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Biomedical subjects

M Calomme

Publications and source records attributed to M Calomme.

10 recordsLinked to original sources
PubMed1999

Screening of seven selected Rwandan medicinal plants for antimicrobial and antiviral activities.

Aqueous EtOH (80%) extracts of seven plants used by Rwandan traditional healers to treat infections, were screened for antibacterial, antifungal, and antiviral activities. Only two of the selected plants showed a true antiviral activity against herpes simplex virus type 1, while all of them exhibited virucidal properties against several enveloped viruses including herpes simplex, measles, Semliki forest, and vesicular stomatitis viruses. Four plants were diversely active against gram-positive bacteria, two of these showing bactericidal effect against the acid-fast Mycobacterium fortuitum. None of the selected plants was active against gram-negative bacteria or the yeast Candida albicans. From a bioassay-guided fractionation procedure using herpes simplex virus type I as the target model, a virucidal mixture, the maesasaponin mixture A, was isolated from the MeOH extract of Maesa lanceolata. The maesasaponin mixture A exhibited a virucidal activity against herpes simplex types 1 and 2, and vesicular stomatitis viruses.

Anti-Bacterial Agents↗
PubMed1998

Structure-activity relationship and classification of flavonoids as inhibitors of xanthine oxidase and superoxide scavengers.

The structure-activity relationship of flavonoids as inhibitors of xanthine oxidase and as scavengers of the superoxide radical, produced by the action of the enzyme xanthine oxidase, was investigated. The hydroxyl groups at C-5 and C-7 and the double bond between C-2 and C-3 were essential for a high inhibitory activity on xanthine oxidase. Flavones showed slightly higher inhibitory activity than flavonols. All flavonoid derivatives except isorhamnetin (30) were less active than the original compounds. For a high superoxide scavenging activity on the other hand, a hydroxyl group at C-3' in ring B and at C-3 were essential. According to their effect on xanthine oxidase and as superoxide scavengers, the flavonoids could be classified into six groups: superoxide scavengers without inhibitory activity on xanthine oxidase (category A), xanthine oxidase inhibitors without any additional superoxide scavenging activity (category B), xanthine oxidase inhibitors with an additional superoxide scavenging activity (category C), xanthine oxidase inhibitors with an additional pro-oxidant effect on the production of superoxide (category D), flavonoids with a marginal effect on xanthine oxidase but with a prooxidant effect on the production of superoxide (category E), and finally, flavonoids with no effect on xanthine oxidase or superoxide (category F).

Enzyme Inhibitors↗
PubMed1998

Evaluation of biological activities of triterpenoid saponins from Maesa lanceolata.

From a bioassay-guided fractionation procedure using Herpes simplex virus type 1 as the target model, a virucidal saponin mixture (maesasaponin mixture B) was isolated from the MeOH extract of leaves of Maesa lanceolata. The maesasaponin mixture B consisted of six homologous oleanane-type triterpenoid saponins 1-6, identified by 1H, 13C, and 2D NMR spectroscopy and mass spectrometry. The maesasaponin mixture B (1-6) showed several biological activities expected for saponins. It exhibited a moderate virucidal activity against enveloped viruses. The maesasaponin mixture B (1-6) was tested for further properties. The saponin mixture was found to be highly hemolytic and molluscicidal: it hemolyzed 50% of human erythrocytes (1% suspension) at a concentration estimated at 1.6 microg/mL and exerted against Biomphalaria glabrata snails a severe toxic effect with LD95 and LD50 values of 4.1 and 2.3 ppm, respectively. In addition, the maesasaponin mixture B (1-6) showed moderate fungistatic and antimutagenic properties. The evaluation of these diverse activities is described.

Animals↗
PubMed1996

Inhibition of bacterial mutagenesis by Citrus flavonoids.

The antimutagenicity of the Citrus flavonoids naringin, hesperidin, nobiletin, and tangeretin against the mutagens benzo[a]pyrene, 2-aminofluorene, quercetin, and nitroquinoline N-oxide was investigated in the Salmonella/microsome assay. Naringin and hesperidin showed a weak antimutagenic activity against benzo[a]pyrene. Tangeretin was antimutagenic against all indirectly-acting mutagens tested, but in general a large molar excess was necessary. Liquid preincubation increased the antimutagenicity of tangeretin against 2-aminofluorene. Nobiletin acted as an antimutagen against benzo[a]pyrene, but it enhanced the mutagenicity of 2-aminofluorene. However, in a liquid preincubation assay nobiletin also exhibited antimutagenicity against 2-aminofluorene. Both tangeretin and nobiletin inhibited the mutagenicity of quercetin. Quercetin itself acted as an antimutagen against 2-aminofluorene in a Salmonella strain (TA1538) where its mutagenicity was not expressed. Quercetin should not merely be regarded as a genotoxic risk factor in the human diet, since its mutagenicity may be inhibited by accompanying compounds including other flavonoids, and since quercetin itself also exhibits an antimutagenic action. Because of the antimutagenic properties the Citrus flavonoids tested, especially tangeretin and nobiletin, might play a role in the chemoprevention of cancer.

Anticarcinogenic Agents↗
PubMed1994

Selenium deficiency triggering intractable seizures.

