Preparative separation of four individual flavonoids in Scutellaria barbata D. Don based on high selectivity polymeric adsorbents with different polarities.

The individual flavonoid component, scutellarin, scutellarein, luteolin and apigenin, in Scutellaria barbata plant was isolated based on the macro porous adsorbent with high adsorption selectivity. These adsorbents were synthesized based on the copolymerization of methyl acrylate and divinylbenzene (MA-co-DVB). So the polarity and the adsorption affinity of these adsorbents can be adjusted through changing MA content in the adsorbents. And then the ability of the adsorbent with different MA contents for isolation of these four individual flavonoid was also investigated. Adsorbents M2 and M4, with MA content of 25% and 45%, respectively, demonstrated the best separation ability. Complete separation of the four flavone compounds was achieved in a continuous process based on combination of adsorbents with different polarities (M2 and M4). Gradient elution using adsorbent M4 separated the four flavonoids into three fractions, which were determined to contain scutellarin, scutellarein and a mixture of luteolin and apigenin. The latter was separated completely by adsorbent M2 subsequently. All four compounds were obtained at high resolution and high recovery yield (96.7%, 94.1%, 95.8% and 93.8%, respectively), suggesting the efficiency of sequentially combined columns with different segregation patterns.

High selective purification of flavonoids from natural plants based on polymeric adsorbent with hydrogen-bonding interaction.

The efficient purification method of high purity flavonoids from natural plants was reported. A series of polymeric adsorbents with novel structure were synthesized based on the copolymerization of methyl acrylate (MA) and ethylene glycol dimethacrylate (EDGMA). Functional groups, such as ester, amino or amide group, were introduced into the adsorbent matrix, respectively, to produce the hydrogen-bonding interaction and enhance the adsorption selectivity towards flavone compounds. The influences of matrix structure and functional groups of synthesized adsorbents on the adsorption selectivity were investigated. The resins were applied to purify flavonoids in natural plants. It was illuminated that the adsorbent No. 3B with 15% EGDMA content and amide groups performed optimal selectivity to flavone compounds in Scutellaria barbata D.Don, from which the purity of flavonoids in extracts was obtained more than 50%, obviously higher than that from commercial adsorbents. The result of adsorption thermodynamics experiment showed that the isosteric adsorption enthalpy of No. 3B was in the range of 25-30 kJ/mol, which testified that the adsorption mechanism was related to hydrogen-bonding interaction. The method showed its universality via good effects on the purification of total flavonoids from Ginkgo biloba L., Radix puerariae and Hypericum perforatum L.