Abstract: Three new cyclohexene epoxides, polysyphoside A, B and C, along with a known compound crotepoxide (4), were isolated from Piper polysyphorum C. DC. Based on spectroscopic analysis, their structures were established as 1-benzoyloxymethylene-2-hydroxy-3-benzoyloxy-1, 6- epoxycyclohex-4-ene (1), 1-benzoyloxymethylene-2-hydroxy-5-benzoyloxy-1, 6-epoxycyclohex-3-ene (2) and 2-hydroxy-3-benzoyloxymethylene-5-benzoyloxy-1, 6-epoxycyclohex-3-ene (3), respectively. It was the first time that(1), (2) and (3) had been isolated from a natural source.

Key words: Piper polysyphorum, Cyclohexene epoxides, Polysyphoxide A, Polysyphoxide B, Polysyphoxide C