One more thing, the right chiral-substituted borane should provide a route to enantiopure THH from harmaline. Otherwise it's possibly a matter of column chroma using a chiral substrate. (But not always: Demystifying racemic natural products in the homochiral world - Nature Reviews Chemistry )(Stritida A (30) in particular resembles THH fairly  closely so Phenomenex Lux Cellulose-2 would possibly be a less desirable choice of column substrate.)

It would be nice to know if there are any other instances of racemic mixtures displaying different fluorescence properties than the pure enantiomers. DL-histidine is less soluble than the enantiopure form, for example ( https://pubs.rsc.org/en/content/articlepdf/2021/ce/d1ce01199e [downloads pdf]) so it is possible to imagine that other physical properties could vary in a similar way - and the intermolecular forces involved in crystallisation could well lead to variations in fluorescence behaviour. In absence of an expert in this specific field, this will require some scouring of the literature.