Salvinorin A, a compound from the hallucinogenic mint Salvia divinorum, is the only known non-nitrogenous and specific kappa-opioid agonist. Several related compounds from Salvia splendens and a series of semisynthetic derivatives, including some with a pyrazoline structural moiety, were tested for their ability to bind to human mu, delta, and kappa opioid receptors. None of these compounds showed high-affinity binding to these receptors. However, one compound (10) showed modest affinity for kappa receptors, suggesting that other naturally occurring neoclerodanes from different Salvia species may have opioid affinity.
Salvinorin A is a unique naturally occurring compound that activates κ-opioid receptors without containing nitrogen. Researchers modified the A ring of salvinorin A and related compounds from Salvia splendens and a non-natural derivative, producing new molecules. When tested for opioid receptor activity, none of these derivatives were active. The absence of activity may be due to the presence of a lactone group at specific positions in the molecular structure.