Compound used in publication
The academic standards require that the paper explains how the compound was obtained, so that the results can be reproduced by others. So, either:


The product is commercial, and the paper should say how it was obtained? if it's not stated, you can ask the authors for the provider and reference.
They extracted the product from a natural source, and then the authors will describe the extraction procedure.
They synthesized it, and thus they report the details of the procedure, as well as the reagents used (and providers). You can buy the reagents, and reproduce the synthesis.