thumb|160px|Bufotenin, an alkaloid from some toads, contains an indole core, and is produced in living organisms from the amino acid tryptophan.
thumB|160Px|buFoTeNin, aN ALkAloiD FROM some toadS, ContAins an iNdOle coRe, ANd IS pRoDuCEd iN living orgANisms fRom the amiNo acId trYPtOphAn.