With Mulungu, I would guess that it MAY at least possess potential to be toxic in overdose. Related trees in the genus Erythrina, some of them contain compounds which act as non-depolarizing nicotinic antagonists at the neuromuscular junction type NAChRs, in other words, they possess paralytic activity of a nature resembling that of curare.
I would guess that the psychoactive plant which degrades to uselessness (unless one wishes to extract norephedrine from it to use in a synthesis of 4-methylaminorex) within days, is Catha edulis, Khat/Qat. It can be kept for a few days in a fridge but not for long, because it contains cathinone, a beta-ketone primary amine, methcathinone does not suffer from this problem, due to the N-alkylation, but cathinone primary amines are very unstable, dimerizing to form inactive pyrazine compounds, this reaction being irreversible. Freshly picked its active fully, likewise when kept cold for a couple of days after first being picked, but much longer than a few days at most, the cathinone will have dimerized, and only the norephedrine/norpseudoephedrine content will be left, aside from the aforementioned pyrazine garbage, and the khat thus becomes useless for its intended purpose.]
I am inclined to agree about those theories as to the aztecs, it is certainly, quite obviously not meant to be used as an infusion of dried plant matter without fermentation, that much is obvious. I am almost certain, that if this is done, the compounds in it that affect the body if the plant Heimia salicifolia is used dried, infused and not fermented, that they, or at least one such biologically active compound is an acetylcholinesterase inhibitor, or else that it possesses effects as an acetylcholine secretagogue, like the venom of the spiders of the genus Latrodectus. Because it feels EXACTLY like either poisoning by a nerve agent, or the effects caused by a bite from one of the widow spiders, black widows, brown widows etc. I'd bet money on it being one of these two modes of action. I would guess that an anticholinesterase is much more likely than an acetylcholine releasing agent, but only because there are a fair few anticholinesterases in nature, but acetylcholine releasing agents are extremely rare, there are only seven that I know of, alpha-latroinsectotoxin, beta-latrotoxin, gamma-latrotoxin, delta-latrotoxin, epsilon-latrotoxin, alpha-latrotoxin (this is a different chemical entity to alpha-latroinsectotoxin, the majority of these are insect-specific, with alpha-latrotoxin being a toxin specifically targeted at killing vertebrates, there is also an alpha-latrocrustatotoxin, targeting specifically, crustaceans. Something I find very strange indeed, given most crustaceans are aquatic and posses a shell which the tiny fangs of a widow could never hope to penetrate. Pill-bugs, woodlice perhaps might be the target as the critters are land living, although, they still have armor,live on the ground away from widow spiders webs.
mg for mg, the venom of the black widow spiders is of a greater lethality than that of cobras, although being both a spider, of small size, and at that, one of araneomorph type 'design' rather than a mygalomorph, which tend to be much larger than araneomorph spiders, the difference between the two groups is that araneomorph spiders have chelicera (fangs) which are oriented such as they pinch together on the horizontal axis, akin to a pair of blacksmith's pincer tongs, a nipping sort of action when they bite, and the araneomorph spiders tend, generally, to be much smaller than the mygalomorphs.
Examples would be for instance, Latrodectus, the black, brown, red widows, the false widows of the genus Steatoda, and your common garden orb-weaver spiders as well as the ubiquitous 'daddy longlegs' or house spider (note the colloquial term daddy longlegs can also be applied to harvestman species, these are not true spiders and are not venomous and pose absolutely no threat to anybody)
Mygalomorphs can be, and usually are, much MUCH larger than their araneomorph relatives and have a fang orientation which strike vertically downwards, akin to a pair of daggers being used to stab a man in the back in an overhand strike, being raised then plunged vertically downwards. Most of the really dangerous venomous spiders are mygalomorphs, although two of the worlds deadliest are araneomorphs of significant size, such as the brazillian wandering spiders (genus Phoneutria, a group of large, very fast and EXTREMELY foul tempered wee bastards, that have even been known, after someone attempted to squash one with a broom, to, rather than get squished, to charge their attacker, legging it up the broom, carrying on up the handle in an attempt to bite their assailant!.
Other examples of mygalomorphs would be the australian funnelwebs (Atrax, Hadronyche), mouse-spiders (Missulena), and wishbone spiders (Aname).
These are araneomorph spiders, but are big, very fast runners and possessed of both a very potent, medically significant venom which is quite capable of killing a healthy adult male human if bitten, their venom acting in various ways dependent upon species, one of the toxins for example acting as an unselective blocker of voltage gated calcium channels, blocking both glutamate release and also blocking reuptake, as well as blocking uptake of calcium ions, and acting as a serotonin 5HT4 receptor agonist and causing release of substance P and other proinflammatory, pain inducing neuropeptides. An unfortunate side effect, aside from paralysis and potentially death, is priapism, in other words, an out of control, very long lasting massive boner that does not subside and can even result in serious damage to or even loss of if untreated, a man's Theresa May.)
The deadliest spider in the world is also a large araneomorph, the members of the genus Sicarius, or six-eyed sand spiders, they are related to Loxosceles, the recluse spiders, although they contain orders of magnitude greater quantities of their extremely potent flesh-rotting, necrotizing sphingomyelinase-D based venom, which has been compared, in the few people known to have been bitten by these spiders to be at least as deadly as the bite of a puff-adder. Two bites I know of, one resulted in the guy dying, IIRC after catastrophic disseminated intravascular coagulation and destruction of erythrocytes, the other one had his arm rotted off. The bite from these spiders essentially flays you alive, dissolves your flesh and causes your blood to clot in your veins, causing thromboses throughout the body and haemolysis. Its like arachnid Ebola, combined with stevens-johnson syndrome added on to the venom of one of the more highly toxic species of viper, or taipan/tiger snake venom.
Luckily people don't come into contact with them unless they know the spiders are there, mainly when spider enthusiasts keep Sicarius species as pets. Not sure which is THE most toxic among the genus but all in all, they are the deadliest spiders known to man, if you do get bitten. The worst thing, is that if you do, there is absolutely nothing that medics can do to cure you, there is no antivenin. Supportive care and painkillers are all that can be done to help a victim bitten by these spiders, although hobbyists report them not to be aggressive, some people even handle theirs by hand! although they are reportedly shy, they are also lightening-quick runners, and large tall tanks are needed to prevent them getting out by taking a run up and hurling themselves up the side of the glass tank walls)
Anyhow, as for sinicuichi, it'd not surprise me one tiny bit if either the plant known as the sun opener is misidentified, since there aren't any aztecs around anymore we can just go and ask about it, or if it isn't, that it requires special preparation in order to detoxify it, like say, fly agaric does, I can't imagine the aztec people would waste their time consuming a foul tasting potion that did nothing but make them feel like giants with giant baseball bats had just run them over in a tank, before getting out and beating the everloving shite out of them with said giant sized bats.
Other examples would be the australian funnelwebs (Atrax, Hadronyche), mouse-spiders (Missulena), and wishbone spiders (Aname)
