Ultrasonic/microwave assisted extraction and diagnostic ion filtering strategy by liquid chromatography–quadrupole time-of-flight mass spectrometry for rapid characterization of flavonoids in Spatholobus suberectus

Spatholobus suberectus is a widely used herb in traditional medicine for the treatment of blood stasis syndrome and related diseases. In this work, a potential ultrasonic/microwave assisted extraction (UMAE) method was developed for efficient sample pretreatment, and a diagnostic ion filtering strategy with liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–Q-TOF-MS) was established for rapid characterization of flavonoids in S. suberectus. The factors of UMAE influencing the extraction yield of flavonoids of S. suberectus were evaluated. The optimal conditions were determined as: microwave power of 300 W, extraction time of 450 s, 70% methanol as extraction solvent, solvent to solid ratio of 20 mL/g, ultrasound power of 50 W, extraction temperature of 80 °C, and one extraction cycle. Compared with commonly used extraction methods, UMAE showed higher efficiency and shorter extraction time for sample preparation. Subsequently, the major diagnostic ions and fragmentation pathways of flavonoids in Q-TOF-MS were summarized with available reference compounds. Using a new diagnostic ion filtering strategy, a rapid screening and identification of thirty-eight compounds was achieved in real S. suberectus samples. The results of this study clearly demonstrate the potential of UMAE for efficient extraction and LC–Q-TOF-MS for rapid and sensitive structural elucidation of flavonoids in S. suberectus, and open perspectives for similar studies on other medicinal herbs.