The present invention discloses a compound of Formula I or pharmaceutically acceptable salt thereof and its preparation method and applications. The new structure of the compound of formula I has not been reported in literature. The compound of formula I is isolated from Isodon forrestii var. forrestii and is a compound functioning as a Trxl selective inhibitor. The present invention further discloses a pharmaceutical composition, preparation of the compound of Formula I and its use for preventing or treating cancer. Iso A of the present invention has the advantages of low toxicity, high safety and strong pharmacological effect, which suggests a potential prospect in pharmaceutical applications.
