Abstract: 【Objective】Study on mechanism of epi-rotenone enantiomorphs, (+)-5’β-epi-rotenone, (-)-5’α- epi-rotenone on insects. 【Method】The symptoms of Bombyx mori, treated with 5’β-epi-rotenone, 5’α- epi-rotenone were different, suggested that mechanism of epi-rotenone enantiomorphs maybe different from that of rotenone. The effects of epi-rotenone enantiomorphs on Na+，K+-ATPase , succinate dehydrogenase , AChE and bovine heart mitochondrial respiratory complex Ⅰwere measured. 【Results】The results indicated that epi-rotenone enantiomorphs had inhibiting effect on the Na+，K+-ATPase in the head of Bombyx mori, but it was found that only 5’α-epi-rotenone had activated effect on Na+，K+-ATPase in the midgut. Epi-rotenone enantiomorphs had activated effect on the activity of succinate dehydrogenase, the difference between 5’β-epi-rotenone and Blank were not significant, but that of 5’α-epi-rotenone and Blank were significant. Epi-rotenone enantiomorphs were no influence on the activity of AChE. Inhibiting effect on mitochondrial respiratory complex Ⅰ with IC50 value of 5’β-epi-rotenone, 5’α-epi-rotenone were 7.81mg/L、54.14mg/L, respectively. 【Conclusion】The differences of poison symptoms and inhibiting effect on enzymes indicated that mechanism of 5’β-epi-rotenone was the same with rotenone, but 5’α- epi-rotenone acted on Na+，K+-ATPase in the midgut and succinate dehydrogenase, besides on mitochondrial respiratory complex Ⅰ.

Key words: Epi-rotenone, Enantiomorph, Mechanism, Mitochondrial respiratory enzymes, Na+, K+-ATPase, Succinate dehydrogenase