Myristicin is a phenylpropene, a natural organic compound present in small amounts in the essential oil of nutmeg and to a lesser extent in other spices such as parsley and dill. Myristicin is a naturally occurring insecticide and acaricide with possible neurotoxic effects on neuroblastoma cells. It has psychoactive properties at doses much higher than used in cooking. Myristicin is a weak inhibitor of monoamine oxidase. Raw nutmeg produces anticholinergic-like symptoms, attributed to myristicin and elemicin.

Intoxications with myristicin or nutmeg essential oil have effects that vary from person to person, but are often reported to be a state somewhere between waking and dreaming; euphoria is reported and nausea is often experienced. Users also report bloodshot eyes and memory disturbances during nutmeg intoxication. In addition to a semiconscious state, myristicin also has been known to induce psychoactive effects, such as visual distortions. The dose required to achieve such an effect varies from person to person and from source to source. Nutmeg intoxication has an extremely long time before peak is reached, sometimes taking up to seven hours, and effects can be felt for 24 hours, with lingering effects lasting up to 72 hours.

In raw nutmeg, only 5-15% of the mass consumed is an essential oil fraction, of which only roughly 4% is myristicin, indicating the amount present overall in the nut is from 0.2-0.6%. While myristicin has been widely accepted as the main psychoactive component of nutmeg (along with elemicin), both the differences in subjective effects observed between nutmeg and synthetic myristicin, as well as the fact that myristicin is not a major component of the seed (therefore is possibly not present in high enough quantities) suggest it does not fully explain the effects of consuming raw nutmeg.

Formal Chemical Name (IUPAC)
6-allyl-4-methoxy-1,3-benzodioxole

References

http://en.wikipedia.org/wiki/Myristicin