Compound stability analysis
Three sets of 10mg of HSG4112 and glabridin were each added to 10ml of
MeOH, 1% HCl in MeOH (v/v%), or 1% NaOH in MeOH (w/v%). At 0, 8, 12,
24, 48, and 72 hr time-point, 1ml aliquots from each condition were
placed in HPLC (LC2030C, Shimadzu, Japan) in order to determine the
content (µg/ml) of respective compounds; 9ml of internal standard (10mg
of (R /S )-3”,4”-dihydro-4’-O-methyl-glabridin dissolved
in 100ml of acetonitrile) was added at each aliquots for data
normalization. HCl, NaOH, MeOH (Sigma-Aldrich Co., St. Lousi, MO, USA),
HPLC-grade acetonitrile and formic acid (Thermo Fisher Scientific,
Waltham, MA, USA), and deionized water (Milli-Q purification system,
Millipore, Bedford, MA, USA) were used. The following HPLC condition was
used: mobile phase (A:B = 80:20) A: 0.1 formic acid (MeOH:ACN3 = 1:3) B:
0.1 formic acid (DI water), column (Syncronis C18, 150 x 2.1mm, 5µm),
flow rate (0.5ml/min), and UV detection (280nm).