Anhalidine is a naturally occurring tetrahydroisoquinoline based alkaloid which can be isolated from Lophophora williamsii; it has also been detected in other cactii and several species of Acacia. It is part of a family of compounds that are structurally related to mescaline. Anhalidine has been found to act as a potent inverse agonist of the serotonin 5-HT<sub>7</sub> receptor.