A new triterpenoid from the leaves of Rhodomyrtus tomentosa (Ait.) Hassk.

A new triterpenoid, 2α, 3β, 23α, 29-tetrahydroxyolean-11, 13 (18)-dien-28, 19β-olide, named as rhodotomoside A (1), together with six known triterpenoids (2-7), were isolated from the leaves of Rhodomyrtus tomentosa (Ait.) Hassk by column chromatography on silica gel, reversed-phase C₁₈ silica gel and semi-preparative HPLC. Their structures were elucidated on the basis of spectroscopic methods, including extensive 1D NMR, 2D NMR and MS spectra. The inhibition rates of α-glucosidase of compound 1 was 77.82%, and exhibited inhibitory activity against α-glucosidase with IC₅₀ value at 0.213 ± 0.016 mg/mL.