data was recorded at 400 MHz for 1H and 100 MHz for 13C
with Varian Inova NMR spectrometers or 600 MHz for 1H and 150 MHz for
13C with an Agilent DD2 NMR spectrometer. LC-MS was conducted
with an Agilent 6120 Quadrupole MSD mass spectrometer equipped with an Agilent
1200 Series Quaternary LC system and an Eclipse XDB-C18 column (150
× 4.6 mm, 5 μm). HR-ESI-MS spectra were recorded on an AB SCIEX
Triple TOF 5600 System. Analytic HPLC was performed with Waters Alliance 2695
separation module equipped with a Waters 2998 diode array detector and an
analytical Apollo C18 column (250 mm × 4.6 mm, 5 μm).
Semipreparative HPLC was performed with a Waters 600 controller and pump
equipped with a 996 diode array detector, 717 plus autosampler, and an Apollo
C18 column (250 × 10 mm, 5 μm) purchased from
Grace. All solvents used were of ACS grade and purchased from Pharmco-AAPER.
Sephadex LH-20 (25–100 μm) was purchased from GE
Healthcare. A solution of resazurin sodium salt (Alfa Aesar) was prepared to 1
mg/mL in sterile distilled water.