Biomedical subjects

P C Schmidt

Publications and source records attributed to P C Schmidt.

At least 19 recordsLinked to original sources

PubMed2005

Antiviral activities of some Ethiopian medicinal plants used for the treatment of dermatological disorders.

Acokanthera schimperi (Apocynaceae), Euclea schimperi (Ebenaceae), Inula confertiflora (Asteraceae), Melilotus elegans (Leguminosae), and Plumbago zeylanica (Plumbaginaceae), are some of the medicinal plants used in Ethiopia for treatment of various skin disorders. In this study, the antiviral activities of the 80% methanolic extracts of these plants have been examined against coxsackievirus B3 (CVB3), influenza A virus and herpes simplex virus type1 Kupka (HSV-1) using cytopathic effect (CPE) inhibitory assays in HeLa, MDCK, and GMK cells, respectively. In parallel, the cytotoxicity was quantified using a crystal violet uptake assay. The antiviral activity of the most active compound was confirmed with plaque reduction assays. The results revealed that the extracts of Acokanthera schimperi and Euclea schimperi showed antiviral activity against all three tested viruses albeit with unequal efficacy. Whereas the Acokanthera schimperi extract exhibited the strongest activity against CVB3, the extract of Euclea schimperi inhibited influenzavirus A replication most effectively. A weak anti-influenzavirus A activity was also exhibited by the other plant extracts tested. In addition, CVB3 was inhibited by the extracts of Plumbago zeylanica and HSV-1 by Inula confertiflora. Thus, the extracts of these plants, particularly those of Acokanthera schimperi, Euclea schimperi and Inula confertiflora which showed activity against CVB3 and HSV-1 support their traditional use in the treatment of skin diseases of viral origin.

Animals↗

PubMed2005

Influence of compacted hydrophobic and hydrophilic colloidal silicon dioxide on tableting properties of pharmaceutical excipients.

The effect of noncompacted and compacted hydrophilic as well as hydrophobic colloidal silicon dioxide (CSD) on tableting properties of three different pharmaceutical excipients used for direct compression, namely, Avicel PH 101, Starch 1500, and Tablettose 80, was investigated. Binary powder mixtures containing 0.5% CSD and 99.5% excipient were compressed on an instrumented single-punch tablet press, and the radial tensile strength/compaction load profiles were examined. The Ryshkewitch-Duckworth relationship shows that the influence of CSD on tablet strength was dependent on the hydrophobic and hydrophilic nature of the CSD and on the compaction characteristics of the excipients. Tablets from each excipient with and without CSDs were subjected to different levels of relative humidity at 20 degrees C for 7 days. The sorption isotherms and the radial tensile strengths of the tablets after the storage period showed that neither hydrophilic nor hydrophobic CSD influenced the tablet properties of Avicel PH 101, Starch 1500, and Tablettose 80. Moreover, ternary powder mixtures containing magnesium stearate as a third component were compressed in order to study the influence of CSD on the deleterious effect of magnesium stearate on the interparticle bonding. The radial tensile strength/compaction load profiles and the residual and ejection forces of tablets made from ternary mixtures showed that CSD eliminated the negative effect of magnesium stearate on interparticle bonding while maintaining the lubrication action, in a manner that was affected by its hydrophobicity/hydrophilicity and by the particle deformation properties of the excipient upon compression.

Cellulose↗

PubMed2004

Comparison between HPLC and HPTLC-densitometry for the determination of harpagoside from Harpagophytum procumbens CO(2)-extracts.

