Abstract: An analytical method to determine flavonoids such as morin hydrate, quercetin and kaempferol in mulberry leaves was proposed using ultrasonic-assisted extraction coupled with HPLC. The extraction solvent used was 1-butyl-3-methylimidazolium chloride ([BMIM]Br). The chromatographic separation was performed on Phenomenex C18 column (250 mm × 4.6 mm, 5 μm) using a mobile phase made up of methanol and 0.1% phosphoric acid at a flow rate of 1.0 mL/min by gradient elution. The detection wavelength and column temperature were set as 365 nm and 34 ℃, respectively. This method showed good linearity in the range of 0.0065–130 μg/mL (r = 0.9999) for morin hydrate, of 0.0064–128 μg/mL (r = 0.9999) for quercetin, and of 0.0042–84 μg/mL for kaempferol. The limit of detection, LOD, (RSN = 3) of this method was 0.99, 1.31 ng/mL and 0.64 ng/mL for morin hydrate, quercetin and kaempferol, respectively. Average recoveries ranging 90.00% to 95.31% were obtained for these three flavonoids (n = 3). This method was simple, fast, accurate, sensitive, cheap and environment-friendly and could provide a scientific way to determine flavonoids in mulberry leaves.

Key words: ionic liquid, ultrasonic assistance, HPLC, flavonoids, mulberry leaves