After going on a wiki spiral I came across this page http://www.agriinfo.in/d...perid=4&topicid=1593
Many acacia apparently have a large percent of tannins in their bark.
The tannins break down at 21 degrees C so it means if you are extracting from a species with a high percentage then it is evident that an acid cook would make the alkaloids much more accessible. With a stb your solvent would be facing a wall of treacle.
Interestingly enough these flavanoids are considered beneficial for humans.

..most studied acacias contain Diol Condensed Tannins (which are related to flavonoids)..as opposed to contain tannic acid..

Ok thanks nen, I read they are also used as a remedy for diarahoea.