Fig. 4

Results of UPLC-ESI-Q-TOF-MS/MS analysis. a Chromatogram of proto catechuic acid-protocatechuic acid dimer after the extraction of [C₁₄H₁₀O₈-H]⁻.a1 Primary MS spectra of protocatechuic acid-protocatechuic acid dimer. a2 Secondary MS spectra of protocatechuic acid-protocatechuic acid dimer. b Chromatogram of gallic acid-gallic acid dimer after the extraction of [C₁₄H₁₀O₁₀-H]⁻. (B1) Primary MS spectra of gallic acid-gallic acid dimer. c Chromatogram of hyperoside-hyperoside dimer after the extraction of [C₄₂H₃₈O₂₄-H]⁻. c1 Primary MS spectra of hyperoside-hyperoside dimer. c2 Secondary MS spectra of hyperoside-hyperoside dimer. d Chromatogram of 2′′-O-galloylhyperin-2′′-O-galloylhyperin dimer after the extraction of [C₅₆H₄₆O₃₂-H]⁻. d1 Primary MS spectra of 2′′-O-galloylhyperin-2′′-O-galloylhyperin dimer. d2 Secondary MS spectra of 2′′-O-galloylhyperin-2′′-O-galloylhyperin dimer. e Chromatogram of quercetin-quercetin dimer upon extraction of [C₃₀H₁₈O₁₄-H]⁻. e1 Primary MS spectra of quercetin-quercetin dimer. e2 Secondary MS spectra of quercetin-quercetin dimer