Frequency-dependent inhibition of neuronal activity by lappaconitine in normal and epileptic hippocampal slices

Therapeutic Potentials of Aconite-like Alkaloids: Bioinformatics and Experimental Approaches

Compounds from plants that are used in traditional medicine may have medicinal properties. It is well known that plants belonging to the genus Aconitum are highly poisonous. Utilizing substances derived from Aconitum sp. has been linked to negative effects. In addition to their toxicity, the natural substances derived from Aconitum species may have a range of biological effects on humans, such as analgesic, anti-inflammatory, and anti-cancer characteristics. Multiple in silico, in vitro, and in vivo studies have demonstrated the effectiveness of their therapeutic effects. In this review, the clinical effects of natural compounds extracted from Aconitum sp., focusing on aconitelike alkaloids, are investigated particularly by bioinformatics tools, such as the quantitative structure- activity relationship method, molecular docking, and predicted pharmacokinetic and pharmacodynamic profiles. The experimental and bioinformatics aspects of aconitine's pharmacogenomic profile are discussed. Our review could help shed light on the molecular mechanisms of Aconitum sp. compounds. The effects of several aconite-like alkaloids, such as aconitine, methyllycacintine, or hypaconitine, on specific molecular targets, including voltage-gated sodium channels, CAMK2A and CAMK2G during anesthesia, or BCL2, BCL-XP, and PARP-1 receptors during cancer therapy, are evaluated. According to the reviewed literature, aconite and aconite derivatives have a high affinity for the PARP-1 receptor. The toxicity estimations for aconitine indicate hepatotoxicity and hERG II inhibitor activity; however, this compound is not predicted to be AMES toxic or an hERG I inhibitor. The efficacy of aconitine and its derivatives in treating many illnesses has been proven experimentally. Toxicity occurs as a result of the high ingested dose; however, the usage of this drug in future research is based on the small quantity of an active compound that fulfills a therapeutic role.

The known, unknown, and the intriguing about members of a critically endangered traditional medicinal plant genus Aconitum

Humanity will always be indebted to plants. In the ongoing scientific era, the 'Herbal Revolution' has helped discover several valuable medicinal plants and associated novel secondary metabolites from the diverse unexplored ecosystems, treating several diseases via phytotherapy. The Aconitum genus comprises several economically-important poisonous mountainous medicinal plant species whose unique biodiversity is on the verge of extinction due to illegal human intervention triggered habitat loss, over-harvesting, and unrestricted trading. Owing to its vast diversity of diterpene alkaloids, most species are extensively used to treat several ailments in rural parts of the world. Irrespective of this, many unexplored and intriguing prospects exist to understand and utilize this critical plant for human benefit. This systematic review tries to fill this gap by compiling information from the sporadically available literature known for ~300 Aconitum spp. regarding its nomenclature and classification, endangerment, plant morphology, ploidy, secondary metabolites, drug pharmacokinetics, conservation, and omics-based computational studies. We also depicted the disparity in the studied model organisms for this diverse genus. The absence of genomic/metagenomic data is becoming a limiting factor in understanding its plant physiology, metabolic pathways, and plant-microbes interactions, and therefore must be promoted. Additionally, government support and public participation are crucial in establishing conservation protocols to save this plant from endangerment.

Emerging Promise of Phytochemicals in Ameliorating Neurological Disorders

BACKGROUND

The field of medicine and synthetic drug development have advanced rapidly over the past few decades. However, research on alternative medicine such as phytochemicals cannot be ignored. The main reason for prominent curiosity about phytochemicals stems from the belief that usage of natural compounds is safer and has lesser detrimental side effects.

OBJECTIVE

The aim of the present review was to discuss in detail with several phytochemicals that have been studied or are being studied in the context of various neurological disorders including depression, Alzheimer's disease, Huntington's disease and even neuroinflammatory disorders such as encephalitis.

METHODS

The potential role of phytochemicals in the treatment or management of symptoms associated with neurological disorders have been included in this article. All data included in this paper has been pooled from various databases including Google Scholar, PubMed, Science Direct, Springer and Wiley Online Library.

RESULTS

Phytochemicals have been widely studied for their therapeutic properties associated with neurological disorders. Using various experimental techniques for both in vivo and in vitro experiments, studies have shown that phytochemicals do have antioxidant, anti-inflammatory and neuroprotective activities which play major roles in the treatment of neurological diseases.

CONCLUSION

Even though there has been compelling evidence of the therapeutic role of phytochemicals, further research is still required to evaluate the safety and efficacy of these medicines. Using previously published papers as foundation for additional research such as preclinical studies and clinical trials, phytochemicals can become a safer alternative to synthetic drugs for treating a spectrum of neurological diseases.