Carbon dioxide (CO(2)) extracts of the secondary roots of Harpagophytum procumbens were quantified by high performance liquid chromatography (HPLC) and high performance thin layer chromatography (HPTLC). An isocratic HPLC method was used for the quantification of the iridoid glucoside harpagoside at 278 nm. A HPTLC assay was developed for the determination of harpagoside after coloration at 509 nm. The diode array detection of both analytical assays were used to examine the purity of harpagoside peaks and compared with the standards, respectively. The assays provide good accuracy, reproducibility and selectivity for the quantitative analysis of harpagoside. The harpagoside contents of 15 different CO(2)-extracts were compared by HPLC and HPTLC-densitometry. The quantitative results of both analytical methods did not show any statistical significance between each other, although a trend to slightly lower mean values could be found for the HPTLC method.

Analgesics↗

PubMed2004

Standardisation and physicochemical characterisation of the extracts of seeds of Glinus lotoides.

Extraction methods were standardised for saponin-containing extracts from the seeds of Glinus lotoides and the effects of some extraction process variables, such as the extracting solvent (various concentrations of methanol in water) and method of extract drying (freeze-drying and vacuum oven-drying), on the physical properties of the extracts were investigated. Physicochemical properties, namely particle size and size distribution, morphology, water uptake profiles and sorption isotherms, densities, flow properties and compaction profiles, of the crude dry extracts of 60% methanol (extract A), 70% methanol (extract B) and 80% methanol (extract C) were investigated. The average particle sizes (X50) of extracts A, B and C were found to be 68.4, 92.1 and 68.5 microm, respectively. Scanning electron micrographs of freeze-dried and vacuum oven-dried extract A showed that the particles are irregular in shape and are compact masses with sharp edges. The percent water uptake by the crude extracts was found to increase with an increase in relative humidities, while the hygroscopicity increased with decreasing methanol ratio of the extracting solvent. The bulk and the true densities of the three extracts (A, B and C) ranged from 0.66 to 0.67 and 1.49 to 1.50 g/ml, respectively. The tapped density (0.94 g/ml) and hence the porosity (56.0%), Carr's index (29.8%) and Hausner ratio (1.42) of extract A were greater than those of extracts B and C. Measurements of angle of repose indicated that all of the extracts exhibit poor flow properties. Compaction studies revealed that extract C has higher compactibility than extracts A and B.

Absorption↗

PubMed2003

Phase solubility studies of pure (-)-alpha-bisabolol and camomile essential oil with beta-cyclodextrin.

(-)-Alpha-bisabolol was found to form an inclusion complex with beta-cyclodextrin (beta-CD) in solution as well as in the solid state. To investigate molecular associations of beta-CD with pure (-)-alpha-bisabolol or (-)-alpha-bisabolol as a component of camomile essential oil, phase solubility studies were undertaken. A B(s) type solubility with an apparent complex constant of 273 M(-1) for the pure (-)-alpha-bisabolol and 304 M(-1) for (-)-alpha-bisabolol as a constituent of the essential oil were obtained. The two curves in the phase solubility diagram reach their plateau at different concentrations of (-)-alpha-bisabolol, 7.04 x 10(-4) M for the pure substance and 2.88 x 10(-4) M for the substance as a component of the essential oil. Although the shapes of the curves are almost similar, the intrinsic solubility's of pure (-)-alpha-bisabolol (4.85 x 10(-4) M) and (-)-alpha-bisabolol as a component of the essential oil (1.82 x 10(-4) M) differ significantly. An inclusion complex having a stoichiometric composition of 2:1 (beta-CD: drug) was obtained. A mechanism of complexation has been proposed on the basis of the stability constant calculated from phase solubility data and the stoichiometric ratio of the solid state complexation.

Chamomile↗

PubMed2002

Rapid quantification of constituents in St. John's wort extracts by NIR spectroscopy.

