Alpha-glucosidase inhibitory activity has been commonly used for the evaluation of antidiabetic
property in vitro. The aim of this study is to investigate and characterize Dalbergia tonkinensis as a
potential source of antidiabetic compounds. The screening of the active parts used, such as trunk bark,
heartwood, and the leaves of Dalbergia tonkinensis indicated that all these extracted parts used with
methanol demonstrated potent α-glucosidase inhibitory activity. The in vitro antidiabetic property of
Dalbergia tonkinensis was notably recorded for the first time and showed activity (EC50 = 0.17–0.78 mg/mL)
comparable to those of reported potent herbal extracts (EC50 = 0.25–4.0 mg/mL) and higher activity
than that of acarbose, a commercial antidiabetic drug (EC50 = 1.21 mg/mL). The stability tests revealed
that the heartwood of Dalbergia tonkinensis extract (HDT) possesses high pH stability with relative
activity in the range of 80–98%. Further bioassay-guided purification led to the isolation of 2 active
compounds identified as sativanone and formononetin from the ethyl acetate fraction and water
fraction of HDT, respectively. These α-glucosidase inhibitors (aGIs) show promising inhibition against
various types of α-glucosidases. Remarkably, these inhibitors were determined as new mammalian
aGIs, showing good effect on rat α-glucosidase. The results suggest that Dalbergia tonkinensis is a
potent source of aGIs and suggest promise in being developed as functional food with antidiabetic
efficacy. The results of this study also enrich our knowledge concerning current biological activity
and constituents of Dalbergia tonkinensis species.