C18-diterpenoid alkaloids in tribe Delphineae (Ranunculaceae): phytochemistry, chemotaxonomy, and bioactivities

This review systematically summarizes the C18-diterpenoid alkaloid (DA) compositions isolated from the genera Aconitum and Delphinium in the Delphineae tribe (Ranunculaceae). A total of 117 distinct C18-DA components have been reported, including 58 lappaconitine-type DAs, 54 ranaconitine-type DAs, and five rearranged-type DAs. These components mainly originated from plants from the subgenus Lycoctonum in the genus Aconitum or less frequently from plants within the genus Delphinium. Natural C18-DAs have exhibited a wide range of bioactivities, including analgesic, antiarrhythmic, anti-inflammatory, anti-tumor, and insecticidal activities, which are closely related to their chemical structures. The high chemical and biological diversities among the reported C18-DA constituents in Delphineae plants indicated their potential as a vast resource for drug discovery. Additionally, the Delphineae plant C18-DAs exhibited chemotaxonomic values and showed a high regularity of distribution at different taxonomic levels; therefore, the Delphineae plant C18-DAs can serve as good chemical molecular markers in the taxonomic treatment of plants within this tribe, especially in the infrageneric division.

Historical ethnobotanical review of medicinal plants used to treat children diseases in Romania (1860s-1970s)

BACKGROUND

Romanian ethnopediatrics has a long history of medicinal plant use. The main objective of the present review was to identify, collect, systematize, and prioritize the available bibliographical data related to medicinal plants traditionally used to treat various pediatric diseases in Romania during the 1860s-1970s.

METHODS

Information was mainly obtained by manual systematic search in various relevant historical works focused on the traditional use of medicinal plants in Romania (1860s-1970s), found in the Archives of Romanian Academy Library and National Romanian Library.

RESULTS

A total of 153 medicinal plants belonging to 52 families were identified as having ethnopediatric significance. The plant traditional indications, targeted body systems, parts used, and way of administration were provided. We have also proposed one index (expressed as percentage) in order to assess the ethnopediatric applicability area of species: ethnopediatric relative therapeutic versatility (ERTV), which was calculated on the basis of the number of distinct uses mentioned for a species. The species identified to have the highest ERTV scores were Dryopteris filix-mas (100%), Gratiola officinalis (85.71%), Allium sativum (71.42%), Eryngium planum (71.42%), Juglans regia (71.42%), Matricaria chamomilla (71.42%), Plantago major (71.42%).

CONCLUSIONS

The present study exposed for the first time to the international scientific community important ethnopediatric information contained in several local Romanian bibliographical resources that could guide the local and international researchers towards new directions of plant valorization.

Inhibitory effects of lappaconitine on the neuronal isoforms of voltage-gated sodium channels

Lappaconitine (LA) has been widely used for postoperative and cancer pain control. LA exhibits excellent analgesic activity with a longer effective time than common local anesthetics such as tetracaine and bupivacaine. However, the mechanisms underlying the featured analgesic activity of LA remain largely unknown. Here, we report that LA is an inhibitor of voltage-gated sodium channel 1.7 (Nav1.7) stably expressed in human embryonic kidney (HEK293) cells. LA inhibited Nav1.7 in a voltage-dependent manner with an IC50 value (with 95% confidence limits) of 27.67 (15.68-39.66) µmol/L when the cell was clamped at -70 mV. In comparison with the quick and reversible inhibition of Nav1.7 by tetracaine and bupivacaine, the inhibitory effect of LA was rather slow and irreversible. It took more than 10 min to achieve steady-state inhibition when LA (300 µmol/L) was administered. Unlike tetracaine and bupivacaine, LA affected neither the voltage-dependent activation nor the inactivation of the channels. Five residues in domain III and domain IV have been reported to be critical for the effects of the two local anesthetics on Nav channels. But our mutant study revealed that only two residues (F1737, N1742) located in domain IV were necessary for the inhibitory activity of LA. The slow onset, irreversibility, and lack of influence on channel activation and inactivation accompanied with the different molecular determinants suggest that LA may inhibit Nav1.7 channels in a manner different from local anesthetics. These results may help to understand the featured analgesic activity of LA, thus benefiting its application in the clinic and future drug development.

