Study On The Main Properties And Biological Activities Of Silybum Marianum Seed Kernel Protein And Oil

Silybum Marianum is compositae herbaceous plant. Its seed is mainly used for extraction of silymarin. Silymarin is the effective component of Silybum Marianum, which mainly exists in the seed shell. Separation of the shell and kernel can not only facilitate efficient extraction of silymarin with high purity, but also facilitate the comprehensive utilization of seed kernel. Seed kernel contains abundant oil and protein therefore it is necessary to study the main properties and biological activities of Silybum marianum oil and protein. The research can not only provide the theoretical basis for the new resources of food development of Silybum marianum seed kernel protein and oil, but also provide the technical support for comprehensive utilization and improve added value of Silybum Marianum.In this dissertation, the basic nutrition composition and physicochemical properties of Silybum marianum seed kernel protein and oil were studied. The researches concering antioxidant and anti-aging activities of Silybum marianum oil and protein hydrolysates were also investigated. The main results were as follows:1. The protein content of Silybum marianum seed kernel defatted powder was47.23%and amino acid composition was reasonable, especially it was rich in glutamic acid and aspartate. Its mineral element content was high, the content of calcium, zinc, copper and other elements were higher than other grain. The oil content in the seed kernel was34.12%, of which unsaturated fatty acid content was77.21%. Linoleic acid was the main unsaturated fatty acid (48.20%). α-VE content in oil was339.42mg/kg.2. The edible security of the Silybum marianum seed kernel defatted powder and the digestion performance of Silybum marianum protein were preliminarily studied. The oral LD50on mice about Silybum marianum seed kernel defatted powde was more than15g/kg. So it belongs to the non-toxic level. In vitro digestibility of Silybum marianum protein using pepsin trypsin and pepsin was studied. High molecular weight proteins in Silybum marianum protein were easier to be hydrolysed than SPI. So Silybum marianum protein had good digestion performance.3. The optimum processing conditions of Silybum marianum protein was determined through response surface methodology. Under the optimized processing conditions as pH11, liquid-solid ratio16:1and50℃, the maximum extraction rate was54.52%.4. Silybum marianum protein was fractionated by the osborne protein classification method and its main properties were studied. Albumin was the main constituent (42.94%), followed by globulin (10.1%). Both total protein and four protein components of Silybum marianum contained abundant glutamic acid, arginine, aspartic acid and leucine. The composition of essential amino acid was balanced. The SDS-PAGE result showed that Silybum marianum protein was mainly composed of protein of middle and low molecular weight. The main bands were in the range of32.4～44.5kD and14.5～4.8kD. Globulin had the highest surface hydrophobic index, albumin was just the reverse of globulin. The processing performance of total protein was better than that of albumin and globulin.5. Neutral protease was the optimal hydrolases for Silybum marianum protein among5proteases which were investigated. The optimum conditions of enzymatic hydrolysis were determined as substrate concentration [S]2%, temperature55℃,[E]/[S]14000U/g, pH7.0, time120min. Under these conditions, the·OH scavenging rate was88.57%. The hydrolysates contained around65%oligopeptide whose molecular weight were smaller than1000Da.6. The stability of antioxidant activity of protein hydrolysates of Silybum marianum was studied. Protein hydrolysates of Silybum marianum had good stabilities in acid and alkaline conditions. NaCl, sucrose and glucose have little effects on the antioxidation activity, while benzoic acid and sorbic acid could reduce the activity. Different metal ions had the different effects on the antioxidation activity. The hydrolysates could keep high activity in vitro digestive system.7. Protein hydrolysates of Silybum marianum were ultrafiltrated consecutively by the ultrafiltration membrane. The antioxidant activities of peptides with different molecular weight were studied.<1kD peptide had the strongest antioxidant activity in vitro, followed by1-3kD peptide and3-10KD peptide in turn.<1kD peptide could inhibit the hemolysis of red blood cells induced by H2O2, the swelling of liver mitochondria and the generation of MDA in mice. It also could improve the activities of Na+-K+-ATPase, Ca2+-Mg2+-ATPase and SDH, and maintain liver mitochondria membrane potential and membrane fluidity.8. Results of anti-aging activity showed that Silybum marianum oil and protein hydrolysates could significantly decrease the blood lipid level and increase the antioxidant capacity of liver and brain in D-galactose-induced aging mice. Both of them could improve liver mitochondria membrane fluidity, membrane potential and the activities of SDH, Na+-K+-ATPase, Ca2+-Mg2+-ATPase, decrease the concentration of caspase-3and improve the activity of Bcl2in the liver and brain of aging mice. Protein hydrolysates of Silybum marianum could significantly reduce the levels of8-OHdG in the liver and brain of aging mice. While Silybum marianum oil could significantly reduce the levels of8-OHdG only in liver. Compared with the model group, there were no significant differences in the levels of8-OHdG in brain. Silybum marianum oil and protein hydrolysates could protect the integrity of the cell morphology of liver and brain of mice. In the test dose range, the middle dose group of protein hydrolysates of Silybum marianum had the best effect. The effect of anti-aging of the hydrolysates was better than Silybum marianum oil.