Faculdade de Ciências da Saúde, Universidade Federal da Grande Dourados, Dourados, MS, Brazil.
Instituto de Pesquisa Pelé Pequeno Príncipe, Faculdade Pequeno Príncipe, Curitiba, PR, Brazil.
J Ethnopharmacol. 2018 Oct 28;225:53-63. doi: 10.1016/j.jep.2018.06.027. Epub 2018 Jun 19.
Luehea divaricata Mart. (Malvaceae) is an important medicinal species that is widely used as a diuretic in the Brazilian Pantanal region. An ethanolic supernatant that was obtained from an infusion of leaves of this species (ESLD) was recently shown to exert hypotensive and diuretic activity. Nevertheless, the secondary metabolites that are responsible for this activity and the molecular mechanisms of pharmacological action remain unknown.
We performed a detailed study to identify possible active metabolites that are present in different ESLD fractions and investigated their effects on renal and peripheral arteriolar tone. We further evaluated their interrelations with sustained diuretic and hypotensive actions.
The ESLD was first obtained from L. divaricata leaves, and liquid-liquid fractionation was performed. The fractions were analyzed by liquid chromatography-mass spectrometry. An ethyl acetate fraction (AceFr), n-butanolic fraction (ButFr), and aqueous fraction (AqueFr) were then orally administered in male Wistar rats in a single dose or daily for 7 days. The doses were previously defined based on the yield that was obtained from each fraction. Hydrochlorothiazide was used as a positive control. Blood pressure, heart rate, urinary volume, pH, density, and urinary sodium, potassium, chloride, and calcium levels were measured. Serum levels of nitrite, thiobarbituric acid reactive species, nitrotyrosine, aldosterone, vasopressin, and plasma angiotensin converting enzyme activity were also measured. Finally, the direct effects of the ButFr on renal and mesenteric arteriolar tone and the role of nitric oxide and prostaglandins in the renal and hemodynamic effects were investigated.
Of the fractions that were tested, only the ButFr exerted significant diuretic and saluretic effects. The AceFr and ButFr also had acute hypotensive effects, but only the ButFr maintained its response after 7 days of treatment. Prolonged treatment with the ButFr increased serum nitrite levels and significantly reduced oxidative and nitrosative markers of stress. Additionally, the ButFr caused a vasodilatory response in the renal and mesenteric arteriolar beds through the release of nitric oxide and prostaglandins. Finally, the diuretic and hypotensive effects of the ButFr were completely blocked by pretreatment with Nω-nitro-L-arginine methyl ester and indomethacin, thus demonstrating the direct involvement of nitric oxide and prostaglandins in these effects.
The ButFr that was obtained from Luehea divaricata exerted sustained diuretic and hypotensive effects. These effects were apparently attributable to the release of nitric oxide and prostaglandins, which reduce renal and peripheral arteriolar tone and lead to an increase in the glomerular filtration rate and a reduction of global peripheral resistance. These findings suggest that the ButFr may be a potential complementary therapy for several conditions in which diuretic and hypotensive effects are required.
Luehea divaricata Mart.（锦葵科）是一种重要的药用物种，在巴西潘塔纳尔地区被广泛用作利尿剂。最近，从该物种的叶子提取的一种醇提上清液（ESLD）被证明具有降压和利尿作用。然而，负责这种活性的次生代谢物以及药理作用的分子机制尚不清楚。
我们进行了详细的研究，以确定存在于不同 ESLD 馏分中的可能的活性代谢物，并研究它们对肾脏和外周小动脉张力的影响。我们进一步评估了它们与持续的利尿和降压作用之间的相互关系。
首先从 L. divaricata 叶子中获得 ESLD，并进行液-液分馏。通过液质联用对馏分进行分析。然后，将乙酸乙酯馏分（AceFr）、正丁醇馏分（ButFr）和水馏分（AqueFr）以单剂量或每日剂量口服给予雄性 Wistar 大鼠，剂量是根据每个馏分的产率预先确定的。氢氯噻嗪用作阳性对照。测量血压、心率、尿量、pH 值、密度以及尿钠、钾、氯和钙水平。还测量了血清中亚硝酸盐、硫代巴比妥酸反应性物质、硝基酪氨酸、醛固酮、血管加压素和血浆血管紧张素转换酶活性的水平。最后，研究了 ButFr 对肾脏和肠系膜小动脉张力的直接影响，以及一氧化氮和前列腺素在肾脏和血液动力学效应中的作用。
在所测试的馏分中，只有 ButFr 表现出显著的利尿和排盐作用。AceFr 和 ButFr 也具有急性降压作用，但只有 ButFr 在 7 天治疗后保持其反应。ButFr 的长期治疗增加了血清中亚硝酸盐水平，并显著降低了应激的氧化和硝化标记物。此外，ButFr 通过释放一氧化氮和前列腺素引起肾脏和肠系膜小动脉床的血管舒张反应。最后，ButFr 的利尿和降压作用被 Nω-硝基-L-精氨酸甲酯和吲哚美辛预处理完全阻断，从而表明一氧化氮和前列腺素直接参与了这些作用。
从 Luehea divaricata 获得的 ButFr 表现出持续的利尿和降压作用。这些作用显然归因于一氧化氮和前列腺素的释放，这降低了肾脏和外周小动脉的张力，导致肾小球滤过率增加和全身外周阻力降低。这些发现表明，ButFr 可能是需要利尿和降压作用的几种情况下的潜在补充治疗方法。
