using a salt-independent orange pectin methylesterase (PME). Constant pH was maintained during deesterification and gelation. If salt or PME was absent, the pectin did not form a gel. The gel strength was influenced by both pH and species of monovalent cation. At pH 5.0, the pectin gel induced by KCl was significantly stronger than the NaCl-induced gel. In contrast, a much stronger gel was produced in the presence of NaCl as compared to KCl at pH 7.0. LiCl did not induce pectin gelation at either pH. Molecular weights of pectins increased from 1.38 x 10(5) to 2.26 x 10(5) during NaCl-induced gelation at pH 7. One proposal to explain these pectin molecular weight changes is a hypothetical PME transacylation mechanism. However, these pectin molecular weight changes can also be explained by metastable aggregation of the enzymatically deesterified low methoxy pectin. We postulate that gelation was induced by a slow deesterification of pectin under conditions that would normally salt out (precipitate) low methoxy pectin in the absence of PME.

Gels↗

PubMed2003

Separation and characterization of a salt-dependent pectin methylesterase from Citrus sinensis var. Valencia fruit tissue.

A pectin methylesterase (PME) from sweet orange fruit rag tissue, which does not destabilize citrus juice cloud, has been characterized. It is a salt-dependent PME (type II) and exhibits optimal activity between 0.1 and 0.2 M NaCl at pH 7.5. The pH optimum shifted to a more alkaline range as the salt molarity decreased (pH 8.5-9.5 at 50 mM NaCl). It has an apparent molecular mass of 32.4 kDa as determined by gel filtration chromatography, an apparent molecular mass of 33.5 kDa as determined by denaturing electrophoresis, and a pI of 10.1 and exhibits a single activity band after isoelectric focusing (IEF). It has a K(m) of 0.0487 mg/mL and a V(max) of 4.2378 nkat/mg of protein on 59% DE citrus pectin. Deblocking the N-terminus revealed a partial peptide composed of SVTPNV. De-esterification of non-calcium-sensitive pectin by 6.5% increased the calcium-sensitive pectin ratio (CSPR) from 0.045 +/- 0.011 to 0.829 +/- 0.033 but had little, if any, effect on pectin molecular weight. These properties indicate this enzyme will be useful for studying the PME mode of action as it relates to juice cloud destabilization.

Carboxylic Ester Hydrolases↗

PubMed2003

Pectin-based systems for colon-specific drug delivery via oral route.

Pectin-derived matrices are now being examined and tested for controlled drug delivery. Pectin is intact in the upper gastrointestinal tract and degraded by colonic microflora. The composition of this microflora remains relatively consistent across a diverse human population. Thus, pectin-derived drug carriers provide promising potential for colon-specific drug delivery. This paper reviews recent developments in pectin-derived formulations. Subjects reviewed include gelation of pectin, calcium cross-linked pectinate, composites of pectin and other polymers, technologies to fabricate pectin into useful drug delivery vehicles, and methods to evaluate release kinetics of incorporated drugs. This article discusses advantages, limitations, and possible future developments in pectin-based formulations with particular emphasis on the field of colon-specific drug delivery.

Administration, Oral↗

PubMed2002

Enzymatic modification of pectin to increase its calcium sensitivity while preserving its molecular weight.

A commercial high-methoxy citrus pectin was treated with a purified salt-independent pectin methylesterase (PME) isozyme isolated from Valencia orange peel to prepare a series of deesterified pectins. A series of alkali-deesterified pectins was also prepared at pH 10 under conditions permitting beta-elimination. Analysis of these pectins using high-performance size exclusion chromatography (HPSEC) with on-line multiangle laser light-scattering, differential viscometer, and refractive index (RI) detectors revealed no reduction in weight-average molecular weight (M(w); 150000) in the PME-treated pectin series, whereas a 16% reduction in intrinsic viscosity (IV) occurred below a degree of esterification (DE) of 47%. In contrast, alkali deesterification rapidly reduced both M(w) and IV to less than half of that observed for untreated pectin. PME treatment of a non-calcium-sensitive citrus pectin introduced calcium sensitivity with only a 6% reduction in the DE. Triad blocks of unesterified galacturonic acid were observed in (1)H nuclear magnetic resonance spectra of this calcium-sensitive pectin (CSP). These results demonstrate that the orange salt-independent PME isozyme utilizes a blockwise mode of action. This is the first report of the preparation of a CSP by PME treatment without significant loss of the pectin's M(w) due to depolymerization.

