Table 5. Comparison of Natural Product and Drug Databases for the Occurrence Rates of the Possibility of Ring–Chain and Prototropic Tautomerism.
| total number of molecules | number of molecules capable of ring–chain
tautomerism |
number of molecules capable of prototropic tautomerism |
||||
|---|---|---|---|---|---|---|
| databases | database type | count | count | % | count | % |
| CHMIS-C | natural products (herbal medicines) | 8572 | 1141 | 13.3 | 4319 | 50.4 |
| NCI-NP | natural products (various types) | 124 701 | 22 875 | 18.3 | 73 005 | 58.5 |
| TCM | natural products (traditional chinese medicines) | 9127 | 1381 | 15.1 | 4875 | 53.4 |
| KEGG MEDICUS | drugs | 12 041 | 2180 | 18.1 | 7313 | 60.7 |
| AMS | screening samples and building blocks | 5 755 574 | 457 710 | 8.0 | 4 369 069 | 75.9 |