Biomedical subjects

Olaf Kelber

Publications and source records attributed to Olaf Kelber.

4 recordsLinked to original sources

PubMed2006

Effects of St. John's wort extract and single constituents on stress-induced hyperthermia in mice.

Emotional or stress-induced hyperthermia (SIH) is the rise of body temperature following exposure to psychological stress and has been demonstrated across species. In the present experiments we used exposure to an open field (OF) as inescapable stressor. Exposure of male BL6/C57J mice to OF stress significantly increased body temperature (DeltaT = 1.8 +/- 0.13 degrees C, p < 0.05). SIH is calculated as the difference (DeltaT = T (2) - T (1)) between the basal temperature (T (1)) and the temperature after exposure to an OF for 10 min (T (2)). Using this experimental design, St. John's wort extract (SJW) as well as various single compounds of it were tested for their ability to affect DeltaT. Anxiolytic drugs (the benzodiazepine diazepam; 5 mg/kg, and the 5HT (1A) receptor agonist buspirone; 10 mg/kg) significantly reduced DeltaT, whereas antidepressants (imipramine and fluoxetine) had no effect on DeltaT. Oral administration of SJW extract significantly reduced DeltaT in doses of 250 and 500 mg/kg. Higher (750 and 1000 mg/kg) as well as a lower dose (125 mg/kg) did not affect DeltaT after stress, indicating a U-shaped dose-response curve. Hypericin (0.1 mg/kg, p. o.) administered 60 min prior to testing significantly decreased DeltaT (p < 0.05) whereas hyperforin (1 - 10 mg/kg, p. o.) had no effect in this test paradigm. The flavonoids hyperoside, isoquercitrin and quercitrin (all at 0.6 mg/kg, p. o.) and rutin (1 mg/kg, p. o.) only partially blocked OF-induced hyperthermia. If compared to all other flavonoids, the quercetin 3-O-glucuronide miquelianin (1.2 mg/kg, p. o.) was the most potent compound tested in this experimental design. From the biflavonoids in SJW, only amentoflavone decreased SIH-induced hyperthermia in a dosage of 0.1 mg/kg. In conclusion, using open field stress as a psychological stressor to induce hyperthermia in mice we were able to detect putative anxiolytic effects of SJW extract and single consituents.

Administration, Oral↗

PubMed2005

Mechanisms involved in the anti-inflammatory effect of a standardized willow bark extract.

A standardized willow bark extract (STW 33-I) has been examined to clarify its possible mechanism of action as an anti-inflammatory agent. Various facets have been investigated in two inflammation models: the 6-day air pouch model in rats, representing the acute state and the adjuvant induced arthritis representing the chronic one. Parameters included leukocytic infiltration, levels of cytokines and prostanoids in blood, and effects on cyclo-oxygenase (COX)-1 and/or COX-2 enzymes as well as effects involving free radical production. The effect of the extract was compared at two dose levels with comparable anti-inflammatory doses of acetylsalicylic acid (CAS 50-78-2, ASA) as a non-selective COX inhibitor, and celecoxib (CAS 169590-42-5) as a selective COX-2 inhibitor. On a mg/kg basis, the extract was at least as effective as ASA in reducing inflammatory exudates and in inhibiting leukocytic infiltration as well as in preventing the rise in cytokines, and was more effective than ASA in suppressing leukotrienes, but equally effective in suppressing prostaglandins. On COX-2, STW 33-I was more effective than ASA. The present findings show that STW 33-I significantly raises GSH (reduced glutathione) levels, an effect which helps to limit lipid peroxidation. The extract was more potent than either ASA or celecoxib. Higher doses of the extract also reduced malondialdehyde levels and raised shows definite superiority to either ASA or celecoxib in protecting the body against oxidative stress. It is therefore evident that STW 33-I is at least as active as ASA on all the parameters of inflammatory mediators measured, when both are given on a similar mg/kg dose. Considering, however, that the extract contains only 24% salicin (molecular weight 286.2), while ASA has a molecular weight of 180.3, it follows that on a molar basis of salicin vs salicylate, the extract contains less than a sixth of the amount of salicin as the amount of salicylate in ASA. Thus it appears that STW 33-I with its lower "salicin" content than an equivalent dose of ASA, is at least as active as ASA on the measured parameters, a fact that leads one to speculate that other constituents of the extract contribute to its overall activity. The presence of polyphenols in STW 33-I probably plays a significant role in enhancing its free radical scavenging properties. The fact that STW 33-I was superior to ASA in this respect would suggest that the extract may have a better anti-inflammatory effect than ASA on a weight to weight basis, with possibly less side effects.

Animals↗

PubMed2004

Comparison of the inhibition of myeloperoxidase-catalyzed hypochlorite formation in vitro and in whole blood by different plant extracts contained in a phytopharmacon treating functional dyspepsia.

Ethanolic extracts from nine medicinal plants are combined in Iberogast (IG). This phytomedicine is successfully used in the treatment of gastrointestinal disorders. Functional gastrointestinal diseases such as non-ulcerous dyspepsia (NUD) are in many cases initiated by, or correlated to, inflammatory processes, where reactive oxygen species (ROS) play a crucial role. In this respect one prominent source of ROS are myeloperoxidase (MPO)-driven oxidation and chlorination reactions, assumed to be mainly responsible for tissue damage. In this study the contribution of the nine extracts to the overall performance of IG was compared with emphasis on MPO produced ROS. Concerning the influence on MPO-dependent chlorination reactions, it turned out that of the nine IG-components Iberis amara extract (IAE) exerted the highest activity. Furthermore, this can impressively be reproduced in an ex vivo experiment with whole blood, where neutrophilic leukocytes are activated by zymosan. Moreover, along with the extract of chamomile flowers, IAE counteracts the pro-oxidative properties of caraway, peppermint and celandine. As a consequence. IG was also efficiently inhibiting MPO-catalysed chlorinations. As shown by the addition of catalase, the pro-oxidative effects of caraway, peppermint and celandine are due to their content of hydrogen peroxide. The latter is probably an autoxidation product of certain monoterpenes in the essential oil part of these extracts. If one of the component extracts of IG is omitted, the antioxidant acitivity is reduced. Thus we conclude that all the single extracts combined in IG are of importance for the therapeutical effect, working in concert.

Cell Survival↗

PubMed2004

Thin-layer chromatography and multivariate data analysis of willow bark extracts.

In most cases the pharmacological activity of plant extracts is not assigned to single components and often not all active ingredients are known. Approaches other than those considering single compounds only to analyze plant material have proven helpful for a better characterization of extracts in their entirety. In this study extracts of willow bark are analyzed by high-performance thin-layer chromatography (HPTLC) and two different pharmacological tests [the 2,2'-azobis (2-amidinopropane) dihydrochloride reaction and the xanthine/xanthine oxidase reaction] with the help of multivariate data analysis. Described are two models using the results of the chromatographic study of 22 various extracts of willow bark and their pharmacological properties. The chromatographic data are obtained by a special TLC scanner that enables measurement of HPTLC tracks simultaneously in the range of lambda = 200-400 nm. Additionally, the developed models are used to predict the activity of another three extracts of willow bark demonstrating the quality of the model.

Chromatography, Thin Layer↗