摘要:

AbstractVesicular packing materials (VP) formed by the cell wall frame of denaturated and extractedWolffia arrhizaandW. columbianawere investigated for possible applications in permeation chromatography. Two types of VP were studied: W0, being fronds extracted with ethanol and water, and W1, obtained from W0by treatment with pancreatic enzymes in order to remove the insoluble protoplast residues. The cell wall material ofW. arrhizais characterized by a high content of pectin which is rich in homogalacturonan with low contents ofL‐rhamnose,D‐galactose andL‐arabinose, and a low degree of esterification. In permeation chromatography on both W0and W1, excluded components formed a sharp peak at an elution volume which was 26‐30% of the total bed volume. The critical size, in terms of Stokes' diameter, for the exclusion of macromolecules by W0is about 5 nm, and this allows for complete exclusion of most proteins. At linear flow rates below 0.1 mL/cm2/min the column length necessary for complete separation of sugars or salts from excluded macromolecules may be less than 10 cm. Because of their smaller particle size the materials prepared fromW. columbianashowed a smaller peak variance for permeable compounds. The potentially low price of the W0material suggests its use as an alternative to gel filtration media for the fast removal of low molecular weight solutes from proteins and other hydrophilic colloidal materials on a technica

ISSN:0958-0344    

DOI:10.1002/pca.2800060502

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSeveral physical and chemical methods for the solubilization and extraction of allantoinase and allantoicase from the unicellular green algaChlamydomonas reinhardtiihave been tested and compared. Of all the methods employed (i.e. freezing‐thawing, extraction at high ionic strength, disruption with the French press, sonication, and detergent solubilization) sonication gave the best results for extraction of both substances, while sodium deoxycholate extracted allantoinase optimally but not allantoicase. Allantoinase and allantoicase were characterized as two separate enzyme proteins differently associated with membranes or located in different cellular compartments. It is also demonstrated that allantoate is enzymatically degradedin vitroby a cell‐free algal extract and that allantoicase is the enzyme responsible for this catabol

ISSN:0958-0344    

DOI:10.1002/pca.2800060503

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractVarious steps in the existing procedure (Slocum, R. D., Flores, H. E., Galston, A. W. and Weinstein, L. H.,Plant Physiol.(1989) 89, 512) for the analysis of agmatine as its benzoyl derivative were found to impair the quantification of agmatine, leading to irreproducible results. Degradation of benzoylated agmatine is a major factor contributing to erratic results, and two mechanisms of degradation have been observed. Firstly, benzoylagmatine undergoes a temperature‐dependent hydrolysis in alkaline solution and this reaction has a half‐life of 168 min at 22°C. Therefore, the benzoylation reaction time and temperature have to be controlled in order to ensure reliable results; a maximum yield of benzoylagmatine may be obtained after incubation for 30 min. Secondly, benzoylagmatine can undergo rapid alkali‐catalysed methanolysis with a half‐life of 12 min at 22°C. Methanolysis produces a degradation product that was originally considered to be agmatine or benzoylurea, but is probablyN‐benzoylmethoxybenzamidomethylene imine. The formation of benzoylagmatine depends on the amount of benzoylchloride added since small volumes of the reagent do not exhaustively derivatize agmatine, hence leading to unreliable results. Mass spectrometry of benzoylagmatine showed that tribenzoylagmatine is the main derivative formed. The suggested modifications to the existing procedure enable the rapid and reliable determination of agmatine in various plan

ISSN:0958-0344    

DOI:10.1002/pca.2800060504

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe indirect spectrophotometric determination of phytic acid with zinc chloranilate has been studied. The method, based on the measurement of chloranilate released by the replacement reaction of phytic acid and zinc chloranilate, could be used to determine phytic acid in the range of 0.3 to 3.0 × 10−5M. The method showed high reproducibility for measuring phytate in foods, and was more rapid than conventional metho

ISSN:0958-0344    

DOI:10.1002/pca.2800060505

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe gas chromatographic separation of the 1‐p‐menthene‐8‐thiol enantiomers has been achieved using heptakis(2,3‐di‐O‐methyl‐6‐O‐TBDMS)‐β‐cyclodextrin as the chiral stationary phase in enantioselective gas chromatography. The sensory evaluation of the pure enantiomers has been realized by enantioselective gas chromatography‐olfactometry. (R)‐1‐p‐menthene‐8‐thiol was found to be of formative influence on the natural odour of grapefuit whilst the odour of the (S)

ISSN:0958-0344    

DOI:10.1002/pca.2800060506

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe influence of sample preparation on the accuracy of13C/12C‐ratios is investigated. Dynamic headspace, simultaneous distillation‐extraction and solvent extraction are used as methods of sample preparation in order to gain access to the volatiles of strawberr

ISSN:0958-0344    

DOI:10.1002/pca.2800060507

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe13C‐nuclear magnetic resonance spectra of some andrographolide derivatives have been assigned based on two‐dimensional correlation spectroscopy (COSY) and correlation via long‐range coupling (COLOC) spectra and comparison with known compounds. The assignment of triacetate of andrographolide, reported in literature, has been re

ISSN:0958-0344    

DOI:10.1002/pca.2800060508

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of different solvents on the extraction of some phenolic compounds from grape seeds was investigated. The main compounds identified by high performance liquid chromatography were gallic acid, (+)‐catechin, (‐)‐epicatechin, the dimeric procyanidins B1 and B2, the trimeric procyanidin C1 and epicatechin gallate. The solvents tested were water, absolute ethanol, 75% ethanol, acetone, 70% acetone, methanol,n‐butanol, diethyl ether, ethyl acetate and a combination of diethyl ether followed by ethyl acetate. Results showed that methanol was the best solvent for the extraction of (+)‐catechin, (‐)‐epicatechin and epigallocatechin, whereas 70% acetone yielded the largest amounts of procyanidins and 75% ethanol yielded the largest amount of gallic acid. The greatest amount of total phenols was extracted b

ISSN:0958-0344    

DOI:10.1002/pca.2800060509

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe edible aroids taro (Colocasia esculenta), tannia (Xanthosoma violaceum), giant taro (Alocasia macrorrhizos), giant swamp taro (Cyrtosperma chamissonis) and elephant foot yam (Amorphophallus paeonifolius) have been shown to contain varying amounts of cyanide in their leaves and stems using a screening assay and a more accurate acid hydrolysis method. The cyanogenic glucoside triglochinin (previously identified in giant taro) was found to be less stable to acid hydrolysis (requiring only 15 min) compared with 50 min hydrolysis for linamarin and lotaustralian (from cassava) under the same experimental conditions. The amounts of cyanide present in the leaves (0‐3 mg HCN/100 g fresh weight) and in the stems (0—0.3 mg HCN/100 g fresh weight) ofColocasiaandXanthosomaare only about 1‐5% of that found in cassava leaves and tubers and are not a cause for concern for human nutrition.Cyrtospermastems andAmorphophallusleaves contain only small amounts of cyanide. In contrast, allAlocasiavarieties contained much more cyanide in leaves (2‐30 mg HCN/100 g fresh weight) and in stems (0.5‐4 mg HCN/100 g fres

ISSN:0958-0344    

DOI:10.1002/pca.2800060510

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0958-0344    

DOI:10.1002/pca.2800060511

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY