Biomedical subjects

Arnold J Vlietinck

Publications and source records attributed to Arnold J Vlietinck.

17 recordsLinked to original sources

PubMed2007

Study of potential systemic oxidative stress animal models for the evaluation of antioxidant activity: status of lipid peroxidation and fat-soluble antioxidants.

Although many compounds have already been tested in-vitro to determine their antioxidant profile, it is necessary to investigate the in-vivo effect of potential antioxidants. However, representative models of systemic oxidative stress have been poorly studied. Here, different potential systemic oxidative stress animal models have been investigated. These included a vitamin E-deficient rat, a diabetic rat and an atherosclerotic rabbit model. Plasma/serum malondialdehyde was measured as a parameter of oxidative damage. Plasma/serum fat-soluble antioxidants were determined as markers of antioxidant defence. We demonstrated that vitamin E-deficient rats were not suitable as a model of systemic oxidative stress, whereas diabetic and atherosclerotic animals showed increased systemic oxidative damage, as reflected by significantly augmented plasma/serum malondialdehyde. Moreover, plasma coenzyme Q9 increased by 80% in diabetic rats, confirming systemic oxidative stress. In view of these observations and economically favouring factors, the diabetic rat appeared to be the most appropriate systemic oxidative stress model. These findings have provided important information concerning systemic oxidative stress animal models for the in-vivo study of antioxidants.

Animals↗

PubMed2006

Antiamoebic activity of iridoids from Morinda morindoides leaves.

An aqueous decoction (dried extract), an 80 % methanolic extract from Morinda morindoides (Rubiaceae) leaves, and five iridoids isolated from the 80 % methanolic extract were evaluated in vitro for their activity against Entamoeba histolytica and their cytotoxicity. The aqueous decoction and the 80 % methanolic extract exhibited a promising antiamoebic activity with IC (50) values of 3.1 +/- 1.7 and 1.7 +/- 0.6 microg/mL, respectively. All tested iridoids displayed antiamoebic activity, the most active being epoxygaertneroside (IC (50): 1.3 +/- 0.4 microg/mL) and methoxygaertneroside (IC (50): 2.3 +/- 0.7 microg/mL) followed by gaertneroside, acetylgaertneroside and gaertneric acid with IC (50) values of 4.3 +/- 1.8, 5.4 +/- 1.4 and 7.1 +/- 1.4 microg/mL, respectively. Synergistic effects between the iridoids tested, or with other constituents, may explain the high activity of the extracts. All extracts and iridoids were devoid of any cytotoxic effect against MT-4 cells at the highest test concentration of 250 microg/mL. These findings support at least in part the traditional use of Morinda morindoides leaves for the treatment of amoebiasis in the Democratic Republic of Congo.

Amebiasis↗

PubMed2006

Anti-infective potential of natural products: how to develop a stronger in vitro 'proof-of-concept'.

Natural products, either as pure compounds or as standardized plant extracts, provide unlimited opportunities for new drug leads because of the unmatched availability of chemical diversity. To secure this, a number of pivotal quality standards need to be set at the level of extract processing and primary evaluation in pharmacological screening models. This review provides a number of recommendations that will help to define a more sound 'proof-of-concept' for antibacterial, antifungal, antiviral and antiparasitic potential in natural products. An integrated panel of pathogens is proposed for antimicrobial profiling, using accessible standard in vitro experimental procedures, endpoint parameters and efficacy criteria. Primary requirements include: (1) use of reference strains or fully characterized clinical isolates, (2) in vitro models on the whole organism and if possible cell-based, (3) evaluation of selectivity by parallel cytotoxicity testing and/or integrated profiling against unrelated micro-organisms, (4) adequately broad dose range, enabling dose-response curves, (5) stringent endpoint criteria with IC(50)-values generally below 100microug/ml for extracts and below 25microM for pure compounds, (6) proper preparation, storage and in-test processing of extracts, (7) inclusion of appropriate controls in each in vitro test replicate (blanks, infected and reference controls) and (8) follow-up of in vitro activity ('hit'-status) in matching animal models ('lead'-status).

Anti-Infective Agents↗

PubMed2005

Bioguided isolation of pharmacologically active plant components, still a valuable strategy for the finding of new lead compounds?

The position of natural products research in the drug discovery and development process nowadays is discussed. A flow chart for the study of plants used in traditional medicine, and the composition of a multidisciplinary research team for the investigation of medicinal plants are presented, and some recommendations are made for the future of bioassay-guided isolations and the use of standardised plant extracts in developing countries.

Medicine, Traditional↗

PubMed2005

Method development and validation for monitoring in vivo oxidative stress: evaluation of lipid peroxidation and fat-soluble vitamin status by HPLC in rat plasma.

