Antihypertensive effects of crude extracts from leaves of Echinodorus grandiflorus

The antihypertensive action of a crude ethanolic extract (EEEG) from leaves of Echinodorus grandiflorus (Alismataceae) was investigated in spontaneously hypertensive rats. The intraperitoneal injection of increasing doses of EEEG (300-1000 mg/kg) elicited dose-dependent reductions in mean arterial pressure (MAP) that were paralleled by reductions of cardiac output and systemic vascular resistance, reaching the maximum of 23 +/- 5%, 13 +/- 3% and 18 +/- 4%, respectively (n = 5, P < 0.05). Comparable reductions of MAP were obtained upon i.v. administration of EEEG (3-100 mg/kg), reaching the maximum decrease of 51 +/- 6% (n = 7; P < 0.001). The blockade of nitric oxide synthesis significantly reduced the hypotension induced by i.v. administration of EEEG. Moreover, the pre-treatment of the animals with a selective antagonist of cholinergic muscarinic receptors or of platelet-activating factor (PAF) receptors partially blunted the cardiovascular effects of EEEG. The i.v. pre-treatment with the selective B(2) bradykinin receptor antagonist HOE 140 or with indomethacin, an inhibitor of the enzyme cyclooxygenase, did not prevent the hypotensive effects induced by EEEG. Finally, the chronic oral treatment with EEEG presented a significant antihypertensive effect that was comparable to that of reference antihypertensive drugs currently used to treat arterial hypertension. It is concluded that EEEG elicits significant acute antihypertensive effects through the release of nitric oxide and the stimulation of cholinergic muscarinic and PAF receptors. Moreover, our results suggest that EEEG may be appropriate to chronic oral treatment of arterial hypertension.     

Pharmacological mechanisms involved in the vasodilator effects of extracts from Echinodorus grandiflorus

We investigated the vascular effects of a crude aqueous extract (AEEG) of Echinodorus grandiflorus (Alismataceae) using the in vitro experimental models of the rabbit isolated aorta and perfused kidney. Echinodorus grandiflorus, a native semi-aquatic plant widely distributed in Brazil, has been extensively used in Brazilian folk medicine for the treatment of high blood pressure and inflammatory diseases. The bolus injection of AEEG (0.1-10 mg) into the rabbit renal circulation pre-contracted with norepinephrine induced marked and dose-dependent vasodilator responses (maximum of 37+/-4%; n=6; P<0.001), which was similar to that induced by injection of 10 mmol acetylcholine (41+/-3%). Moreover, AEEG elicited a significant and concentration-dependent relaxation in the endothelium-intact, but not endothelium-denuded aortic rings, reaching the maximum of 81+/-5% (n=7, P<0.001). Inhibition of the nitric oxide-cGMP pathway with L-NAME (100 microM) or Methylene Blue (20 microM) reduced maximum relaxation induced by AEEG from 81+/-5% to 46+/-3 and 45+/-3%, respectively (n=7, P<0.001). A similar reduction was obtained with the incubation of the aortic rings with the selective PAF receptor antagonist WEB 2086 (10 microM) (from 81+/-5% to 55+/-3%; n=7; P<0.01). Conversely, blockade of muscarinic receptors with atropine (10 microM) did not affect the vasodilator effects of AEEG, while inhibition of the enzyme cyclooxigenase not only did not block, but rather potentiated vasodilation induced by AEEG (n=7, P<0.001). Finally, blockade of Ca(2+)- and ATP-activated K(+) channels using the specific blockers charydbotoxin (100 nM) and glibenclamide (3 microM), respectively, did not modify aortic relaxation induced by AEEG. We conclude that water-soluble extracts from leaves of Echinodorus grandiflorus elicit an endothelium-dependent, nitric oxide and PAF receptor-mediated vasodilation in rabbit aortic rings, which does not appear to involve the generation of vasodilating prostaglandins or the activation of K(+) channels. This potent vasodilator effect of the extracts was confirmed in the isolated rabbit renal circulation.     

泽泻饮片质量控制方法研究

目的:探讨泽泻炮制饮片的质量控制指标可行性。方法:采用高效液相色谱法测定泽泻饮片中24-乙酰泽泻醇A和23-乙酰泽泻醇B的含量;采用照相机和Adobe Photoshop软件获取饮片外观信息,评判不同产地泽泻炮制饮片的色泽差异。结果:各炮制饮片中24-乙酰泽泻醇A和23-乙酰泽泻醇B总量均大于0.08%,泽泻饮片色泽均匀性在10～2.5,泽泻饮片色度差在2～8个色度单位。结论:所选质控指标可反映泽泻饮片的内在质量,可用于中药泽泻的质量控制。     

Renaissance remedies: Antiplasmodial protostane triterpenoids from Alisma plantago-aquatica L. (Alismataceae)

Aim of the study

In a preliminary screen of extracts from plants used as antimalarial remedies used in Europe in the 16th and 17th, the ethyl acetate extract of Alisma plantago-aquatica L. (Alismataceae) was active against Plasmodium falciparum K1 strain with 77% growth inhibition at 4.9 μg/ml. The aim of this study was to isolate and identify the substances responsible for this antiplasmodial activity.

Materials and methods

With HPLC-based activity profiling in combination with HPLC hyphenated methods (HPLC-PDA, -MSn, HR-MS, and off-line microprobe NMR) the activity was assigned to time windows, and the substances contained therein were characterised chemically. The active compounds were isolated with semi-preparative HPLC and structures were elucidated with high resolution mass spectrometry, and 1D and 2D NMR spectroscopy.

Results

Four compounds were isolated and identified as protostane triterpenoids alisol A, alisol B 11-monoacetate, alisol B 23-monoacetate, and alisol G. Their IC₅₀s against Plasmodium falciparum ranged from 5.4 to 13.8 μM.

Conclusions

This is the first report of antiplasmodial activity from protostanes triterpenoids, and the first result of our ongoing project of screening for antiprotozoal natural products from remedies used in European renaissance medicine.     

泽泻及复方制剂的化学成分及药理活性的研究进展

目的介绍泽泻植物及复方制剂的研究概况和研究进展。方法以最近几年发表的国内外文献为依据,从化学成分和药理活性作用等方面对泽泻及复方制剂的研究进展做一综述。结果与结论泽泻植物的化学成分结构独特,药理活性多样,具有重要的药用价值。