In the present study, L. ferrugineus methanol extract (LFME) was evaluated for its blood pressure lowering effect in anesthetized normotensive Sprague Dawley (SD) rats and its spasmogenic effect in isolated guinea pig ileum. The possible mechanism(s) of action were also investigated. LFME was obtained by Soxhlet extraction. The rats were fasted overnight and anesthetized with sodium pentobarbitone (60 mg/kg i.p.). LFME was administered in i.v. boluses in the concentrations of 25, 50, 100 and 200 mg/kg respectively, with concomitant monitoring of mean arterial pressure (MAP). It was found that LFME dose-dependently reduced MAP. An i.v. bolus injection of atropine significantly decreased the blood pressure lowering effect of LFME. Similarly, L-NAME (Nomega-nitro-L-arginine methyl ester) significantly lowered both the MAP and the action duration. Conversely, no significant change in MAP was seen following i.v. injections of neostigmine, hexamethonium, prazosin and propranolol. LFME also produced a dose-dependent contractile effect in guinea pig ileum. This contraction was significantly reduced in atropine pre-incubated tissue segments, yet it was significantly enhanced in the presence of neostigmine. No appreciable change in the ability of LFME to contract guinea pig ileum was seen in the presence of hexamethonium. Accordingly, it can be postulated that LFME possesses a marked hypotensive effect that can be attributed to stimulation of muscarinic receptors and/or stimulation of nitric oxide (NO) release. Moreover, LFME retains a considerable spasmogenic action due to its cholinergic properties. The hypotensive and spasmogenic effects of LFME justify its traditional uses.
Winged bean seed (WBS) is an underutilized tropical crop. The current study evaluates its potential to reduce blood pressure (BP) in spontaneously hypertensive rats and finds that it reduces BP significantly, in a dose-dependent manner. Five peptides with the sequences, RGVFPCLK, TQLDLPTQ, EPALVP, MRSVVT and DMKP, have been characterized in terms of their stability against ACE via in vitro and in silico modelling. All peptides exhibited IC50 values between 0.019 and 6.885 mM and various inhibitory modes, including substrate, prodrug and true inhibitor modes. The toxicity status of non-Current Good Manufacturing Practice (non-CGMP) peptides is evaluated and the results show that such peptides are toxic, and thus are not suitable to be tested in animals, particularly in repeated-dose studies. In short, WBS hydrolysate demonstrated in vitro ACE inhibitory properties and in vivo blood pressure lowering efficacy in rat models, fostering its potential as a functional food ingredient. Non-CGMP grade peptides are toxic and unfit for testing in animal models.
Poor aqueous solubility and unfavourable de-esterification of olmesartan medoxomil (a selective angiotensin II receptor blocker), results in low oral bioavailability of less than 26%. Improvement of oral bioavailability with prolonged pharmacodynamics activity of olmesartan in Wistar rats had been approached by nanoemulsification strategy in our previous article [Colloid Surface B, 115, 2014: 286]. In continuation to that work, we herewith report the biodistribution behaviour and 28-day repeated dose sub-chronic toxicity of olmesartan medoxomil nanoemulsion in Wistar rats following oral administration. The levels of olmesartan in collected biological samples were estimated using our validated LC-MS/MS technique. Our biodistribution study showed significantly higher brain concentrations of olmesartan (0.290 ± 0.089 μg/mL, 0.333 ± 0.071 μg/mL and 0.217 ± 0.062 μg/mL at 0.5, 2.0 and 8.0 h post dosing, respectively) when administered orally as nanoemulsion formulation as compared to the aqueous suspension. In addition, the olmesartan nanoemulsion was found to be safe and non-toxic, as it neither produced any lethality nor remarkable haematological, biochemical and structural adverse effects as observed during the 28-days sub-chronic toxicity studies in experimental Wistar rats. It is herewith envisaged that the developed nanoemulsion formulation approach for the delivery of olmesartan medoxomil via oral route can further be explored in memory dysfunction and brain ischemia, for better brain penetration and improved clinical application in stroke patients.
The seeds of Swietenia macrophylla King (SM) (Meliaceae) are used as a folk medicine for the treatment of hypertension in Malaysia. However, the antihypertensive and vasorelaxant effects of SM seeds are still not widely studied. Thus, this study was designed to investigate the in vivo antihypertensive effects and in vitro mechanism of vasorelaxation of a 50% ethanolic SM seed extract (SM50) and the fingerprint of SM50 was developed through tri-step Fourier transform infrared (FTIR) spectroscopy. The vasorelaxant activity and the underlying mechanisms of SM50 were evaluated on thoracic aortic rings isolated from Sprague-Dawley rats in the presence of antagonists. The pharmacological effect of SM50 was investigated by oral administration of spontaneously hypertensive rats (SHRs) with three different doses of SM50 (1000, 500, and 250 mg/kg/day) for 4 weeks and their systolic blood pressure (SBP) and diastolic blood pressure (DBP) values were measured weekly using tail-cuff method. The tri-step FTIR macro-fingerprint of SM50 showed that SM50 contains stachyose, flavonoids, limonoids, and ester, which may contribute to its vasorelaxant effect. The results showed that the vasorelaxant activity of SM50 was mostly attributed to channel-linked receptors pathways through the blockage of voltage-operated calcium channels (VOCC). SM50 also acts as both potassium channels opener and inositol triphosphate receptor (IP3R) inhibitor, followed by β2-adrenergic pathway, and ultimately mediated through the nitric oxide/soluble guanylyl cyclase/cyclic 3',5'-guanosine monophosphate (NO/sGC/cGMP) signaling pathways. The treatment of SM50 also significantly decreased the SBP and DBP in SHRs. In conclusion, the antihypertensive mechanism of SM50 was mediated by VOCC, K+ channels, IP3R, G-protein-coupled β2-adrenergic receptor, and followed by NO/sGC/cGMP signaling mechanism pathways in descending order. The data suggested that SM50 has the potential to be used as a herbal medicament to treat hypertension.