The effectiveness of pressurized hot water extraction (PHWE) of anthraquinones from Morinda citrifolia was evaluated by determining the capability of the extracts to scavenge the free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) in vitro, as compared with the extracts obtained by other conventional extraction methods such as ethanol extraction in stirred vessel, Soxhlet extraction, and ultrasound-assisted extraction (UAE). It was found that PHWE and solvent extraction with Soxhlet resulted in extracts that have the highest antioxidant activity. In addition, PHWE could recover similar amount of anthraquinones, compared with Soxhlet extraction, and is therefore proven to be a promising benign alternative to organic solvent extraction. In addition, the solubility of anthraquinones in pressurized hot water was determined and mathematically modeled. (c) 2006 Published by Elsevier B.V.