Every year I prepare rue medicine soon after harvesting in the late autumn when it has this extremely strong harmaline dominant content + effect. Eating the seeds is really overwhelmingly powerful which is good but it does border on toxicity easily and I assume this is because of excessive harmaline. The medicine I prepare never had this harshness and I had never given thought to this before. This year, I prepared the medicine without vinegar for the first time to see how it turns out. I was expecting it to be weaker than usual, but to my surprise, it is unusually powerful and harsh, similar to raw seeds. I have been reading that acid + long boiling duration might be converting harmaline to both harmine and thh, but I am not clear whether people have been able to verify this in experiments... I wonder if I reboiled the medicine adding vinegar, it would transform... I will report if I do it.

There is some info on the topic here here

Acidic Zinc reduction works well for Harmaline -> THH as shown in the forum. I'm not sure about boiling for a long time (+ added vinegar). Maybe concentration and type of metal pot matters. Any tests you run would be interesting (even if no conversion happens).

Boiling for a long time in an aluminum pot could easily have an effect and vinegar would accelerate this.
I have not seen that scientifically tested but, when describing ayahuasca preparation in the jungle, Terence McKenna was adamant that it must be an aluminum pot that's used to make really good aya. It is also chemcially feasible since aluminum is an even stronger reducing agent than zinc and its well known that cooking acidic things, like tomatoes, in aluminum pots will slowly dissolve the pot.

Dithy, have you tried baking the seeds prior to preparation?

Sabnock turned me onto it, and it seems to completely remove the effects of the toxic chemicals present in the raw seeds if one baked them in an oven at 350F for 15-18 minutes.

It's thought that those nasties are cooked off at that temp, while leaving the harmalas intact.

Aluminium salts would also precipitate tannins.

Would aluminium toxicity be an issue at all?

We would need to see some analyses for aluminium content of ayahuasca brews, perhaps.

It won't be on the scale of the Camelford water poisoning incident, at least.