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See detailUnusual Amino Acids and Monofluoroacetate from Dichapetalum michelsonii (Umutambasha), a Toxic Plant from Rwanda
Esters, Virginie ULg; Karangwa, Charles; Tits, Monique ULg et al

in Planta Medica (2013), 79

In the course of our investigations on Umutambasha in order to identify its convulsant principles, small quantities of monofluoroacetate were observed in stem bark, leaves, and fruits of this plant newly ... [more ▼]

In the course of our investigations on Umutambasha in order to identify its convulsant principles, small quantities of monofluoroacetate were observed in stem bark, leaves, and fruits of this plant newly identified as Dichapetalum michelsonii Hauman. Conclusive evidence for a monofluoroacetate presence came from its isolation from the freeze-dried extract of stem bark. Three free unusual amino acids, named N-methyl-α-alanine, N-methyl-β-alanine, and 2,7-diaminooctan-1,8-dioic acid, described for the first time in a plant, and known trigonelline were also isolated from the stem bark of D. michelsonii. Structure elucidations were mainly achieved by spectroscopic methods (1H-NMR, 2D-NMR, MS) and by comparison with authentic references. These unusual amino acids were detected by a fast, reliable TLC analysis in all our batches of Umutambasha, suggesting that they could be used for identification purposes in case of human or livestock intoxications. Finally, EEG recordings and behavioural observations performed in mice suggested that the convulsive patterns produced by Umutambasha are the consequence of monofluoroacetate presence in D. michelsonii. [less ▲]

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See detailArmes non létales
Robbe, Cyril ULg; Lemaire, Eric ULg; Papy, Alexandre et al

in Beauthier, Jean-Paul (Ed.) Traité de médecine légale (2011)

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See detailCharacterization of the neurotoxicity induced by the extract of Magnistipula butayei (Chrysobalanaceae) in rat: Effects of a new natural convulsive agent
Karangwa, Charles; Esters, Virginie ULg; Tits, Monique ULg et al

in Toxicon (2007), 49(8), 1109-1119

This study was designed to document convulsant and neurotoxic properties of extracts of a tropical tree, Magnistipula butayei subsp. Montana, and to investigate the involvement of the glutamatergic system ... [more ▼]

This study was designed to document convulsant and neurotoxic properties of extracts of a tropical tree, Magnistipula butayei subsp. Montana, and to investigate the involvement of the glutamatergic system in these effects. Continuous behavioral observations and electroencephalographic (EEG) records were obtained after per os administration of an aqueous extract of Magnistipula (MBMAE) in rats. MBMAE (800 mg/kg) induced behavioral changes resembling motor limbic seizures: staring and head tremor, automatisms, forelimb clonic movements and violent tonic-clonic seizures leading to death in all animals. Concomitantly, important seizure activity that gradually evolved to epileptiform activity was recorded on the EEG. Moreover, c-Fos immunohistochemistry has revealed an increased c-Fos expression in the dentate gyrus and in piriform, peri- and entorhinal cortices 2 and 4h after treatment. This expression pattern suggested that the mechanism of action for the MBMAE is similar to that observed in glutamate-induced models of epilepsy. The MBMAE increased cell death also in hippocampal cell cultures. Furthermore, the build-up of convulsive activity and epileptic discharges induced by MBMAE in rat were abolished by MK-801, an NMDA receptor antagonist. Our study suggests that MBMAE contains a potent toxin, with a powerful neurotoxic activity in rat, and corresponding to a new natural component(s) that act as an NMDA-mediated convulsant molecule. [less ▲]

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See detailValidation of a high-performance thin-layer chromatography/densitometry method for the quantitative determination of glucosamine in a herbal dietary supplement
Esters, Virginie ULg; Angenot, Luc ULg; Brandt, V. et al

in Journal of Chromatography. A (2006), 1112(1-2), 156-164

A quantitative densitometric high-performance thin-layer chromatography (HPTLC) method was developed for the determination of glucosamine in a dietary supplement containing dried extracts of the main ... [more ▼]

A quantitative densitometric high-performance thin-layer chromatography (HPTLC) method was developed for the determination of glucosamine in a dietary supplement containing dried extracts of the main plants traditionally used for rheumatic disorders. The HPTLC method was chosen in order to circumvent the tedious and time-consuming sample preparation steps necessarily performed before using HPLC methods when analysing complex matrixes. Glucosamine was separated from the plant extracts on a silica gel 60 F(254) HPTLC plate using a saturated mixture of 2-propanol-ethyl acetate-ammonia solution (8%) (10:10:10, v/v/v). The plates were developed vertically up to a distance of 80 mm. For visualization, the plate was dipped into a modified anisaldehyde reagent and heated at 120 degrees C for 30 min in a drying oven. Glucosamine appeared as brownish-red chromatographic zones on a colourless background. Densitometric quantification was performed at lambda = 415 nm by reflectance scanning. The HPTLC method was successfully validated by applying the novel validation protocol proposed by a commission of the "Societe Francaise des Sciences et Techniques Pharmaceutiques" (SFSTP). In the pre-validation phase, the appropriate response function was determined, while in the validation phase the method showed good performance thereby fulfilling its objective of quantifying accurately. The relative standard deviations for repeatability and intermediate precision were between 4.9 and 8.6%. Moreover, the method was found to be accurate, as the two-sided 95% beta-expectation tolerance interval did not exceed the acceptance limits of 85 and 115% on the whole analytical range (800-1,200 ng of glucosamine). [less ▲]

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See detailChemical and biological investigations of a toxic plant from Central Africa, Magnistipula butayei subsp montana
Karangwa, Charles; Esters, Virginie ULg; Frederich, Michel et al

in Journal of Ethnopharmacology (2006), 103(3), 433-438

Magnistipida butayei subsp. montana (Chrysobalanaceae) is known, in the Great Lakes Region, to possess toxicological properties. In this paper, we investigated the acute toxicity (dose levels 50-1600 mg ... [more ▼]

Magnistipida butayei subsp. montana (Chrysobalanaceae) is known, in the Great Lakes Region, to possess toxicological properties. In this paper, we investigated the acute toxicity (dose levels 50-1600 mg/kg) of its aqueous extract, administered orally to adult Wistar rats. This study demonstrated that the freeze-dried aqueous extract (5%, w/w) possesses high toxicity. The extract caused hypothermia, neurological disorders, including extensor reflex of maximal convulsive induced-seizures at about 2h after the administered dose, and death occurred (LD50 = 370 mg/kg) in a dose dependent manner. Blood parameter evaluation revealed slight variations, but these might not have clinical relevance. Histological examination of internal organs (lungs, liver, heart and kidneys) did not reveal any abnormality in the treated group compared to the control. Therefore, it can be concluded that Magnistipida butayei subsp. montana aqueous extract, given orally, is toxic and that its target is the central nervous system. General phytochemical screening revealed that the plant did not contain significant amounts of products known to be toxic, such as alkaloids or cardioactive glycosides, but only catechic tannins, amino acids, saponins and other aphrogen principles in the three parts of the species (fruit, leave and bark). (c) 2005 Elsevier Ireland Ltd. All rights reserved. [less ▲]

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