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Jan Schripsema

Publications and source records attributed to Jan Schripsema.

7 recordsLinked to original sources
PubMed2006

Revision of the structures of citrifolinin A, citrifolinoside, yopaaoside A, yopaaoside B, and morindacin, iridoids from Morinda citrifolia L. and Morinda coreia Ham.

[Structure: see text] Citrifolin A was revised to dehydromethoxygaertneroside (2). Citrifolinoside and yopaaoside A were found to be identical, and their structures were revised to the new structure dehydroepoxymethoxygaertneroside (5). Yopaaoside B was revised to citrifolinoside A (9), and morindacin was revised to borreriagenin (11).

Glucosides↗
PubMed2005

1H NMR quantification in very dilute toxin solutions: application to anatoxin-a analysis.

A complete procedure is described for the extraction, detection and quantification of anatoxin-a in biological samples. Anatoxin-a is extracted from biomass by a routine acid base extraction. The extract is analysed by GC-MS, without the need of derivatization, with a detection limit of 0.5 ng. A method was developed for the accurate quantification of anatoxin-a in the standard solution to be used for the calibration of the GC analysis. 1H NMR allowed the accurate quantification of microgram quantities of anatoxin-a. The accurate quantification of compounds in standard solutions is rarely discussed, but for compounds like anatoxin-a (toxins with prices in the range of a million dollar a gram), of which generally only milligram quantities or less are available, this factor in the quantitative analysis is certainly not trivial. The method that was developed can easily be adapted for the accurate quantification of other toxins in very dilute solutions.

Bacterial Toxins↗
PubMed2005

Benzophenones from Hypericum carinatum.

Two new benzophenones were isolated from the leaves of Hypericum carinatum. Their structures were established on the basis of 2D NMR spectroscopic analyses and mass spectrometry as cariphenone A (6-benzoyl-5,7-dihydroxy-2,2,8-trimethyl-2H-chromene) (1) and cariphenone B (8-benzoyl-5,7-dihydroxy-2,2,6-trimethyl-2H-chromene) (2). Five known compounds, the phloroglucinol derivative uliginosin B (3), 1-eicosanol, sitosterol, stigmasterol, and campesterol, were also characterized. Compounds 1-3 were evaluated for their total antioxidant capacity through a total radical-trapping parameter assay. Only compound 1 showed moderate antioxidant activity, exhibiting inhibition of chemiluminescence similar to that of quercetin at the same concentration.

Antioxidants↗
PubMed2004

N,beta-D-Glucopyranosyl vincosamide, a light regulated indole alkaloid from the shoots of Psychotria leiocarpa.

From leaves of Psychotria leiocarpa, an indole alkaloid was isolated to which the structure N,beta-D-glucopyranosyl vincosamide (1) was assigned. This represents the first report of an N-glycosylated monoterpenoid indole alkaloid. In field-grown plants highest amounts of 1 were found in the leaves (2.5% of dry wt) and fruit pulp (1.5% dry wt). Lower amounts were found in the stems (0.2% dry wt) and the seeds (0.1% of dry wt), whereas the alkaloid was not detected in the roots. The accumulation of 1 in aseptic seedlings was also restricted to the shoots and increased with plant age and light exposure, independent of the supply of sucrose in the culture medium.

Darkness↗
PubMed2002

Two new diprenylated coumarins from Flindersia brayleyana.

Flindersia brayleyana F. Muell. contains the diprenylated coumarins 1 and 2, in addition to the known coumarins braylin (3) and brayleyanin (4). The structures of the new natural products were elucidated by extensive NMR analysis and mass spectra.

Brazil↗
PubMedDate not supplied

Assay of quadranguloside, the major saponin of leaves of Passiflora alata, by HPLC-UV.

An HPLC method with UV detection has been developed and validated in order to quantify quadranguloside, the main saponin of the leaves of Passiflora alata. The analysis was achieved by simple isocratic elution (with acetonitrile:aqueous phosphoric acid) using a Nova-Pak phenyl column. The amount of quadranguloside present in aqueous extracts from leaves of P. alata was estimated to be 22.2% (w/w), corresponding to 0.8% (w/w) in relation to dried leaves. The assay method described is simple, rapid, accurate and sensitive, and may form part of future drug authentication protocols.

Brazil↗