Monitoring in vivo oxidative stress implicates the evaluation of damage and defence parameters by well-established, validated methods. We report two optimized and validated HPLC methods for measurement of malondialdehyde (MDA) and fat-soluble vitamins in rat plasma. For the MDA method, optimization experiments of the thiobarbituric acid test resulted in the addition of 1% butylhydroxytoluene to the reaction mixture and in a heating time reduction to 40 min, ensuring inhibition of further lipid peroxidation during the test. Validation experiments showed good linearity, precision and recovery. The use of HPLC with coulometric array detection technology permits simultaneous and sensitive analysis of different fat-soluble vitamins and related compounds (tocopherols, retinoids, carotenoids and coenzyme Q10), which are identified by both retention time and electrochemical characteristics. Furthermore, this method is extended to the analysis of coenzyme Q9, the predominant homologue in rats. Validation experiments with rat plasma gave good results.

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↗

PubMed2003

Phytoestrogens: recent developments.

Phytoestrogens are polyphenolic non-steroidal plant compounds with estrogen-like biological activity. Based on their chemical structure, phytoestrogens can be classified into four main groups, i. e., isoflavonoids, flavonoids, stilbenes, and lignans. For each group, the chemistry, dietary sources and biotransformation of the most interesting compounds will be discussed. Since phytoestrogens are structurally very similar to the estrogen 17beta-estradiol, they may exhibit selective estrogen receptor modulating activities. Therefore, special attention will be given to the hormonal effects of various isoflavonoids, including genistein, daidzein, coumestrol and equol, several prenylated flavonoids, especially 8-prenylnaringenin, and the stilbene resveratrol. Furthermore, their non-hormonal effects will be discussed briefly. Finally, the latest developments on the potential protective properties of phytoestrogens and phytoestrogen-containing foods against hormone-dependent breast and prostate cancers and cardiovascular diseases, and as estrogen replacement therapy for postmenopausal women will be discussed.

Antineoplastic Agents, Phytogenic↗

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↗

PubMed2003

Anticomplement and antioxidant activities of new acetylated flavonoid glycosides from Centaurium spicatum.

In addition to the three acetylated flavonol glycosides, quercetin 3- O-[(2,3,4-triacetyl-alpha-rhamnopyranosyl)-(1-->6)]-beta-galactopyranoside, quercetin 3- O-[(2,3,4-triacetyl-alpha-rhamnopyranosyl)-(1-->6)]-3-acetyl-beta-galactopyranoside, and quercetin 3- O-[(2,3,4- triacetyl-alpha-rhamnopyranosyl)-(1-->6)]-4-acetyl-beta-galactopyranoside, which have recently been isolated from Centaurium spicatum (L.) Fritsch (Gentianaceae), a new pentaacetylated flavonoid glycoside was isolated from the same plant. Structure elucidation, especially the localization of the acetyl groups, and complete (1)H- and (13)C-NMR assignments, was carried out using one- and two-dimensional NMR methods, including (1)H- and (13)C-NMR, DEPT-135 and DEPT-90, and gradient-assisted experiments such as DQF-COSY, TOCSY, HSQC and HMBC. The structure of the new flavonoid glycoside was established as quercetin 3- O-[(2,3,4-triacetyl-alpha-rhamnopyranosyl)-(1-->6)]-3,4-diacetyl-beta-galactopyranoside. The anticomplement and antioxidant activities of these compounds were evaluated. The triacetylated flavonoid glycoside showed the highest activity in the two assays.

Antioxidants↗

PubMed2003

The application of liquid chromatography-electrospray ionization mass spectrometry and collision-induced dissociation in the structural characterization of acylated flavonol O-glycosides from the seeds of Carrichtera annua.

The flavonoid fraction from the seeds of Carrichtera annua was studied using high-performance liquid chromatography simultaneously coupled to a photodiode array detector (LC/UV-DAD) and a mass spectrometer equipped with an electrospray source (LC/ESI-MS). Collision-induced dissociation (CID) mass spectral data obtained off-line by nanospray (nano-ESI) analysis provided a wealth of complementary structural information, which was consistent with structures established by NMR or led to the proposal of base structures of the flavonol O-glycosides present in the Carrichtera annua seed extract. The flavonoid fraction was found to contain 12 structurally related flavonol O-glycosides. Eleven flavonoids, of which several were new compounds, were acylated with one or more benzoyl, feruloyl or sinapoyl groups. These acyl groups gave rise to characteristic product ions in the [M + H](+) and [M + Na](+) CID spectra as well as to radicalar acid-related product ions at high-energy collisional activation. In addition to the characterization of the acyl substituents, the mass spectral data allowed the identification of the aglycone, the determination of the base structure and the differentiation of several positional isomers.

Acylation↗

PubMed2002

Herbal remedy-associated acute renal failure secondary to Cape aloes.

Use of traditional herbal remedies is common in Africa, and many patients who visit traditional healers do not need to resort to Western medicine. Acute renal failure is one of the most serious complications resulting from the use of traditional remedies, however, which accounts for 35% of all cases of acute renal failure in Africa. Traditional remedies rarely have been analyzed, and little is known about their nephrotoxicity. We report a case of a 47-year-old man from Soweto, South Africa, who developed acute oliguric renal failure and liver dysfunction after ingestion of an herbal remedy. The patient's renal function recovered slowly, and dialysis was discontinued after several weeks, although serum creatinine did not return to the normal range. Mass spectrometric and chromatographic analysis of the herbal remedy used by the patient revealed the presence of Cape aloes, a previously described nephrotoxin.

