Alright, I gave it a read. Here's what I have:
Methodology seems reasonable. I don't think their voucher specimen is in an online database so I didn't take a look at it; I am presuming accurate identification in the absence of any indications to the contrary.
There is an odd quirk in naming conventions though: They refer to 5-MeO-DMT as as 5-methoxy-bufotenine. Since bufotenine is 5-hydroxy-DMT, that name would suggest a compound with
two substituents at the 5-position (a hydroxy- and a methoxy- group), which would not be a stable compound. Normally if you're naming 5-MeO-DMT as a bufotenine derivative, you'd name it O-methylbufotenine. But I digress. The paper makes clear that "5-methoxy-bufotenine" refers to 5-MeO-DMT.
The most significant data are the reported concentrations of bufotenine and 5-MeO-DMT. From an ethanol extraction, they found 0.326% bufotenine and 0.307% 5-MeO-DMT (percentages by dry weight of stem bark). Water extraction (boiling for 24 hours) yielded a bit less: 0.232% bufotenine and 0.153% 5-MeO-DMT. Still, significant concentrations.
Of secondary significance is the concentrations reported for 5-MeO-NMT (0.088% with ethanol, 0.0495% with water)and 2-Me-6-MeO-THβC (0.014% with ethanol, 0.010% with water). The activity of these compounds is something of an open question. The activity of monomethyl tryptamine analogs is, at best, assumed to be weaker or more subtle than di-alkyl tryptamines. And while the latter compound is a β-carboline, it is only present in very small concentrations and is unlikely to significantly inhibit MAO.
Some of the citations in the paper leave me curious about the motivation behind the work. They cite Ott's
Ayahuasca Analogues and Schultes & Hofmann's
Plants of the Gods when mentioning that the plant was used to prepare ayahuasca. This suggests a casual interest in the plants and their use, rather than a rigorous scientific/ethnobotanical interest. The more reasonable citations would have been Schultes' 1975 article (number 13 in the "De plantis toxicariis..." series) and Schultes' & Raffauf's
Healing Forest.
When calculating potential concentrations of the compounds in an ayahuasca brew, they estimate that 4 grams of stem bark is used in a "common ayahuasca dose". I don't see any basis for that estimate in the paper they cite, but admittedly I just skimmed it. And really, for this species in particular, any dosage estimates are purely conjecture.
Curiously, Queiroz
et al. cite Ott's Pharmañopo Psychonautics article at one point, but then go on to contradict it by saying "Bufotenine alone, however, has not been reported to be orally active"
The data is scant, but there is reason to believe that bufotenine and 5-MeO-DMT are orally active without MAOI. Much of the testimony from ingesting the purified compounds comes from a single individual (Jonathan Ott), but
Nexus member Pharmacognosis has chimed in with his 5-MeO-DMT experience as well. There is also plenty of evidence that
Anadenanthera seeds, which generally contain mostly bufotenine or 5-MeO-DMT, are traditionally used orally without MAOI admixture (see Torres & Repke's excellent book on the subject).
In summary, this analysis gives justification to the reported use of
T. mucronata as a basis for a psychoactive brew. It does not, however, get us any closer to solving the mystery of
T. methystica presented by endlessness's analysis. Based on that analysis, neither bufotenine nor 5-MeO-DMT are present in
T. methystica... so how it's active (if it's active?) is an unresolved question.