A new steroidal saponin, mannioside A (1), was isolated from the stem bark of Dracaena mannii, together with the known pennogenin (2), pennogenin-3-O-$eta$-D-glucopyranoside (3) and pennogenin-3-O-$alpha$-L-rhamnopyranosyl-($1{ ightarrow}2$)-[$alpha$-L-rhamnopyranosyl-($1{ ightarrow}3$)]-$eta$-D-glucopyranoside (4). Their structures were determined using 1D- and 2D-NMR spectroscopy and mass spectrometry. Compounds 1 and 3 significantly inhibited carrageenan-induced paw edema in the rat; compound 4 was moderately active whereas 2 showed very weak activity.