5E- and 5Z-farnesylacetones from Sargassum siliquastrum as novel selective L-type calcium channel blockers

Potential Role of Seaweed Polyphenols in Cardiovascular-Associated Disorders

The beneficial effects of various polyphenols with plant origins on different cardiovascular-associated disorders, such as hypertension, diabetes mellitus type 2 and metabolic syndrome are well known. Recently, marine crude-drugs are emerging as potential treatments in many noncommunicable conditions, including those involving the cardiovascular system. Among the active compounds responsible for these activities, seaweed polyphenols seem to play a key role. The aim of the present review is to summarise the current knowledge about the beneficial effects reported for edible seaweed polyphenols in the amelioration of these prevalent conditions, focusing on both preclinical and clinical studies. This review will help to establish the basis for future studies in this promising field.

A novel antihypertension agent, sargachromenol D from marine brown algae, Sargassum siliquastrum, exerts dual action as an L-type Ca2+ channel blocker and endothelin A/B2 receptor antagonist

We isolated the novel vasoactive marine natural products, (5E,10E)-14-hydroxy-2,6,10-trimethylpentadeca-5,10-dien-4-one (4) and sargachromenol D (5), from Sargassum siliquastrum collected from the coast of the East Sea in South Korea by using activity-guided HPLC purification. The compounds effectively dilated depolarization (50mMK+)-induced basilar artery contraction with EC50 values of 3.52±0.42 and 1.62±0.63μM, respectively, but only sargachromenol D (5) showed a vasodilatory effect on endothelin-1 (ET-1)-induced basilar artery contraction (EC50=9.8±0.6μM). These results indicated that sargachromenol D (5) could act as a dual antagonist of l-type Ca2+ channel and endothelin A/B2 receptors. Moreover, sargachromenol D (5) lowered blood pressure in spontaneous hypertensive rats (SHRs) 2h after oral treatment at a dose of 80mg/kg dose and the effect was maintained for 24h. Based on our ex vivo and in vivo experiments, we propose that sargachromenol D (5) is a strong candidate for the treatment of hypertension that is not controlled by conventional drugs, in particular, severe-, type II diabetes-, salt-sensitive, and metabolic disease-induced hypertension.

DL0805-2, a novel indazole derivative, relaxes angiotensin II-induced contractions of rat aortic rings by inhibiting Rho kinase and calcium fluxes

AIM

DL0805-2 [N-(1H-indazol-5-yl)-1-(4-methylbenzyl) pyrrolidine-3-carboxamide] is a DL0805 derivative with more potent vasorelaxant activity and lower toxicity. This study was conducted to investigate the vasorelaxant mechanisms of DL0805-2 on angiotensin II (Ang II)-induced contractions of rat thoracic aortic rings in vitro.

METHODS

Rat thoracic aortic rings and rat aortic vascular smooth muscle cells (VSMCs) were pretreated with DL0805-2, and then stimulated with Ang II. The tension of the aortic rings was measured through an isometric force transducer. Ang II-induced protein phosphorylation, ROS production and F-actin formation were assessed with Western blotting and immunofluorescence assays. Intracellular free Ca(2+) concentrations were detected with Fluo-3 AM.

RESULTS

Pretreatment with DL0805-2 (1-100 μmol/L) dose-dependently inhibited the constrictions of the aortic rings induced by a single dose of Ang II (10(-7) mol/L) or accumulative addition of Ang II (10(-10)-10(-7) mol/L). The vasodilatory effect of DL0805-2 was independent of endothelium. In the aortic rings, pretreatment with DL0805-2 (1, 3, and 10 μmol/L) suppressed Ang II-induced Ca(2+) influx and intracellular Ca(2+) mobilization, and Ang II-induced phosphorylation of two substrates of Rho kinase (MLC and MYPT1). In VSMCs, pretreatment with DL0805-2 (1, 3, and 10 μmol/L) also suppressed Ang II-induced Ca(2+) fluxes and phosphorylation of MLC and MYPT1. In addition, pretreatment with DL0805-2 attenuated ROS production and F-actin formation in the cells.

CONCLUSION

DL0805-2 exerts a vasodilatory action in rat aortic rings through inhibiting the Rho/ROCK pathway and calcium fluxes.