New triterpenes from Salacia hainanensis Chun et How with α-glucosidase inhibitory activity

Fractionation of the methanol extract from the roots of Salacia hainanensis Chun et How showing the potent inhibitory activity on α-glucosidase afforded two new lupane derivatives, 3α,28-dihydroxy-lup-20(29)-en-2-one (1) and 3α-hydroxy-lup-20(29)-en-2-one (2), a new friedelane derivative, D:A-friedo-oleanane-7α,30-dihydroxy-3-one (3), and a novel natural product, 2,3-seco-lup-20(29)-en-2,3-dioic acid (4), along with four known compounds (5-8). Their structures were established on the basis of spectral analysis, especially on the data afforded by 2D NMR and high-resolution mass spectra experiments. All of them showed a much stronger inhibiting activity on α-glucosidase than the positive control (acarbose, IC₅₀ = 5.83 μM). Constituents with α-glucosidase inhibitory activity from this plant are reported for the first time.