In the present study, we tested a 50% ethanolic extract of Orthosiphon stamineus plants and its isolated bioactive compound with respect to their α-glucosidase and α-amylase inhibitory activities.
The mode by which Loranthus ferrugineus methanol extract antagonizes and/or modulates norepinephrine-induced vasoconstriction was investigated in rat aortic rings. The vascular effects of three different concentrations of this extract were challenged against cumulative additions of norepinephrine. Phentolamine, a nonselective α-adrenoceptor antagonist, verapamil, an L-type calcium channel blocker, and papaverine, a phosphodiesterase inhibitor, were used in three different concentrations as positive controls. Log concentration-response curves and double-reciprocal plots were constructed for the extract and each vasorelaxant. To characterize antagonism reversibility, the norepinephrine maximum contractile effect was examined before extract addition to the aortic ring chamber and after its removal. Phentolamine shifted the norepinephrine log concentration-response curve to the right with no significant depression in the maximum response. Similar to verapamil and papaverine, the extract produced a rightward shift in norepinephrine log concentration-response curve and a significant drop in maximum response. The double-reciprocal plots showed comparable y-intercept values for all phentolamine concentrations, a characteristic of competitive antagonism. In contrast, different y-intercept values on double-reciprocal plots were obtained for each concentration of extract, verapamil, and papaverine, typical of noncompetitive antagonism. The norepinephrine maximum contractile response was approximately similar before the addition of extract and after its removal. The data collectively showed that L. ferrugineus methanol extract exerted its vascular effect by reversible noncompetitive antagonism of norepinephrine-induced vasoconstriction. These findings add to the understanding of the cardiovascular mechanisms by which L. ferrugineus, a plant traditionally used for the management of hypertension, elicits its action.
This study aimed to elucidate the mechanism(s) of the spasmogenic action of Loranthus ferrugineus in isolated guinea pig ileum. Thus the contractile responses of guinea pig ileum to graded additions of either L. ferrugineus methanol extract or its n-butanol fraction were tested in the presence and absence of various pharmacological interventions. The data showed that L. ferrugineus methanol extract and the n-butanol fraction produced a concentration-dependent spasmogenic effect in isolated guinea pig ileum segments. These effects were significantly inhibited in the presence of 1 microM atropine. In contrast, the response to the lowest concentrations of L. ferrugineus methanol extract (0.25, 0.5 and 1 mg/mL) and n-butanol fraction of L. ferrugineus (0.125, 0.25 and 0.5 mg/mL) were considerably enhanced in the presence of 0.05 microM neostigmine. Neither L. ferrugineus methanol extract nor n-butanol fraction contractile responses were affected upon the incubation of the ileal segments with 100 microM hexamethonium. The results of this study show that the spasmogenic effect of L. ferrugineus is possibly mediated through a direct action on intestinal muscarinic receptors. It is suggested that the bioactive constituents of L. ferrugineus serve as a substrate for acetylcholinesterase.
We investigated the vascular responses and the blood pressure reducing effects of different fractions obtained from the methanol extract of Loranthus ferrugineus Roxb. (F. Loranthaceae). By means of solvent-solvent extraction, L. ferrugineus methanol extract (LFME) was successively fractionated with chloroform, ethyl acetate and n-butanol. The ability of these LFME fractions to relax vascular smooth muscle against phenylephrine (PE)- and KCl-induced contractions in isolated rat aortic rings was determined. In another set of experiments, LFME fractions were tested for blood pressure lowering activity in anesthetized adult male Sprague-Dawley rats (250-300 g, 14-18 weeks). The n-butanol fraction of LFME (NBF-LFME) produced a significant concentration-dependent inhibition of PE- and KCl-induced aortic ring contractions compared to other fractions. Moreover, NBF-LFME had a significantly higher relaxant effect against PE- than against high K+-induced contractions. In anesthetized Sprague-Dawley rats, NBF-LFME significantly lowered blood pressure in a dose-dependent manner and with a relatively longer duration of action compared to the other fractions. HPLC, UV and IR spectra suggested the presence of terpenoid constituents in both LFME and NBF-LFME. Accordingly, we conclude that NBF-LFME is the most potent fraction producing a concentration-dependent relaxation in vascular smooth muscle in vitro and a dose-dependent blood pressure lowering activity in vivo. The cardiovascular effects of NBF-LFME are most likely attributable to its terpenoid content.
