Ultrasonic microwave-assisted extraction coupled with high-speed counter-current chromatography for the preparation of nigakinones from Picrasma quassioides (D.Don) Benn.

Introduction: Nigakinones are the main effective compounds of Picrasma quassioides (D. Don) Benn and are widely used in traditional Chinese medicine, therefore a rapid and efficient separation and purification method is necessary.

Objective: To develop a new method based on ultrasonic microwave-assisted extraction (UMAE) and high-speed counter-current chromatography (HSCCC) for the rapid separation and purification of nigakinone and methylnigakinone from P. quassioides (D.Don) Benn.

Methodology: Response surface methodology (RSM) was used to optimise the extraction conditions of UMAE: 10.0 g of original sample was extracted with 210 mL of 90% (v/v) aqueous methanol at 60°C for 13 min, ultrasonic power was 100 W and microwave power was dynamically adjusted to the given temperature. After extraction, the extract was introduced into the HSCCC and separated with a hexane:ethyl acetate:methanol:2% acetic acid (9:11:9:11, v/v/v/v) solvent system.

Results: About 2.1 mg nigakinone with purity of 96.8% was obtained in one step within 200 min, methylnigakinone was also obtained with a purity of 75.6%. Their chemical structures were identified with ESI-MS and ¹H-NMR.

Conclusion: UMAE coupled with HSCCC was found to be a promising and feasible alternative method to separate and purify alkaloids from natural herbs such as P. quassiodes.