Cardiovascular disorders including coronary heart disease, stroke and peripheral vascular diseases have been stated as leading cause of morbidity and mortality all through world. Hypertension is an important uninterrupted, constant and autonomous risk factor for concomitant cardiovascular diseases and is a worldwide menace on account of lifelong use, allied undesired and non-curative effects of the available therapeutic drugs. Inefficiency, high cost and undesirable effects of current drug therapy against hypertension create a prerequisite to unveil new sources of drugs. Pakistan is blessed with medicinal flora with more than 6,000 species of medicinal plants. Plants by containing different variety of biologically active constituents, with variable mechanism of action that may work synergistically, offer greater advantage than single entity to prevent complex disease like hypertension. Due to these reasons, two medicinal plants have been selected claimed to be effective for various cardiovascular diseases in present research work. In current study, antihypertensive, diuretic, cardiac and vasorelaxant effects of aqueousmethanolic crude extract/fractions of Crataegus songarica C. Koch (fruits) and Asphodelus tenuifolius Cavan (seeds) were evaluated. Initially, acute hypotensive effect of crude extract of both plants was evaluated at various doses (100, 250, 500 mg/kg) in normotensive rats by using non-invasive blood pressure measuring apparatus. Data obtained in this study, demonstrated that crude extracts of both plants have significantly decreased blood pressure and heart rate in the dose dependent manner with maximum effect at 500 mg/kg. Further studies were carried out to evaluate preventive effect of crude extract of both plants on hypertension and metabolic alterations in glucose induced hypertensive rats. The crude extracts of both plants significantly prevented, blood pressure elevation and various metabolic alterations including hyperglycemia, insulin resistance, dyslipidemia, oxidative stress and aortic endothelial dysfunction in glucose-induced hypertensive rats. The crude extract of both plants were subjected to acute, sub-chronic and cytotoxicity studies to determine their safety profile. During acute toxicity testing, both extracts were found safe and no mortality was observed at the dose as high as 5g/kg. The results of Sub-chronic toxicity experiments in sprague-dawely rats exhibited that both plant extracts were safe and no significant signs of toxicity were shown. Moreover, no anomalous alterations were documented in liver enzymes and lipid profile of treated animals. In addition, cytotoxicity studies also validated the safety of both crude extracts. Keeping in view the protective potential against hypertension and safety profile of both crude extracts, further experiments were designed. Crude extract of both plants were subjected to activity guided fractionation by using different polarity based solvents i.e. hexane, dichloromethane, ethyl acetate and n-butanol. Butanol and aqueous soluble fractions of C. songarica were used for pharmacological studies, whereas, ethyl acetate, dichloromethane and hexane soluble fractions were not utilized due to their insufficient quantity. For A. tenuifolius, dichloromethane, butanol and aqueous soluble fractions were investigated for pharmacological studies, whereas ethyl acetate soluble fraction due to insufficient quantity and hexane soluble fraction of A. tenuifolius due to insolubility in any solvent were not used for further studies. As crude extract of both plants produce hypotensive effect in normotensive rats measured via non-invasive BP measuring apparatus. To further validate this hypotensive effect in normotensive rats and to explore their underlying mechanism of action, we have used invasive blood pressure measuring technique and evaluated all extract/fraction for their hypotensive effect in anesthetized rats. Results has revealed that all the extract/fractions of both plants produce dose dependent hypotensive effect in anesthetized rats with most potent effect produced by aqueous fractions of both plants. Moreover, possible involvement of acetylcholine, prostaglandins, angiotensin converting enzyme and nitric oxide in hypotensive action of most active fraction of both plants was determined. Data revealed that, hypotensive effect of aqueous soluble fraction of C. songarica (AS-CS) was reduced in the presence of LNAME and atropine, whereas, presence of indomethacin, hexamethonium and captopril did not alter the hypotensive effect pointing towards the fact that hypotensive effect of AS-CS might be produced through nitric oxide pathway activated by muscarinic receptors. In contrast, hypotensive effect of aqueous soluble fraction of A. tenuifolius (AS-AT) was reduced in the presence of atropine, whereas, presence of L-NAME, indomethacin, hexamethonium and captopril did not alter the hypotensive effect of AS-AT demonstrating that muscarinic receptors are involved in hypotensive effect. Diuretics enhances excretion of large amount of water and salts from body in order to decrease blood volume and blood pressure, therefore, further studies were designed to appraise the acute diuretic effect at various doses of crude extract (100, 250 and 500 mg/kg) and fractions (100, 200 and 300 mg/kg) of both plants. The diuretic potential was estimated by urine analysis for volume and electrolyte concentrations after 6 hr of treatment with extract/fractions. Data obtained showed that, acute treatment with extract/fractions of both plants exhibited significant diuretic potential. However, 300 mg/kg dose of aqueous soluble fraction of both plants