This research aims to develop an UHPLC method, based on core-shell column(i.e. superficially porous particles), for simultaneous determination of eight isoflavonoids including formononetin,(6αR,11αR)-3-hydroxy-9,10-dimethoxypterocarpan, calycosin-7-O-β-D-glucopyranoside,(3R)-7,2-dihydroxy-3,4-dimethoxyisoflavone, calycosin, ononin,(6αR,11αR)-9,10-dimethoxypterocarpan-3-O-β-D-glucopyranoside, and(3R)-7,2-dihydroxy-3,4-dimethoxyisoflavan-7-O-β-D-glucopyranoside in Astragali Radix. The analysis was performed on an Agilent Poroshell EC-C_(18 )column(2.1 mm×100 mm, 2.7 μm) with 0.2% formic acid solution(A)-acetonitrile(B) as mobile phase for gradient elution. The flow rate was 0.5 mL·min~(-1), with column temperature of 40 ℃ and the wavelengths were set at 260 and 280 nm. According to the results, all calibration curves showed good linearity(R~2>0.999 8) within the tested concentration ranges. Both the intra-and inter-day precisions for 8 isoflavonoids were less than 0.80%, with the mean recovery at the range of 94.71%-104.6%. Thus, the newly developed UHPLC method using core-shell column owned the advantages in terms of rapid analysis, low column pressure and less solvent consumption, thus enabling the usage of conventional HPLC systems. Meanwhile, quantitative evaluation was carried out for 22 batches of commercial Astragali Radix. It has been found that great variations occurred for the content of the individual isoflavonoids among different batches; in contrast, the total content of total 8 isoflavonoids(>0.1%) was stable in most samples, indicating that it was reasonable to involve all isoflavonoids as the chemical markers for the quality control of Astragali Radix.
Keywords: Astragali Radix; core-shell column; isoflavonoids; quantitative evaluation.