I think Aspartame (splenda) can be reduced to aspartic acid under basic conditions but don't quote me on that. Try looking at apspartic acid and aspartame since those are NMDA agonists although might not be competitive enough or have a high enough affinity to do much.
Also, I'm pretty sure Seroquel is a potent 5-HT2a/c antagonist, not agonist although I can't remember about 1a. Also, FWIW, I've used Seroquel to successfully abort LSD, DXM, Mescaline, mushroom and DMT trips with success and those both have serotonergic effects (although the affinities are relatively low, they are actually analogous, etc) but I was young and had no idea about serotonin syndrome. If you have naloxone that might work too.
Personally, I would start thinking of having your trip sitter (guessing you don't have one) take you to an ER because you took Tramadol and either substance by itself can be toxic in ODs, but especially when taken together (serotonin syndrome) and especially considering that Tramadol lowers the seizure threshold. The "shakey" feeling sounds pretty troubling...
Obviously, be more careful next time.