Biomedical subjects

Sabine Van Miert

Publications and source records attributed to Sabine Van Miert.

11 recordsLinked to original sources

PubMed2005

Antileishmanial activity, cytotoxicity and QSAR analysis of synthetic dihydrobenzofuran lignans and related benzofurans.

A series of synthetic dihydrobenzofuran lignans and related benzofurans were evaluated for their cytotoxicity in a screening panel consisting of various human tumour cell lines, and for their antiprotozoal activity against L. donovani (axenic amastigotes), chloroquine resistant Plasmodium falciparum (strain K1), Trypanosoma brucei rhodesiense and T. cruzi, and for cytotoxicity on L6 cells. No promising cytotoxicities against human tumour cell lines were observed for newly synthesised compounds, but the dimerisation product of some lipophylic esters of caffeic acid, such as compound 2g, showed a high activity against chloroquine-resistant P. falciparum (strain K1) (IC50 0.43 microg/mL) and L. donovani (axenic amastigotes) (IC50 0.12 microg/mL), which was confirmed in an infected macrophage assay (IC50 0.19 microg/mL). QSAR models for the cytotoxic and antileishmanial activity were generated using Quasar receptor surface modelling.

Animals↗

PubMed2005

Phytochemical investigation and antioxidant activity of Duranta repens.

The ethylacetate fraction of the methanol extract of Duranta repens L. (Verbenaceae) showed radicalscavenging activity in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Three compounds were isolated from this fraction, i.e. the phenylethanoid glycoside acteoside, the iridoid lamiide and the saponin pseudo-ginsenoside-RT1. Acteoside showed an IC50 of 3.05 +/- 0.09 microg/mL in the DPPH assay, while lamiide and pseudo-ginsenoside-RT1 were not active.

Free Radical Scavengers↗

PubMed2005

Structural characterization of flavonol di-O-glycosides from Farsetia aegyptia by electrospray ionization and collision-induced dissociation mass spectrometry.

This study reports the application of mass spectrometric methods to characterize unknown flavonoids of the herb Farsetia aegyptia Turra (Crucifereae). High-performance liquid chromatography was performed in combination with UV-photodiode array detection (LC/UV-DAD) and electrospray ionization mass spectrometry (LC/ESI-MS) in both positive and negative ion modes. Collision-induced dissociation (CID) mass spectral data were obtained off-line by nanospray (nano-ESI) analysis, which provided a wealth of information and led to the structural proposal of the flavonol di-O-glycosides present in the herb extract. In addition to the mass spectral data, we also report NMR data for the major compound which allowed the completion of its structural elucidation. The Farsetia aegyptia Turra herb extract was found to contain three flavonol di-O-glycosides containing a monosaccharidic residue linked to the 3-O position and a disaccharidic residue linked to the 7-O position; the major compound was characterized as the new flavonoid, isorhamnetin 3-O-alpha-L-arabinoside 7-O-[beta-D-glucosyl-1 --> 2]-alpha(L)rhamnoside. Different types of CID spectra, i.e., low-energy [M+H]+, [M+Na]+ and [M--H]- spectra as well as high-energy [M+Na]+ spectra, were evaluated with respect to their utility to locate the O-linked saccharidic residues in flavonol di-O-glycosides and to determine the sequence in the disaccharidic part. In agreement with previously published data, the 3-O-glycosyl residue was more readily lost from the protonated molecule than the 7-O-glycosyl residue. The opposite behavior was noted for the fragmentation of the deprotonated and sodiated molecules. Radical ions were observed in the high-energy [M+Na]+ CID spectra which provided supporting information on the glycosylation positions.

Brassicaceae↗

PubMed2005

Isoneocryptolepine, a synthetic indoloquinoline alkaloid, as an antiplasmodial lead compound.

