Norditerpenoid alkaloids of Delphinium denudatum as cholinesterase inhibitors

New amide and diterpene alkaloids with anticholinesterase activity from Delphinium cyphoplectrum roots

BACKGROUND

The cholinergic hypothesis posits a robust correlation between the onset of Alzheimer's disease and a pronounced deficit in acetylcholine, a pivotal neurotransmitter crucial for the central cholinergic nervous system's function, pivotal for memory and learning. Diterpene alkaloids exhibit intricate and distinctive chemical structures that facilitate their passage through the blood-brain barrier. Moreover, their potent pharmacological attributes render them promising candidates for addressing central nervous system disorders.

OBJECTIVES

This investigation aims to scrutinize the alkaloidal composition of Delphinium cyphoplectrum (Ranunculaceae) roots, further exploring their anticholinesterase inhibitory activity and mode of inhibition.

METHOD

Innovative chromatography techniques were repetitively employed to purify the alkaloids. Acetylcholinesterase (AChE) inhibition assays were conducted using Ellman's tests. The mode of inhibition was meticulously characterized through Michaelis-Menten, and Lineweaver-Burk plots. Conducting molecular docking studies, we employed the AUTO DOCK 4.2 software package.

RESULTS

Eight alkaloids were identified including five C19-diterpene alkaloids (6,14,16,18-tetramethoxy-1,7,8-trihydroxy-4-methylaconitane (1), 6,16,18-trimethoxy-1,7,8,14-tetrahydroxy-4-methylaconitane (2), 6,8,16,18-tetramethoxy-1,7,14-trihydroxy-4-methylaconitane (3), 6,14,16-trimethoxy-1,7,8,18-tetrahydroxy-4-methylaconitane (4), and 14-O-acetyl-8,16-dimethoxy-1,6,7,18-tetrahydroxy-4-methylaconitane (5)), an epoxy C18-diterpene alkaloid (6,8,16-trimethoxy-1,7,14-trihydroxy-3,4-epoxyaconitane (6)), a known (pyrrolidin-2-one (7) and an undescribed amide alkaloid (1-(2'-hydroxylethylamine)-3,5,5,-trimethyl-1,5-dihydro-2H-pyrrol-2-one (8). All diterpene alkaloids underwent assessment for acetylcholinesterase (AChE) inhibition assay and displayed noteworthy AChE activity, surpassing that of the reference drug (with IC50 values of 13.7, 21.8, 23.4, 28.2, 40.4, and 23.9 for compounds 1-6, respectively, in comparison to 98.4 for Rivastigmine). Analysis of Michaelis-Menten and Lineweaver-Burk plots represents an uncompetitive mode of inhibition for compound 1 on AChE. Notably, computational docking simulations indicated that all diterpene alkaloids were accommodated within the same enzymatic cleft as the reference ligand, and displaying superior free binding energy values (from - 10.32 to -8.59 Kcal.mol-1) in contrast to Rivastigmine (-6.31 Kcal.mol-1).

CONCLUSION

The phytochemical analysis conducted on the roots of Delphinium cyphoplectrum yielded the identification of eight alkaloidal compounds including one C18-diterpene, five C19-diterpene, one pyrrolidine and one amide alkaloids. AChE inhibition assay and molecular simulations unveiled remarkable significant potency attributed to the C19-diterpene alkaloids by the order of 1 > 2 > 3,6 > 4 > 5. Presence of hydroxyl group on C-1, C-7, C-8, C-14, and C-18 increased the effect. The best in vitro activity was recorded for compound 1 able to bind to Asp72 in the narrow region of PAS, while interacting by pi-sigma with Phe330 at the hydrophobic region of the gorge involving the acyl and choline binding site. This observation underscores the substantial promise of this category of natural products in the realm of drug discovery for Alzheimer's Disease, offering a compelling avenue for further research and therapeutic development.

