I'm convinced that the alkaloids in B. caapi are heavily complexed with other things (tannins?).
My reasoning behind this: harmala acetates are horribly bitter and mixing them into caapi brews doesn't really make them less bitter. However, if I simmer such a mix for 15 minutes, the bitterness disappears - presumably due to complexation. If added harmala acetates undergo complexation in caapi brews, it makes sense that the same would happen to the naturally occurring harmala salts during the decocting.

My question is: if that's indeed the case, does it pose a problem in the simple A/B caapi extraction? E.g. some of the alkaloids being trapped in water-soluble complexes and not precipitating? Or does the base de-complex them?

Interesting question. Generally tannins are known to cause complexes with proteins. Although alkaloids have been used as a way to analyze tannins and tannins have been used as a way to precipitate and analyze alkaloids.

Here is an example of whats called the tannic acid test for alkaloids:

https://www.youtube.com/watch?v=IAFDYmqXYMk

Here are some publications that discuss topic although one is not in english and the other I is very old and can't find full text:

https://pubs.rsc.org/en/.../an/an9295400316/unauth#!divAbstract

https://www.jstage.jst.g..._9_854/_article/-char/en

I wonder if some kind of tannic acid precipitation could be useful in alkaloid extractions??

That's a distinct possibility. Tannic acid is quite readily available for winemaking supplies.

One thing we need to bear in mind - and I've mentioned this before - is that there are several different types of tannins. Besides the condensed gallic acid units of tannic acid itself, we have the somewhat similar ellagitannins, the condensed flavonoids of the gallocatechins, and the Lamiaceous pseudo-tannins as typified by rosmarinic acid.

Distinguishing the type of tannin for the plant material concerned is at least worthy of consideration when developing extraction procedures.

Still, it seems like the precipitation of a number of alkaloids is fairly generic with a wide range of tannins and polyphenols.

Would the presence of acetic acid (which is stronger than tannic acid) prevent such precipitation?

I think that would depend on concentration of acetic acid. If pH is too low then yea I think it would prevent.



For sure tannins is quite a broad term and the structures can get wild.