Phytoconstituents of Endiandra kingiana; antidiabetic effects and molecular docking studies on alpha-amylase and alpha-glucosidase

Phytochemical investigation on the bark of E. kingiana plant afforded ten compounds, including six polyketides namely kingianin A 1, kingianin B 2, kingianin E 3, kingianin F 4, kingianin K 5 and kingianin L 6, three endiandric acids; kingianic acid A 7, tsangibeilin B 8 and endiandric acid M 9, and one sesquiterpene; daibuoxide 10. All compounds were separated as racemic mixture by recycling high-performance liquid chromatography (RHPLC), except for daibuoxide. Their structures were elucidated by detailed spectroscopic and comparative literature data analysis. This is the first report on the presence of the sesquiterpene; daibuoxide in Endiandra genus. In vitro enzymatic bio-evaluation of the isolated compounds against alpha-amylase and alpha-glucosidase showed that 4 demonstrated the best alpha-amylase and alpha-glucosidase inhibitory activity with IC50 values of 181.54 +/- 6.27 mu g/mL and 237.87 +/- 0.07 mu g/mL, respectively. In addition, molecular docking analysis confirmed the alpha-amylase and alpha-glucosidase inhibitory activities demonstrated by 4.