The effects of various sedative cyclopeptides and peptide alkaloids from the Zizyphus species on calmodulin-dependent $Ca^{2+}$ -ATPase and phosphodiesterase were Investigated. Calmodulin-induced activation of $Ca^{2+}$-ATPase was strongly inhibited by sanjoinine-A dialdehyde (IC_{50}$, 2.3$mu extrm{m}$), -Ah1 (IC_{50}$, 4.0$mu extrm{m}$), -A (IC, 4.6$mu extrm{m}$), and -G2 (IC_{50}$, 7.2$mu extrm{m}$), while calmodulin-induced activation of phosphodiesterase was strongly inhibited by both deachuine- S10 (IC_{50}$, 4.9$mu extrm{m}$) and sanjoinine-D (IC_{50}$, 9.0$mu extrm{m}$). The inhibitory activity of the various cyclopeptides and peptide alkaloids on $Ca^{2+}$-ATPase was found to correlate well with their Sedative activity.