Determination of protoberberine alkaloids in Rhizoma Coptidis by ERETIC ¹H NMR method

An alternative quantification approach called ERETIC (Electronic REference To access In vivo Concentrations) utilizing electronic reference-based proton nuclear magnetic resonance (¹H NMR) spectroscopy techniques has been successfully introduced in our present study to simultaneously determine the contents of five major active protoberberine alkaloids (berberine, coptisine, jatrorrhizine, palmatine and epiberberine) in Rhizoma Coptidis, one of the most commonly used traditional Chinese medicines (TCM). The NMR experimental conditions including deuterated solvent, relaxation delay time, and ERETIC transmitter power level were optimized, and the developed method was validated in terms of precision, reproducibility, stability, accuracy, recovery, and limit of quantification (LOQ). The recoveries of the five tested alkaloids ranged between 89.94 and 97.72% for berberine, 90.87 and 100.05% for coptisine, 98.35 and 107.57% for jatrorrhizine, 95.37 and 101.26% for palmatine, and 93.18 and 98.00% for epiberberine, respectively, and LOQ was 0.1 mM for berberine. The high universality, accuracy, reproducibility, and efficiency of the ERETIC method demonstrated in this work suggest that this method could serve as a highly potential quantification alternative for quality assessment of TCM.