Extraction and Activity Study of Quinoa Saponins by Ultrasound Negative Pressure Method
Chenopodium quinoa Willd. is a dicotyledonous plant in the Amaranthaceae family, native to the Andes mountains of South America. It has comprehensive nutritional content, significant health benefits, and strong ability to withstand adversity and stress. Among them, saponins are its main nutrients, which have biological activities such as antioxidant and free radical scavenging, analgesic, anti-inflammatory, and antifungal properties, and can be used as raw materials in the pharmaceutical industry. In the study of the biological activity of quinoa saponins, it is mainly focused on antioxidant activity, antibacterial activity, and immune enhancement. Based on traditional extraction methods, Dong et al. obtained the optimal extraction process combination for total saponins from quinoa bran through response surface design: ethanol concentration of 75%, ultrasonic temperature of 45 ℃, solid-liquid ratio of 15mL/g, and ultrasonic time of 1.5h. Under these conditions, the saponin yield can reach (2.370+0.22)%. Du et al. isolated quinoa seed coat saponins using high-speed countercurrent chromatography. To further improve the extraction rate of quinoa saponins, domestic and foreign scholars have introduced auxiliary effects such as ultrasound and microwave to improve the extraction method of quinoa saponins.
This article uses white quinoa seeds as raw materials and introduces external negative pressure based on ultrasound assisted extraction method to explore the effects of ultrasound time, temperature, and negative pressure operating conditions on the extraction rate of quinoa saponins. The optimal process conditions for ultrasound negative pressure assisted extraction of quinoa saponins were obtained through response surface experiments, providing data support for efficient and green extraction of quinoa saponins and related product development. The crude extract of quinoa saponins was separated and purified using saturated n-butanol extraction method to obtain total quinoa saponins. In vitro activity experiments were conducted to investigate its antioxidant activity. This will provide important reference for the production and preparation of quinoa saponins, as well as their application and mechanism in medicine and functional foods. It will also be beneficial for their further development and utilization, expanding the application scope and commercial value of quinoa, and achieving the full and efficient utilization of quinoa resources.

Using ultrasound negative pressure assisted extraction of saponins from quinoa seeds, a single factor (ultrasound time, ultrasound temperature, and negative pressure) experiment was conducted to investigate the effects of ultrasound time, ultrasound temperature, and negative pressure on the yield of quinoa saponins. The optimal extraction process conditions for quinoa saponins were obtained by response surface methodology: ultrasound time of 20 minutes, ultrasound temperature of 59 ℃, and negative pressure of 0.064 MPa. Under these conditions, the yield of quinoa saponins was the highest (11.95 ± 0.034 mg/g), which was close to the predicted yield of quinoa saponins (12.37 mg/g). The order of the influence of three factors on the yield of quinoa saponins is: negative pressure>ultrasound temperature>ultrasound time. The study on the antioxidant activity of quinoa saponins purified by n-butanol extraction showed that within the selected concentration range (0-0.25mg/mL), quinoa saponins had strong reducing power and the ability to scavenge DPPH free radicals, which were positively correlated with their concentration. When the concentration reached 0.25mg/mL, the DPPH free radical scavenging rate reached (78.93 ± 2.025)%.