The roots of Codonopsis lanceolata afforded tangshenoside I(1) and $eta$-adenosine (2) as $alpha$-glucosidase inhibitors. Their structures were unambiguously determined by 1D and 2D NMR data including HMQC and HMBC experiments. Compounds 1 and 2 exhibited weak $alpha$-glucosidase inhibitory activities in vitro with $IC_{50}$ of 1.4 and 9.3 mM, respectively.