A quantitative near-infrared reflectance spectroscopy (NIRS) method was established for the determination of two major constituents (hyperforin and I3,II8-biapigenin) in St. John's wort extracts. Hyperforin was chosen due to the fact that it is found in a concentration range from 1 to 5%, a common one for NIRS determinations. I3,II8-Biapigenin on the other hand was selected as a constituent with very low concentrations (0.1-0.7%) but an extensive chromophore that allows very precise measurements in the ultraviolet (UV) and thus exact reference values that are vital for proper NIRS calibrations. Reference measurements were performed by reversed-phase high performance liquid chromatography (HPLC), determining the constituents' content in 35 pharmaceutical dry extracts of different origins. The reference method was validated according to the ICH guideline Q2B. Using partial-least squares (PLS) regression a multivariate calibration was done for the two ingredients each (PLS1). Satisfactory calibration statistics were obtained for hyperforin with a root mean square error of calibration (RMSEC) of 0.17 and a root mean square error of prediction (RMSEP) of 0.22 at a concentration range from 1 to 6% in the dry extracts. Due to the very low concentrations of I3,II8-biapigenin the accuracy of prediction is somewhat lower. However, it is possible to obtain very good results and reliable prediction by dividing the concentration range at 0.35%. The study emphasizes the potential of NIRS as a rapid and highly effective alternative method to conventional quantitative analysis of plant extracts.

Apigenin↗

PubMed2002

In vitro deposition of the respirable fraction of dry powder inhalations determined by laser diffractometry and inertial impaction.

Particle size analysis of drug and excipient is of particular interest for dry powder inhalation (DPI) formulations development and quality control. In this work, the deposition in the upper, the medium and the lower (i.e. the respirable fraction) Twin Impinger compartments of sodium cromoglycate (SCG), lactose (as excipient) and a 1:1 mixture thereof was determined by chemical analysis using a DPI device--the Micro-hale--and compared with the results obtained by laser diffractometry for the same fractions. The analytical method for the SCG determination consisted of ultraviolet spectrophotometry and, for the lactose, high performance liquid chromatography with refractive index detection was used. Laser diffractometry as a quickly operating routine method can substitute the chemical analysis in order to evaluate the respirable fraction, under the conditions of the present work and therefore making formulation development easier and quicker.

Administration, Inhalation↗

PubMed2001

The effect of conjugated linoleic acid on platelet function, platelet fatty acid composition, and blood coagulation in humans.

Despite extensive research on conjugated linoleic acid (CLA) showing multiple beneficial effects in animal models, little is known about the role of dietary CLA in human health. To investigate if the beneficial effects of CLA seen in animal models are relevant to humans, we conducted a study with 17 healthy female volunteers who lived in the Metabolic Research Unit of the Western Human Nutrition Research Center for 93 d. This paper reports only the results from this study that are related to the effects of CLA supplementation on blood coagulation, platelet function, and platelet fatty acid composition. Throughout the study, the subjects were fed a low-fat diet (30 en% fat, 19 en% protein, and 51 en% carbohydrate) consisting of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly assigned to either an intervention group (n = 10) whose diet was supplemented with 3.9 g/d of CLA or a control group (n = 7) who received an equivalent amount of sunflower oil consisting of 72.6% linoleic acid with no detectable CLA. Platelet aggregation was measured in platelet-rich plasma using adenosine diphosphate, collagen, and arachidonic acid agonists. No statistical difference was detected between the amount of agonist required to produce 50% aggregation of platelet-rich plasma before and after the subjects consumed the CLA, with the exception of a decrease in response to collagen. This decrease was found in both control and intervention groups with no significant difference between the groups, suggesting that both linoleic acid (sunflower oil) and CLA might have similar effects on platelet function. The prothrombin time, activated partial thromboplastin time, and the antithrombin III levels in the subjects were determined. Again, there was no statistically significant difference in these three parameters when pre- and post-CLA consumption values were compared. The in vivo bleeding times were also unaffected by CLA supplementation (10.4 + 2.8 min pre- and 10.2 + 1.6 min postconsumption). Platelet fatty acid composition was not markedly influenced by the consumption of dietary CLA, although there was a small increase in the amount of the 9 cis,11 trans-18:2 isomer normally present in platelets after feeding CLA for 63 days. In addition, small amounts of the 8 trans,10 cis-18:2 and the 10 trans,12 cis-18:2 isomers were detected in the platelets along with traces of some of the other isomers. Thus, when compared to sunflower oil, the blood-clotting parameters and in vitro platelet aggregation showed that adding 3.9 g/d of dietary CLA to a typical Western diet for 63 d produces no observable physiological change in blood coagulation and platelet function in healthy adult females. Short-term consumption of CLA does not seem to exhibit antithrombotic properties in humans.

