| Litchi is a subtropical representative fruit. Our country is its mian producing country. With the development of litchi juice, wine and canned food processing, the amount of the litchi pericarp keeps increasing. Making good uese of this resource becomes a key issue. Our previous studies found that litchi pericarp is rich in procyanidins and other phenolics. Its procyanidins is mainly A-type. We also confirmed that litchi pericarp procyanidins had antiatherosclerotic activity through animal experiments. However, procyanidins in litchi pericarp are a group of compounds with different degree of polymerization and different linking mode between constitutional units. The differences in antiatherosclerotic activity and action mechanism of each compound are unknown. Therefore, the changes of phenolics profiles and antioxidant activity in litich pericarp under different storage temperature were compared to determine litich pericarp storage condition. A murine Raw264.7 macrophage derived foam cell model was established to investigate the action of litchi pericarp procyanidins on cholesterol metabolism homeostasis and then to reveal its dose and structure-activity-relationship. The results are as follows.(1) The changes of litich pericarp phenolics profiles and antioxidant activity under different storage temperature:compared the changes of the content of total procyanidins, total phenolics, total flavonoids, total anthocyanins, phenolic composition and antioxidant activity in litich pericarp storaged under the condition of 30 ℃ and 40 ℃. The results showed that litchi pericarp storaged at 30 ℃ for 72 h, the content of its phenolic compounds and antioxidant activity were significantly decreased (P<0.05). The content of total procyanidins, total phenolics, total flavonoids, total anthocyanins decreased from 84.42,116.95,97.64,1.73 mg/g DW to 44.07,72.70,53.15,0.48 mg/g DW, which reduced 47.80%,37.84%,45.56%,73.02% respectively. The content of epicatechin, procyanidins A2, procyanidins B2, caffeic acid, quercetin -3-O- rutinoside -7-O-α-L-rhamnosidase, ferulic acid decreased from 9.83,17.61,4.71,0.76,1.63,0.82 mg/g DW to 5.04,12.09,2.47,0.44,1.18,0.51 mg/g DW, which reduced 48.73%,31.35%,47.56%,42.11%,27.61%,37.80% respectively. The ORAC and CAA antioxidant activity decreased from 1777.01 μmol TE/g DW and 100.89 μmolQE/g DW to 1360.70 μmolTE/g DW and 34.30 μmol QE /g DW, which reduced 23.43% and 66.01% respectively. However, the content of phenolic compounds and antioxidant activity could almost keep 50% above. Litich pericarp storaged at 4 ℃ for 7 d, the content of its phenolic compounds and antioxidant activity were significantly decreased (P<0.05). The content of total procyanidins, total phenolics, total flavonoids, total anthocyanins decreased from 84.42,116.95,97.64,1.73 mg/g DW to 63.96,93.3,61.33,1.06 mg/g DW, which reduced 24.24%,41.26%,37.19%,20.17% respectively. The content of epicatechin, procyanidins A2, procyanidins B2, caffeic acid, quercetin -3-O- rutinoside-7-O-α-L-rhamnosidase, ferulic acid decreased from 9.83,17.61,4.71,0.76,1.63, 0.82 mg/g DW to 7.26,13.71,2.37,0.61,1.24,0.51 mg/g DW, which reduced 19.74%, 23.93%,37.80%,26.14%,22.15%,49.68% respectively. The ORAC and CAA antioxidant activity decreased from 1777.01 μmolTE/g DW and 100.89 μmolQE/g DW to 1463.93 μmolTE/g DW and 41.67 μmolQE/g DW, which reduced 17.62% and 58.70% respectively. However, the content of phenolic compounds and antioxidant activity could almost keep 50% above. Which shows that low temperature is more conducive than room temperature to protect litchi pericarp phenolic compounds, and room temperature storage is just suitable for a short time storage of litich pericarp, but low temperature storage is suitable for litich pericarp to storage for a long time.(2) The establishment of macrophage foam cell model:Used 30,50,80,100 μg/mL ox-LDL to stimulate murine Raw264.7 macrophage to induce foam cell model. The results showed that 100 μg/mL ox-LDL stimulated murine Raw264.7 macroph-age for 24 h, after Oil Red O staining, the red lipid droplets in cells and the volume of cells significantly increased, and the cells extended pseudopodia, which was consis-tent with foam cell morphological characteristics. Compared with normal cells, the total cholesterol (TC) content was significantly increased, cholesterol ester/total cholesterol (CE/TC) was more than 50%, which revealed that using 100 μg/mL ox-LDL stimulating macrophage for 24 h could successfully induce macrophage foam cell formation.(3) The regulation of litchi pericarp procyanidins ingredients on macroph-age foam cell cholesterol metabolism:compared the effects of different content of procyanidins A2, procyanidins B2 and epicatechin on cholesterol intake and efflux of macrophage foam cells. The results showed that the three procyanidins ingredients could inhibite cholesterol intake of macrophage cell. At a concentration of 40 μg/mL, the CE/TC values of procyanidins A2, procyanidins B2 and epicatechin were 17.75%, 41.76%,36.40% respectively, which is the minimal. At the condition of low (10 μg/mL), medium (20 μg/mL), high (40 μg/mL) dose, the inhibition of procyanidins A2 on macrophage cholesterol intake was significantly stronger than that of procyanidins B2 and epicatechin (P<0.05). At the condition of medium (20μg/mL) and high (40 μg/mL) dose, the inhibition of epicatechin on macrophage cholesterol intake was stronger than that of procyanidins B2. The three procyanidins ingredients can promote cholesterol efflux of macrophage cell. At a concentration of 40 μg/mL, the cholesterol efflux rates of procyanidins A2, procyanidins B2 and epicatechin were 49.82%,31.22%,39.09% respectively, which were the maximum. At the condition of low (10 μg/mL), medium (20 μg/mL), high (40 μg/mL) dose, the promotion of procyanidins A2 on macrophage cholesterol efflux was significantly stronger than that of procyanidins B2 and epicatechin (P<0.05), and the promotion of epicatechin on macrophage cholesterol efflux was stronger than that of procyanidins B2. Which shows that the activity of procyanidins A2 in the inhibition of cholesterol intake and the promotion of cholesterol efflux of macrophage foam cells is the best, this may be related to the existence of C2-O-C7 key combination between its constitutional units. |
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