Recently, the fruits of Hylocereus polyrhizus, known as red dragon fruit, have received much attention from growers worldwide. However, there is little toxicological information regarding the safety of repeated exposure to these fruits. The present study evaluated the potential toxicity of a methanol extract of H. polyrhizus fruit after acute and subchronic administration in rats. In the acute toxicity study, single doses of fruit extract (1250, 2500 and 5000 mg/kg) were administered to rats by oral gavage, and the rats were then monitored for 14 days. In the subchronic toxicity study, the fruit extract was administered orally to rats at doses of 1250, 2500 and 5000 mg/kg/day for 28 days. There was no mortality or signs of acute or subchronic toxicity. There was no significant difference in body weight, relative organ weight or hematological parameters in the subchronic toxicity study. Biochemical analysis showed some significant changes, including creatinine, globulin, total protein and urea levels. No abnormality of internal organs was observed between treatment and control groups. The lethal oral dose of the fruit extract is more than 5000 mg/kg and the no-observed-adverse-effect level (NOAEL) of the extract for both male and female rats is considered to be 5000 mg/kg per day for 28 days.
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.
The present study aimed to investigate the mechanisms underlying the anti-inflammatory and anti-angiogenic effects of ethyl-p-methoxycinnamate isolated from Kaempferia galanga.
The aim of the present study was to verify the anti-inflammatory activity of Orthosiphon stamineus leaf extracts and to identify the active compound(s) contributing to its anti-inflammatory activity using a developed HPLC method. Active chloroform extract of O. stamineus was fractionated into three fractions using a dry flash column chromatography method. These three fractions were investigated for anti-peritoneal capillary permeability, in vitro nitric oxide scavenging activity, anti-inflammatory and nitric oxide (NO) inhibition using carrageenan-induced hind paw edema method. The flavonoid rich chloroform extract fraction (CF2) [containing sinensetin (2.86% w/w), eupatorin (5.05% w/w) and 3'-hydroxy-5,6,7,4'-tetramethoxyflavone (1.101% w/w)], significantly reduced rat hind paw edema, NO and decreased dye leakage to peritoneal cavity at p < 0.05. IC(50) of in vitro NO scavenging of CF2 was 0.3 mg/mL. These results suggest that the anti-inflammatory properties of these CF2 may possibly be due to the presence of flavonoid compounds capable of affecting the NO pathway.
Averrhoa carambola is a species of tree native to tropical Southeast Asia. It possesses antioxidant and anti-hyperlipidemia effects and has traditionally been used to treat a variety of ailments. However, the presence of oxalic acid in its fruits might restrict its consumption by individuals suffering from kidney disease, and caramboxin can cause neurotoxicity. In this study, we evaluated the acute and sub-chronic toxicity of the methanolic extract of A. carambola leaves (MEAC) in male and female rats. In the acute study, female rats were given a single oral dose of 5000 mg/kg of MEAC and closely examined for distinct indications of toxic effects during the first 4 h, periodically for 48 h, and daily thereafter for 14 days. Rats of both sexes were employed in the sub-chronic investigation for the 28-day repeated dose oral toxicity study. Results of the acute study revealed the safety of MEAC up to a dose of 5000 mg/kg where the rats did not show changes or signs of toxicity. In the sub-chronic toxicity study, MEAC (250, 500, and 1000 mg/kg) administration did not affect the body weight, food, and water consumption, motor coordination, behavior, or mental alertness in the treated rats. In addition, no variations in hematological or biochemical markers were found in MEAC-treated rats. In conclusion, these findings pinpoint the safety of MEAC at doses up to 5000 mg/kg. The leaves of A. carambola could be safely consumed by people with kidney disease to treat other ailments.