Objective: To investigate the chemical constituents of Euphorbia pekinensis

and evaluate the toxicity of the obtained compounds by using zebrafish embryo. Method: The roots of Euphorbia pekinensis were extracted with 95% ethanol and then extracted with ethyl acetate to obtain the ethyl acetate fraction. The ethyl acetate fraction was then separated and purified by silica gel column chromatography

medium pressure column chromatography and preparative liquid chromatography methods

while their structures were identified by physical and chemical properties and spectral data combined with literature. At the same time

the model organism zebrafish embryo was used to evaluate the acute toxicity of each compound in E. pekinensis. The zebrafish embryo normally developed for 24 h was selected to. determine the 96 h-LC100 and 96 h-LC0 of each compound in preliminary experiment. Then in the formal experiment

eight concentrations and a blank control group were set for each compound. Development and death of zebrafish embryos at 96 h after administration were observed. The experiment was repeated for three times to calculate 96 h median lethal concentration (96 h-LC50)of different compounds on zebrafish embryos. Result: Sixteen compounds were isolated from the ethyl acetate fraction of E. pekinensis

and identified as tetradecanoic acid(1)

tirucallol(2)

5α-eupha-8

24-dien-3β-(3)

butyl myristate(4)

octacosyl(2E)-3-(4-hydroxy-3-methoxyphenyl)acrylate(5)

24-propylcholesterol(6)

stigmasterol(7)

(3β)-stigmast-5-en-3-ylpalmitate(8)

α-spinasterol(9)

pinostrobin(10)

oleic acid(11)

manool(12)

linoleic acid(13)

pekinenal(14)

neomotiol(15)

and(3β)-3-hydroxyanosta-8

24-diene-7

11-dione(16). Conclusion: compounds 4

8

10-13 and 16 were isolated from this plant for the first time. In the evaluation of toxicity by using zebrafish embryos

the toxic compounds were compounds 10

12

14 and 16.