Esculetin derivatives 4a-4j (including six novel hydroxylated/halogenated derivatives 4a, 4d, 4e, 4f, 4g, 4h) were synthesized through Perkin reaction with 2,4,5-trihydroxybenzaldehyde and appropriate phenylacetic acid as raw materials, and screened for alpha-glucosidase and alpha-amylase inhibitory activities.Among these compounds, compound 3-(3-iodophenyl)-6,7-dihydroxy-2H-chromen-2-one (4d) showed promising hypoglycemic activity with half maximal inhibitory concentration (IC50) values of 0.18±0.03 mM and 1.82±0.18 mM against α-glucosidase and α-amylase, resp., classifying it as a mixed-type inhibitor.Compound 4d could statically quench the intrinsic fluorescence of enzymes, which bound to enzymes mainly through hydrogen bonding and hydrophobic interactions affecting the microenvironment of proteins.Compound 4d also exhibited antioxidant activity, which demonstrated good scavenging effects for 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals.Furthermore, compound 4d still maintained a certain degree of hypoglycemic and antioxidant activities after simulated gastrointestinal digestion.The oral toxicity study showed that compound 4d had no significant effect on the serum biochem. indexes and organs of mice, indicating its safety profile.This study suggests that esculetin may be a potential skeleton to the development of hypoglycemic drugs.
