A new iridoid glucoside was isolated from the whole plant of Ajuga spectabilis Nakai (Jaran-cho; Labiatae). This compound was obtained as white plate-like crystal and named as Jaranidoside. It has a molecular formula $C_{17}H_{26}O_{12}$ and mp $128{sim}130^{circ}C$. The structure of the Jaranidoside was assumed from data of chemical reactions and PMR specturum of the compound. To determine the most favorable conformation, informations on the proton coupling and chemical shift were used. Jaranidoside exhibited a stimulating activity on smooth muscle and cardiac muscle. No antimicrobial activity on five microorganism strains was observed.
