Spirosteroids and α-glucosidase inhibitory norlignans from Asparagus racemosus Willd. roots

Three undescribed spirosteroids, asparacemosones A-C, an undescribed spiro-21-norsteroid, asparacemosone D, along with seven known compounds were isolated from Thai herbal plant Asparagus racemosus Willd. roots. Their structures were elucidated by spectroscopic analysis including NMR, UV, IR and mass spectrometry. The absolute configurations of asparacemosones A, B, and D were determined by single crystal X-ray diffraction using CuKα radiation. Among the isolated compounds, the norlignan nyasol and three acetylenic norlignans demonstrated potent α-glucosidase inhibition, with IC₅₀ values ranging from 0.003 to 0.004 μM which is 5 × 10⁴ fold more potent than the standard acarbose.