Sustainable Recovery of Bioactive Compounds from Nelumbo nucifera via Ultrasound-Assisted Extraction Optimized Using 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 power (40, 65, and 90%). Optimal conditions—10 minutes at 57.45°C and 90% power (18.45 kHz)—achieved a high total phenolic content (TPC) of 119.584 mg GAE/g, total flavonoid content (TFC) of 0.057 mg QE/g, and strong antioxidant activity (DPPH: 90.87%, ABTS: 92.43%). The process demonstrated excellent energy efficiency, with reduced energy consumption (888.012 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. The combination of low-temperature operation, reduced solvent and energy use, and effective preservation of heat-sensitive bioactives highlights 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.