Chromatographic Fingerprint and Quantitative Analysis of Commercial Pheretima aspergillum (Guang Dilong) and Its Adulterants by UPLC-DAD

Guang Dilong is a Traditional Chinese Medicine prepared from the dried body of Pheretima aspergillum (E. Perrier), a species of earthworm. However, preparations of Guang Dilong may be adulterated by other species and a method of quality control is needed. A method was developed to analyze and authenticate commercial Guang Dilong, utilizing ultra-high performance liquid chromatography (UHPLC) coupled with diode array detection (DAD). Equipment included an Acquity UPLC HSS T3 column (100 mm × 2.1 mm, 1.8 μm). The mobile phase consisted of acetonitrile and 0.01% formic acid, pumped at 0.3 mL/min. Wavelength detection was at 260 nm. Twenty-two batches of confirmed P. aspergillum samples (reference) from different sources and 20 batches of adulterated samples were analyzed to establish a reference fingerprint for commercial Guang Dilong. Five peaks in the fingerprints of the reference batches were identified as characteristic; six characteristic peaks in the fingerprints of the adulterants were identified by comparing their retention time with those of the references. The total 42 batches of samples were compared with the reference fingerprint, and the fingerprints of the P. aspergillum samples were similar. The UHPLC-DAD method can simultaneously determine the contents of six compounds (hypoxanthine, xanthine, uridine, inosine, guanosine, and adenosine) in the reference and adulterated batches. The six compounds showed good regression (r > 0.9999) within test ranges. The recovery (accuracy) was 98.25 to 101.68%, with relative standard deviation <2.67%. In summary, this UHPLC-DAD method combines chromatographic fingerprint with quantification analysis and could be readily used as an efficient quality control method for Guang Dilong.