HPLC-ESI-MS analysis of the fermentation culture of Sa. erythraea EX103.

Total ion current chromatogram (i), and reconstructed base peak chromatograms for 6-deoxy-Er-A (ii), Er-A (iii), 6-deoxy-Er-B (iv), Er-B (v), 6-deoxy-Er-C (vi), Er-C (vii), 6-deoxy-Er-D (viii), and Er-D (ix) are recorded. Note that 6-deoxy-Er-A and Er-B, as well as 6-deoxy-Er-C and Er-D share the same molecular weights and similar polarities, their base peaks are thus overlapping.