Cluster A contained 26 compounds and typically exhibited elevated baseline signals, particularly in the fingerprint region. It comprised aromatic, amide, or ester groups and is characterized by a complex structure (except 69 and 4892, Figures and). An image of this superposition is shown in Figures and. The pairs of individual branches had similar chemical structures. However, the similarities between the pairs of branches located far apart were small. The A-1-1-2-1 branch exhibited a naphthalene structure. The baseline for compound 4892 was particularly high at approximately 2000-4000 cm -1 , yet it was classified within the cluster. The A-1-1-2-2-1 branch contained an aromatic ring and an amino group. Its spectrum was similar in part to the fingerprint region with C-H stretching at approximately 3000 cm -1 . Owing to the complexity of the structures in this branch, partial structural similarities is similar, but the TC was low. The A-1-1-2-2-2 cluster exhibited peaks corresponding to C-H, N-H, and C=O stretches, and its chemical structure was similar to that of the B and D clusters. Notably, quinine di-1,1'-oxide was assigned to a different cluster than quinine.