How are psilocybin and psilocin chemically related to LSD?

Psilocybin and psilocin are chemically related to LSD primarily through their classification as indole alkaloids. Both psilocybin and psilocin are indole hallucinogens that share a structural similarity to LSD, as well as to other substances like bufotenine, harmine, and ibogaine.1234

These compounds are functionally linked by their ability to interact with serotonin, an indole amine neurotransmitter in the brain. While LSD is a potent synthetic drug derived from ergot alkaloids, psilocybin and psilocin are naturally occurring principles found in various psilocybin mushrooms. Structurally, psilocybin and psilocin are very closely related to one another; psilocybin differs from psilocin specifically by the presence of a phosphate group attached to the molecule at the oxygen atom. All three substances are known for producing similar hallucinogenic experiences by altering the action of serotonin in brain tissue.314