The antiprotozoal activities of three naturally occurring isomeric indoloquinoline alkaloids, i.e., cryptolepine (1), neocryptolepine (2), and isocryptolepine (3), and two dimeric indoloquinoline alkaloids, cryptoquindoline (6) and biscryptolepine (7), originally obtained from the plant Cryptolepis sanguinolenta, were compared with those of a new synthetic indoloquinoline isomer, isoneocryptolepine (4), and a quaternary derivative, N-methyl-isocryptolepinium iodide (5). The latter compounds showed a high antiplasmodial activity against the chloroquine-resistant Plasmodium falciparum strain K1 (IC50 of 0.23 +/- 0.04 and 0.017 +/- 0.004 microM, respectively), while the cytotoxicity (L6 cells) was 4.32 +/- 0.04 and 12.7 +/- 2.0 microM, respectively. Isoneocryptolepine (4) was found to act as an inhibitor of beta-hematin formation and as a DNA-intercalating agent.

Alkaloids↗

PubMed2004

Anthranoid compounds with antiprotozoal activity from Vismia orientalis.

A phytochemical investigation of the 80% ethanolic extract of stem bark of Vismia orientalis Engl. (Guttiferae or Clusiaceae), a plant used in traditional medicine in Tanzania, resulted in the isolation and spectroscopic characterisation of 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone, emodin, vismione D and bianthrone A1. Vismione D exhibited a broad range of antiprotozoal activities against Trypanosoma brucei rhodesiense and T. cruzi (IC50 < 10 micrograms/mL), Leishmania donovani (IC50 0.37 micrograms/mL) and Plasmodium falciparum strain K1 (IC50 1.0 microgram/mL). However, it was also slightly cytotoxic against human L6 cells (IC50 4.1 micrograms/mL). Emodin showed antileishmanial activity (IC50 2.0 micrograms/mL), while its IC50 against L6 cells was 20.3 micrograms/mL. Other antiprotozoal activities observed for emodin against both Trypanosoma species and P. falciparum, for bianthrone A1 against T. b. rhodesiense and P. falciparum, and for 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone against T. b. rhodesiense, L. donovani and P. falciparum were in the range of 10 to 50 micrograms/mL. None of the compounds showed antibacterial or antiviral (including also HIV) activity.

Animals↗

PubMed2003

Interactions of cryptolepine and neocryptolepine with unusual DNA structures.

Cryptolepine, the main alkaloid present in the roots of Cryptolepis sanguinolenta, presents a large spectrum of biological properties. It has been reported to behave like a DNA intercalator with a preference for GC-rich sequences. In this study, dialysis competition assay and mass spectrometry experiments were used to determine the affinity of cryptolepine and neocryptolepine for DNA structures among duplexes, triplexes, quadruplexes and single strands. Our data confirm that cryptolepine and neocryptolepine prefer GC over AT-rich duplex sequences, but also recognize triplex and quadruplex structures. These compounds are weak telomerase inhibitors and exhibit a significant preference for triplexes over quadruplexes or duplexes.

Alkaloids↗

PubMed2003

Complement-inhibiting iridoids from Morinda morindoides.

Morinda morindoides (Baker) Milne-Redhead (syn. Gaertnera morindoides Bak.) is one of the most popular medicinal plants in the Democratic Republic of Congo. In relation to its traditional use against rheumatic pains, fractionation of both the EtOAc- and the n-BuOH-soluble fraction of the 80% MeOH extract of the leaves, guided by the anticomplementary activity on the classical activation pathway, yielded eight novel iridoids (1-8), all containing a spirolactone functionality. Their structure was elucidated using spectroscopic methods. Gaertneroside 1, acetylgaertneroside 2, and gaertneric acid 5 were found to inhibit the activation of the classical pathway of the complement system, with IC(50) values between 58 and 69 microM. In addition to the biologically active flavonoids reported before from the same plant, these complement-inhibiting iridoids may contribute at least in part to the traditional use against rheumatic pains.

Complement Inactivator Proteins↗

PubMed2003

Isolation of mangiferin from Bombax malabaricum and structure revision of shamimin.

