| Diacylglycerol (DAG) is a natural component of most edible oils. The consumption of DAG has been claimed to reduce body fat accumulation, body weight and prevent obesity. Microemulsions which comprise of a mixture of water, oil and surfactants, are thermodynamically stable, transparent isotropic solutions with long-term stability and particle sizes ranging from 5 to 100 nm. Microemulsion is an excellent delivery vehicle for nutriments. The main research objectives were to prepare a 1,3-DAG microemulsion (1,3-DAGM) with excellent solubility in water, good stability and high bioavailability, and evaluate the bioavailability and safety of 1,3-DAGM.(1) The preparation of 1,3-diacylglycerol microemulsionBased on the single factor experiment, uniform design and orthogonal experimental design were adopted to select the optimal formula and optimize the preparation technics. Optimised microemulsion formulation composed of 25% 1,3-DAG,11% food-grade surfactants (28.33% decaglyceryl monolaurate,13% hexaglyceryl trioleate,13.99% Tween 80 (ethoxylated-20 EO-sorbitan monooleate), 22.03% Span 80 (Sorbitan monooleate),1.57% sucrose ester SE-11,1.84% SE-13, 19.24% sodium caseinate),5% sorbitol and 59% distilled water. All the surfactants and co-surfactants were added to the DAG oil, followed by adding distilled water. After stirring, the mixture was emulsified via a high pressure homogenizer and microfluidizer in succession.(2) The properties of 1,3-diacylglycerol microemulsionThe stability of microemulsion was evaluated via particle diameter, the conductivity at different temperatures, and the range of dilution in water and electrolyte solution and the centrifugal stability as well. After these trials, oil/water (O/W) diacylglycerol microemulsion was prepared successfully, the particle diameter at 95.8nm. Besides, the microemulsion has good stability below 80℃, excellent oxidative stability, a wide water dilution range and its physical structure insusceptible to the common electrolyte in food systems.(3) The bioavailability of 1,3-diacylglycerol microemulsionThe fatty acid (FA) concentration in serum of all rats at 0,6 and 24-hour after oral administration of 1,3-DAGM and 1,3-DAG oil were examined. The results showed that the FA concentration of 1,3-DAGM group was significantly higher than that of DAG oil group at 6-hour after treatment. We continued to administer rats with 1,3-DAGM and 1,3-DAG oil intragastrically for 2 weeks to detect their digestibility. There was no significant difference on body weight between two groups. However, the total food consumption of rats treated with 1,3-DAGM was evidently less than that of 1,3-DAG oil. Based on the FA concentration in serum and fat excretion in feces, we can conclude that the absorbtion of 1,3-DAG in 1,3-DAGM group was significantly higher than that in 1,3-DAG oil. Furthermore, the contents of fatty acids (18:2n-6,18:1,18:3n-3, total MUFA, total PUFA, total n-6 PUFA) in fecal lipids were significantly lower in 1,3-DAGM group than that in 1,3-DAG oil group, which indicated that 1,3-DAGM has an excellent bioavailability.(4) Safety evaluation of 1,3-diacylglycerol microemulsionThe oral acute toxicity study revealed that 20 ml/kg body weight of 1,3-DAGM was safe for the growth of mice. As for the 30 days feeding study in rats, the general condition, body weight, hematology indexes had no abnormal change. However, there was significant difference in the liver/body weight and kidney/body weight of the high dose (20 ml/kg·bw) of male rats and the high dose group of female rats compared with control group. In the pathohistological examination of organs, we found that the liver foliole was surrounded by some fat dripping. This phenomenon could attribute to the high bioavailability of 1,3-DAGM, which would give rise to accumulate too many nano-particles in cells to metabolize normally for the liver. Further study on the toxicity of a long-term 1,3-DAGM intake may provide more powerful evidences for the safety evaluation of 1,3-DAGM.
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