Neither of the guessed herbs are potent enough to produce the obvious hallucinogenic-like response/acting (hand gestures and jaw wagging/tongue flapping is as good as taken directly from Johnny Deep's portrayal of severe tripping in Fear and Loathing in Las Vegas). Fear and Loathing in Las Vegas (3/10) Movie CLIP - The Hotel on Acid (1998) HD
Of the three mentioned drugs assumed to be ingested, opium in any notable dose would simply lead to dream-state sleep, betel nut is a stimulant and would merely produce an excited state, as for kratom - don't make me laugh. Even if you combined all 3 in large doses, again, no.
Obviously not mushrooms, we've seen many a mushroom trip ("food of the gods" variety, not magic mushrooms, though similar chemically yet as different to Ayahuasca as Saliva is to Ibogaine).
Datura is a possibility, although unlikely, though some can be partial to its power & although not become addicted can be "seduced" by the proposed knowledge and feelings of magical power it is reported to facilitate, shall we say.
In the original scene Yidu is shown chopping and preparing numerous herbs, Chinese medicine is renowned for having active and inactive ingredients, likely of the 8 or so shown only 2 or 3 are psychoactive, possibly having an accumulative action - returning to Ayahuasca (though I stress this is extremely unlikely, not only based on the shown preparation but it is of South American origin), my point is as follows: the actual plant typically named Ayahuasca (Banisteriopsis caapi) is NOT the psychoactive part but aids in the absorption of the DMT-containing Psychotria viridis. I'd propose something similar is ingested in the scene hence the "need" for numerous herbs, stalks etc. (Often medicines contents we're "trade secrets" of healers hence the addition of numerous inactive herbs/spice, whatever.)
So to conclude, I have not proved what is ingested but believe I have disproved the suggested actual hallucinogenic (not stimulant (betel nut) or hypnotic opium/kratom) though betel nut, lime, wrapped in a leaf (hence the red mouth/lip scenario) (I must add this is "plugged" as a quid similar to chewing tobacco, not shown in show... so oh and you are 100% not to swallow betel nut, it is absorbed through the mouth facilitated by the lime, the leaf component is merely flavoring and "packaging") so it "may" have been part of the final concoction but highly unlikely - therefore I say the search is still on but it's in the realm of hallucinogenics of which there are literally 100's upon 100's of choices.
I simple wiki search provides a number of possibilities Wiki - Chinese "Herbals"
Having read a little of the above wiki post (Henbane, Various Mushrooms, and at least 4 other powerful sounding plants as well as the fore-mentioned Datura were all used in china, although I don't think it's Datura there's another side of me thinking it might be combined with the plant I mention below "Maogen: Ranunculus japonicus".
There are still 6 or 7 other possibilities not including cannabis (yes it can cause hallucinations but not in the external appearance seen in the show.
Fly agarica and forms of psylocybin mushrooms are also well documented in China,
As I mentioned above, "Maogen: Ranunculus japonicus" is a plant whose negative effects are "sometimes with blood-spitting" though considered extremely poisonous (maybe the intent? She is most definitely a sorceress as suggested in her tale on the ships as a prisoner and why she was left alone) anyway it's "bad effects" are counteracted with licorice (more mouth discoloration) all to produce the red saliva scenario..
In any case, I think it's a bit of this, a bit of (maybe) that plant "Ranunculus japonicus", a bit of another, all with hallucinogenic properties and prepared to reduce negative effects (she was seen crumbling 1 ingredient, chopping others, using a mortar & pistle thus a bunch of herbs to ease their ingestion.
At least Toads are 100% ruled out.
please excuse the "choppiness" of this post, it was edited a number of times and hardly proof read. I wont get any prizes for correct spelling now will I? :)