| Quercetin (QT) is a kind of hydroxy flavonoids, which widely exists in all kinds of plants in nature. Studies have shown that quercetin has many biological activities such as antibacterial, anti-inflammatory, antioxidant and antihypertensive effects. In addition, the most striking feature of quercetin is its strong oxidation resistance. Although quercetin had broad-spectrum biological function of activity, its applications in areas such as functional food were greatly restricted due to its poor water solubility and instability when exposed to factors such as light and heat. In this study, three kinds of quercetin-loaded micro/nano carrier system were prepared in order to improve its bioavailability.Firstly, through lipid screening and emulsifier selection, the GMS/GML/ODO (6:9:10) were chosen as the lipid composition of nanostructured lipid carriers (NLCs) and Tween-20/PGFE-6/SE-11 were chosen as the emulsifier composition. QT-NLCs were prepared by high pressure homogenization (HPH) method. Through the Single factor experiment, the process parameters were obtained:High shear speed 10000 rpm, shear time 30 s, the preparation temperature 70 ℃, homogenization pressure of 600bar, homogenization cycles 3 times. Tween-20/PGFE-6/SE-11 system presented particle size of 105nm, PDI of 0.243, zeta potential of -31.9 mV, encapsulation efficiency of 94.9%. Physical stability test showed that the system had good stability. The effect of different biological freeze-dried agent on freeze-drying technology was investigated. Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis proved that quercetin was entrapped in lipid nanoparticles in amorphous state. In in vitro release experiments, the release rate of NLC in simulated intestinal gastric juice was low, indicating the lipid nanoparticles can effectively protect the quercetin and eventually be absorbed by the body in the form of carriers. In vitro digestion experiment showed that QT-NLC can improve the bioavailability of active substances quercetin. DPPH radical scavenging test demonstrated QT-NLC had good antioxidant capacity. Cell toxicity test proved that QT-NLC had no obvious toxicity when the concentration of quercetin in system under 0.5 ug/mL. In addition, the QT-NLC had a good stability in fluid drinks.Secondly, on the basis of the previous section of lipid and emulsifier screening, GMS/GML/ODO (6:9:10) and PGFE-10/PGFE-6/SE-11 were chosen as the lipid and emulsifier composition of lipid nanoparticles. The process parameters of HPH method were optimized using the Single factor experiment. The PGFE-10/PGFE-6/SE-11 system had particle size of 124 nm, PDI of 0.221, zeta potential of -35.5 mV, and encapsulation efficiency of 93.50%. The system had a good physical stability. The freeze-dried process results showed that the freeze-dried effect of lipid nanoparticles was best when glucose was added as freeze-dried protective agent. FT-IR and Raman spectra experiments proved that quercetin was entrapped in lipid nanoparticles. QT-NLC showed slower release rate compared to free quercetin, meanwhile, the release of QT-NLC in simulated gastric juice and simulated intestinal juice were fitted to Higuch equation and Ritger-Peppas equation, respectively. In vitro digestion experiment showed that QT-NLC had a good stability in simulated digestive juices and could improve the bioavailability of active substances quercetin. DPPH radical scavenging test and super oxygen anion clearance test indicated that QT-NLC had good antioxidant activity. CCK-8 cell toxicity test proved that quercetin itself had no toxicity to cells, however, QT-NLC showed toxicity to cells when the quercetin concentrations were beyond certain concentration limit, which were consistent with the nucleus morphological analysis. In addition, the QT-NLC system had a good compatibility with liquid beverage. Both aforementioned quercetin lipid nanoparticles showed potential applications in the field of functional food, but there were still some defects, such as system containing PEG, high temperature instability, etc.Nanoemulsions (NEs) are widely used nanometer carriers in food field, in this paper the QT-NEs were prepared by HPH method. The PGFE-10/PGFE-6/SE-11 were used as emulsifiers and through Single factor experiment, the effects of different liquid lipid composition and content, emulsifier content and homogenization process parameters on NE properties were examined, respectively, and finally the QT-NEs system composition and optimum technological conditions were determined:liquid lipid ODO (10%), PGFE-10/PGFE-6/SE-11 emulsifier content 8%; The preparation temperature of 70 ℃, homogenization pressure of 600 bar, homogenization cycles of 3 times. The QT-NEs had particle size of 147 nm, PDI of 0.186, zeta potential of -49.7 mV and encapsulation efficiency of 84.7%. The QT-NE system had a good physical stability. The QT-NEs system showed no effect on the taste and appearance of fluid drinks. The QT-NEs system released faster in simulated gastric juice stage and presented a slow-release rate in simulated intestinal fluid phase, in addition, the release of QT-NEs in the whole drug release process was fitted to First-order equation. QT-NEs showed a good performance in in vitro digestion model, and NEs could better improve the bioavailability of quercetin compared with the lipid nanoparticles. DPPH radical scavenging test and super oxygen anion clearance test suggested that QT-NEs has good antioxidant activity in vitro. Both MTT and CCK-8 cell toxicity tests proved that the QT-NEs had no toxicity on Hela cell when the concentrations were below 200 mg/L, which were well verified by the nuclear shape analysis results. In conclusion, NEs could be used to deliver various of functional active ingredients and has a great application prospect in the food industries, etc. |
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