ABSTRACT
The method of quantitative nuclear magnetic resonance spectroscopy (qNMR) for determination of epigoitrin in Radix Isatidis was established based on solid phase extraction (SPE).The twice ultrasonic extraction method using pure water was used for fully extracting epigoitrin in sample, and then the extraction was enriched and concentrated by poly-Sery MCX SPE cartridge.The effect of sample pretreatment and qNMR experimental conditions was investigated.The qNMR experiment conditions were selected using DMSO as solvent, calibrated 2,3,5-triiodobenzoate as internal standard, and P1(pulse width)=14.1 μs, d1(pulse delay time)=5 s, NS(number of scan)=256.The .1H-NMR peaks of δ 5.365-5.399 (H-7b, d, 1H) of epigoitrin were chosen as the quantitative peaks.Method validation was performed including precision (intra-day precision RSD was 0.5%, and the inter-day precision was 0.8%), linearity (correlation coefficient r>0.9991), LOD (0.05 mg/g, standard curve method) and LOQ (0.19 mg/g, S/N≥150).The recoveries of the SPE-qNMR were 97.4%-101.7%.The result showed that the method was stable, accurate and reliable.With this method the epigoitrin in a real Radix Isatidis was determined to be <0.19-1.26 mg/g.SPE combining with qNMR could extend the application field of qNMR, especially in the detection of low-content component in complex samples.
ABSTRACT
A quantitative nuclear magnetic resonance spectroscopic ( qNMR) method was established for the simultaneous determination of resveratrol and polydatin in Polygonum Cuspidatum traditional Chinese herb cuts and granule. The 2_step ultrasonic extraction method using 80% alcohol and acetone was used for fully extracting these two components in samples before qNMR determination. The qNMR experimental conditions were investigated and deuterated dimethyl sulphoxide_deuterium oxide (10∶1, V/V) was selected as solvent, the pulse delay time was 5 s, the scan number was 32, 2,3,5_triiodobenzoate was used as internal standard which was calibrated with primary standard substance of potassium hydrogen phthalate. The 1 H_NMR peaks atδ6. 388-6. 391 ( d, 2H) of resveratrol and δ 6. 322-6. 330 ( t, 1H) of polydatin were chosen as the quantitative peaks. Method validation was performed in terms of precision ( RSD0. 999), limit of detection (0. 23 g/L for resveratrol and 0. 24 g/L for polydatin) and limit of quantitation ( resveratrol 0. 69 g/L, polydatin 1. 57 g/L), recovery ( resveratrol 97. 7% -103 . 5%, RSD=2 . 4%, polydatin 94 . 5%-99 . 2%, RSD=1 . 6%, including the sample extraction and preparaton process) . The results showed the reliability of qNMR for traditional Chinese medicine assay. The resveratrol and polydatin in Polygonum Cuspidatum real cuts and granule samples were experimental determined as 3. 57-5. 69 mg/g and 12. 73-24. 07 mg/g, respectively.