α -Glucosidase inhibitory constituents from the roots of Uvaria siamensis (Scheff.) L.L.Zhou, Y.C.F.Su & R.M.K.Saunders

A previously undescribed 2-(4-hydroxyphenyl)-1-tetralone derivative, (2 R)-2-hydroxy-6,7-methylenedioxy-2-(4-hydroxyphenyl)-1-tetralone (1), together with a new flavanone, (2S)-6-acetoxy-5-hydroxy-7-methoxyflavanone (2), were successfully isolated from Uvaria siamensis (Scheff.) L.L.Zhou, Y.C.F.Su & R.M.K.Saunders roots collected in Vietnam. Alongside these new compounds, five known flavones (3-7) were also obtained. The chemical identities of all isolated compounds were established through comprehensive spectroscopic analyses, comparison with literature data, and TD-DFT ECD calculations. In vitro assays evaluating α-glucosidase inhibition revealed that 1 and 3-7 showed potent inhibitory effects (IC₅₀ 0.05-18.9 μM), while 2 exhibited no significant activity (IC₅₀ > 256 μM). All active compounds were more potent than the reference inhibitor acarbose (IC₅₀ 179 ± 6.02 μM). Among them, compounds 5 and 7 showed the most potent inhibitory activity (IC₅₀ 0.06 ± 0.01 and 0.05 ± 0.01 μM, respectively).