| With the Syringa oblata lind L. leaf as raw material, the solid polyphenol extract was obtainedfrom the treatment of drying, smashing, and extracting leaf, and then purifying and freeze-dryingextract. The conditions for extracting and purifying were determined. The inhibition of extract onthe oxidation of low-density lipoprotein, which was induced by cupric in vitro, the scavengingactivity of extract on free radicals and the antioxidation of extract in two edible oils were allevaluated.1. The optimum extracting conditions for the polyphenol extract from Syringa oblata LindL. leaf according to the screening experiment were selected. The ratio of raw material to solvent,the concentration of ethanol, temperature, times and time of the extraction were following: 1: 10,50%, 40℃, twice for 2 h. The extracting rate of polyphenols was 88.9%.2. The S-8 macroporous resin had better static adsorption and static desorption thanNKA-Ⅱmacroporous resin. The S-8 macroporous resin was more suitable to purify the rudeextract.3. The optimum purifying conditions for the rude extract to the screening experiment wereselected. The flow velocity for dynamic adsorption was 2.0 BV·h-1. For dynamic desorption, theconcentration of ethanol was 70%, the flow velocity of ethanol was 2.0 BV·h-1, and the volume ofthe ethanol was 4 BV. The recovery of polyphenols was 79.4%.4. Through oxidative modification of low-density lipoprotein (LDL) which was induced bycupric in vitro, the formation of MDA, lipofuscin, and the relative electrophoretic mobility of LDLoxidized were determined. The results showed that the extract had good inhibition to the LDLoxidation.1) When the addition levels of the extract of Syringa oblata Lind L. leaf were 50mg·L-1～400mg·L-1, the inhibition to the formation of MDA in Ox-LDL were significant. The inhibiting extentswere 10.0%～71.9% respectively. There is strong correlation between dose and effect.2) When the addition levels of the extract of Syringa oblata Lind L leaf were 50 mg·L-1～400mg·L-1, the inhibition to the formation of lipofuscin in Ox-LDL were significant. The inhibitingextents were 29.2%～56.2% respectively. There is strong correlation between dose and effect.3) When the addition levels of the extract of Syringa oblata Lind L.leaf were 100 mg·L-1, 200mg·L-1, 400 mg·L-1, the inhibition to the relative electrophoretic mobility of Ox-LDL weresignificant. The inhibiting extents were 17.5%, 22.4% and 31.2% respectively.5. The scavenging activity of extract from Syringa oblata Lind L.leaf on hydroxyl free radicaland superoxide anion free radical were studied. The final results showed that the extract hadsignificantly scavenging activity to the hydroxyl free radical. The addition levels of the extract of Syringa oblata Lind L.leaf were 0.0078%～0.250%. The scavenging extents were 20.8%～96.2%,respectively. The extract had higher scavenging activity to hydroxyl free radical than ascorbic acid.When the addition levels of ascorbic acid were 0.0625% and 0.125%, the scavenging extents were87.4% and 91.1%. The addition levels of the extract of Syringa oblata Lind L.leaf were 60 mg·L-1,240 mg·L-1 and 960 mg·L-1, it had some scavenging activity to the superoxide anion free radical.The scavenging activity of the extract to the superoxide anion free radical was increased asaddition level increased. But the extract had lower scavenging activity to superoxide anion freeradical than ascorbic acid. Only when the addition level of the extract was 240 mg·L-1, it had thesame scavenging activity as ascorbic acid which was 100 mg·L-1.6. The extract from Syringa oblata Lind L. leaf had good antioxidation on the lard and refinedsoybean oil. The effect was similar to that of propyl gallate when they were at the same additionlevel (0.01%). When the addition levels increased to 0.05% and 0.1%, the antioxidation of theextract still increased in the two edible oils. But the extent increased was not significant. Thismeant that when the addition level of the extract was 0.01～0.05% in the experiment, it had thesame antioxidation as propyl gallate. When the addition level was 0.1%, the storage temperaturewas 60±1℃, 25 days later, the POV of lard sample was 14.5 meq·kg-1(GB≤16 meq·kg-1) andthe POV of refined soybean oil was 9.4 meq·kg-1(GB≤10 meq·kg-1), which conformed tonational standard. |
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