Has anyone had this problem? I brewed a bit of shredded vine from a friend's property and the liquid had a bright green glow under blacklight but when I add base nothing precipitates and the tea clears up and no longer glows. It seems as if alkaloids are just disappearing, any ideas?

Still can't figure this out.

Wich base did you use ?
Can you verify by PH ?

I'm using a light lye solution as usual but getting no precipitation from a tea that appears to have MAOI.

If you can test the PH, it should be a good info.
While basing my rue tea, with sodium carbonate, i experienced something that seems similar to you, So i added a few drop of concentrated solution (NaOH) and it precipited.
i don't have a UV lamp to check that.
Another info seen recently on the nexus, some proteins or other compound glow at UV light (not only harmalas glow)