Sustainable recovery of bioactive compounds from Nelumbo nucifera using ultrasound-assisted extraction optimized through response surface methodology

Abstract

Nelumbo nucifera (lotus flower) is a promising natural source of phenolic compounds, flavonoids, and alkaloids, recognized for their potent bioactive and antioxidant properties. This study optimized a green extraction approach, ultrasound-assisted extraction (UAE) to enhance the yield of these functional compounds while minimizing environmental impact. A response surface methodology (RSM) using a Box–Behnken design (BBD) was employed to investigate the effects of extraction time (10, 25, and 40 min), temperature (50, 60, and 70 °C), and ultrasonic full power rate at 20.5 kHz (40, 65, and 90% power rate). Optimal conditions, 10 min at 57.45 °C and 90% (18.45 kHz), achieved a high total phenolic content (TPC) of 114.52 mg GAE per g, total flavonoid content (TFC) of 0.057 mg QE per g, and strong antioxidant activity (DPPH, 90.91%, ABTS, 91.61%, and ferric reducing antioxidant power, FRAP, 0.072 mg TE per g). The process demonstrated excellent energy efficiency, with reduced energy consumption (617.97 kJ) compared to conventional thermal extraction methods. Thermodynamic analysis confirmed spontaneous extraction of phenolic and antioxidant compounds (negative ΔG), while entropy changes (ΔS) indicated process irreversibility and thermal sensitivity. Overall, UAE operation reduced solvent, saved energy, and effectively preserved heat-sensitive bioactive compounds, highlighting the environmental advantages of UAE. This study underscores UAE as a sustainable and scalable technique for extracting functional compounds, offering considerable potential for applications in food, nutraceutical, and pharmaceutical industries committed to green processing technologies.