Selective Extraction of Flavonoids from Sophora flavescens Ait. by Mechanochemistry

Abstract

Flavonoids from Sophora flavescens were selectively extracted by mechanochemical-promoted extraction technology (MPET) after using response surface methodology to determine the optimal extraction parameters. The highest yield of 35.17 mg/g was achieved by grinding the roots with Na₂CO₃ (15%) at 440 rpm/min for 17.0 min and water was used as the sole solvent with a ratio of solvent to solid material of 25 mL/g. Flavonoids prepared by MPET demonstrated relatively higher antioxidant activities in subsequent DPPH and hydroxyl radical scavenging assays. Main constituents in the extracts, including kurarinol, kushenol I/N and kurarinone, were characterized by HPLC-MS/MS, indicating good selective extraction by MPET. Physicochemical property changes of powder during mechanochemical milling were identified by scanning electron microscopy, X-ray powder diffraction, and UV-Vis diffuse-reflectance spectroscopy. Compared with traditional extraction methods, MPET possesses notable advantages of higher selectivity, lower extraction temperature, shorter extraction time, and organic solvent free properties.

Keywords: Sophora flavescens Ait.; flavonoids; mechanochemical-promoted extraction technology; response surface methodology; selectivity.

Figure 1

Effects of different solid reagents on flavonoids yield (a): (1) blank group: no solid reagent; (2) sodium borate; (3) diatomaceous earth; (4) basic aluminum oxide; (5) Ca₂CO₃; (6) NaHCO₃; (7) Na₂CO₃; (8) control group: conventional agitation of unmilled S. flavescens powder and unmilled Na₂CO₃; (9) control group: conventional agitation of milled S. flavescens powder and unmilled Na₂CO₃; Effect of Na₂CO₃ and NaHCO₃ concentration on flavonoids yield (b). Data are presented as mean ± SD (n = 3).

Figure 2

UV-Vis absorption spectra.

Figure 3

Response surface (3D) showing the effect of variables on total flavonoid extraction. (a) rotational speed and grinding time; (b) solvent to material ratio and rotational speed; (c) solid reagents and rotational speed; (d) solvent to material ratio and grinding time; (e) solid reagents and grinding time; (f) solvent to material ratio and solid reagents.

Figure 4

HPLC for different extraction methods: (a) conventional heating extraction; (b) mechanochemical-promoted extraction technology.

Figure 5

Antioxidant activities of flavonoids. (a) DPPH radical scavenging activity; (b) hydroxyl radical scavenging activity. Data were presented as mean ± SD (n = 3).

Figure 6

SEM micrograph of: (a) physical mixture; (b) mechanochemical mixture.

Figure 7

X-ray diffraction spectra of (a) physical mixture; (b) mechanochemical mixture.

Figure 8

UV-Vis diffuse-reflectance spectra of: (a) physical mixture; (b) mechanochemical mixture.