Anticonvulsant effects of Fuzi total alkaloid on pentylenetetrazole-induced seizure in mice

We investigated the anticonvulsant effect of acute Fuzi total alkaloid (FTA) in seizure induced by the GABAA-receptor antagonist pentylenetetrazole (PTZ). FTA significantly increased the seizure latency and decreased the mortality in PTZ-treated mice. Administration of PTZ increased c-Fos expression in the hippocampus, medial prefrontal cortex, and piriform cortex; and this PTZ-induced effect was inhibited by FTA in a dose-dependent manner. Furthermore, the effects of FTA on PTZ-induced seizure and c-Fos expression were reversed by the GABAA/benzodiazepine receptor-selective antagonist flumazenil. These findings suggest that the anticonvulsant effects of FTA may be related to modulation of GABAA-benzodiazepine receptor complex.

Songorine, a diterpenoid alkaloid of the genus Aconitum, is a novel GABA(A) receptor antagonist in rat brain

Songorine, a diterpenoid alkaloid isolated from the genus Aconitum, was recently found to enhance the excitatory synaptic transmission in rat hippocampus. The mechanism underlying the effects was examined in the present study. The alkaloid at 0.1-300 microM inhibited the specific binding of [(3)H]muscimol to Triton-treated synaptic membranes of rat brain in a concentration-dependent manner (IC(50)=7.06 microM; 95% confidence limits: 3.28-10.84 microM). Scatchard analysis and Lineweaver-Burk double reciprocal plot of [(3)H]muscimol saturation binding data indicate a non-competitive inhibition of the alkaloid on the gamma-aminobutyric acid(A) (GABA(A)) receptor. In acutely dissociated rat hippocampal neurons the alkaloid did not elicit current response, but markedly inhibited the GABA-induced inward current (IC(50)=19.6 microM). The results suggest that songorine is a novel non-competitive antagonist at the GABA(A) receptor in rat brain.

Irreversible block of human heart (hH1) sodium channels by the plant alkaloid lappaconitine

The roots from Aconitum sp. plants have long been used in Chinese herbal medicine for treating pain and various heart conditions. The principal component of Aconitum remedies is usually aconitine, a site 2 neurotoxin that may induce severe neurological symptoms and cardiovascular collapse. Some Aconitum species also contain lappaconitine, the structure of which is remarkably similar to that of aconitine. In contrast to aconitine, a sodium channel agonist, lappaconitine reportedly blocks voltage-gated sodium channels in heart tissue. The results in the present study demonstrate that lappaconitine blocks cloned human heart (hH1) sodium channels under whole-cell, voltage-clamp conditions. Lappaconitine binding has several characteristics in common with the binding of site 2 neurotoxins, such as aconitine and batrachotoxin. For example, lappaconitine binds almost exclusively to open channels, but has little affect on resting or inactivated channels. Moreover, lappaconitine binding is inhibited by bupivacaine, a tertiary amine local anesthetic. Whereas site 2 neurotoxins often irreversibly modify channel kinetics, lappaconitine irreversibly blocks the channels. Finally, channels containing lysine substitutions within the local anesthetic receptor region at residues F1760 or N1765 are resistant to block by bupivacaine or lappaconitine. Given that site 2 neurotoxins and local anesthetics have nonidentical but overlapping binding regions, these data suggest that lappaconitine irreversibly blocks hH1 channels by binding to the site 2 receptor.

Antagonism of the aconitine-induced inexcitability by the structurally related Aconitum alkaloids, lappaconitine and ajacine

Aconitine, lappaconitine and ajacine are structurally related alkaloids occurring in several species of the Aconitum genus. While aconitine is known to activate the voltage-dependent sodium channel, lappaconitine has been reported to block this channel. To investigate a possible antagonism of the aconitine action on neuronal activity by lappaconitine and the closely related alkaloid ajacine, we have performed extracellular recordings of stimulus evoked population spikes and field excitatory postsynaptic potential (EPSP) in rat hippocampal slices. Aconitine (10-100 nM) diminished the amplitude of the orthodromic population spike in a concentration-dependent manner. When aconitine was applied in presence of 10 microM lappaconitine, the concentration-response curve was shifted to the right. Furthermore, the complete suppression of the population spike evoked by 100 nM aconitine was reversed by 10 microM lappaconitine. The action of lappaconitine was mimicked by ajacine, however, the latter alkaloid was less potent. Both lappaconitine and ajacine shifted the input-output relationship of the presynaptic fiber spike as function of the stimulation intensity and of the field EPSP as function of the presynaptic fiber spike to the right. After pharmacological isolation, the presynaptic fiber spike was decreased by both compounds in a frequency-dependent manner indicative for a use-dependent action. Thus, electrophysiologically these alkaloids seem to inhibit predominantly the excitability of the afferent fibres and, in consequence, neurotransmission between Schaffer collaterals and the CA1 neurons, thereby suppressing the firing of the latter. Ajacine and lappaconitine inhibited stimulus-triggered epileptiform population bursts in area CA1 elicited by omission of Mg(2+) as well as spontaneously occurring epileptiform discharges in area CA3 elicited by omission of Mg(2+) and elevation of K(+). It is concluded that the inhibitory and antiepileptiform effect of ajacine and lappaconitine is mediated by a frequency-dependent inhibition of the voltage-dependent sodium channel, thereby decreasing the excitability which might be important for filtering high frequency bursts of action potentials characteristic for epileptiform activity in the hippocampus. Moreover, these alkaloids are naturally occurring antagonists of the sodium channel activator aconitine.

