Simultaneous vacuum-ultrasonic assisted extraction of bioactive compounds from lotus leaf

An effective vacuum-ultrasonic assisted extraction (VUAE) technique had been developed to extract bioactive compounds from lotus leaf for the first time. Single factor and response surface methodology were used to optimize the process, respectively. The most optimal results were obtained under the optimized conditions including 60 °C boiling temperature, 56% ethanol concentration, 12-mL/g liquid-to-solid ratios, and 26 min extraction time. Compared with conventional heat reflux extraction (HRE), modern ultrasonic-assisted extraction (UAE), and vacuum-assisted extraction (VAE), the VUAE technique remarkably obtained higher extraction efficiency and greater antioxidant capacity in a shorter extraction time, which indicated that the combination of vacuum and ultrasound was beneficial and greatly increased the effectiveness of the extraction procedure. Scanning electron microscope (SEM) images also revealed that a certain degree of vacuum can accelerate the deformation of the tissue structure and the osmotic dehydration inside the cell. Combined with the cavitation effect of ultrasonic treatment, the cell walls tended to disrupt more easily, which greatly enhanced the process of mass transfer by the use of VUAE. The results demonstrated that VUAE is an effective technique for extracting bioactive compounds from lotus leaf, and it demonstrates broad application prospects in the fields of medicine and food chemistry.