New prenyl flavanone and diarylbutanol from Uvaria siamensis stem bark and their α -glucosidase inhibitory activity.

One new prenyl flavanone ( 1 ), (2 S )-8-prenyl-5,6-dihydroxy-7-methoxyflavanone, and one new diarylbutanol ( 2 ), (7' S )-3'-hydroxy-linderagatin-A, were isolated from the stem bark of Uvaria siamensis (Annonaceae), along with five known compounds, eriodictyol ( 3 ), quercetin ( 4 ), paprazine ( 5 ), N - trans -caffeoyltyramine ( 6 ), and N - trans -feruloyltyramine ( 7 ). Their structures were determined through extensive spectroscopic analyses and comparison with the literature. The α -glucosidase inhibitory potential of 1-7 was evaluated. Compound 6 showed the highest inhibitory activity against α -glucosidase and exhibited superior potency compared to the positive control, with an IC 50 value of 0.12  μ M.