该研究旨在探讨林檎叶在L-NNA诱导的小鼠高血压模型中的预防作用。林檎叶提取物可降低高血压小鼠收缩压（SBP）、平均血压（MBP）、舒张压（DBP）。林檎叶提取物作用高血压小鼠后，小鼠血清、心脏、肝脏、肾脏、胃中的一氧化氮（NO）含量均高于模型组，丙二醛（MDA）含量低于模型组。林檎叶提取物作用高血压小鼠后血清内皮素-1(ET-1)、血管内皮生长因子-A(VEGF-A)、E-selectin水平降低，但降钙素基因相关肽（CGRP）水平升高。林檎叶提取物作用高血压小鼠可使小鼠心脏和血管组织中的血红素加氧酶-1(HO-1)、神经元型一氧化氮合酶（nNOS）、内皮型一氧化氮合成酶（eNOS）、受体活性修饰蛋白2(RAMP2) mRNA表达上调，肾上腺髓质素（ADM）、诱导型一氧化氮合酶（iNOS）表达下调。分析结果显示，林檎叶提取物含有金丝桃苷、异槲皮苷、二氢槲皮素、槲皮苷、橙皮苷、杨梅素、异黄芩苷、新橙皮苷二氢查尔酮、槲皮素，含量分别为104.92、83.05、15.14、242.83、60.24、13.87、125.53、11.23、28.92 mg/g。同时高浓度林檎叶提取物具有更好的预防作用，与高血压药物卡托普利相近。这些结果表明，林檎叶对实验性高血压具有良好的预防作用。

The preventive effect of Malus leaves extract in a model of L-NNA-induced hypertension mice was investigated in this study. The systolic blood pressure (SBP), i.e. the blood pressure (MBP) and diastolic blood pressure (DBP) in hypertensive mice were reduced by treatment with Malus leaf extract. After treatment of hypertension mice with Malus leaf extract, the levels of nitric oxide (NO) in the serum, heart, liver, kidney, and stomach of the mice were higher than those in the model group, while the levels of malondialdehyde (MDA) were lower than those in the model group. The serum levels of endothelin-1 (ET-1), vascular endothelial growth factor-A (VEGF-A), E-selectin were decreased, but the level of calcitonin gene related peptide (CGRP) was increased in hypertension mice treated with Malus leaf extract. The mRNA expression of heme oxygenase-1 (HO-1), neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS) and receptor activity modifying protein 2 (RAMP2) in heart and vascular tissues of hypertensive mice were up-regulated, and the expressions of adrenomedullin (ADM), and inducible nitric oxide synthase (iNOS) d were down- regulated by Malus leaf extract. The results showed that Malus leaf extract contain hyperoside, isoquercitrin, dihydroquercetin, quercitrin, hesperidin, myricetin, isobaicalin, neohesperidin dihydrochalcone and quercetin, and the contents were 104.92, 83.05, 15.14, 242.83, 60.24, 13.87, 125.53, 11.23 and 28.92 mg/g, respectively. Meanwhile high concentration of Malus leaf extract had better preventive effect, which was close to the hypertension drug captopril. These results suggest that leaves of Malus leaf have a good preventive effect on experimental hypertension.