Honokiol trimers and dimers via biotransformation catalyzed by Momordica charantia peroxidase: Novel and potent α-glucosidase inhibitors

Ten honokiol oligomers (1–10), including four novel trimers (1–4) and four novel dimers (5–8), were obtained by means of biotransformation of honokiol catalyzed by Momordica charantia peroxidase (MCP) for the first time. Their structures were established on the basis of spectroscopic methods. The biological results demonstrated that most of the oligomers were capable of inhibiting α-glucosidase with significant abilities, which were one to two orders of magnitude more potent than the substrate, honokiol. In particular, compound 2, the honokiol trimer, displayed the greatest inhibitory activity against α-glucosidase with an IC50 value of 1.38 μM. Kinetic and CD studies indicated that 2 inhibited α-glucosidase in a reversible, mixed-type manner and caused conformational changes in the secondary structure of the enzyme protein. These findings suggested that 2 might be exploited as a promising drug candidate for the treatment of diabetes.

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