Table 1. HPLC analysis condition for DHNA

Item	Operation condition
HPLC system	YL9100 Plus HPLC System (Young In, Korea)
Column	TSKgel ODS-100V column phase C18 (4.6 × 150 mm, 5 μm; TOSOH, Japan)
Solvent	Solvent A: 0.1% formic acid in waterSolvent B : 0.1% formic acid in acetonitrile
Gradient	0 min (A 80%, B 20%) → 10 min (B 100%) → 13 min (B 100%) → 15 min (A 80%, B 20%) → 20 min (A 80%, B 20%)
Column temperature	40°C
Flow rate	1 mL/min
Injection volume	20 μL
UV detection	UV 254 nm