Abstract: The contents of polyphyllin Ⅱ in the five-year-old Paris polyphylla Smith var. chinensis（Franch）.Hara, Paris qiliangiana H.Li, J.Yang & Y.H.Wang and Paris thibetica Franch. from three Paris in Enshi were compared and analyzed, and the gas chromatography （GC） was established. The DPPH free radical scavenging activities of three Paris polyphylla extracts were detected and their antioxidant activities were studied. The method for detecting polyphyllin Ⅱ extracted with ethyl acetate was as follows：Using FID detector, the temperature programming was 0~3 min, 60 ℃, the temperature increased to 280 ℃ at 3 ℃/min, and maintained for 20 min; injection port temperature was 310 ℃; the carrier gas was nitrogen （99.999%）; the flow rate was 1.0 mL/min; injection volume was 5 μL, no split. The results showed that the standard curve of polyphyllin Ⅱ standard by GC was Y=0.845X+72.18, and the linearity was good within the concentration range of 512.5~164 00.0 ng/μL,with R²> 0.999 5. The limit of detection was 40.5 ng/μL and the limit of quantitation was 130.6 ng/L. The recovery was 96.93%~98.33% with RSD of 2.72%. GC analysis showed that the contents of polyphyllin Ⅱ were 0.104 mg/g, 0.098 mg/g and 0.015 mg/g in P. polyphylla,P. thibetica and P. qiliangiana, respectively. The IC₅₀ values of the three extracts of P. polyphylla,P. qiliangiana, and P. thibetica were 2.372 mg/mL, 2.461 mg/mL and 2.473 mg/mL, respectively, which exhibited strong to weak bacteriostatic activity. The detection method for polyphyllin II was accurate, reliable, simple, sensitive and suitable. The content of the active ingredient polyphyllin Ⅱ in the P. polyphylla in Enshi area was the highest, followed by P. thibetica, and P. qiliangianawas the lowest. The extracts of three Paris plants had certain antioxidant capacity, and P. polyphylla had the strongest antioxidant capacity.

Key words: P. polyphylla, P. thibetica, P. qiliangiana, polyphyllin Ⅱ, antioxidation