Figure 5.

(a) Expanded region of tr-NOESY spectrum of the complex rosmarinic acid–BSA, recorded with mixing time of 350 ms at 600 MHz, showing the presence of negative NOEs of bound ligand. (b) Expanded region of tr-NOESY spectrum of the complex caffeic acid–salvianic acid–BSA, recorded with mixing time of 700 ms at 800 MHz showing the presence of negative NOEs, which are related to the protons of caffeic acid (labelled in red) and presence of positive NOEs, which are related to the protons of the major stereoisomer of salvianic acid (labelled in blue). For the minor isomer of salvianic acid only trivial NOEs between the H2 and H3 protons, which are overlaid with the zero-order artefacts of scalar coupling, are present.