Study On Extraction, Antioxidant Activity And Microencapsulation Of Opuntia Dillenii Haw. Polysaccharides

Polysaccharides, widely exist in plants, animals and microorganisms and have a great number of important biological functions, such as immunomodulatory, antioxidant activities, antidiabetic effects, blood lipid-lowering effects and anti-tumour activities. The research and development of polysaccharides attract increasing attention. Numerous studies have shown that Opuntia dillenii Haw. polysaccharides (ODP) as the main active components of Opuntia dillenii Haw. have multiple important pharmacological activities. In the present work, extraction, antioxidant activity and microencapsulation of ODP were studied using Opuntia dillenii Haw. as raw material. The obtained results of this study were as follows:1. Using the2-4months old Opuntia dillenii Haw. as the raw material, the optimal parameters for hot water extraction of ODP were obtained using the single factor and orthogonal test design method as follows:ratio of water to raw material,60:1mL/g; extraction time,3h; extraction temperature,95℃; and extraction times,2.Under these conditions, the extraction rate was (30.90±0.20)%, the purity of ODP was (85.92±0.19)%, and the protein content was (0.63±0.02)%. Under the optimal condition, the extraction rate of ODP extracted from2-4months old Opuntia dillenii Haw.(T-ODP) were compared with that from more than5months old Opuntia dillenii Haw.(O-ODP). The results showed that the extraction rate and the purity of T-ODP were significantly higher than those of O-ODP. The protein content in ODP showed no significant differences between T-ODP and O-ODP.2. The antioxidant activities of ODP in vitro were investigated by determining their l,l-Diphenyl-2-picrylhydrazyl radical (DPPH·), hydroxyl radical (·OH) and superoxide anion free radical (O2-·) scavenging activities. The results showed that both T-ODP and O-ODP had potent scavenging effects on DPPH·and·OH and scavenged the free radicals in a concentration-dependent manner. At the concentration of6.4mg/mL, the scavenging percentages of T-ODP to DPPH·and·OH were60.48%and39.62%, respectively, and those of O-ODP to DPPH·and·OH were58.13%and46.20%, respectively. However, the scavenging percentages of T-ODP and O-ODP to O2-·were low, with37.44%and29.12%, respectively.3. The microencapsulation technology was also studied. ODP-Ms were prepared by a double emulsion (W/O/W) solvent evaporation technique, and the single factor and orthogonal experiments were used to optimize the formulation according to ODP-Ms encapsulation efficiency. The results demonstrated that the optimum conditions for a high encapsulation efficiency were as follows:ODP concentration,10mg/mL; stirring rate for the primary emulsion preparation,20000rpm; stirring rate for the second emulsion preparation,8000rpm; PLGA concentration,70%. The ODP-Ms with high encapsulation efficiency (85.35%) was obtained under the optimum conditions.4. The physicochemical properties of ODP-Ms were investigated using a scanning electron microscope (SEM) and a differential scanning calorimetry (DSC). The results showed that the ODP-Ms possed a spherical or nearly spherical shape, with smooth surface and uniform size. Glass transition temperature (Tg) of ODP-Ms was50.55℃, indicating that the ODP-Ms was stable in room temperature. The ODP-Ms was stable at4℃for6months in the test of stability. Using phosphate buffer solution (PBS) as the release medium, the release characteristy of the ODP-Ms in vitro was investigated. The accumulative release ratio was up to89.14%in a continuous period of26days. The in vitro release profiles could be expressed by Higuchi equation.