Salvia Botany - Salvia divinorum has large green leaves, hollow square stems and white flowers

Salvia divinorum has large green leaves, hollow square stems and white flowers with purple calyces. The plant grows to well over 1m in height. Unlike other species of salvia, Salvia divinorum produces few seeds, and those seldom germinate. For an unknown reason, pollen fertility is reduced. There is no active pollen tube inhibition within the style, but some event or process after the pollen tube reaches the ovary is aberrant. Partial sterility is often suggestive of a hybrid origin, although no species have been recognized as possible parent species. The ability to grow indistinguishable plants from seeds produced by self pollination also weakens the hybrid theory of origin, instead implying inbreeding depression, or an undiscovered incompatibility mechanism. The plant is mainly propagated by cuttings or layering. Although isolated strands of S. divinorum exist, these are thought to have been purposely created and tended by the Mazatec people. For this reason, it is considered a true cultigen, not occurring in a wild state.

For more details on this topic, see Salvinorin A.

Salvinorin A

The active constituent is a trans-neoclerodane diterpenoid known as Salvinorin A, chemical formula C₂₃H₂₈O₈. Unlike other known opioid-receptor ligands, salvinorin A is not an alkaloid - it does not contain a basic nitrogen atom.

When considered by weight alone, salvinorin A is the most potent naturally-occurring psychoactive compound known. It is active at doses as low as 200 µg. Research has shown that salvinorin A is a potent and selective k-Opioid (kappa-Opioid) receptor agonist. It has been reported that the effects of salvinorin A in mice are blocked by k-Opioid receptor antagonists. This makes it unlikely that another mechanism contributes independently to the compound’s effects. Salvinorin A is unique in that it is the only naturally occurring substance known to induce a visionary state via this mode of action. Salvinorin A has no actions at the 5-HT_2A serotonin receptor, the principal molecular target responsible for the actions of classical hallucinogens.
Salvinorin's potency should not be confused with toxicity. Rodents chronically exposed to dosages many times greater than those to which humans are exposed did not show signs of organ damage.

Many other terpenoids have been isolated from S. divinorum, including other salvinorins and related compounds named divinatorins and salvinicins. None of these compounds has shown significant (sub-micromolar) affinity at the k-Opioid receptor, and there is no evidence that they contribute to the plant's psychoactivity.