So I tried too a small extraction of "Black Caapi Shredded" sold by a UK based vendor, and similar to what Amygdala reported...
33g of shredded root where brewed in 250ml water + 500mg fumaric acid x4, extract was reduced and basified with 2,5g NaOH dissolved in water, and after the first results excess base was added (2,5g more) to make sure that everything crashed out.
Precipitates are dark and barely distinguishable from the basified solution, even after settling. UV light gave no visible fluorescence... basic solution looks dark grey/green and the solids look quite similar, with a more brownish tint, under black light.
This doesn't look like caapi at all. I will try to siphon out the water and clean the precipitates, but it's all very dark in there.
"The Menu is Not The Meal." - Alan Watts