Isolation and identification of the anti-isohumulones and the anti-acetylhumulinic acids

The Anti-Iso-Alpha-Acids: Concept and Review of Current Research

“…Modification and degradation of the 4-methyl-3-pentenoyl side chain at C-4 can lead to deacylated anti-acetylhumulinic acid (10, Fig. 3) in the same way as described previously (11,21,22). In contrast to the series of the isohumulones, compound 10 is the main representative (6.1%) of this series because further degradation to deacylated anti-humulinic acid (11, Fig.…”

“…This reaction is, however, of minor importance and occurs with less than 2% yield (10). The result is a completely new series of deacylated derivatives, which we were able to isolate and identify (11). Deacylated antiisohumulone (9, Fig.…”

“…The latter phenomenon is, indeed, much more difficult to realize and has, up to now, only been observed in well-defined oxidative circumstances (14,19). On the other hand, the better watersolubility of the anti-isohumulones implies that they have better potential for use in the brewing process than do the isohumulones (11). A highly reliable analysis of the anti-isohumulones in beer is, again, hampered by the overwhelming presence of the isohumulones, but we do have indications for their occurrence in beer.…”

“…These are conducted in aqueous buffer solutions, either at pH 5.4 or 11. The exact conditions, resembling those prevailing in the brewing kettle, are described elsewhere (6,8,9,11). The acyloin isomerization of 1 compound 6 yields predominantly epimeric isohumulones via stereoselective ketonization at C-5 (23,26) (Fig.…”

“…3). The CM and trans epimers have been separated, purified, and completely characterized (yield: 0.2%) (11). Further degradation to the anti-humulinic acids (8, Fig.…”