Objective: To explore the protection of active fractions from Pseudostellariae Radix on primary cultured cardiac myocytes injury induced by norepinephreine(NE). Method: four fractions from Pseudostellariae Radix : petroleum ether extract

acetic ether extract

N-butanol extract

and water extract

were obtained by systematic solvent extraction. The primary cultured cardiac myocytes were prepared from the 1-3 d SD neonatal rat

and then 200 μL cell suspension was cultured in 96 well plates by 1×105/mL. Preincubated with different fractions extracted from 0.1

0.25 g crude Pseudostellariae Radix /mL 30min

and then the cardiac myocytes injury was reproduced by 1 μmol·L-1 NE for 24 h. The degree of cardiac myocytes injury was detected by MTT assay. Result: The N-butanol and water fractions extracted from Pseudostellariae Radix could significantly protect primary cultured cardiac myocytes against NE-induced injury by increasing the A570 (P< 0.05 compared with NE group). Further studies suggested that N-butanol fraction eluted by 25% ethanol and polysaccharides fraction extracted from water fraction at 0.1

0.25 g crude Pseudostellariae Radix /mL could significantly inhibit the decrease of A570 induced by NE (P<0.05 or P<0.01). Conclusion: Primary screening of bioactive fractions indicated that the N-butanol and water fractions extracted from Pseudostellariae Radix protect primary cultured cardiac myocytes against NE-induced injury. Further studies showed that N-butanol extract eluted by 25% ethanol and polysaccharides from Pseudostellariae Radix are the major bioactive fractions which inhibit NE-induced primary cultured cardiac myocyte injury.