Phenylethylamine or Phenethylamine (PEA) is a natural monoamine alkaloid, trace amine, and also the name of a class of chemicals with many members well-known for psychoactive drug and stimulant effects. Studies suggest that phenylethylamine functions as a neuromodulator or neurotransmitter in the mammalian central nervous system. It is biosynthesized from the amino acid phenylalanine by enzymatic decarboxylation. Besides mammals, phenethylamine is found in many other organisms and foods such as chocolate, especially after microbial fermentation. It is sold as a dietary supplement for purported mood and weight loss-related therapeutic benefits; however, orally ingested phenethylamine is usually inactive on account of extensive first-pass metabolism by monoamine oxidase (MAO) into phenylacetic acid, preventing significant concentrations from reaching the brain.