Three new compounds, magnolianone (1), erythro-honokitriol (2), and threo-honokitriol (3), together with 14 known compounds, magnaldehyde (4), magnatriol B (5), randaiol (6), obovatol (7), magnolignan B (8a and 8b), magnolol, honokiol (9), p-hydroxylbenzaldehyde, coniferaldehyde, coniferol alcohol, syringaldehyde, syringaresinol, and acteoside, were isolated from the MeOH-soluble part of a water extract of the stem bark of Magnolia officinalis. Among these compounds, 2-8b were studied for anti-inflammatory and antioxidative activities. Compound 7 displayed more potent antioxidative potential than 9. Compounds 4-7 effectively inhibited LPS-induced NO production, whereas 5 and 6 were more potent than 9.