ISSN:0958-0344    

DOI:10.1002/pca.2800020102

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractPlanar chromatography (PLC) is gaining importance in the analysis of natural products. Sophisticated instrumentation has become available in this field. Major progress in planar chromatography has been achieved through the development of forced‐flow techniques. Progress has also been made in the capillary‐controlled flow techniques with the use of modified development chambers. A large variety of stationary phases is available and strategies to optimize mobile phase compositions in PLC have been developed. The detection and quantitation in PLC has improved through direct coupling of PLC with spectroscopic methods with and the use of modern, computerized scanning densitomet

ISSN:0958-0344    

DOI:10.1002/pca.2800020103

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractProtocols for the extraction and quantification by high‐performance liquid chromatography of purine alkaloids from cocoa beans,Theobroma cacaoplants and tissues cultivatedin vitrohave been developed. These allow the rapid determination of 7‐methylxanthine, 3‐dimethylxanthines and caffeine from complex mixtures and represent improvements over published methods. Alkaloids were extracted in boiling water and the extracts clarified by precipitation and filtration. Chromatography was carried out using C18reverse‐phase columns with isocratic elution. The eluate was monitored routinely at 280 nm and compounds quantified using external standards. Estimations of purine alkaloid recoveries were better than 98% for caffeine, theobromine and theophylline. Reproducibility of replicate injections averaged 99% with coefficients of variation between replicate extractions typically less than 5% except for small samples (i.e., less than 0.2 g dry weight). Results for cocoa nibs and shells; roots, stem, green and red leaves of the cocoa plant; callus and suspension‐cultured cells and growth media from one type of cocoa are

ISSN:0958-0344    

DOI:10.1002/pca.2800020104

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe root bark ofZanthoxylum budrungahas been found to contain dihydrochelerythrine,N‐norchelerythrine, (±)‐evodiamine, zanthobungeanine and lupeol. NMR spectral studies (1H,13C,1H homonuclear COSY, HETCOR, DIFNOE and selective INEPT) carried out on these alkaloids have enabled the accurate chemical shift assignments for dihydrochelerythrine, (±)‐evodiamine and zanthobungeanine to be esta

ISSN:0958-0344    

DOI:10.1002/pca.2800020105

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractForty‐eight different ginger oils from nine countries spanning four continents have been investigated by dual capillary gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). All oils were found to contain the same five major sesquiterpene hydrocarbons. Two of them were isolated in one step from an Indian oil by an efficient reversed phase high performance liquid chromatographic (RP‐HPLC) separation. The other three were isolated by a combination of RP‐HPLC and preparative capillary GC. They were identified by UV, MS,1H NMR and13C NMR as α‐zingiberene (1), β‐bisabolene (2), (E,E)‐α‐farnesene (3), β‐sesquiphellandrene (4) andar‐curcumene (5). The reported absence of some of these compounds in earlier studies could in many cases be explained by unsatisfactory separations, misidentifications and confusio

ISSN:0958-0344    

DOI:10.1002/pca.2800020106

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA new reversed phase high‐performance liquid chromatographic method was used to quantify iridoid content in plant extracts. Two varieties ofPenstemon rydbergiifrom different locations in the Western United States were found to contain the iridoid glycosides euphroside, aucubin, geniposidic acid and plantarenaloside together with the phenylpropanoid glycoside verbascoside. While one variety showed a tenfold dominance of plantarenaloside over euphroside, the reverse was true of the other variety. The previously reported new iridoid glycoside pinifolin was shown to be an artefact from plantarenaloside since it could be isolated from a boiled extract, but not from a cold extrac

ISSN:0958-0344    

DOI:10.1002/pca.2800020107

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractAn improved method is described for the characterization of phenolic compounds using post‐column shift reagents following their separation by high performance liquid chromatography (HPLC). Modifications include the use of NaOH to adjust the pH of the column effluent, prior to introducing the AICI3and H3BO3reagents, and the use of commercially available spin chambers for efficiently mixing the effluent with the reagents, resulting in a negligible loss of resolution. Shifts obtained by the HPLC post‐column derivatization and the conventional procedure are compara

ISSN:0958-0344    

DOI:10.1002/pca.2800020108

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractOn‐line coupled multidimensional gas chromatography (DB‐5/Lipodex D)/mass spectrometry was used for direct chiral evaluation of δ‐hexa‐, δ‐octa‐, δ‐deca‐ and, in part, δ‐dodecalactone in various fruits. Whereas in raspberry the (S)‐enantiomers predominated [enantiomeric excess (ee) values from 45.0 to 100%], the (R)‐enantimomers prevailed in apricot, coconut, greengage, mango, pineapple, plum and yellow plum (ee values from 14.4 to 100%). Variations between (S)‐ and (R)‐enantiomers depending on chain length were found in red and yellow passion fruit, peach and strawberry. δ‐Hexalactone in greengage and pineapple as well as δ‐dodecalactone in coconut were found to occur in these fruits in approximately racemic form [ee values 10.8% (R) and 4.4% (R)

ISSN:0958-0344    

DOI:10.1002/pca.2800020109

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

ISSN:0958-0344    

DOI:10.1002/pca.2800020110

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

ISSN:0958-0344    

DOI:10.1002/pca.2800020101

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY