2024-03-19T11:27:25+01:00 https://library.wur.nl/oai
oai:library.wur.nl:wurpubs/380116 2024-03-11 edurep openaire public
urn:nbn:nl:ui:32-380116 2024-03-11 urn:nbn:nl:ui:32-380116/mods Recent developments in the rapid analysis of plants and tracking their bioactive constituents van Beek T.A. 070558221 0000-0002-9843-7096 0000000083822771 aut Tetala K.K.R. 314605185 0000000389008529 aut Koleva I. aut Dapkevicius A. aut Exarchou V. aut Jeurissen S.M.F. aut Claassen F.W. 31462158X 0000000390446219 aut van der Klift E.J.C. 314603069 0000000394508472 aut text info:eu-repo/semantics/article 2009 10.1007/s11101-009-9125-9 67651154170 000268238000007 en Natural products chemistry has witnessed many new developments in the last 5 years like extractions with subcritical water and ionic liquids, LC/HRMS and LC/SPE/cryo-NMR, UHPLC, TLC/MS, MS-based preparative HPLC, comprehensive chromatography (GC × GC, LC × LC), high-throughput screening, introduction of monolithic columns, miniaturisation, and automated structure identification. Nevertheless identifying bioactive constituents in complex plant extracts remains a tedious process. The classical approach of bioassay guided fractionation is time-consuming while off-line screening of extracts does not provide information on individual compounds and sometimes suffers from false positives or negatives. One way out of this is by coupling chromatography with chemical or biochemical assays, so called high resolution screening. An example is the development of HPLC on-line assays for antioxidants. By the post-column addition of a relatively stable coloured radical like DPPH¿ or ABTS¿+, radical scavengers are detected as negative peaks because in a reaction coil they reduce the model radical to its reduced, non-coloured form. When combined with LC/DAD/MS and LC/SPE/NMR, reliable identification of active constituents becomes possible without the necessity of ever isolating them in a classical sense. Also for finding leads for new drugs, combining HPLC with biochemical assays is interesting but technically more difficult. Most enzymes do not work at the organic modifier concentrations commonly encountered in RP-HPLC and the reaction time is often longer requiring dilution and lengthy coils respectively. Therefore, new techniques have to be implemented to gain the required sensitivity for on-line enzyme assays. For stable analytes, high temperature LC offers a solution to the organic modifier problem. When enzymes are highly expensive, like those used in the screening for Cytochrome P450 inhibitors, miniaturisation to chip format may offer a way out. Microreactors (chips) are not only useful for miniaturising larger assays but also offer completely new prospects in phytochemical analysis. One such application is in the sample clean-up of acids and bases like alkaloids. In a lay-out of three parallel channels of 100 ¿m width with the middle one containing organic phase and the two outer ones water of high pH (feed phase) and low pH (trapping phase) such a chip replaces two classical LLE steps but is much faster and requires less solvents and less manpower input. VLAG Toxicology Organic Chemistry 2-dimensional gas-chromatography biochemical detec desorption electrospray-ionization mass-spectrometric detection natural-products nuclear-magnetic-resonance performance liquid-chromatography radical scavenging compounds thin-layer-chromatography VLAG Toxicologie Organische Chemie Phytochemistry Reviews 8 2 387 399 15687767 urn:nbn:nl:ui:32-380116/obj 2024-03-11 http://purl.org/eprint/accessRights/OpenAccess