摘要:

AbstractThe recent recognition of polyhydroxy alkaloid glycosidase inhibitors as a unique class of alkaloids has generated considerable interest in the isolation of additional members, in addition to the analysis and detection of those currently known. The different properties of this group from those of conventional alkaloid classes requires novel approaches to such problems. The methods most suitable for extraction, isolation, structural elucidation, detection and analysis are critically reviewed. Application of such methods should lead to further expansion of this class of compound, providing significant information regarding structure‐activity relationship

ISSN:0958-0344    

DOI:10.1002/pca.2800040502

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractAlthough cinnamyl alcohol dehydrogenase is an important enzyme in the biosynthesis of lignins, its localization at the tissue and cellular levels is not well known. A quantitative cytochemical method has been devised to determine the localization and level of activity of this enzyme in plant tissues. Unexpectedly, the enzyme activity was present not only in the developing xylem elements and phloem fibres, but also in the epidermal and subepidermal layers of both roots and shoots. This pattern of localization implies that several distinct sites of cinnamyl alcohol dehydrogenase exist and that the role of this enzyme could be different according to the cell types in which it is located.

ISSN:0958-0344    

DOI:10.1002/pca.2800040503

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractDeficiencies in the widely used Hakomori method of methylation are described. Evidence is given that this method of linkage analysis often gives levels of undermethylation which hamper the detailed study of complex carbohydrates from plant cell walls. A modified method using sodium hydroxide as base is described which is capable of fully methylating polymers for which the Hakomori method generally fails and which does not promote the carbohydrate oxidation typical of a former procedure using this reagent. An explanation of its efficacy is advanced. Analyses of retrograded, α‐amylase‐resistant starches obtained by the modified method are repo

ISSN:0958-0344    

DOI:10.1002/pca.2800040504

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractAn ion pair high performance liquid chromatographic (HPLC) system for emetic alkaloids was improved using sodium 1‐heptanesulphonate as a counter ion. This HPLC system enabled the simultaneous determination of emetine, cephaeline and protoetnetine in the leaf extract of a regenerated plant ofCephaelis ipecacuanh

ISSN:0958-0344    

DOI:10.1002/pca.2800040505

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractA simple and rapid procedure for the simultaneous determination of monoterpenes and diterpenoid resin acids of conifer stem oleoresin is described; it involves tissue extraction with methyltert‐butyl ether and methylation of the resin acids with CH2N2. The resin acid methyl esters and the monoterpenes are then analysed in a single gas chromatographic step. Enantiomer composition of the major monoterpene constituents is determined, after preliminary purification by thin layer chromatography, by capillary gas chromatography on a cyclodextrin column. The method is applicable to conifer species of high resin content (Iodgepole pine) and low resin content (grand fir

ISSN:0958-0344    

DOI:10.1002/pca.2800040506

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractA reversed phase high performance liquid chromatographic procedure for standardizing a popular hepatoprotective Indian herb “Bhumyamlaki” (Phyllanthus amarus) on the basis of two of its bioactive lignans, phyllanthin and hypophyllanthin, has been developed. The method has been found to be sensitive, precise and to record more than 98% recovery of the two lignans. The leaves ofP. amaruswere found to contain the highest amounts of phyllanthin (0.7% w/w) and hypophyllanthin (0.3% w/w) as compared to the other parts of the pl

ISSN:0958-0344    

DOI:10.1002/pca.2800040507

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractSupercritical fluid extraction with CO2, performed in a home‐made system, of rhizomes ofDorstenia bryoniifoliaMart, ex Miq. (Moraceae) and of bark roots ofBrosimum gaudichaudiiTrécul (Moraceae) afforded crude extracts that were analysed by high resolution gas chromatography (HRGC). TheD. bryoniifoliaextract contained, besides the previously reported pimpinelin and isobergapten, the furocoumarins psoralen, bergapten, isopimpinelin and the triterpenes α‐ and β‐amyrin and the acetate of the latter. TheB. gaudichaudiiextract contained a number of terpenoids as well as the previously reported psoralen and bergapten. Supercritical fluid extraction gave extracts qualitatively similar to those obtained by Soxhlet extraction with hexane and, together with off‐line HRGC, was shown to be a fast and accurate technique to be used in rapid phytochemical e

ISSN:0958-0344    

DOI:10.1002/pca.2800040508

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractTwo optically enriched theaspirone isomers, i.e. (2S,5S)‐( − )‐theaspirone 2b and (2S,5R)‐( + )‐theaspirone 2c (ee‐values: 86% and 88% respectively), were obtained from quince juice by solvent extraction, flash chromatography and subsequent preparative high performance liquid chromatography (HPLC). Their absolute stereochemistry was assigned by circular dichroism spectroscopy. LiAlH4reduction of 2b and 2c yielded 8‐hydroxytheaspirane isomers 3b and 3c which were subjected to thermal treatment at pH 3 leading to vitispirane isomers 1b and 1c. In the same manner, vitispirane racemates 1a/1b and 1c/1d were obtained from the synthetic theaspirones 2a/2b and 2c/2d which had been separated by multi‐layer coil countercurrent chromatography/HPLC. The optically enriched reference compounds were used to determine the order of elution in the course of enantio‐separation of 1a‐1d which was achieved by multidimensional gas chromatography (MDGC) using DB‐Wax and 2,6‐dimethyl‐3‐pentyl‐β‐cyclodextrin capillary columns. Using on‐line coupled MDGC‐mass spectrometry in the single ion monitoring mode, enantiodifferentiation of 1a‐1d as well as 2a‐2d from a

ISSN:0958-0344    

DOI:10.1002/pca.2800040509

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0958-0344    

DOI:10.1002/pca.2800040511

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0958-0344    

DOI:10.1002/pca.2800040512

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY