Inhibition of coreopsin against α-amylase/α-glucosidase and synergy with acarbose

Coreopsin is a flavonoid from Coreopsis tinctoria. The inhibition of coreopsin and synergy with acarbose against alpha-amylase (PPA) or alpha-glucosidase (SCG) were explored. As a result, coreopsin exhibited stronger inhibition on PPA/SCG than that of acarbose. Combination of coreopsin (4.11 mu M) with acarbose (132.77 mu M) had significant synergistic effect on PPA, while combination of coreopsin (5.76 mu M) and acarbose (121.7 mu M) had significant synergy on SCG. Coreopsin, acarbose and acarbose-coreopsin inhibited PPA in mixed-type mode. Acarbose competitively inhibited SCG, whereas coreopsin and acarbose-coreopsin inhibited SCG in mixed-type mode. Fluorescence analysis conformed that coreopsin could synergize with acarbose by increasing the binding ability of acarbose to PPA/SCG. Compared with acarbose or coreopsin, acarbose-coreopsin complexes resulted in more conformational changes of PPA/SCG, revealing that the complexes had stronger inhibitory ability than acarbose or coreopsin alone. The detail binding information of coreopsin, acarbose or acarbose-coreopsin to PPA /SCG was revealed by computer simulation.