Influence of polyphenolic compounds isolated fromRubus coreanum on catecholamine release in the rat adrenal medulla

Depressor action and vasorelaxation of methylene chloride fraction extracted from Rubus coreanum

Introduction

The present study was designed to examine whether methylene chloride (CH₂Cl₂) fraction extracted from Rubus coreanum affects the contractility of the isolated thoracic aortic strips and blood pressure of normotensive rats.

Methods

One of the common carotid arteries or of the femoral arteries was catheterized with a polyethylene tubing. The tubing was connected to a pressure transducer, and pulse of the mean arterial blood pressure was recorded on a biological polygraph continuously.

Results

The CH₂Cl₂ fraction (range, 200 to 800 μg/mL) significantly depressed both phenylephrine (PE, 10 μM)- and high K⁺ (56 mM)-induced contractile responses of the isolated thoracic aortic strips in a concentration-dependent fashion. In the simultaneous presence of N^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME) (an inhibitor of nitric oxide [NO] synthase, 300 μM) and the CH₂Cl₂ fraction (400 μg/mL), both PE- and high K⁺-induced contractile responses were recovered to the significant level of the corresponding control response in comparison with inhibition of CH₂Cl₂ fraction treatment alone. Moreover, in the simultaneous presence of the CH₂Cl₂ fraction after pretreatment with 0.4% CHAPS (3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate), both PE- and high K⁺-induced contractile responses were recovered to the significant level of the corresponding control response compared to the inhibitory response of CH₂Cl₂ fraction treatment alone. Also, in anesthetized rats, the CH₂Cl₂ fraction (range, 0.3 to 3.0 mg/kg) injected into a femoral vein dose-dependently produced depressor responses. This hypotensive action of the CH₂Cl₂ fraction was greatly inhibited after treatment with phentolamine (1 mg/kg), chlorisondamine (1 mg/kg), L-NAME (3 mg/kg/30 min), or sodium nitroprusside (30 μg/kg/30 min). Intravenous infusion of the CH₂Cl₂ fraction (range, 1.0 to 10.0 mg/kg/30 min) markedly inhibited norepinephrine-induced pressor responses.

Discussion

Taken together, these results demonstrate that the CH₂Cl₂ fraction causes vascular relaxation in the isolated rat thoracic aortic strips as well as hypotensive action in anesthetized rats. These vasorelaxation and hypotension of the CH₂Cl₂ fraction seem to be mediated at least by the increased NO production through the activation of NO synthase of the vascular endothelium and the inhibitory adrenergic modulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s40885-014-0006-1) contains supplementary material, which is available to authorized users.

Immature Rubus coreanus Shows a Free Radical-Scavenging Effect and Inhibits Cholesterol Synthesis and Secretion in Liver Cells

Rubus coreanus fruits have been employed as a traditional medicine for centuries in the Asia-Pacific region. Its pharmacological action differs according to the different extraction methods utilized and the degree of fruit ripening. In this study, we determined the cellular effect of different ethanol extracts of mature and immature Rubus coreanus fruits in human hepatic cell line, HepG2 cells. The antioxidant activity, effect on superoxide dismutase activity and cholesterol biosynthesis efficiency was also evaluated. Immature Rubus coreanus extract showed higher antioxidant capability, compared with that of its mature fractions. Cellular antioxidant proteins including HO-1, Cu/Zn-superoxide dismutase and catalase were highly expressed in the presence of Rubus coreanus. Cholesterol levels in HepG2 cells treated with the water fraction of immature Rubus coreanus were significantly reduced. This antihyperlipidaemic action of Rubus coreanus is a consequence of cholesterol biosynthesis and extracellular secretion in HepG2 cells. These results indicate that among different ethanol fraction of mature and immature Rubus coreanus fruit extracts, water extract of immature fruit extract shows higher antioxidant as well as higher antihyperlipidaemic action.

Rubus coreanusInhibits Oxidized-LDL Uptake by Macrophages Through Regulation of JNK Activation

Oxidized low-density lipoprotein (oxLDL) contributes to atherosclerosis in part by being taken up into macrophages via scavenger receptors and leading to foam cell formation. Herbal compounds that have been used to treat blood stasis (a counterpart of atherosclerosis) for centuries include extracts of medicinal plants in the Rosaceae and Leguminosae families. In this study, we investigated the effect of the unripe Rubus coreanus (Korean black raspberry) fruit extract on oxLDL uptake by murine macrophage cells. In the presence of Rubus coreanus extract (RCE), Dil-labeled oxLDL uptake was inhibited in a dose-dependent manner. SP600125, a specific JNK inhibitor, inhibited the uptake of Dil-oxLDL into macrophages. RCE also inhibited JNK phosphorylation in a time- and dose-dependent manner in macrophages treated with oxLDL. These results indicate that among the mitogen-activated protein kinases, JNK phosphorylation is inhibited by RCE, which is likely the mechanism underlying the RCE-induced inhibition of oxLDL uptake by macrophages.