Abstract: Subcritical water was used to extract polyphenol from pine bark. Its effects on the polyphenol yield were investigated.The DPPH radical scavenging activity of polyphenol by subcritical water extraction was determined. The results showed that the optimum process conditions were extraction temperature 150 ℃, extraction time 5 min, liquid-feed ratio 20∶1, and extraction pressure 4 MPa. Under this condition the yield of polyphenol was 4.86 %. Compared with the ultrasound-assisted extraction and heat reflux extraction, the subcritical water extraction improved the yields of polyphenol by 33.52 % and 37.68 %, respectively. The polyphenol extracted by subcritical water had a better DPPH radicals scavenging activity than that of the antioxidant BHA(7.82 mg/L). The half inhibitory concentration (IC₅₀) of the polyphenol was 7.10 mg/L.

Key words: pine bark, subcritical water, polyphenol, DPPH