produced most potent and significant diuretic effect. Involvement of acetylcholine, prostaglandins and nitric oxide was determined in diuretic action of most potent fractions by using pharmacological antagonists/inhibitors. Data obtained showed that diuretic activity of aqueous soluble fraction of C. songarica (AS-CS, 300 mg/kg) was reduced in the presence of L-NAME and atropine, whereas, presence of indomethacin failed to alter the diuretic action, exhibiting the involvement of nitric oxide pathway activated by muscarinic receptors. In contrast, diuretic action of aqueous soluble fraction of A. tenuifolius (AS-AT, 300 mg/kg) was reduced in the presence of atropine, whereas, presence of L-NAME and indomethacin did not alter the diuretic action demonstrating the involvement of muscarinic receptors in diuretic activity. Most active fractions i.e. AS-CS (300 mg/kg) and AS-AT (300 mg/kg) were further subjected to prolong diuretic activity (7 days treatment). At the end of 7 days treatment, effect of both active fractions on angiotensin converting enzyme and erythrocyte carbonic anhydrase activity were determined with in-vitro assays. Moreover, in-vitro renal Na+/K+/ATPase activity at various concentrations of extract was also analyzed using kidney of normal rats. Data obtained revealed that AS-CS showed significant angiotensin converting enzyme inhibitory activity with no effect on erythrocyte carbonic anhydrase and renal Na+/K+/ATPase activity. In contrast, AS-AT did not show any of the enzymatic activity. Various drugs produce their antihypertensive effect through negative inotropic and chronotropic actions, therefore, studies were carried out to evaluate the effect of crude extract/fractions of both plants in isolated rat heart using Langendorff technique. Results has revealed that crude extracts and fractions of both plants significantly decrease the force of contraction and heart rate in isolated perfused rat hearts except aqueous soluble fraction of A. tenuifolius (AS-AT), which produced noteworthy increase in force of contraction and heart rate. Aqueous soluble fraction of C. songarica (AS-CS) and butanol soluble fraction of A. tenuifolius (BS-AT) produced most potent negative inotropic and chronotropic effect. Vasorelaxant drugs are well known to reduce peripheral vascular resistance and blood pressure. Studies were carried out to determine the co-relation of antihypertensive effects of the both plants with vasorelaxant activity. For this purpose, extract/fractions of both plants were evaluated for their vasorelaxant activity in isolated porcine coronary arteries. Result obtained showed that crude extracts/fractions of both plants produced a dose dependent vasorelaxant effects in U46619 pre-contracted porcine coronary artery rings except aqueous soluble fraction of A. tenuifolius, which initially produced significant vasoconstriction followed by mild vasorelaxation at higher concentrations. C. songarica produced endothelium dependent vasorelaxation, whereas, A. tenuifolius produced endothelium independent vasorelaxant activity in U46619 pre-contracted rings. Interestingly, the vasorelaxant effects of aqueous fraction of C. songarica (AS-AT) and butanol fraction of A. tenuifolius (BS-AT) were more potent and significant among other fractions. Therefore, these fractions were selected for further investigations to characterize the possible mechanism (s) of endothelium dependent relaxation response to AS-CS and endothelium independent relaxation response to BS-AT. To understand the mechanism of endothelium dependent vasorelaxation of aqueous soluble fraction of C. songarica (AS-CS), experiments were carried out to explore the involvement of nitric oxide (NO), prostacyclin (PGI2), potassium and calcium channels, NO/sGC/cGMP pathway, PI3kinase/Akt-eNOS signaling pathway, reactive oxygen species and various receptors (muscarinic, estrogen, bradykinin, tachykinin receptors) for nitric oxide activation. It was observed that relaxation induced by AS-CS was significantly reduced by pretreatment with L-NAME and ODQ. In contrast, indomethacin had no effect on the AS-CS vascular effect, suggesting the involvement of the NO/sGC/cGMP pathway. The vascular effect of AS-CS was significantly reduced by pre-contraction of PCAs with KCl. Moreover, in the presence of non-selective K+ channel blocker tetraethylammonium (TEA), the vasorelaxant response induced by increasing concentrations of AS-CS was significantly attenuated, suggesting the involvement of potassium channels in the vasorelaxation effect of AS-CS. In the present study, LY249002 (PI3-kinase inhibitor) and PP2 (Src tyrosine kinase inhibitor), both attenuated the AS-CS-induced vasorelaxation lending support to the idea that AS-CS induces vasorelaxation via activation of a PI3 kinase/Akt-eNOS signaling pathway. These data were further confirmed by experiments showing an increase p-AKT and p-eNOS production in PCAs in the presence of AS-CS detected with confocal microscope. Furthermore, PEG-catalase (hydrogen peroxide inhibitor), diethyldithiocarbamate (superoxide dismutase inhibitor) and MnTMPyP significantly prevented the AS-CS induced vasorelaxation, supporting a role for reactive oxygen species in eNOS activation pathway. These findings were validated through experiments presenting an increase in ROS production in the endothelium of PCAs in the presence of AS-CS detected through confocal microscope. Relaxation responses to AS-CS were also attenuated in the absence of extracellular calcium that was further supported by experiments showing that AS-CS inhibits calcium-induced contraction of the PCA. In order to determine whether components of the AS-CS