The aim of this study was to investigate and optimize the most important factors affecting the extraction of Acanthopanax giraldii HARMS polysaccharides (AHPs) by ultrasound-assisted extraction (UAE) technology in a systemic manner. The ranges of four factors, including extraction temperature, liquid/solid ratio, extraction time, and ultrasonic power, were first determined by a single-factor experiment, followed by optimization of the UAE conditions using the Box-Behnken design (BBD) for maximum AHPs production. In our study, the models developed from the experimental design predicted the experimental data well and had a high determination coefficient (R2=0.9387). The optimized conditions for AHPs extraction were as follows: extraction temperature, 58°C; liquid/solid ratio, 25 : 1; extraction time, 73 min; and ultrasonic power, 85 W. Under these optimized conditions, the polysaccharide yield was 1.532±0.037% (n=3), being very close to the predicted value of 1.546% by the model. In addition, to investigate whether there was a difference of AHPs content between UAE and traditional hot water extraction (THWE), Fourier-transform (FT) IR spectral analyses was performed. The results showed that the functional groups of the polysaccharides extracted by either UAE or THWE were fundamentally identical. Furthermore, AHPs extracted by UAE could promote macrophage activation, such as enhanced phagocytosis and increased cytokine (interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α)) secretion in RAW264.7 cells. In conclusion, optimization of the UAE conditions by response surface methodology (RSM) was a promising method to improve the extraction yield of AHPs. AHPs extracted by the optimized UAE method can maintain their polysaccharide structure and biological activity.
Keywords: Acanthopanax giraldii; polysaccharide; response surface methodology (RSM); ultrasound-assisted extraction.