High-pressure ultrasonic-assisted extraction of polysaccharides from Mentha haplocalyx: Structure, functional and biological activities

In the present study, Mentha haplocalyx polysaccharides (MHP) were extracted using a high-pressure ultrasound-assisted extraction (HUAE) method. Response surface methodology (RSM) was used to select the conditions for the extraction of MHP; this method predicted that optimized extraction is obtained using 300 W of ultrasonic power, an extraction temperature and time of 70 °C and 28 min, respectively, and 29 mL of water for every gram of raw material used in the extraction. Results showed that MHP mainly contained neutral sugar (69.09 ± 0.81%), uronic acid (3.89 ± 0.14%), and protein (7.97 ± 0.42%). Specifically, MHP was comprised of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose with molar percentages of 2.13, 0.89, 1.14, 3.79, 39.3, 44.85, and 7.89%, respectively, and with an average molecular weight of 59.58 kDa for its major component (accounting for 66.20% of MHP). Functional analyses demonstrated that MHP exhibits favorable oil-holding capacity, foaming qualities, emulsifying capacity, hygroscopicity, and moisture retention capacity. The results obtained from the X-ray diffraction pattern and rheological measurements confirmed a semi-crystalline nature of the sample and shear thinning behavior of MHP, respectively. Additionally, in vitro antioxidant activity experiments suggested that MHP exhibits strong DPPH and hydroxyl radical scavenging activities and considerable reducing power. The results presented herein have larger implications for the use of MHP as a functional additive in the food and pharmaceutical industries.