extract could be acting through endothelial receptors (muscarinic, estrogen, bradykinin or tachykinin receptors), PCA rings were pre-incubated with antagonists of these four receptors. Neither atropine, win64338, nor L760735 inhibited the relaxation to AS-CS, indicating that neither muscarinic, bradykinin B2, nor tachykinin NK1 receptors are involved in the relaxation response. On the other hand, both tamoxifen and ICI 182, 782 significantly reduced the ASCS induced vasorelaxation in PCAs, indicating the involvement of estrogen receptors. To understand the mechanism of endothelium independent vasorelaxation of butanol soluble fraction of A. tenuifolius (BS-AT), a separate set of experiments were carried out to explore, involvement of potassium and calcium channels, role of intracellular/extracellular calcium, cAMP, cGMP and myosin light chain kinase signaling pathway. The vascular effect of BSAT was not affected by pre-contraction of PCAs with KCl. Moreover, tetraethylammonium (nonselective K+ channel blocker) also did not affect the vasorelaxant effect of BS-AT, indicating that K+ channel activation is not involved in the vasorelaxant effect of BS-AT. Incubation of PCA rings with ODQ (sGC inhibitor), did not affect the response of BS-AT. It was also found that BS-AT, did not produced shifting of concentration response curve of the endothelium-independent vasodilator forskolin, ruling out the involvement of cGMP and cAMP pathway. However, pretreatment with increasing concentrations of BS-AT suppressed in dose dependent fashion the cumulative contraction response induced by CaCl2, BAY K8644 and U46619. These data were further supported by experiments to determine the relaxation effect of BS-AT in the absence of extracellular calcium. The relaxation response was attenuated, indicating at least a partial role for extracellular calcium. However, relaxations to BS-AT were also reduced after depletion of intracellular stores with cyclopiazonic acid, indicating that BS-AT could be acting through inhibition of calcium influx and inhibition of release of intracellular calcium, or inhibition of the signaling pathway downstream of calcium. Further evidence that BS-AT is acting to inhibit the calcium signaling pathway came from experiments using ionomycin. This was confirmed by showing that the ionomycin-induced contraction were inhibited in the presence of BS-AT indicating that components within BS-AT are acting downstream of calcium influx. Therefore, phosphorylation of myosin light chain kinase (MLCs) was detected by Western blotting and was indicated by a shift in the observed molecular weight. In the presence of BS-AT, there was no shift in the molecular weight of MLCs, indicating an inhibition of MLC phosphorylation. Moreover, in order to test whether components of BS-AT could be acting as Rho kinase inhibitors, relaxation responses to BS-AT was evaluated in the presence of Y- 27632 (Rho kinase inhibitor). Vasorelaxant effect of BS-AT was not reduced, which would rule out the involvement of Rho kinase as a mechanism. The phytochemical profile of extract/fractions of both plants were analyzed by GC-MS, HPLC-DAD and LC-DAD-MS analysis. 10 different chemical constituents were identified by GC-MS in Crataegus extract/fractions including certain constituents having anti-oxidant activity i.e. 5‑Hydroxymethylfurfural and (E)-stilbene. Whereas, GC-MS analysis of A. tenuifolius exhibited 20 different chemical constituents with certain compounds having antioxidant activity i.e. 2, 5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), 5- hydroxymethylfurfural, cis-stilbene and 2, 3-dihydro-3, 5-dihydroxy-6-methyl-4H-pyran-4- one. HPLC-DAD analysis showed the presence of rutin, caffeic acid, apigenin, quercetin and kaempferol in extract/fractions of both plants, whereas, gallic acid was found only in C. songarica and myricetin was found only in A. tenuifolius. LC-DAD-MS analysis detected and identified eighteen compounds in A. tenuifolius including dihydroxycoumarin, harmine and harmaline and some sugar derivatives such as hexitol, hexonic acid, di-O-hexoside and tri-O-hexoside. In addition, thirty-nine compounds were detected and identified in C. songarica, including gallic acid and their glycosylated derivatives, glycosylated flavonoids (flavononols, flavones, and flavonols), caffeic acid derivatives and hydrolysable tannins. In conclusion, the data generated in this study laid credence to the beneficial role of A. tenuifolius and C. songarica in the management of hypertension. Both plants were found safe and no signs of toxicity or adverse effects were observed during toxicity studies. C. songarica produce hypotensive, diuretic and vasorelaxant effect mediated by NO/cGMP pathway. Aqueous soluble fraction of C. songarica was found most active for aforesaid activities. Whereas, A. tenuifolius induced hypotensive effect was mediated by its diuretic and vasorelaxant activity. Aqueous soluble fraction produced maximum diuretic effect by activation of muscarinic receptors, whereas, butanol soluble fraction of A. tenuifolius produce most potent vasorelaxant effect by inhibiting calcium-dependent signaling pathway within vascular smooth muscle. It is further concluded that no single chemical entity could be accountable for the reported pharmacological activities in both plants, since numerous phytochemicals have been recognized in both plants as revealed from aforesaid investigations. Hence, further investigations about isolation of pure active principle(s), interpretation of their structural formulas and elucidation of their precise mechanism(s) of antihypertensive action would be required." xml:lang="en_US