Excellent question. I thought the yellow stuff was naturally-sourced material. Synthesis using zinc reduction will definitely produce racemic material (presumably you didn't use a chiral auxiliary...) The natural material at least has a chance of being in enantiomeric excess. Running the 2-d tlc should help clear up whether the spots are THH and only THH.

Has anyone else replicated this yellow fluorescence with natural, optically pure THH? Is the weaker fluorescence of the synthed material due to some paradoxical self-quenching that only occurs through the two enantiomers 'fighting' each other?! Or is there something, some impurity, from the reduction process that is affecting the result? Traces of zinc? Dimers?

It would be fantastic to see results from specific tests on separated enantiomers compared with the racemic material, and also borohydride-produced material compared with the stuff made using zinc, maybe even THH synthesised from 6-MeO-T via Pictet-Spengler.

I still find your results very intriguing!