Efficient, rapid, and high-yield synthesis of aryl Schiff base derivatives and their in vitro and in silico inhibition studies of hCA I, hCA II, AChE, and BuChE

This study reports a rapid and efficient synthesis of four novel aryl Schiff base derivatives. Biological activity and molecular modeling studies were conducted to evaluate the inhibitory effects of these compounds on human carbonic anhydrases (hCA) and cholinesterases. The results indicate that the triazole-ring-containing compounds have strong inhibitory effects on hCA I, hCA II, acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) targets. Besides comparing the Schiff bases synthesized in our study to reference molecules, we conducted in silico investigations to examine how these compounds interact with their targets. Our studies revealed that these compounds can occupy binding sites and establish interactions with crucial residues, thus inhibiting the functions of the targets. These findings have significant implications as they can be utilized to develop more potent compounds for treating the diseases that these target proteins play crucial roles in or to obtain drug precursors with enhanced efficacy.

C19-diterpene alkaloids from Delphinium turkmenum lipsky

The genus Delphinium is a rich source of diterpene alkaloids. Chemical investigation on an alkaloid rich extract of the whole parts of Delphinium turkmenum resulted in the isolation of three C19-diterpene alkaloids (1-3) and a palmitic acid derivative (4). The chemical structures were elucidated by analysis of 1D and 2D-NMR and comparison the data with those reported in the literature. Notably, all isolated compounds were reported for the first time from D. turkmenum.

Neuropharmacological Potential of Diterpenoid Alkaloids

This study provides a narrative review of diterpenoid alkaloids (DAs), a family of extremely important natural products found predominantly in some species of Aconitum and Delphinium (Ranunculaceae). DAs have long been a focus of research attention due to their numerous intricate structures and diverse biological activities, especially in the central nervous system (CNS). These alkaloids originate through the amination reaction of tetra or pentacyclic diterpenoids, which are classified into three categories and 46 types based on the number of carbon atoms in the backbone structure and structural differences. The main chemical characteristics of DAs are their heterocyclic systems containing β-aminoethanol, methylamine, or ethylamine functionality. Although the role of tertiary nitrogen in ring A and the polycyclic complex structure are of great importance in drug-receptor affinity, in silico studies have emphasized the role of certain sidechains in C13, C14, and C8. DAs showed antiepileptic effects in preclinical studies mostly through Na⁺ channels. Aconitine (1) and 3-acetyl aconitine (2) can desensitize Na⁺ channels after persistent activation. Lappaconitine (3), N-deacetyllapaconitine (4), 6-benzoylheteratisine (5), and 1-benzoylnapelline (6) deactivate these channels. Methyllycaconitine (16), mainly found in Delphinium species, possesses an extreme affinity for the binding sites of α7 nicotinic acetylcholine receptors (nAChR) and contributes to a wide range of neurologic functions and the release of neurotransmitters. Several DAs such as bulleyaconitine A (17), (3), and mesaconitine (8) from Aconitum species have a drastic analgesic effect. Among them, compound 17 has been used in China for decades. Their effect is explained by increasing the release of dynorphin A, activating the inhibitory noradrenergic neurons in the β-adrenergic system, and preventing the transmission of pain messages by inactivating the Na⁺ channels that have been stressed. Acetylcholinesterase inhibitory, neuroprotective, antidepressant, and anxiolytic activities are other CNS effects that have been investigated for certain DAs. However, despite various CNS effects, recent advances in developing new drugs from DAs were insignificant due to their neurotoxicity.

Natural Inhibitors of Cholinesterases: Chemistry, Structure-Activity and Methods of Their Analysis

This article aims to provide an updated description and comparison of the data currently available in the literature (from the last 15 years) on the studied natural inhibitors of cholinesterases (IChEs), namely, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). These data also apply to the likely impact of the structures of the compounds on the therapeutic effects of available and potential cholinesterase inhibitors. IChEs are hitherto known compounds with various structures, activities and origins. Additionally, multiple different methods of analysis are used to determine the cholinesterase inhibitor potency. This summary indicates that natural sources are still suitable for the discovery of new compounds with prominent pharmacological activity. It also emphasizes that further studies are needed regarding the mechanisms of action or the structure-activity correlation to discuss the issue of cholinesterase inhibitors and their medical application.