Calcium↗

PubMedDate not supplied

Flash extraction of pectin from orange albedo by steam injection.

Pectin was acid extracted from orange albedo by steam injection heating under pressure. Extraction times ranged from 2 to 6 min at a pressure of about 15 psi. Solubilized pectin was characterized by HPSEC with online light scattering and viscosity detection. Molar mass (M), radius of gyration (R(g)), and intrinsic viscosity ([eta]) all decreased with increasing extraction time when heating temperature was 120 degrees C. At heating times of 3 min, M(w) ranged from 4.9 to 4.5 x 10(5), R(gz) was about 44 nm, and [eta](w) ranged from 8.4 to 7.9 dL/g. Chromatography revealed that solubilized pectin distributions were bimodal in nature at 3 min extraction time and trimodal when the extraction time was 6 min. Scaling law exponents obtained for the highest molar mass fractions were consistent with a very compact spherical structure. For the intermediate fraction, scaling law exponents were consistent with a less compact spherical structure comparable to a random coil. In the case of the low molar mass fractions, scaling law exponents were consistent with a structure more asymmetric in shape. These results are consistent with earlier results which indicated that pectin distributions were mixtures of two or more of the following due to disaggregation during extraction: spherical aggregates, hydrogen bonded network structures, and partially or fully disaggregated components of network structures which could include branched structures, rods, segmented rods, and kinked rods.

Chromatography↗

PubMedDate not supplied

Nanostructure of native pectin sugar acid gels visualized by atomic force microscopy.

Height and phase shift images of high methoxyl sugar acid gels (HMSAG) of pectin were obtained by atomic force microscopy in the tapping mode. Images revealed that pores in these gels were fluid and flattened out when measured as a function of time. These images revealed for the first time the structure of adsorbed sugar on pectin in the hydrated native gels and how the pectin framework is organized within these gels. Segmentation of images revealed that the underlying pectin framework contained combinations of rods, segmented rods, and kinked rods connected end to end and laterally. The open network of strands was similar to pectin aggregates from 5 mM NaCl solution imaged earlier by electron microscopy (Fishman et al., Arch. Biochem. Biophys. 1992, 294, 253). Area measurements revealed that the ratio of bound sugar to pectin was in excess of 100 to 1 (w/w). Furthermore, images indicated relatively small differences in the organization of native commercial citrus pectin, orange albedo pectin, and lime albedo pectin gels at optimal pH as determined in this study. The findings are consistent with earlier gel strength measurements of these gels. In addition, values of gel strength were consistent with values of molar mass and viscosity of the constituent pectins in that they increased in the same order. Finally, we demonstrated the advantage of simultaneous visualization of height and phase shift images for observing and quantitating the nanostructure of relatively soft gels which are fully hydrated with a buffer.

Citrus aurantiifolia↗

PubMedDate not supplied

Pectin/zein beads for potential colon-specific drug delivery: synthesis and in vitro evaluation.

Novel complex hydrogel beads were prepared from two edible polymers: pectin, a carbohydrate from citrus fruits, and zein, a protein from corn. The pectin/zein complex hydrogels did not swell in physiological environments, but hydrolyzed in the presence of pectinases. An in vitro study showed the capacity of the hydrogels to endure protease attack and residence time variation. The physical and biological properties of the new hydrogels were attributed to molecular entanglement of the two polymers. The pectin networks were stabilized by the bound zein molecules. In turn, the pectin networks shielded the bound zein from protease digestion.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMedDate not supplied

Pectin gel vehicles for controlled fragrance delivery.

Using citronellal as a model compound, pectin gels formulations were evaluated for the controlled fragrance release by kinetic and static methods. The pectins with higher degrees of esterification induced a stronger molecular association with the nonpolar fragrance. This resulted in a prolonged duration of fragrance release and the limitation of fragrance adsorption to the receptor skin layers. The increase in pectin concentrations suppressed the fragrance release by a diffusion mechanism. Blocking the carboxyl groups of pectin with calcium ions reduces the hydrophilicity of pectin and provides physical barriers for citronellal diffusion. The pectin/calcium microparticles are promising materials for controlled fragrance release.

Acyclic Monoterpenes↗