Acute Kidney Injury↗

PubMed2002

Antiviral and antioxidant activity of flavonoids and proanthocyanidins from Crataegus sinaica.

The antiviral and antioxidant activity of some fractions and of a series of flavonoids and proanthocyanidins obtained from Crataegus sinaica (Rosaceae) was evaluated. The O-glycosidic flavonoids and the oligomeric proanthocyanidins exhibited significant inhibitory activity against herpes simplex virus type 1 (HSV-1), which was shown to be due to an extracellular mechanism for procyanidin C-1. Procyanidin C-1 also had the highest antioxidant activity in both the microsomal lipid peroxidation and the hydroxyl radical scavenging assay. In addition to the previously reported phenolic compounds, the pentacyclic triterpenoid ursolic acid (1) and a tetrameric (2) and pentameric procyanidin (3) are reported for the first time.

Animals↗

PubMed2002

Inhibitory activity on binding of specific ligands to the human angiotensin II AT(1) and endothelin 1 ET(A) receptors: bioactive benzo[c]phenanthridine alkaloids from the root of Bocconia frutescens.

A bioassay-guided fractionation of the 80 % ethanolic extract from Bocconia frutescens L. roots, showing a dose-dependent inhibitory effect towards both [(3)H]-angiotensin II and [(3)H]-BQ-123 binding to the human angiotensin II AT 1 and endothelin 1 ET(A) receptors, led to an alkaloidal subfraction as the only responsible fraction for the activity of the whole extract. Among the alkaloids present in this fraction sanguinarine and chelerythrine were significant inhibitors of [(3)H]-angiotensin II binding (hAT 1 receptor), with IC(50) values within the micromolar range. On the contrary, the [(3)H]-BQ-123 binding (ET(A) receptor) was only weakly inhibited. Moreover, other members of the isoquinoline alkaloid family such as chelidonine and some protoberberine alkaloids exhibited no affinity for the two receptors. The present work shows the possible structure-activity relationship for these benzophenanthridine alkaloids on a screening bioassay using both stably transfected Chinese hamster ovary (CHO) and the human neuroblastoma SK-N-MC cells. Furthermore, the ability of these compounds to block AT(1) and/or ET(A) receptors may provide some justification for the traditional use of Bocconia frutescens L. to control hypertension.

Alkaloids↗

PubMed2002

In vitro inhibition of [3H]-angiotensin II binding on the human AT1 receptor by proanthocyanidins from Guazuma ulmifolia bark.

A bioassay-guided fractionation of the 70% acetone extract of the bark of Guazuma ulmifolia Lam. on the inhibition of angiotensin II binding to the AT 1 receptor led to the isolation and identification of bioactive oligomeric and polymeric proanthocyanidins consisting mainly of (-)-epicatechin units. The displacement of [3H]-angiotensin II binding was dose-dependent and correlated with the degree of polymerization of the different fractions containing proanthocyanidins. A strong displacement was seen for the residual fraction suggesting that the most active substances corresponding to the highly polymerized proanthocyanidins. Angiotensin II AT 1 receptor binding might be considered as a potentially interesting biological activity of proanthocyanidins contributing to the very broad spectrum of biological activities of the condensed tannins.

Angiotensin II↗

PubMed2002

In vitro antioxidant profile of phenolic acid derivatives.

Several caffeic acid esters isolated from propolis exhibit interesting antioxidant properties, but their in vivo use is compromised by hydrolysis of the ester bond in the gastrointestinal tract. Therefore, a series of caffeic acid amides were synthesized and their in vitro antioxidant profile was determined. A series of hydroxybenzoic acids, hydroxycinnamic acids, and the synthesized caffeic acid amides were tested for both their 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and microsomal lipid peroxidation-inhibiting activity. Some of the highly active antioxidants were further tested by means of electron paramagnetic resonance for their hydroxyl radical scavenging activity. Since a promising antioxidant compound should show a lipid peroxidation-inhibiting activity at micromolar level and a low cytotoxicity, the cytotoxicity of the phenolic compounds was also studied. In all the assays used, the caffeic acid anilides and the caffeic acid dopamine amide showed an interesting antioxidant activity.

Antioxidants↗

PubMedDate not supplied

Electronic structure calculations as a tool for investigating acyl migrations in ester saponins.

The possibility of acyl migrations in ester saponins from Maesa lanceolata was investigated by molecular mechanics and electronic structure calculations carried out on the major constituent maesasaponin IV3 (3beta-O-[[alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-galactopyranosyl-(1-->3)]-[beta-D-galactopyranosyl-(1-->2)]-beta-D-gluco-pyranuronyl]-21beta-angeloyloxy-22alpha-propanoyloxy-13beta,28-oxido-olean-16alpha, 28alpha-diol). It was confirmed that acyl migrations could occur in rings D and E of maesasaponins.

Esters↗