Repeated column chromatography of the n-BuOH fraction of the 70% EtOH of the dried leaves of Bombax malabaricum led to the isolation of mangiferin, a xanthone. Mangiferin was identified by UV, 1H- and 13C-NMR spectroscopy and electrospray mass spectrometry. It was found to be identical to shamimin, a compound for which originally a flavonol structure was proposed, and the structure of which has to be revised.

Bombax↗

PubMedDate not supplied

Characterisation of new oligoglycosidic compounds in two Chinese medicinal herbs.

A series of caffeic acid derivatives (3,5-dicaffeoyl-quinic acid, 3,4-dicaffeoyl-quinic acid, and 4,5-dicaffeoyl-quinic acid), and the new compound beta,3,4-trihydroxyphenethyl-O-[beta-apiofuranosyl-(1-->4)-alpha- rhamnopyranosyl-(1-->3)]-(4-O-caffeoyl)-beta-glucopyranoside (wedelosin), as well as three known flavonoid glycosides (quercetin 3-O-beta-glucoside, kaempferol 3-O-beta-apiosyl-(1-2)-beta-glucoside, and astragalin or kaempferol 3-O-beta-glucoside) were isolated from the Chinese medicinal herb Wedelia chinensis. Wedelosin showed an inhibitory activity on both the classical and the alternative activation pathway of the complement system. Another Chinese medicinal herb, Kyllinga brevifolia, yielded two known flavonoid glycosides [kaempferol 3-O-beta-apiosyl-(1-2)-beta-glucoside and isorhamnetin 3-O-beta-apiosyl-(1-2)-beta-glucoside], and a new quercetin triglycoside [quercetin 3-O-beta-apiofuranosyl-(1-->2)-beta-glucopyranoside 7-O-alpha-rhamnopyranoside]. The latter compound showed a moderate anti-viral activity.

Antiviral Agents↗

PubMedDate not supplied

Quality control of roots of Eleutherococcus senticosus by HPLC.

An HPLC method based on several known methods for the determination of eleutherosides B and E was developed, optimised and validated in terms of linearity, precision (repeatability and intermediate precision on different days and at different concentration levels) and accuracy (recovery). The extraction procedure, the extraction solvent and the extraction yield were evaluated and optimised. A reversed-phase RP-18 column gradient eluted with a two-phase system consisting of phosphoric acid:water (0.5:99.5) and acetonitrile was used to evaluate the samples; detection was at 220 nm. Although eleutherosides B and E are commercially available, they are very costly, and therefore ferulic acid was chosen as external standard. The correction factors for the response of ferulic acid against both eleutherosides were determined and validated. This method, accepted by the European Pharmacopoeia Commission, will be included in the monograph on Eleutherococcus senticosus roots to assay the content of eleutherosides B and E.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

In vitro inhibition of beta-haematin formation, DNA interactions, antiplasmodial activity, and cytotoxicity of synthetic neocryptolepine derivatives.

Neocryptolepine, a minor alkaloid of Cryptolepis sanguinolenta, was investigated as a lead for new antiplasmodial agents, because of its lower cytotoxicity than cryptolepine, the major alkaloid. Synthetic 2- or 3-substituted neocryptolepine derivatives were evaluated for their biological activity. In addition to the antiplasmodial activity (Plasmodium falciparum chloroquine-sensitive and -resistant) also the cytotoxicity (MRC-5 cells) was determined. Several compounds such as 2-bromoneocryptolepine showing higher and more selective antiplasmodial activity than neocryptolepine were obtained. Several functional assays and in vitro tests were used to obtain additional information on the mechanism of action, i.e., the beta-haematin formation inhibitory assay (detoxification of haem) and the DNA-methylgreen displacement assay (interaction with DNA). It could be demonstrated that the 2- or 3-substituted neocryptolepine derivatives investigated here have about the same potency to inhibit the beta-haematin formation as chloroquine, indicating that inhibition of haemozoin formation makes at least an important contribution to their antiplasmodial activity, although their in vitro antiplasmodial activity is still less than chloroquine.

Alkaloids↗