To identify the chemical constituents with hypoglycemic activity in Salacia hainanensis Chun et How, this study was carried out on the roots of S. hainanensis. By means of a bioassay-guided method, three new triterpenoids (2β,3β-dihydroxylup-20(29)-ene [compound 1], 30-hydroxy-D:A-friedo-olean-1-en-3-one [compound 2], and 24,25,26-trihydroxytirucall-7-en-3-one [compound 3]) along with three known compounds (olibanumol J [compound 4], 21α-hydroxy-D:A-friedo-olean-3-one [compound 5], and 29-hydroxy-D:A-friedo-olean-3-one [compound 6]) were isolated from the EtOAc part and were shown to have effective α-glucosidase inhibitory activity. Their structures were established on the basis of spectral analysis, especially according to the data obtained by two dimensional nuclear magnetic resonance spectroscopic and high-resolution mass spectra experiments. All compounds with the exception of compound 2 showed much stronger inhibitory activity against α-glucosidase than did the positive control (acarbose, IC50 1.02 μM).Graphical abstractHighlights► We studied the constituents with hypoglycemic activity in Salacia hainanensis. ► With bioassay-guided method, we focused on the bioactive EtOAc part. ► In this part, three new and three known triterpenoids were obtained. ► These compounds inhibited α-glucosidase activity more strongly than acarbose.

Magnoline (1), a new isoquinoline derivative, was isolated from the leaves of Magnolia sieboldii K. Koch (Magnoliaceae). Its structure was elucidated on the basis of spectral analysis including 1D, 2D NMR and HR-TOF-MS.