I think saying rue is toxic or contains toxic alkaloids is an exageration.
By weight, rue is definitely much stronger than caapi in terms of harmala quantity. Of course if people take more than their appropriate dose, things will get very uncomfortable (same with caapi or any other drug really), but that does not mean it is toxic. A large dose of most psychedelics can get very uncomfortable even if you`re still far off from the actual physically toxic dosages.
I think sometimes people mean
vasicine/vasicinone/deoxyvasicine which are generally considered `unwanted` and are present in syrian rue. But I think those alkaloids are only a problem if you`re a pregnant woman because they are uterotonic and abortifacient. Otherwise they might even have medicinal properties (brochodilator, expectorant, etc). I think in terms of LD50 toxicity they are safer than harmalas even.
There is a published report about a guy consuming 150g of rue to ease his pain after eating 1kg sheep testicles (lol), and while there were negative acute effects (vomiting, convulsion), after some hours the person was fine.
I don`t recommend overdosing on these plants of course, I think the 3-5g rue is enough for 99.9% of the people for MAO inhibition, and even those that for some reason want to experience the power of harmalas on their own in larger amounts, it still won`t be too much more than that.
This thread might also be of interest:
By the way ryusaki, do you do 3x boils when making rue tea? do you powder them before or pressure cook?