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Table 1 Example of a molecular formula search for C15H12O7 in different chemical databases. Search date: July 2007

From: Metabolomic database annotations via query of elemental compositions: Mass accuracy is insufficient even at less than 1 ppm

Database name Compounds found Total database entries
Chemical Abstracts (CAS) 181 24,000,000
Beilstein Database (MDL) 166 8,000,000
Dictionary of Natural Products (DNP) 129 170,000
PubChem (NIH) 19 800,000
Available Chemicals Directory (MDL) 6 400,000
ChemIDplus (NIH) 6 370,000
KEGG (Kyoto University) 3 13,000
NIST05 (NIST mass spectral database) 2 163,000
MOLGEN molecular isomer generator (allowing 2 benzene groups; 1 ether group, 1 keto group; 5 hydroxy groups) 788,000 -