The Portal features a class of compounds we termed Historical Compounds. These small molecules are typically non-selective or not sufficiently potent compared with other available chemical probes to merit the probe designation. We opted for the name "Historical Compounds" to provide a category that allows us to distinguish them from chemical probes. The title recognizes that many of these compounds were once valuable, for example if they were the first compound available to study a protein target or target family. We also recognize that some scientists select non-specific compounds for experiments precisely because they are non-specific, as these compounds allow them to impact the activity of many proteins at the same time. Our goal with this category of compounds is not to indicate that they cannot be useful in research. Rather, we hope to discourage the misapplication of these reagents as if they were chemical probes (i.e., specific and selective tools for a particular target).
In the Portal, historical compounds can be readily distinguished from chemical probes: they are catalogued without much of the detailed validation information that accompanies a probe, they feature a generic Historical compound image, and they are not rated by our SAB. To ensure there is no confusion, each historical compound is also designated by a generic and specific note to clarify the categorization. The generic note simply indicates that it is a historical compound; the specific note provides some context for why it is considered a historical compound. For an example, please visit the staurosporine page.