Two children with severe neurodevelopmental retardation and elevated liver function tests developed intractable seizures during the first year of life. Detectable neurometabolic conditions have been ruled out. At the time of seizures evidence for systemic selenium deficiency could be documented. The youngest patient, who manifested intractable fits from the fourth day of life, died at the age of ten months. Neuropathologic examination was consistent with Progressive Neuronal Degeneration of Childhood (PNDC) with liver disease or formerly known as Alpers disease. In the oldest child, whose diet was normally balanced, fits started from the age of 11 months and features of long-standing selenium deficiency became apparent from the age of 1 1/2 years and consisted of liver function disturbances, depigmented hair and osteoarthropathy. Oral substitution with selenium supplements in both children (3-5 micrograms/kg body weight) resulted in reduction of seizures and improvement of the EEG recordings after two weeks while liver function became normal. Two of the seleno-dependent enzymes Glutathione Peroxidase (GPX) and Phospholipid Hydroperoxide Glutathione Peroxidase (PHGPX) are speculated to play a key-role in the defence of neuronal cells against oxygen radical formation and peroxidative processes. Our findings support the hypothesis that the presence of selenium depletion in the brain amongst patients with epilepsy constitutes an important triggering factor for the origin of intractable seizures and subsequent neuronal damage.

Atrophy↗
PubMed1993

Isolation of a dihydrobenzofuran lignan from South American dragon's blood (Croton spp.) as an inhibitor of cell proliferation.

Dragon's blood is a red viscous latex extracted from the cortex of various Croton spp. (Euphorbiaceae), most commonly Croton lechleri, Croton draconoides (or Croton palanostigma), and Croton erythrochilus. It is used in South American popular medicine for several purposes, including wound healing. Bioassay-guided fractionation of dragon's blood, using an in vitro test system for the stimulation of human umbilical vein endothelial cells, has resulted in the isolation of a dihydrobenzofuran lignan, 3',4-O-dimethylcedrusin or 4-O-methyldihydrodehydrodiconiferyl alcohol [2-(3',4'-dimethoxyphenyl)-3-hydroxymethyl-2,3-dihydro-7-methoxybenzo furan-5- propan-1-ol] [1] as the biologically active principle. A related compound, 4-O-methylcedrusin [2-(3',4'-dimethoxyphenyl)-3-hydroxymethyl-2,3-dihydro-7-hydroxybenzo furan-5- propan-1-ol] [2], and the alkaloid taspine [3], also isolated from dragon's blood, were not active in the same assay. A cell proliferation assay, measuring the incorporation of tritiated thymidine in endothelial cells, showed that compound 1 did not stimulate cell proliferation, but rather inhibited thymidine incorporation, while protecting cells against degradation in a starvation medium.

Alkaloids↗
PubMedDate not supplied

Structure-activity relationship of flavonoids with superoxide scavenging activity.

The superoxide scavenging activities of 12 flavonoids were measured. The superoxide anions were generated by a hypoxanthine-xanthine oxidase system and measured by the nitrite method. The results showed that the scavenging ability enhanced with an increasing number of hydroxyl groups in ring B. Substitution at C3 position with a hydroxyl group increased the activity. Compared to a methoxyl group or a glycoside in this position, a free hydroxyl group showed the highest activity. A saturated C2-C3 bond showed a higher activity than a unsaturated bond. The absence of a carbonyl group at C4 position increased the activity.

Flavonoids↗
PubMedDate not supplied

Effects of selenium supplementation on thyroid hormone metabolism in phenylketonuria subjects on a phenylalanine restricted diet.

Type I 5'-deiodinase was recently characterized as a selenocysteine-containing enzyme in humans and other mammals. Up to now, the effect of selenium (Se) supplementation on thyroid hormone metabolism in humans has only been reported in the very peculiar nutritional environment of Central Africa, where combined severe iodine and Se deficiency occurs. In this study, a group of phenylketonuria subjects with a low selenium status, but a normal iodine intake were supplemented with selenium to investigate changes in their thyroid hormone metabolism. After 3 wk of selenium supplementation (1 microgram/kg/d), both the concentrations of the prohormone thyroxine (T4) and the metabolic inactive reverse triiodothyronine (rT3) decreased significantly. Clinically, the phenylketonuria subjects remained euthyroid before and after selenium supplementation. The individual changes of plasma Se and glutathione peroxidase activity were closely associated with individual changes of plasma T4 and rT3.

Adolescent↗
PubMedDate not supplied

Seleno-lactobacillus. An organic selenium source.

Lactic acid bacteria are nonpathogenic bacteria commonly used in food processing. An evaluation was made of the capacity to concentrate selenium in species of Lactobacillus. A selenium concentration of 1 microgram/mL in the culture medium yielded in a bacterial content of 400 micrograms/g dry biomass. Dialysis and TCA precipitation experiments of a native intracellular extract proved that at least 80% of the total selenium is associated with organic molecules. Seleno-cysteine was identified as the only seleno-amino acid present in the intracellular selenoproteins. This study shows that species of the lactic acid bacteria are able to concentrate selenium intracellular as seleno-cysteine, which could be applied in supplementation studies.

Autoradiography↗