Syringin 4-O-beta-glucoside, a new phenylpropanoid glycoside, and costunolide, a nitric oxide synthase inhibitor, from the stem bark of Magnolia sieboldii.

Syringin 4-O-beta-glucoside (1), a new phenylpropanoid glycoside, and costunolide (2) were isolated from the stem bark of Magnolia sieboldii. The structures were determined by spectroscopic and chemical methods. Costunolide (2) exhibited strong nitric oxide synthase inhibitory activity in the endotoxin-activated murine macrophage, J774.1.