Determination of synephrine in herbal plants using an isotopically labeled internal standard HPLC–MS/MS method

Abstract

We developed a rapid, precise, and sensitive method to quantify synephrine in herbal plants, using methanol–water solution (8:2, v/v) as the extracting agent and high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) for analysis. To mitigate matrix effects, we employed synephrine-13C2, 15N as an internal standard and separated synephrine using a reverse-phase column. We established a highly accurate standard curve (R2 ≥ 0.9997). The method demonstrated excellent intra-day recoveries (96.35 %–103.19 %) at three spiked concentrations (0.5, 10, 100 μg/g), with minimal standard deviations (<4.84 %). The limits of detection and quantification of this method were 0.1 μg/g and 0.5 μg/g, respectively. Using this approach, we analyzed synephrine content in 24 herbal plants. Substantial concentrations of synephrine were found in Citri Reticulatae Pericarpium Viride (13.204 mg/g) and Aurantii Fructus Immaturus (7.077 mg/g), whereas the remaining species either exhibited lower concentrations or were devoid of synephrine. This approach fulfills the requirements for synephrine detection.