Identification and characterization of a novel fermented substance produced by edible Aspergillus oryzae AO-1 that inhibits DPP-IV activity.

We identified a novel fermented substance (FKA) produced by the edible Aspergillus oryzae strain AO-1 that inhibited dipeptidyl peptidase IV (DPP-IV) (IC(50) = 3.41 mg · mL(-1)). HPLC analysis of FKA showed specific one metabolite (WYK-1), which inhibited DPP-IV (IC(50) = 6.98 μM). WYK-1 was identified as a tetrahydroxyisoquinoline derivative. Interestingly, we examined 60 strains of A. oryzae, AO-1 was the only A. oryzae strain that produces WYK-1. This is the first report that an edible A. oryzae strain produces a DPP-IV inhibitor such as WYK-1. This study also suggests that FKA has applications in the development of novel antihyperglycemic therapeutics or functional foods.
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