That's a good post. For example this article
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2992378/
Presents some disturbing evidence about the liver damage that FKB might cause, but it also contains this table
View attachment 4687
The paper does not say how the "water extraction" is done. Is it kneaded in a bag, and is the FKB and KL content of all the suspended particles measured? Or is it extracted the same way as with the other solvents: agitated and then centrifuged and the liquid on top decanted? The latter method will produce a very weak solution, which appears to be the case. Now it is interesting that the FKB/KL ratio is 0.06 in the acetone extract, but it is a factor of 10 smaller in the water extract. But nobody actually drinks "water extract", they drink mud containing everything that is in the root.
Another interesting thing is: clearly the relative solubility of FKB is lower than KLs in very polar solvents (water), than in semi-polar solvents (acetone, alcohol). What does that suggest about CO2? CO2 is a
non-polar solvent. If the trend continues one would expect there to be
more FKB in CO2 extract than in alcoholic extracts. Do vendors of extract products measure FKB? I don't see that in ROH's COA. They probably should measure that.
So, I don't know, I am thoroughly confused now, and fully admit that I am not an expert on this stuff. Just asking questions here.