Blood pressure lowering effect and vascular activity of Phyllanthus niruri extract: The role of NO/cGMP signaling pathway and ß-adrenoceptor mediated relaxation of isolated aortic rings.

ETHNOPHARMACOLOGICAL RELEVANCE: Phyllanthus niruri have a long history of use in the traditional treatment of various ailments including hypertension. Literature reports have indicated that it is a potent antihypertensive herbal medication used traditionally. AIM OF THE STUDY: This study was carried out to investigate the antihypertensive and vasodilatory activity of four solvents extracts of P. niruri namely; petroleum ether (PEPN), chloroform (CLPN), methanol (MEPN) and water (WEPN), with the aim of elucidating the mechanism of action and identifying the phytochemical constituents. MATERIALS AND METHODS: Male Spontaneous Hypertensive Rats (SHRs) were given oral gavage of P. niruri extract daily for two weeks and the blood pressure was recorded in vivo. We also determine the vasodilation effect of the extracts on rings of isolated thoracic aorta pre-contracted with phenylephrine (PE, 1 µM). Endothelium-intact or endothelium-denuded aorta rings were pre-incubated with various antagonists like 1H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 10 µM) and Methylene blue (MB 10 µM), sGC inhibitors; Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME, 10 µM) a nitric oxide synthase (NOS) inhibitor; atropine (10 µM), a cholinergic receptor blocker; indomethacin (10 µM), a cyclooxygenase inhibitor and various K+ channel blockers such as glibenclamide (10 µM) and tetraethyl ammonium (TEA 10 µM) for mechanism study. RESULTS: SHRs receiving P. niruri extracts showed a significant decrease in their blood pressure (BP) when compared to the baseline value, with PEPN being more potent. The extracts (0.125-4 mg/mL) also induced vasorelaxation on endothelium-intact aorta rings. PEPN elicited the most potent maximum relaxation effect (Rmax). Mechanism assessment of PEPN showed that its relaxation effect is significantly suppressed in endothelium-denuded aorta rings. Pre-incubation of aorta rings with atropine, L-NAME, ODQ, indomethacin, and propranolol also significantly attenuated its relaxation effect. Conversely, incubation with TEA and glibenclamide did not show a significant effect on PEPN-induced relaxation. CONCLUSION: This study indicates that the antihypertensive activity of P. niruri extract is mediated by vasoactive phytoconstituents that dilate the arterial wall via endothelium-dependent pathways and ß-adrenoceptor activity which, in turn, cause vasorelaxation and reduce blood pressure.

Mechanisms underlying the vascular relaxation activities of Zingiber officinale var. rubrum in thoracic aorta of spontaneously hypertensive rats.

OBJECTIVE: To evaluate vasorelaxant and vasoconstriction effects of Zingiber officinale var. rubrum (ZOVR) on live rats and isolated aortic rings of spontaneously hypertensive rats (SHRs). METHODS: Extracts of ZOVR were subjected to in-vivo antihypertensive screening using noninvasive blood pressures in SHRs. The most potent extract, ZOVR petroleum ether extract (ZOP) was then fractionated using n-hexane, chloroform and water. Isolated thoracic aortic rings were harvested and subjected to vascular relaxation studies of n-hexane fraction of ZOP (HFZOP) with incubation of different antagonists such as Nω-nitro-l-arginine methyl ester (L-NAME, 10 µmol/L), indomethacin (10 µmol/L), methylene blue (10 µmol/L), atropine (1 µmol/L), glibenclamide (10 µmol/L), prazosin (0.01 µmol/L), and propranolol (1 µmol/L). RESULTS: During the screening of various ZOVR extracts, ZOP produced the most reduction in blood pressures of SHRs and so did HFZOP. HFZOP significantly decreased phenylephrine-induced contraction and enhanced acetylcholine-induced relaxation. L-NAME, indomethacin, methylene blue, atropine, and glibenclamide significantly potentiated the vasorelaxant effects of HFZOP. Propranolol and prazosin did not alter the vasorelaxant effects of HFZOP. HFZOP significantly suppressed the Ca2+-dependent contraction and influenced the ratio of the responses to phenylephrine in Ca2+-free medium. CONCLUSION: This study demonstrates that ZOP may exert an antihypertensive effect in the SHR model. Its possible vascular relaxation mechanisms involve nitric oxide and prostacyclin release, activation of cGMP-KATP channels, stimulation of muscarinic receptors, and transmembrane calcium channel or Ca2+ release from intracellular stores. Possible active compounds that contribute to the vasorelaxant effects are 6-gingerol, 8-gingerol and 6-shogaol.

Phytochemistry and medicinal properties of Phaleria macrocarpa (Scheff.) Boerl. extracts.

Phaleria macrocarpa, commonly known as Mahkota dewa is a medicinal plant that is indigenous to Indonesia and Malaysia. Extracts of P. macrocarpa have been used since years in traditional medicine that are evaluated scientifically as well. The extracts are reported for a number of valuable medicinal properties such as anti-cancer, anti-diabetic, anti-hyperlipidemic, anti-inflammatory, anti-bacterial, anti-fungal, anti-oxidant and vasorelaxant effect. The constituents isolated from different parts of P. macrocarpa include Phalerin, gallic acid, Icaricide C, magniferin, mahkoside A, dodecanoic acid, palmitic acid, des-acetylflavicordin-A, flavicordin-A, flavicordin-D, flavicordin-A glucoside, ethyl stearate, lignans, alkaloids andsaponins. The present review is an up-to-date summary of occurrence, botanical description, ethnopharmacology, bioactivity and toxicological studies related to P. macrocarpa.

Uterotrophic, fetotoxic and abortifacient effect of a Malaysian variety of Plumbago rosea L. on isolated rat uterus and pregnant mice.

Traditionally Plumbago rosea L. is used as an abortifacient in the Southeast Asian region. Methanolic root extract of a local species of Plumbago rosea L. was studied to evaluate its traditional antifertility claim. Interestingly, it was found to possess dose related inhibitory effect on uterine contractile responses elicited by oxytocic agents on isolated uteri of pregnant and pseudo-pregnant rats. Furthermore, it was found to possess significant (p < 0.05) fetotoxic activity along with mild abortive potential in pregnant mice when given orally at high doses (400 and 800 mg kg(-1)) once daily for ten days starting from day 10 of gestation. The results derived indicated possible presence of utero-active compound (s) in this plant that inhibited oxytocic agents induced uterine motility. Moreover, pronounced fetotoxic and mild abortifacient potentials observed at higher doses in pregnant mice might support its accredited traditional use to avoid unwanted pregnancy.