Aspergillusol A, an alpha-glucosidase inhibitor from the marine-derived fungus Aspergillus aculeatus

A new tyrosine-derived metabolite, aspergillusol A (4), was isolated on a gram scale, together with a methyl ester of 4-hydroxyphenylpyruvic acid oxime (5) and secalonic acid A, from the marine-derived fungus Aspergillus aculeatus CRI323-04. The tetraol in 4 was identified as erythritol by comparison of the 1H NMR spectrum of its benzoylated derivative with those of benzoylated erythritol (7) and D-threitol (8), as well as by cellulose-based chiral HPLC analysis. Aspergillusol A (4) selectively inhibited alpha-glucosidase from the yeast Saccharomyces cerevisiae, but it was inactive toward the alpha-glucosidase from the bacterium Bacillus stearothermophilus.