| Apples (Malus domestica Borkh) are one of the tasty and delicious fruits, and also have high nutrition. People ate apples from the ancient times, and apples are still the most common consumed fruits up to now around the world. Huge amounts of evidence have proved that apple polyphenols (AP) have extensive nutritional activities in vivo, including antioxidants and antitumor activities and so on. AP also have small side effects at the same time. As the development of modern scientific research, AP have been used in the food and health food fields besides their extraction, separation and purification.The present study mainly researched on apple polyphenols extracted from Red Fuji apples using 80% methanol, and HPLC was used in qualitative and quantitative analysis of AP. The relatively high active apple peel polyphenols (APP) were chosen as the nutritional content to intervene high choline-induced liver injuries and vascular endothelial cell injuries. The main researches were as follows:(1) 80% methanol was used as the solvent and ultrasonic-assisted extraction (40 kHz,250 W of power,35℃) was conducted to get the extracts, and the filtered extracts were evaporated and lyophilized continuously, the powder was defined as apple peel polyphenols (APP) and apple flesh polyphenols (AFP). The extraction ratio was 8.6% and 7.9% respectively. Colorimetric method showed that total phenolic in APP and AFP was 557.5±20.1 mg GAE/100g and 134.2±10.4 mg GAE/100g separately, the total flavonoids in APP and AFP was 282.1±11.5 mg RE/100g and 102.8±9.1 mg RE/100 g, respectively.(2) The HPLC analysis showed that apples were rich in polyphenols. There were 8 components detected in APP, which were rutin, quercitrin, hyperoside, chlorogenic acid, epicatechin, quercetin, caffeic acid, phloretin in turn, and the corresponding contents were 65.3 mg/g,23.7 mg/g,8.7 mg/g,4.1 mg/g,0.7 mg/g,0.5 mg/g,0.4 mg/g,0.1 mg/g in turn. Only 6 components were analyzed in AFP, which were 1.8 mg/g chlorogenic acid,0.03 mg/g caffeic acid,0.1 mg/g epicatechin,1.0 mg/g rutin,1.2 mg/g hyperoside, and 1.8 mg/g quercitrin.(3) Choline model experiments:as compared with the normal group, the activities of AST and ALT rised to 8.821±2.01 mmol/L and 8.109±1.623 mmol/L separately in the 3% Choline group (p<0.01). In terms of the targets associated with the antioxidant and lipid peroxidation of liver, MDA levels rised to 2.74±0.334 nmol/g prot. while the activities of SOD and GSH decreased to 203.33±14.712 U/mg prot and 8.39± 0.9912U/mg prot, respectively. In the choline group, high dose of choline induced abnormal activities and injuries in the liver. As with the serum levels of TC, TG, LDL, they all increased 1-1.5 times while the levels of HDL decreased compared with the normal group (p<0.01), which proved that high choline diet caused metabolic disorders of lipid protein. Additionally, the ratio of NO/ET-1 raised (p<0.01), the levels of IL-6 went up to 1.8787±0.0013 mlU/L. All of these proved that high choline diet induced disorders and injuries in animals. The histopathology examinations showed the corresponding results with the results of biomarkers.(4) In the experimental animals treated with high dose of choline, livers of mice were damaged and also showed the degradation of antioxidant activities and the increasing of free radicals. After the treatment of APP, it demonstrated protection activity on liver, and at the dose of 900mg/kg·bw, it had the best protection effects. As compared with the model group, the serum activities of ALT and AST were decreased to 116.32±11.316 U/L and 110.28±8.017 U/L, respectively. The levels of MDA in liver homogenate reduced to 2.308±0.119 nmol/g prot while the activities of SOD and GSH-Px increased to 342.19±19.040 U/mg prot and 103.57±9.503 U/mg prot, separately. H&E and Oil Red O showed the same results with the biomarkers.(5) After experimental animals eating high dose choline for a long time, the serum lipid levels showed VEC disorders and injuries. However, after the treatment of APP, serum TC, TG, LDL levels showed different degrees of down trending while HDL levels increased compared with the model group (p<0.01). NO secreted by the VEC 2.527± 0.0289 μmol/L and ET-1 lowered to 11.00±0.057 pg/mL; in addition, TXB2 lowered to 103.72±10.015 pg/mL while 6-keto-PGFla went up to 80.14±14.113 ng/mL which certified VEC injury had been repaired. Additionally, the molecular marker related to VEC including CRP and IL-6 showed a reduced trend (which reduced to 1.303±0.138 ng/mL and 52.34±4.09 pg/mL,p<0.01). All the level changes of markers showed clear dose-dependent manner. Histopathology results showed that with the treatment of APP, the cell necrosis and apoptosis phenomenon has been repaired which were consistent with the biochemical markers.
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