When buying or researching supplements, it would be pretty cool to note what form the supplement is in. Beyond the state of the supplement (powder or solution; supplements tend to not be sold in a gaseous or plasma phase) or the delivery vesicle (tablet, capsule, powder, etc.) the actual molecule can vary.
Some compounds are simple. Caffeine is caffeine. If you look at the molecule its just going to be the caffeine molecule. At this moment in time, there are no fancy and stylish changes to the molecule to change its properties around.
Other supplements tend to have the same basic structure with slight modifications on it. Carnitine is a basic amino acid that is commonly sold in one of four forms; L-Carnitine, Acetyl-L-Carnitine, Carnitine-L-Tartrate, or Glycine Propionyl-L-Carnitine. ALCAR and GPLC are just the carnitine molecule bound to a small side-chain (acetyl group in the first one, a propionic acid in the second one) and LCLT is a salt of carnitine. The properties of carnitine are changed around a little bit with each form, with LCLT having a quicker spike in the blood, GPLC being nicer to blood flow, and ALCAR being nicer to the brain.
For all intents and purposes, a parent molecule that has these changes made to it should be treated as a completely different molecule. We got a bit lucky with Carnitine as all the forms do still act like L-Carnitine, but just a little bit different or 'specialized' if you will. Not all compounds are so straight forward.
Take, for example, the bioflavonoid kaempferol. If we add two sugars we actually get the completely different supplemental profile of Horny Goat Weed, the active component of horny goat weed. Usually adding sugars changes properties slightly, as we can see with the bioactivities of cyanidin and its 3-glucoside. The changes are physically kinda the same, but the effects of the new compound are drastically changed.
So the entire point of this post, aside from cleverly putting forth the large scale of changes that we recently made to the caffeine and carnitine pages? Its that not all forms of the same molecule are the same, and should be researched independently.