Fig 9. Base-peak HPLC-ESI-MS chromatogram of the methanol extract of the strain HMS174-TYR^OP-HT^OP-ALR-K.

The two peaks circled in red are hydroxytyrosol (HT; left) and internal standard (dinitrophenol, IS, right). At the mass spectrum the characteristic ions of HT are denoted (pseudomolecular ion [M-H]- of HT at m/z 153.0562, the [M+FA-H]- adduct ion of HT with formic acid and the pseudodimer ion [M+M-H]- of HT), produced during the ionization process.