The effects of major variables of supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE) processes on the recoveries of target compounds and activity of Magnolia officinalis (Magnolia) bark extracts were studied by employing the L-9 (3)(4) Taguchi design matrix. In SFE, the percentage of extractable solids (ES) and those of the active principles, honokiol and magnolol, were strongly affected by extraction pressure and temperature. Selectivity for magnolol over honokiol, as expressed by the magnolol:honokiol ratio, was found to be predominantly influenced by SFE pressure (>50%), with lowest pressure setting at 20 MPa resulting in approximately 35:1 selectivity in favour of magnolol. In comparison, the magnolol:honokiol ratio obtained by the exhaustive Soxhlet extraction was 10:1. Particle size was an insignificant factor in SFE but was a strong influence on PLE performance due to better penetrative ability of supercritical CO2 into the plant matrix. Although SFE extracts had lower quantitative recoveries compared to PLE and SFE, extracts obtained demonstrated greater antioxidant activity. (C) 2009 Elsevier B.V. All rights reserved.