The Fragments tab visualises the resulting fragments. Similar to the Molecules tab, the resulting fragments are displayed on multiple pages. In addition to the SMILES representation and the 2D structure of each fragment, one column shows a randomly selected parent molecule of the corresponding fragment (see Figure ). The Frequency column indicates how often the corresponding fragment appears in the fragmented set of molecules. The column Molecule Frequency contains the number of molecules in which this fragment appears. In Figure , the five most frequent fragments (functional groups and alkane remnants) resulting from the Ertl algorithm analysis of the COCONUT natural product database are displayed. The most frequent fragment is a hydroxy group connected to an aliphatic carbon atom. Almost as frequently, a single aliphatic carbon atom or methyl group was detected, followed by an ether group that is only half as frequent. In fourth place, there is a hydroxy group connected to an aromatic carbon atom, as it results, i.a., from a phenol (the aromatic character of the attached carbon atom is indicated in the SMILES representation of the group, "[H]Oc", by lower-case letter notation; this corresponds to the fragment depiction where the carbon atom is not fully saturated with hydrogen atoms). The fifth most frequent FG is an alkene group occurring 165,396 times. The fragments are sorted according to their absolute frequency in Figure . If they would be sorted according to their molecule frequency, the ranking would be different with the methyl group being at the top. The comparatively high number of hydroxy groups detected in absolute numbers as opposed to the molecule frequency means that natural products usually have multiple substituents of this type (3.3 on average, dividing the frequency by the molecule frequency). One type of structure that may be responsible for this trend is glycosidic moieties that occur frequently in natural products . The results of this proof-ofconcept analysis using MORTAR are in general agreement with an analogous systematic study of functional group frequencies in natural products conducted by Ertl et al. .