A review: Pharmacokinetics and pharmacology of aminoalcohol-diterpenoid alkaloids from Aconitum species

ETHNOPHARMACOLOGICAL RELEVANCE

Aconitum medicinal materials, such as Aconitum carmichaelii Debeaux (Chinese: Wutou/) and Aconitum kusnezoffii Reichb. (Chinese: Caowu/), are a kind of important Traditional Chinese Medicine (TCM) with great medicinal value. Statistics show that there are over 600 efficient TCM formulations comprising Aconitum medicinal materials. But high toxicity limits their clinical application. Clinically, the Aconitum medicinal materials must undergo a complex processing process that includes soaking, steaming, and boiling with pharmaceutical excipients, which makes highly toxic ester diterpenoid alkaloids are hydrolyzed to form less toxic aminoalcohol-diterpenoid alkaloids (ADAs).

AIM OF THE STUDY

This review aims to summarize the pharmacokinetic and pharmacological activities of low-toxicity ADAs, providing a reference for future ADAs research and drug development.

MATERIALS AND METHODS

Accessible literature on ADAs published between 1984 and 2022 were screened and obtained from available electronic databases such as PubMed, Web of Science, Springer, Science Direct and Google Scholar, followed by systematic analysis.

RESULTS

ADAs are secondary products of plant metabolism, widely distributed in the Aconitum species and Delphinium species. The toxicity of ADAs as pharmacodynamic components of Aconitum medicinal materials is much lower than that of other diterpenoid alkaloids due to the absence of ester bonds. On the one hand, the pharmacokinetics of ADAs have received little attention compared to other toxic alkaloids. The research primarily focuses on aconine and mesaconine. According to existing studies, ADAs absorption in the gastrointestinal tract is primarily passive with a short T_max. Simultaneously, efflux transporters have less impact on ADAs absorption than non-ADAs. After entering the body, ADAs are widely distributed in the heart, liver, lungs, and kidney, but less in the brain. Notably, aconine is not well metabolized by liver microsomes. Aconine and mesaconine are excreted in urine and feces, respectively. ADAs, on the other hand, have been shown to have a variety of pharmacological activities, including cardiac, analgesic, anti-inflammatory, anti-tumor, antioxidant, and regenerative effects via regulating multiple signaling pathways, including Nrf2/ARE, PERK/eIF2α/ATF4/Chop, ERK/CREB, NF-κB, Bcl-2/Bax, and GSK3β/β-catenin signaling pathways.

CONCLUSIONS

ADAs have been shown to have beneficial effects on heart disease, neurological disease, and other systemic diseases. Moreover, ADAs have low toxicity and a wide range of safe doses. All of these suggest that ADAs have great potential for drug development.

Poisonous Piperidine Plants and the Biodiversity of Norditerpenoid Alkaloids for Leads in Drug Discovery: Experimental Aspects

There are famous examples of simple (e.g., hemlock, Conium maculatum L.) and complex (e.g., opium poppy, Papaver somniferum L., Papaveraceae) piperidine-alkaloid-containing plants. Many of these are highly poisonous, whilst pepper is well-known gastronomically, and several substituted piperidine alkaloids are therapeutically beneficial as a function of dose and mode of action. This review covers the taxonomy of the genera Aconitum, Delphinium, and the controversial Consolida. As part of studying the biodiversity of norditerpenoid alkaloids (NDAS), the majority of which possess an N-ethyl group, we also quantified the fragment occurrence count in the SciFinder database for NDA skeletons. The wide range of NDA biodiversity is also captured in a review of over 100 recently reported isolated alkaloids. Ring A substitution at position 1 is important to determine the NDA skeleton conformation. In this overview of naturally occurring highly oxygenated NDAs from traditional Aconitum and Delphinium plants, consideration is given to functional effect and to real functional evidence. Their high potential biological activity makes them useful candidate molecules for further investigation as lead compounds in the development of selective drugs.