Different effects on [3H]noradrenaline uptake of the Aconitum alkaloids aconitine, 3-acetylaconitine, lappaconitine, and N-desacetyllappaconitine in rat hippocampus

The effect of the Aconitum alkaloids aconitine, 3-acetylaconitine, lappaconitine, and N-desacetyllappaconitine to inhibit [3H]noradrenaline uptake was investigated in rat hippocampal synaptosomes. Aconitine and 3-acetylaconitine, which are known to activate sodium channels, had comparable inhibitory potencies and yielded Ki (inhibitor constant) values of 230 +/- 66 nM and 316 +/- 96 nM, respectively. In contrast, lappaconitine and N-desacetyllappaconitine failed to inhibit [3H]noradrenaline uptake. When either lappaconitine or N-desacetyllappaconitine was applied in combination with aconitine, [3H]noradrenaline uptake was not affected. The sodium channel blocker tetrodotoxin enhanced [3H]noradrenaline uptake, whereas uptake was completely blocked in sodium-free incubation medium. The inhibitory action of aconitine and 3-acetylaconitine on [3H]noradrenaline uptake was blocked by addition of tetrodotoxin. Patch clamp studies performed on cultured rat hippocampal neurons revealed an inhibitory action of lappaconitine and N-desacetyllappaconitine on whole cell sodium currents. It is concluded that the blockade of [3H]noradrenaline uptake evoked by aconitine and 3-acetylaconitine is mediated indirectly by an increased sodium concentration in the synaptosomes.

Inhibition of rat hippocampal excitability by the Aconitum alkaloid, 1-benzoylnapelline, but not by napelline

The effects of the two structurally related Aconitum alkaloids, 1-benzoylnapelline and napelline, were investigated by extracellular recording of the stimulus-evoked population spike in the CA1 region of rat hippocampal slices in vitro. 1-Benzoylnapelline (1-100 microM) exerted a depressant action on the orthodromic as well as on the antidromic population spike. Napelline failed to evoke a significant effect at concentrations up to 100 microM. The inhibitory action induced by 1-benzoylnapelline was enhanced when the frequency of electrical stimulation was increased. In contrast, reversal of the inhibitory effect was accelerated when stimulation frequency was decreased. The activity-dependent mode of action of 1-benzoylnapelline raised the question of whether the drug is effective to suppress epileptiform activity. The results obtained from experiments on epileptiform hippocampal slices revealed a reduction of the burst duration and of the number of spikes in the burst as well as attenuation of the amplitude of the population spikes. These data support the conclusion that 1-benzoylnapelline, in contrast to the structurally related compound, napelline, has an activity-dependent inhibitory action on central neurons.

Structure-dependent differences in the effects of the Aconitum alkaloids lappaconitine, N-desacetyllappaconitine and lappaconidine in rat hippocampal slices

Lappaconitine, a C19 diterpenoid alkaloid from Aconitum sinomontanum has been reported to possess analgesic and antiinflammatory properties in vivo and to inhibit neuronal activity in brain slices. In the present study the effect of lappaconitine has been compared with the effects of its main metabolite N-desacetyllappaconitine and the structurally related alkaloid lappaconidine. For comparison of drug effects population spikes and field excitatory postsynaptic potentials (EPSPs) evoked by stimulation of stratum radiatum or the alveus were studied in normal rat hippocampal slices and in slices treated with low Mg2+-medium. At concentrations of 3-100 microM, both lappaconitine and N-desacetyllappaconitine inhibited population spikes elicited by stratum radiatum and alvear stimulation as well as the field EPSP recorded in CA1 stratum radiatum. The drug-induced depression of field potential responses was increased with rising stimulus frequency, indicating an activity-dependent mode of action. The effect of N-desacetyllappaconitine on each parameter investigated was significantly stronger than the effect of lappaconitine. Despite the structural relationship, lappaconidine failed to affect neuronal excitability in concentration below 100 microM, and an increase in stimulus frequency did not potentiate its effect. Moreover, lappaconitine and N-desacetyllappaconitine suppressed epileptiform activity induced by bicuculline or by omission of Mg2+ from the bathing medium.