Surprising UV Fluorescence in TLC of Mescaline-Containing Cacti

[Grasshoppers]

I recently applied the TLC approach we commonly use for Phalaris alkaloid profiling to several mescaline containing cactus samples, and the results were unexpected.

After storage in a dark box, the plates developed intense fluorescence. Based on these observations, it seems plausible that the intrinsic fluorescence of cactus alkaloids can provide meaningful insight into their chemical profiles without the need for additional visualization reagents.

I want to emphasize that this type of analysis is very simple, fast, and inexpensive, relying on readily available materials. The observations suggest that, under appropriate conditions, alkaloid profiles in cacti may be examined with minimal analytical overhead.


275nm wet plate


275nm dry plate


275nm 1 week


365nm wet plate


365nm dry plate


365nm 1 week

 

[aizoaceous]

Very interesting. I believe mescaline is usually visualized with ninhydrin or another similar stain. That's reasonably available (it's often used to reveal latent fingerprints as a science demonstration) but messy and inconvenient. UV by quenching of the plate fluorescence is not preferred due to weak absorption at the usual 254 nm.

Have you confirmed this works with pure (recrystallized a few times) mescaline, and that the Rf corresponds to mescaline? Does the fluorescence develop faster with heat? With an oxidizing stain similar to those used by Kato et al. for tryptamines?

 

[Grasshoppers]

I did not systematically investigate the cause of the observed fluorescence, but I speculate that several factors may be involved.

1. Mescaline may have undergone side-chain oxidation, analogous to its known in vivo metabolism, forming compounds such as 3,4,5-trimethoxyphenylacetic acid (TMPA) or 3,4,5-trimethoxybenzoic acid (TMBA). These compounds, or further demethylated derivatives with catechol-like structures, could exhibit blue fluorescence when excited at ~275 nm, as some methoxylated aromatic acids are known to emit in the 400–450 nm range. The mildly acidic silica gel on the TLC plate may have catalyzed such transformations, particularly from the freebase.
2. The freebase form may partially volatilize, become protonated by the silica surface, or interact with plate components, altering its photophysical properties. Co-spotted cactus alkaloids or other impurities could also contribute to the observed fluorescence.

This observation was incidental to ongoing work on high-DMT Phalaris lines. I will share further insights if additional mescaline-related findings emerge. Those cultivating cacti and interested in analytical testing are encouraged to explore this phenomenon further.