Jos a Hoogmartens

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Ajuga remota is the most frequently used medicinal herb for malaria treatment in Kenya. Its two known isolates ajugarin-1 (1) and ergosterol-5,8-endoperoxide (3) and a new isolate 8-O-acetylharpagide (2) were evaluated for their in vitro antiplasmodial activity. Ajugarin-1 was moderately active, with an IC(50) of 23.0 +/- 3.0 microM, as compared to(More)
In this paper, the performance of a previously developed classification system applied to pharmaceutical chromatographic analyses, is investigated. The separation of seven different drug substances from their respective impurities was studied. The chromatographic procedure for acetylsalicylic acid, clindamycin hydrochloride, buflomedil hydrochloride,(More)
A useful column characterisation system should help chromatographers to select the most appropriate column to use, e.g. when a particular chromatographic column is not available or when facing the dilemma of selecting a suitable column for analysis according to an official monograph. Official monographs of the European Pharmacopoeia and the United States(More)
Selection of RP-LC columns with suitable selectivity for a given analysis is difficult. For example, the European Pharmacopoeia (Ph. Eur.) and other official compendia for drug analysis only give a general description of the stationary phase in the operating procedure of a liquid chromatographic method. The need for a general test method to characterise(More)
Pulsed electrochemical detection (PED) with a triple step potential-time waveform has been used successfully for the direct detection of several non-chromophoric aminoglycosides at alkaline pH following ion-pair liquid chromatography (LC). This direct detection method has helped to overcome the various flaws observed in the analysis of aminoglycosides using(More)
An analytical method that allows simultaneous analysis of sorbic acid and its degradation products was developed using static headspace gas chromatography (HS-GC). AT-Aquawax-DA, the capillary column used, showed good selectivity and separation towards sorbic acid and its degradation products. Sorbic acid degradation was investigated in both acidic and(More)
Decomposition products of tylosin A were isolated using open column chromatography and preparative liquid chromatography. Two decomposition products, formed in slightly alkaline medium, were identified as epimers of tylosin A aldol, one of which has been described previously. Another decomposition product was formed on exposure of a tylosin A solution to(More)
The use of CE for rapid assessment of metabolic stability of drugs with cytochrome P450 (CYP) enzymes, based on relative rates of reduced nicotinamide adenine dinucleotide phosphate (NADPH) consumption and nicotinamide adenine dinucleotide phosphate (NADP) production, was investigated. The separation conditions were as follows: capillary, 80.5 cm (75 microm(More)
A liquid chromatographic (LC) method for the analysis of erythromycin and related substances has been adapted from an isocratic method developed by Chepkwony et al. (2001). The suitability of the method for general application as a compendial (pharmacopoeia) method has been assessed by means of an interlaboratory (collaborative) study. The method involves(More)
Two laboratories collaborated to examine the selectivity of four isocratic liquid chromatography (LC) methods for the separation of ampicillin and its related substances. The United States Pharmacopeia (USP) assay method gave the best selectivity. Similar selectivity was obtained on C18 columns as well as on C8 and poly(styrene-divinylbenzene) copolymer(More)