While studying production of phenols, I found that gallic acid (precursor to pyrogallol) is commonly extracted from tannin.

We know tannins are a huge part of the Mimosa root bark so maybe tannins could be extracted from either spent root bark of even before alkaloid extraction.

If tannins were removed, the whole extraction might be more convenient since the presence of tannins make this a "dirty work" (at least for me).

Since I can also make further use of tannin (especially hydrolyzable gallotannins), this took my interest.

Here is a nice publication about tannins in electronic form:

Tannin Handbook

I have currently little time to study this so I am leaving it for discussion for now...

Have you heard of egg-white fining? A low tech method used in the wine industry and I always use it on my MHRB brews. And I wonder what difference it makes in extractions.

I heard about it w.r.t. cactus extraction, but not MHRB... I will look it up. Anything that will clarify the mother liquor would be of great help.

I would also like to extract the hydrolyzable tannin, namely the gallic acid. This will be very useful in one of my chem projects, but synthesis is denied here so I won't elaborate. Just that gallic acid is of some value and it would be nice to obtain it from MHRB instead of throwing it out.

Using egg whites can def help to remove tannins from a brew if you dont want them but im not sure that will be of use if you actually want the tannins, since now you'll have a mess of coalesced egg proteins and tannins. Not sure how easy it is to separate it.

Another question I'd have to you blue.magic is, how will you know you have what you want? Do you have any type of analysis or way of testing to know if you have gallic acid?

Although I've never done it, I've heard that freezing a MHRB brew and thawing it results in gunk settling at the bottom of the jar and clears up the brew nicely. It seems to be the tannins that give the brew its murkiness, so I'm guessing this simple freeze-thaw procedure will do a good job at separating the tannins from the alkaloids and water?

I have to study this first, it seems to be a large topic. But this has been done industrially and all steps of the process seem to be doable at home.

It seems they autoclave the wood chips to release tannins, then simply separate them as aqueous extract for further purification.

https://www.tannins.org/how-to-extract-tannin/

You would have to check that MHRB tannins actually contain any gallic acid, as there are several different types of tannins.

Okay after some more learning, I got little bit more concerned about tannins of acacias, in particular MHRB.

My A/B extractions often end up in emulsified mess even though I dilute the mother liquor, use different solvents, different amounts of base etc.

Now I found that MHRB might actually be a pretty bad candidate for acid-base extraction. First of all, it is rich saponins, which are actually emulsifiers or soaps (!). They have both polar and nonpolar parts of the molecule, thus can bring the two solvents together (something we don't want).

MHRB also contains simple phenolic compounds such as catechol and pyrogallol. If one adds too much of a strong base (NaOH, KOH), reactive phenolates/alkoxides are formed. I used to add just a lots of base, but now I am more careful...

Strong bases also hydrolyze tannins. This applies only to so called "hydrolyzable tannins". These are ester of carboxylic acids (e.g. EGCG = epigallocatechin gallate, is a gallocatechin ester of gallic acid). NaOH or KOH with break the ester bond, releasing the carboxylic acid as sodium/potassium salt. I found that re-acidifying the mother liquor causes HUGE precipitation and thickening. This might be caused by the gallic acid as it has poor water solubility, but maybe just caused by the acid salt formation.

Fortunately, MHRB seems to contain mostly non-hydrolyzable (i.e. condensed) tannins. These have varying water solubility and might be responsible for the changes in mother liquor viscosity depending on temperature.

Condensed tannins can be removed with formaldehyde, which causes their polymerization and subsequent precipitation in a so called Phenol-formaldehyde resin (the tannins are cross linked by methylene bridges: -CH2- coming from the formaldehyde: O=CH2) . This is certainly not advisable as formaldehyde is hazardous for amateurs. The resinification process might also trap alkaloids.
There are interesting studies into the utilization of such resins, even from Mimosa tenuiflora specifically.

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After looking into these topics, I will try filtering re-acidified mother liquor before final basification and extraction. This will be done to remove impurities of the phenolic kind.

I will also revisit dry teks and using other solvents (acetone, ethanol etc.) to avoid issues of hydrolysis.

Finally, I will revisit using weaker base, like sodium carbonate (Na2CO3) instead of sodium hydroxide (NaOH), to prevent ester hydrolysis and the formation of alkoxides.

Initial extraction from damp basified MHRB paste with acetone OR with ethanolic ammonia followed by re-acidification, filtering and then extraction.

Looking forward to an update on this. Thanks for sharing your research so far.

Here you can download the tannin book pdf. you can also find LOTS of chem books in this great site!