A fast,sensitive, and high‐throughput method for the simultaneous quantitation of three ellagitannins from Euphorbiae pekinensis Radix in rat plasma by ultra‐HPLC–MS/MS

A fast, sensitive, and high‐throughput ultra‐HPLC–MS/MS method has been developed and validated for the simultaneous determination of three main active constituents of Euphorbiae pekinensis Radix in rat plasma. After addition of the internal standard, plasma samples were extracted by liquid–liquid extraction with ethyl acetate/isopropanol (1:1, v/v) and separated on a CAPCELL PAK C₁₈ column (100 × 2.0 mm, 2 μm, Shiseido, Japan), using a gradient mobile phase system of methanol/water. The detection of the analytes was performed on a 4000Q UHPLC–MS/MS system with turbo ion spray source in the negative ion and multiple reaction‐monitoring mode. The linear range was 1.0–1000 ng/mL for 3,3′‐di‐O‐methyl ellagic acid‐4′‐O‐β‐d ‐glucopyranoside (i), 1.5–1500 ng/mL for 3,3′‐di‐O‐methyl ellagic acid‐4′‐O‐β‐d ‐xylopyranoside (ii), and 5.0–5000 ng/mL for 3,3′‐di‐O‐methyl ellagic acid (iii). The intra‐ and interday precision and accuracy of all the analytes were within 15%. The extraction recoveries of the three analytes and internal standard from plasma were all more than 80%. The validated method was first successfully applied to the evaluation of pharmacokinetic parameters of compounds 1 , 2 , and 3 in rat plasma after intragastric administration of the Euphorbiae pekinensis Radix extract.