Semi-preparative separation of dihydromyricetin enantiomers by supercritical fluid chromatography and determination of anti-inflammatory activities.

Dihydromyricetin, extracted from Ampelopsis grossedentata, has been widely used as one of Chinese health products in recent years. However, limited chiral separation method hinders the studies of pharmacological and pharmacokinetic activity differences of (+)-dihydromyricetin, (-)-dihydromyricetin, and (±)-dihydromyricetin. Herein, we developed a supercritical fluid chromatography approach for chiral separation of dihydromyricetin. Firstly, effects of chiral stationary phase, co-solvent, and flow rate of mobile phase have been investigated in detail. The resolution of 5.11 was achieved for dihydromyricetin enantiomers on amylose tris(3, 5-dimethylphenylcarbamate)-coated chiral stationary phase with the CO₂-methanol mixture (60:40, v/v). With respect to the enantiomeric purity, production rate and solvent consumption of 15 stacked injections, sample loading for semi-preparative separation of dihydromyricetin was optimized in three given equivalents set by volume overloading. Along with increase of sample loading per injection from 40 mg to 120 mg, the productivity of dihydromyricetin increased from 0.07 g (racemate)/g (chiral stationary phase) /24 h to 0.27 g (racemate) /g (chiral stationary phase)/24 h, and the consumption of methanol significantly reduced from 5.86 L/g (racemate) to 1.76 L/g (racemate). Moreover, (-)-dihydromyricetin exhibited better anti-inflammatory activity in TLR 2-related Raw 264.7 cells than (+)-dihydromyricetin and (±)-dihydromyricetin.