Phytochemical and pharmacological information collected in the course of these authors' studies has been insufficient to definitely establish the mechanism of oral activity in two Amazonian hallucinogens. However, it has provided phytochemical data and in-vitro pharmacological evidence that indicates, in the case of ayahuasca, that the original hypothesis proposed to explain the oral activity has not been disproved. Certainly ayahuasca contains high enough concentrations of beta-carbolines to effectively inhibit MAO and by this mechanism the active hallucinogenic constituent DMT may be protected from peripheral degradative metabolism. The alternative mechanism proposed in the above discussion may also be implicated in the pharmacology of ayahuasca, but at least it is not necessary to invoke this mechanism for ayahuasca. In the case of the orally ingested Myristicaceous preparations, however, these investigations indicate that MAO inhibition - whether due to beta-carbolines or some other constituents - is almost certainly not the mechanism responsible for their oral activity. The pastes do not contain more than traces of beta-carbolines, they show poor activity as MAOIs and their oral activity, when present, is not correlated with the presence of beta-carbolines. Some alternative mechanism must therefore be invoked to explain the oral activity of these Myristicaceous pastes. Two such alternatives have been discussed above. One is that the oral activity is due to biologically active constituents other than tryptamines. The other possibility is that the active tryptamines are protected from peripheral degradation by constituents that inhibit hepatic MAOs, the enzymes responsible for 6-hydroxylation and N-oxidation of tryptamine derivatives. MAO inhibitors require the presence of a methylenedioxyphenyl configuration as the active pharmacophore, and Virola spp. are excellent sources of compounds possessing this moiety. Unfortunately, neither alternative mechanism can be proven or disproven until more has been learned about the in-vivo metabolism of DMT and related compounds. An obvious place to start would be to study the metabolism of orally administered DMT in the presence of known MAO inhibitors.