Extraction and purification of total flavonoids from Zanthoxylum planispinum Var. Dintanensis leaves and effect of altitude on total flavonoids content

To investigate the impact of varying altitudes on the functional components of the leaves of Zanthoxylum planispinum var. Dintanensis, this research collected leaf samples from three different elevations: 610 m, 833 m, and 1083 m. Utilizing water and ethanol as extraction solvents, the study optimized extraction parameters via an ultrasonic-assisted technique to maximize the yield of total flavonoids. Following extraction, five types of macroporous adsorption resins were employed for purification. Significant flavonoid constituents within the purified extracts were qualitatively analyzed using liquid chromatography-mass spectrometry (LC-MS). The antioxidant activity of the extracts was also assessed pre- and post-purification. Findings indicated that water was a more effective solvent than ethanol for flavonoid extraction, yielding optimal results at 70 °C, with a solid-to-liquid ratio of 1:70, 30 min, and 480 W. Conversely, ethanol extraction yielded optimal results at a concentration of 65%, a liquid-to-solid ratio of 1:30, 60 °C, 30 min, and 360 W. Among the tested resins, AB-8 demonstrated the highest efficacy for purifying flavonoid extracts, with adsorption data conforming best to the Freundlich isotherm model. Optimal conditions for AB-8 purification included a crude extract concentration of 2.50 mg/mL, pH 5, and temperature 25 °C, eluted with 10 mL of 60% (v/v) ethanol. A notable increase in total flavonoid content was observed, rising from an average of 3.43-16.00%, with a recovery yield of 82.12%. Leaves collected at 830 m contained the highest total flavonoid content, with rutin predominating over naringenin chalcone and naringenin. At 1083 m, naringenin chalcone was most abundant, while the highest concentration of naringenin was recorded at 610 m. This study provides optimized protocols for the extraction and purification of total flavonoids from Z. planispinum var. Dintanensis leaves, contributing to the development of potential applications for these bioactive compounds in various fields.