..the alkaloids are only (as far as i know) in the darker outer bark (infact in the inner layers where the capillaries are)..in other words the outer 5mm or so..to my knowledge there are no alkaloids in the paler wood core (the central 1-3cm in your picture)..though, there could be flavonoids, and there's one report of trace 5meo in A. maidenii core wood [see acacia thread here]..it's worth someone doing the experiment..