Examples of the UHPLC–DAD–MS/MS fingerprints recorded
by the Engström method in a single run for the E. calycogona subsp. miracula leaf sample: (A) UV traces at 280 nm, (B) HHDP fingerprint, (C)
galloyl fingerprint, (D) (epi)gallocatechin fingerprint, (E) PD oligomer
fingerprint, (F) PD polymer fingerprint, with the inset showing the
PD extension unit (bold line) and terminal unit (dashed line) fingerprints
after 30 smoothing operations to the raw data, (G) (epi)catechin fingerprint,
(H) PC oligomer fingerprint, and (I) PC polymer fingerprint, with
the inset showing the PC extension unit (solid line) and terminal
unit (dashed line) fingerprints after 30 smoothing operations to the
raw data. The five main UV peaks at panel A are presented by flavonol
glycosides and caffeoyl quinic acids that can be detected by the Engström
method as well (kaempferol, quercetin, myricetin, and quinic acid
fingerprints). The peaks with asterisks show the tannins that could
be characterized by the help of the 2D fingerprints and the full-scan
mass spectra.