*2.9. Purification of Mangiferin Glycosides*

The purification process was a previously described method [41]. A 100 mL reaction mixture containing 50% (*w*/*v*) maltodextrin, 1 mg/mL mangiferin, 5.6 μg/mL *Pg*MA, and 50 mM PB (pH 7) was incubated at 65 ◦C for 24 h. After the large-scale reaction, an equal volume of methanol was added to stop the transglycosylation. The mixture was then filtrated through a 0.2 μm nylon membrane, and the filtrate was injected in a preparative YoungLin HPLC system (YL9100, YL Instrument, Gyeonggi-do, South Korea) equipped with a preparative C18 reversed-phase column (10 μm, 20.0 i.d. × 250 mm, ODS 3; Inertsil, GL Sciences, Eindhoven, The Netherlands) for the purification of biotransformation products. The operational conditions for the preparative HPLC analysis were the same as those in the HPLC analysis. The elution corresponding to the peak of the metabolite in the HPLC analysis was collected, condensed under a vacuum, and then crystallized by freeze drying. Finally, 20.1 mg of compound (**1**) and 9.3 mg of compound (**2**) were obtained, and the structures of the compounds were confirmed with nucleic magnetic resonance (NMR) and mass spectral analyses. The mass analysis was performed using the Finnigan LCQ Duo mass spectrometer (ThermoQuest Corp., San Jose, CA, USA) with electrospray ionization (ESI). 1H- and 13C-NMR, distortionless enhancement by polarization transfer (DEPT), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC), correlation spectroscopy (COSY), and nuclear Overhauser effect spectroscopy (NOESY) spectra were recorded on a Bruker AV-700 NMR spectrometer at ambient temperature. Standard pulse sequences and parameters were used for the NMR experiments, and all chemical shifts were reported in parts per million (ppm, *δ*).

The composition of compound (**1**) was as follows: light yellow powder; mp 233–235 ◦C; ESI/MS *m/z*: 583.4 [M-H]−, 565.3, 331.0, 300.9, 259.3; 1H-NMR (DMSO-*d6*, 700 MHz): H*δ* 3.05 (1H, t, *J* = 5.6 Hz, H-4), 3.15 (1H, d, *J* = 6.3 Hz, H-2), 3.20 (1H, t, *J* = 9.1 Hz, H-3 ), 3.29 (1H, t, *J* = 9.1 Hz, H-4 ), 3.33 (1H, m, H-5 ), 3.35 (1H, m, H-5), 3.38 (1H, m, H-3), 3.46 (1H, m, H-6a), 3.52 (1H, d, *J* = 9.1 Hz, H-6b), 3.62 (1H, d, *J* = 9.8 Hz, H-6 a), 3.70 (1H, dd, *J* = 11.2, 4.2 Hz, H-6 b), 4.02 (1H, br, H-2 ), 4.58 (1H, d, *J* = 9.1 Hz, H-1 ), 4.73 (1H, *J* = 4.2 Hz, H-1), 6.36 (1H, s, H-4), 6.86 (1H, s, H-5), and 7.37 (1H, s, H-8). 13C-NMR (DMSO-*d6*, 175 MHz): C*δ* 60.6 (C-6), 66.9 (C-6 ), 70.0 (C-4), 70.2 (C-2 , 4 ), 72.1 (C-2), 72.5 (C-3), 73.2 (C-1 ), 73.3 (C-5), 78.9 (C-3 ), 79.7 (C-5 ), 93.3 (C-4), 98.7 (C-1), 101.3 (C-9a), 102.6 (C-5), 107.5 (C-2), 108.1 (C-8), 111.8 (C-8a), 143.7 (C-7), 150.8 (C-10a), 154.0 (C-6), 156.2 (C-4a), 161.7 (C-1), 163.8 (C-3), and 179.1 (C-9).

The composition of compound (**2**) was as follows: light yellow powder; mp 227–229 ◦C; ESI/MS *m/z*: 745.3 [M-H]−, 727.3, 403.3, 385.0, 331.0, 313.2, 301.2; 1H-NMR (DMSO-*d6*, 700 MHz): H*δ* 3.03 (1H, t, *J* = 9.1 Hz, H-4), 3.19 (1H, dd, *J* = 9.1, 3.5 Hz, H-2), 3.21 (1H, m, H-3 ), 3.23 (1H, m, H-2), 3.30 (1H, m, H-4 ), 3.34 (1H, m, H-4), 3.36 (1H, m, H-5 ), 3.38 (1H, m, H-3), 3.41 (1H, br, H-2 ), 3.42 (1H, m, H-5), 3.44 (2H, m, H-6), 3.46 (1H, m, H-5), 3.55 (2H, m, H-6), 3.60 (1H, m, H-3), 3.64 (1H, m, H-6 a), 3.71 (1H, m, H-6 b), 4.58 (1H, d,

*J* = 9.8 Hz, H-1 ), 4.75 (1H, d, *J* = 3.5 Hz, H-1), 4.95 (1H, d, *J* = 3.5 Hz, H-1), 6.36 (1H, s, H-4), 6.86 (1H, s, H-5), and 7.37 (1H, s, H-8). 13C-NMR (DMSO-*d6*, 175 MHz): C*δ* 60.0 (C-6), 60.7 (C-6), 67.2 (C-6 ), 69.8 (C-4), 70.2 (C-2 , 4 ), 70.8 (C-5), 71.6 (C-2), 72.6 (C-2), 73.1 (C-3), 73.2 (C-1 ), 73.3 (C-3), 73.4 (C-5), 78.9 (C-3 ), 79.7 (C-5 ), 79.8 (C-4), 93.3 (C-4), 98.6 (C-1), 100.9 (C-1), 101.3 (C-9a), 102.6 (C-5), 107.4 (C-2), 108.1 (C-8), 111.7 (C-8a), 143.7 (C-7), 150.8 (C-10a), 154.0 (C-6), 156.2 (C-4a), 161.8 (C-1), 163.8 (C-3), and 179.1 (C-9).
