Selective extraction of nuciferine from Nelumbo nucifera Gaertn. leaves via heat reflux method: process optimisation and efficiency evaluation

leaves at different maturity stages and optimised the heat reflux extraction process for nuciferine and total alkaloids. Alkaloid content reached a maximum at the 1-month-old stage. Nuciferine was the major alkaloid, accounting for more than 70% of the total alkaloid content. Initial optimisation using the one-factor-at-a-time approach determined extraction conditions of 96% ethanol, 60 °C, a liquid-to-solid ratio of 8:1, 60 min extraction time, and three extraction cycles, which yielded 3.36 ± 0.05 mg/g dry material of total alkaloids. Response surface methodology was then applied to further optimise the process by considering factor interactions. The optimal conditions were 87% ethanol, 70 °C, and a liquid-to-solid ratio of 8 mL/g. The experimental results achieved 3.19 mg/g nuciferine and 4.24 mg/g total two alkaloids, showing improved extraction efficiency compared with previous studies.