Chemical composition and <i>α</i> ‐glucosidase inhibitory activity of <i>Cheilocostus speciosus</i> rhizomes

Abstract Cheilocostus speciosus is a well‐known medicinal rhizome, particularly in India and the Arabian countries, used as a folk medicine. Although the resources of this plant are vibrant in Vietnam, scientific data on its chemical composition and bioactivities remain limited. In this study, extracts of n ‐hexane, ethyl acetate, and n ‐butanol were prepared from the rhizomes of C. speciosus growing in Vietnam. Their α‐glucosidase inhibitory activity was evaluated to select the most promising fraction for further investigation of its chemical composition. The obtained results showed that the n ‐hexane extract exhibited the highest α‐glucosidase inhibitory capacity among extracts (IC 50 = 34.35 µg mL −1 ), being stronger than acarbose (IC 50 = 122.20 mM). From this extract, six compounds were isolated, namely diosgenin ( 1 ), pennogenin ( 2 ), diosgenone ( 3 ), diosbulbisin A ( 4 ), isonuatigenone ( 5 ), and (22β,25R)‐7‐oxo‐spirosta‐3,5‐diene ( 6 ). Their molecular structure was elucidated using nuclear magnetic resonance spectroscopy and high‐resolution electrospray ionization mass spectrometry, along with comparison to reference data. Among these compounds, compound 6 has not been previously reported as a natural phytocomponent. Such achievements confirmed the medicinal value of Vietnamese C. speciosus and significantly expanded scientific knowledge of its phytochemistry and bioactivity.