Mesaconitine

Eur J Pharmacol. 2002 Feb 2;436(3):217-25.

Mesaconitine-induced relaxation in rat aorta: involvement of Ca2+ influx and nitric-oxide synthase in the endothelium.[Pubmed: 11858801]

Aconiti tuber, roots of aconite (Aconitum japonicum), is an oriental herbal medicine used for centuries in Japan and China to improve the health of persons with a weak constitution and poor metabolism.
METHODS AND RESULTS:
We investigated the effects of Mesaconitine, one of the aconite alkaloids in Aconiti tuber, on the contraction and free intracellular Ca2+ concentration ([Ca2+]i) level in isolated rat thoracic aorta. Mesaconitine at 30 microM inhibited 3 microM phenylephrine-induced contraction in the endothelium-intact, but not endothelium-denuded, aortic rings. The effect of Mesaconitine was dependent on external Ca2+ concentrations. The relaxation induced by Mesaconitine was abolished by N(omega)-nitro-L-arginine methyl ester (0.1 mM, an inhibitor of nitric-oxide synthase), as well as the relaxation induced by acetylcholine. Acetylcholine induced relaxation in two phases in our conditions; the initial phase was transient and external Ca2+ -independent, and the second phase was sustained and external Ca2+ -dependent. Treatment with 100 nM thapsigargin, which depleted intracellular Ca2+ stores, inhibited acetylcholine-induced, but not Mesaconitine-induced, relaxation. Mesaconitine increased the [Ca2+]i level in endothelial cells by influx of Ca2+ from extracellular spaces.
CONCLUSIONS:
These findings suggest that Mesaconitine-induced Ca2+ influx and activation of nitric-oxide synthase in endothelial cells and, thus, induced vasorelaxation in rat aorta.

Eur J Pharmacol. 1998 Jan 26;342(2-3):183-91.

Inhibition of stimulus-triggered and spontaneous epileptiform activity in rat hippocampal slices by the Aconitum alkaloid mesaconitine.[Pubmed: 9548384]

The aim of the present study was to investigate if the plant alkaloid, Mesaconitine, which has been reported to have antinociceptive effects via stimulation of the noradrenergic system, inhibits epileptiform field potentials.
METHODS AND RESULTS:
The experiments were performed as extracellular recordings on rat hippocampal slices. Epileptiform activity was induced by omission of Mg2+ from the bathing medium or by addition of bicuculline and stimulus-evoked population bursts were recorded in the CA1 region. Spontaneous epileptiform activity was elicited by perfusing a nominally Mg2+-free bathing medium with high K+ concentration (5 mM). Both stimulus-triggered and spontaneous epileptiform activity was attenuated in a concentration-dependent manner by Mesaconitine (30 nM-1 microM). The inhibitory effect was rather variable in appearance when lower concentrations (30 and 100 nM) of Mesaconitine were applied. Pretreatment of the slices with the alpha-adrenoceptor antagonist yohimbine (1 microM) prevented the effect of Mesaconitine.
CONCLUSIONS:
It is concluded that the inhibitory action of Mesaconitine at low concentration is mediated via alpha-adrenoceptors.

Planta Med. 1994 Oct;60(5):391-4.

Antinociceptive mechanism of the aconitine alkaloids mesaconitine and benzoylmesaconine.[Pubmed: 7997462 ]

We explored the possible role of the specific regions in the brain stem on the antinociceptive actions of Mesaconitine (MA) and benzoylmesaconine (BM) by the microinjection of MA and BM into nucleus reticularis paragigantocellularis (NRPG), nucleus raphe magnus (NRM), and periaqueductal gray (PAG). MA microinjected into NRPG, NRM, or PAG elicited a dose-dependent antinociceptive action, whereas BM injected into NRM or PAG elicited a dose-dependent antinociceptive action but not in NRPG. The NRM appeared to be the most sensitive region among the three tested locations.

Xenobiotica. 2011 Jan;41(1):46-58.

Characterization of metabolites and human P450 isoforms involved in the microsomal metabolism of mesaconitine.[Pubmed: 21105783]

Mesaconitine (MA), a major Aconitum alkaloid, provides effects against rheumatosis with high toxicity.
METHODS AND RESULTS:
To supply information for clinical safety, this study aims to investigate the metabolism of MA in male human liver microsomes (MHLMs) and the CYP isoforms involved in its metabolism. Metabolism studies were performed in vitro using MHLMs. Selective chemical inhibitors and recombinant human cytochrome P450 enzymes were used to confirm that the CYP isoforms contributed to MA metabolism. A total of nine metabolites were found and characterized in the MHLM incubations. The metabolic pathways were demethylation, dehydrogenation, hydroxylation, and demethylation-dehydrogenation. Results showed that the inhibitor of CYP3A had a strong inhibitory effect; the inhibitors of CYP2C8, CYP2C9, CYP2C19, and CYP2D6 had modest inhibitory effects, whereas inhibitors of CYP1A2 and CYP2E1 had no obvious inhibitory effects on MA metabolism. Recombinant human cytochrome P450 isoforms CYP3A4 and CYP3A5 contributed greatly to the formation of MA metabolites, and CYP2C8, CYP2C9, and CYP2D6 played a minor role in the formation of MA metabolites.
CONCLUSIONS:
MA could be transformed into at least nine metabolites in MHLMs. MA might be metabolized by CYP3A4, CYP3A5, CYP2C8, CYP2C9, and CYP2D6 in MHLMs.

Eur J Pharmacol. 1982 Aug 13;82(1-2):65-71.

Mechanism of inhibitory action of mesaconitine in acute inflammations.[Pubmed: 6127222]

METHODS AND RESULTS:
Mesaconitine (MA) inhibited carrageenin-induced hind-paw edema in sham-operated mice as well as adrenalectomized mice. Hind-paw edema produced by subplantar injection of histamine, serotonin and prostaglandin E1 was suppressed by MA, indicating that it elicits the antiinflammatory activity at the early exudative stage of inflammations. However, MA did not affect the biosynthesis of the prostaglandins. Trazoline and propranolol had no effect on the inhibitory activity of MA on carrageenin-induced hind-paw edema. MA when administered i.c. at the doses where it shows marked analgesic activity produced dose-dependent antiinflammatory responses on paw edema produced by carrageenin and on vascular permeability accelerated by acetic acid and agar.
CONCLUSIONS:
The inhibitory activity of morphine on carrageenin-induced paw edema failed to be potentiated by the concurrent administration of MA, demonstrating that the mechanism of the antiinflammatory activity of MA involves the central nervous system.