Objective      To isolate the antiendotoxin active components (LPS) from Paeonia suffruticosa Andr (PSA) using biosensor and purification technology and assess their bioactivities in vitro and in vivo.       Methods      LPS were isolated from PSA using biosensor

silica gel column chromatography

polyamide chromatography

and IEC-HPLC. Inhibitory effect of LPS on antiendotoxin-mediated secretion of cytokines from RAW264.7 and protective effect of LPS on mice against antiendotoxin and heat killed E.coli (HK-E.coli) were studied.       Results      PSA-3

an antiendotoxin active component with a high binding ac

tivity to lipid A

isolated from PSA

could inhibit TNF-α release from LPS-mediated RAW264.7（P

45 μg

0.05

P

90

180 μg

0.01）. The protective efficiency of PSA-3 on mice was 50% against lethal LPS dose（P0.01）and lethal HK-E.coli dose

respectively（P0.05）. PSA-1 with a lower binding activity to lipid A had no inhibitory and protective effect on mice against LPS and HK-E.coli.       Conclusion      PSA-3

a component isolated from PSA

has a high binding activity to lipid A and an antagonistic effect on LPS both in vivo and in vitro.