Adult↗

PubMed2001

The effect of conjugated linoleic acid on plasma lipoproteins and tissue fatty acid composition in humans.

Conjugated linoleic acid (CLA) has been suggested by some animal studies to possess antiatherogenic properties. To determine, in humans, the effect of dietary CLA on blood lipids, lipoproteins, and tissue fatty acid composition, we conducted a 93-d study with 17 healthy female volunteers at the Metabolic Research Unit of the Western Human Nutrition Research Center. Throughout the study, subjects were fed a low-fat diet [30 energy percent (en%) fat, 19 en% protein, and 51 en% carbohydrate] that consisted of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly assigned to either an intervention group (n = 10) supplemented daily with capsules containing 3.9 g of CLA or a control group (n = 7) that received an equivalent amount of sunflower oil. The CLA capsules (CLA 65%) contained four major cis/trans geometric isomers (11.4% 9 cis-,11 trans-18:2; 10.8% 8 trans-,10 cis-18:2; 15.3% 11 cis-,13 trans-18:2; and 14.7% 10 trans-,12 cis-18:2) and their corresponding cis/cis (6.74% total) and trans/trans (5.99% total) varieties in smaller amounts. Fasting blood was drawn on study days 30 (end of the stabilization period), 60 (midpoint of the intervention period), and 93 (end of the intervention period). Adipose tissue samples were taken on days 30 and 93. CLA supplementation for 63 d did not change the levels of plasma cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and triglycerides. The weight percentage of CLA in plasma increased from 0.28 +/- 0.06 to 1.09 +/- 0.31 (n = 10, P < 0.05) after the supplementation. The 9 cis-,11 trans-isomer was the most prominent variety followed by the 11 cis-,13 trans- and 10 trans-,12 cis-isomers in lesser amounts. CLA in adipose tissue was not influenced by the supplementation (0.79 +/- 0.18 to 0.83 +/- 0.19 wt%) (n = 10) and the 9 cis-,11 trans-variety was the only isomer present. Thus, contrary to findings from some animal studies, CLA does not seem to offer health benefits, in the short term, regarding the prevention of atherosclerosis in humans. CLA supplementation for 2 mon did not alter the blood cholesterol or lipoprotein levels of healthy, normolipidemic subjects. The supplementation did increase CLA in the plasma but only 4.23% of the ingested CLA was present in the plasma at any given time. No adverse effect of CLA supplementation was detected in this study.

Adipose Tissue↗

PubMed2001

Polymorphic changes of thiamine hydrochloride during granulation and tableting.

Thiamine hydrochloride was granulated using an instrumented fluidized bed granulator (Hüttlin HKC 05-TJ). Granules consisting of pure thiamine hydrochloride were produced using an aqueous solution of thiamine hydrochloride as the granulating liquid. The effects of process variables such as inlet air temperature, spray rate, and amount of granulating liquid on granule properties are described. Particle size distributions of granules depended mainly on the amount of granulating liquid sprayed into the powder bed. Granules were tableted on a rotary tablet press at four different compression forces. Crushing strengths and disintegration times of all tablets were found to be very low after manufacture, but increased considerably after 4 months of storage at room temperature. Granular materials showed "caking" under the same storage conditions. These changes could be attributed to alterations of the polymorphic form of thiamine hydrochloride. The water-free form, being present directly after granulation, absorbs humidity very fast and is transformed into the monohydrate, which is stable at room temperature. Loss of water takes place during the drying phase of the granulation process and on storage of the substance at temperatures of 50 degrees C and 80 degrees C. During storage at room temperature while exposed to humidity, a transformation into the hemihydrate was observed. This polymorph is transformed during thermal analysis at about 190 degrees C to a water-free form that is stable at higher temperatures.

