The active principle in Salvia divinorum is salvinorin A, a trans-neoclarodane diterpenoid. 

               O

          ____//

 ___     O    \

O  \\___/    H_\____

|___/  /\      /    \

 ---  H  \____/_CH3  \

              \      /

             H_\____/_CH3

               /    \

             _/      \__C=O

            O-\      /  |

               \____/   OCH3

               /

          O=C-O

            |

          CH3

 

Salvinorin A is active in humans at 200-500 micrograms, and is thus many times more potent than any other plant-based hallucinogen.  Doses of 1000mg/kg in mice did not produce fatalities (this is 5000 times the effective dose for humans!) 

 

Salvinorin A may be extracted from fresh or dried leaves [...]