The procedure for allicin synthesis could be improved. The time for HPLC analysis of allicin was shortened by the application of different isocratic elution systems. Calibration was performed by use of an allicin/silica gel adsorbate as external standard and its allicin content could be confirmed by different methods. L-(+)-Alliin was synthesized and applied as external standard for the quantitative determination of alliin by HPLC. Diastereoisomers had been separated by repeated recrystallization. Fresh ALLIUM SATIVUM bulbs from different origins were analyzed with respect to allicin content after complete enzymatic conversion of alliin; allicin contents found were in the range of 0.4%. The corresponding alliin contents were in the range of 0.9%. For a comparative evaluation of the alliin- and the allicin-HPLC determination methods, commercially available garlic preparations were analyzed, demonstrating that both methods are appropriate. However, the application of the HPLC system for allicin determination, in addition to providing information on the alliin-dependent allicin-generating capacity, enables the simultaneous quantification of allicin transformation products, such as ajoenes, dithiins, and alkyl sulfides. It was found that, for quantitative GLC analysis of allicin, allicin has to be used as an external standard.
Constituents of crushed garlic bulbs ( ALLIUM SATIVUM L.), such as allicin, ( E/Z)-ajoene, and the vinyldithiins, were synthesized and purified by an LC method. Purity was proved by TLC, HPLC, and GC systems. Identity was confirmed by comparison with spectral data from the literature. In order to establish external standards, silica gel adsorbates of the respective substances were prepared. For quantitative determination of allicin and its transformation products, an isocratic HPLC method was developed. Calibration was performed by the use of these external standards, and by comparison to an internal standard. The influence of different media on allicin transformation, including the ( E/Z)-ratio of the ajoenes, has been elaborated.
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