Calorimetry, Differential Scanning↗

PubMed2001

[Protein analysis of enzyme tablets].

Enzyme tablets with butyrylcholine esterase (CHE) and peroxidase (POD) partly lose enzymatic activity during compaction at a pressure of 495 MPa. Compared to solutions of the original enzyme, no changes of ultraviolet absorbance and fluorescence intensity in the tablet solutions were found. Only small changes were observed in the far ultraviolet circular dichroism spectra. Neither missing nor additional bands were detected with polyacrylamide gel electrophoresis. Heated (150 degrees C) solid starting material with CHE and POD showed still part of its original enzymatic activity. The ultraviolet absorbance increased with continued heating until precipitation occurred. The circular dichroism spectra are changed clearly.

Butyrylcholinesterase↗

PubMed2001

Pharmaceutical applications of supercritical carbon dioxide.

The appearance of a supercritical state was already observed at the beginning of the 19th century. Nevertheless, the industrial extraction of plant and other natural materials started about twenty years ago with the decaffeination of coffee. Today carbon dioxide is the most common gas for supercritical fluid extraction in food and pharmaceutical industry. Since pure supercritical carbon dioxide is a lipophilic solvent, mixtures with organic solvents, especially alcohols, are used to increase the polarity of the extraction fluid; more polar compounds can be extracted in this way. The main fields of interest are the extraction of vegetable oils from plant material in analytical and preparative scale, the preparation of essential oils for food and cosmetic industry and the isolation of substances of pharmaceutical relevance. Progress in research was made by the precise measurement of phase equilibria data by means of different methods. Apart from extraction, supercritical fluid chromatography was introduced in the field of analytics, as well as micro- and nanoparticle formation using supercritical fluids as solvent or antisolvent. This review presents pharmaceutical relevant literature of the last twenty years with special emphasis on extraction of natural materials.

Carbon Dioxide↗

PubMed2000

Interactions during aqueous film coating of ibuprofen with aquacoat ECD.

During the development of a coated ibuprofen formulation a sticking tendency occurred when applying Aquacoat ECD. This interaction indicated the formation of a eutectic mixture. The compatibility of the components of Aquacoat ECD with ibuprofen was investigated by differential scanning calorimetry. Cetyl alcohol, a stabilizing excipient in Aquacoat, was found to form a eutectic system with ibuprofen. It was characterized by the construction of a phase diagram with 33 mol% ibuprofen and an onset temperature of 40.5 degrees C. Wide-angle X-ray diffraction was used to identify the polymorphic forms of cetyl alcohol. The results confirmed the amorphous state in the aqueous dispersion in contrast to the beta(0)- and gamma(4)-polymorphs of solid cetyl alcohol.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Development of disintegrating multiple-unit tablets on a high-speed rotary tablet press.

Enteric coated bisacodyl pellets were compressed into divisible disintegrating tablets on a high speed rotary tablet press and investigated for pellet damages. The degree of pellet damages was examined via the bisacodyl dissolution during the acid treatment of' the drug release test for enteric coated articles according to USP 23. The damages depended on the type of filler-binder used and settings of the tablet press. Avicel PH 101 proved to be the most suitable filler-binder, effecting homogeneous distribution of the pellets within the tablets, as could be shown by image analysis of coloured pellets. The speed of the tablet press had noo influence on the pellet damages using Avicel PH 101 as a filler-binder, however, tablets containing 70% (w/w) of coated pellets did not fulfil the requirements of USP 23, despite optimum elasticity and coating thickness of a new Eudragit FS 30 D coating. Reducing the proportion of pellets to 60% per tablet, less than 10% of bisacodyl were released within 2 h during acid treatment thus fulfilling the requirements of the USP 23.

Solubility↗

PubMed2000

Development of matrix-based theophylline sustained-release microtablets.

Microtablets containing high theophylline content (from 60% to 80%) based on a Eudragit RS PO matrix were produced on a rotary tablet press. The influence of the compaction pressure, the plasticizer content used for the granulation of theophylline particles, and the amount of theophylline on the drug release were investigated. The effects of surface area and the addition of magnesium stearate as a hydrophobic agent on the drug release were studied. The storage stabilities of the release rate at room temperature and at 50 degrees C were also determined. Dissolution profiles expressed as percentage of theophylline dissolved were obtained over 8 hr in 900 ml of purified water at 37 degrees C and 75 rpm. It was observed that the compaction pressure (from 200 MPa to 250 MPa) had no effect on the theophylline release. The use of triethyl citrate (TEC) as a plasticizer in the granulation of theophylline enhanced the physical properties of the microtablets. Theophylline content in the range 60% to 80% did not affect the drug release. The theophylline release obtained was a function of the quotient surface area/tablet weight and therefore was dependent on the tablet diameter. To reduce the dissolution rates, magnesium stearate was added in a concentration up to 50% of the matrix material. Tablets of this hydrophobic formulation fulfilled the requirements of USP 23 for theophylline sustained-release preparations. Storage at room temperature for 3 months and at 50 degrees C for 2 months showed no significant influence on the theophylline release.

Acrylic Resins↗

PubMed2000

Some physicochemical properties of mefenamic acid.

Mefenamic acid is a problematic drug in granulation, tableting, and dissolution due to its poor solubility, hydrophobicity, and tendency to stick to surfaces. In most cases, the specifications of a drug by the pharmacopoeia include identification and purity, but they do not describe the physicochemical drug properties precisely. To characterize the mefenamic acid particle size, surface area measurements, X-ray pattern, differential scanning calorimetry (DSC), wettability, crystal habit, and compression behavior of different batches from two manufacturers were investigated. Due to larger particle size and better wettability, mefenamic acid of Il Yang type was easier to handle in a granulation process. The compression behavior of both types was nearly the same, although particle size, crystal habit, and wettability were very different.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Factors influencing capping and cracking of mefenamic acid tablets.

The tendency of capping and longitudinal cracks of mefenamic acid tablets was evaluated in relation to the amount of the binder, the influence of the granulation technique, and the relative humidity of the granules. Tablets made from fluidized bed granules using methylcellulose in the granulating liquid showed significantly lower capping and longitudinal cracks than tablets from conventional granules prepared by wet granulation using methylcellulose as a dry binder.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Evaluation of validation of a fully instrumented Hüttlin HKC 05-TJ laboratory-scale fluidized bed granulator.

The instrumentation and validation of a laboratory-scale fluidized bed apparatus is described. For continuous control of the process, the apparatus is instrumented with sensors for temperature, relative humidity (RH), and air velocity. Conditions of inlet air, fluidizing air, product, and exhaust air were determined. The temperature sensors were calibrated at temperatures of 0.0 degree C and 99.9 degrees C. The calibration of the humidity sensors covered the range from 12% RH to 98% RH using saturated electrolyte solutions. The calibration of the anemometer took place in a wind tunnel at defined air velocities. The calibrations led to satisfying results concerning sensitivity and precision. To evaluate the reproducibility of the process, 15 granules were prepared under identical conditions. The influence of the type of pump used for delivering the granulating liquid was investigated. Particle size distribution, bulk density, and tapped density were determined. Granules were tableted on a rotary press at four different compression force levels, followed by determination of tablet properties such as weight, crushing strength, and disintegration time. The apparatus was found to produce granules with good reproducibility concerning the granule and tablet properties.

Calibration↗