Evaluation of α-glucosidase inhibitory activity led to the isolation of six triterpene saponins from the aerial parts of Glinus oppositifolius including one new and five known constituents. The structure of the new saponin, glinoside C (1), was established as 16-O-(β-D-glucopyranosyl)-3β,12β,16β,21α,22-pentahydroxy hopane by extensive use of 1-D, 2-D NMR and mass spectral techniques. The other constituents identified were 3-O-(β-D-xylopyranosyl)-spergulagenin A (2), spergulacin (3), spergulin A (4), spergulacin A (5) and spergulin B (6). Compound 1 exhibited the greatest inhibition of the enzyme with IC50 of 127 ± 30 µM. Kinetics study for the compound 1 demonstrated mixed type of inhibition (Ki = 157.9 µM).