Extraction Of Fish Oil From Tilapia Viscera And Preparation And Characterization Of Nanoliposomes Containing Fish Oil

Fish oil, which is a rich source of long-chain n-3 polyunsaturated fatty acids (PUFA), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has been widely used in biological systems because of its special biological activity. However, the polyunsaturated fatty acids are extremely susceptible to oxidation. The strong odour and taste associated with its water insolubility incurs numerous challenges in the production and storage of foods enriched with fish oil. Liposomes, as a new technology for microencapsulating, can be a solution to this problem. Therefore, this paper was mainly concerned with the extraction of fish oil from the viscera of tilapia, then fish oil was embedded using liposome technology, at last, the protective effects of fish oil and its nanoliposomes during hepatic ischemia reperfusion injury (IRI) and its mechanism in rat model were explored.The extraction technology of fish oil from tilapia viscera by enzyme hydrolysis method was optimized, and the basic physical and chemical characteristics and fatty acid composition of fish oil were analyzed. The single factor experiment and response surface methodology was used to determine optimum conditions for extraction of fish oil from the tilapia viscera. Maximum yield was obtained when the temperature, pH, liquid-material ratio and enzyme concentration were 50℃癈,7.5,5:1, and 3400 U/g, respectively. Under this condition, the extraction rate offish oil was 88.95%. The result showed that the relative content of saturated fatty acid (SFA) of crude fish oil and refined fish oil extracted from tilapia viscera ranged from 36.66% to 32.19%, the compositions mainly were palmic acid; the monounsaturated fatty acids (MUFA) were present at 38.13% to 39.05%, the compositions mainly were oleic acid; polyunsaturated fatty acids (PUFA) 25.18% to 29.31%, the compositions mainly were linoleic acid. These results indicated that the fish oil extracted from tilapia viscera was a kind of high nutritional quality fat.Uncoated liposomes (un-L) and carboxymethylchitosan (CMCS)-coated liposomes (CM-L) containing fish oil were prepared by thin firm evaporation-sonication method, and their characteristics, stability and release behavior in vitro were studied. The mean diameters of liposomes with different CMCS concentration ranged from 97.70 to 218.15 nm. The CMCS coating increased the mean diameter of liposomes, but no effect on entrapment efficiency. The stabilities of un-L and CM-L stored at 4℃ were better than 25℃. Moreover, the CM-L was significantly more stable than un-L when stored at 25℃. The release behaviors of un-L and CM-L were governed by two distinct stages and first-order model was the most suitable model for the whole release procedure. The diffusion and erosion release mechanisms may coexist for the full controlled release from the nanoliposomes.A model of segmental warm hepatic IR (70%) on Male Sprague-Dawley rats was established. The SD rats were randomly divided into five experimental groups (each containing twelve rats):(1) a sham control group (S group); (2) an IR control group (IR group); (3) a group treated with fish oil before the IR (FO group); (4) a group treated with un-L before the IR (un-L group); (5) a group treated with CM-L before the IR (CM-L group). After the reperfusion, blood and hepatic tissue samples were collected, and the contents of AST, ALT, y-GT, LDH, IL-6, IL-10, and TNF-a in serum, and the MDA, SOD and MPO concentration in liver were determined. The pathological changes of liver were observed. The AST, ALT, y-GT, LDH, MDA, MPO, TNF-a and IL-6 contents of IR group were higher than that of S group. The SOD and IL-10 values of IR group were lower than that of S group. It was observed that AST, ALT, y-GT, LDH, MDA, MPO, TNF-a and IL-6 values significantly decreased, and SOD and IL-10 values increased with FO, un-L and CM-L pretreatment. Likewise, FO, un-L and CM-L pretreatment also significantly reduced the extent of hepatocyte apoptosis and necrosis (HE/TUNEL) and attenuated the NF-κB activation in liver. Dietary fish oil supplementation attenuated hepatic IR injury and could be considered as a nutritional therapeutic aimed at ameliorating IR injury.