In Vitro and In Silico Investigation of Diterpenoid Alkaloids Isolated from Delphinium chitralense

This study reports the isolation of three new C₂₀ diterpenoid alkaloids, Chitralinine A–C (1–3) from the aerial parts of Delphinium chitralense. Their structures were established on the basis of latest spectral techniques and single crystal X-rays crystallographic studies of chitralinine A described basic skeleton of these compounds. All the isolated Compounds (1–3) showed strong, competitive type inhibition against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in comparison to standard allanzanthane and galanthamine however, chitralinine-C remained the most potent with IC₅₀ value of 11.64 ± 0.08 μM against AChE, and 24.31 ± 0.33 μM against BChE, respectively. The molecular docking reflected a binding free energy of −16.400 K Cal-mol⁻¹ for chitralinine-C, having strong interactions with active site residues, TYR334, ASP72, SER122, and SER200. The overall findings suggest that these new diterpenoid alkaloids could serve as lead drugs against dementia-related diseases including Alzheimer’s disease.

Inhibitory potential of nitrogen, oxygen and sulfur containing heterocyclic scaffolds against acetylcholinesterase and butyrylcholinesterase

Heterocycles are the key structures in organic chemistry owing to their immense applications in the biological, chemical, and pharmaceutical fields. Heterocyclic compounds perform various noteworthy functions in nature, medication, innovation etc. Most frequently, pure nitrogen heterocycles or various positional combinations of nitrogen, oxygen, and sulfur atoms in five or six-membered rings can be found. Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes is a popular strategy for the management of numerous mental diseases. In this context, cholinesterase inhibitors are utilized to relieve the symptoms of neurological illnesses like dementia and Alzheimer's disease (AD). The present review focuses on various heterocyclic scaffolds and their role in designing and developing new potential AChE and BChE inhibitors to treat AD. Moreover, a detailed structure-activity relationship (SAR) has been established for the future discovery of novel drugs for the treatment of AD. Most of the heterocyclic motifs have been used in the design of new potent cholinesterase inhibitors. In this regard, this review is an endeavor to summarize the biological and chemical studies over the past decade (2010-2022) describing the pursuit of new N, O and S containing heterocycles which can offer a rich supply of promising AChE and BChE inhibitory activities.

Green synthesis of gold nanaoparticles using Delphinium Chitralense tuber extracts, their characterization and enzyme inhibitory potential

Green synthesis has been introduced as an alternative to chemical synthesis due to the serious consequences. Metal nanoparticles synthesized through green approach have different pharmaceutical, medical and agricultural applications. The present study followed a green and simple route for the preparation of potentially bioactive gold nanoparticles (Au NPs). Au NPs were prepared via green synthesis approach using crude basic alkaloidal portion of the tuber of Delphinium chitralense. The green synthesized Au NPs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) fourier transform infrared (FTIR), and UV-Visible spectrophotometer. Morphological analysis shows that Au NPs have cubic geometry with different sizes. UV-Vis spectroscopic analysis confirmed the synthesis of Au NPs while XRD proved their pure crystalline phase. The Au NPs showed promising dose dependent inhibition of both AChE and BChE as compared to the crude as well as standard drug.

The diterpenoid alkaloids

The diterpenoid alkaloids are a family of extremely important natural products that have long been a research hotspot due to their myriad of intricate structures and diverse biological properties. This chapter systematically summarizes the past 11 years (2009-2019) of studies on the diterpenoid alkaloids, including the "so-called" atypical ones, covering the classification and biogenetic relationships, phytochemistry together with 444 new alkaloids covering 32 novel skeletons and the corrected structures, chemical reactions including conversion toward toxoids, synthetic studies, as well as biological activities. It should be noted that the synthetic studies, especially the total syntheses of various diterpenoid alkaloids, are for the first time reviewed in this treatise. This chapter, in combination with our four previous reviews in volumes 42, 59, 67, and 69, will present to the readers a more completed and updated profile of the diterpenoid alkaloids.

Diterpenoid Alkaloids from the Aerial Parts of Aconitum flavum Hand.-Mazz

Sixteen diterpenoid alkaloids (DAs), including six aconitine-type alkaloids (5 and 9 - 13), seven 7,17-seco-aconitine-type alkaloids (1 - 4, 6 - 8), two napelline-type alkaloids (14 and 15) as well as one veatchine-type alkaloid (16), were isolated from the aerial parts of Aconitum flavum Hand.-Mazz. In which, flavumolines A - D (1 - 4) were four new ones, and flavumoline E (5) was reported as natural compound for the first time. Their chemical structures were elucidated by the analysis of extensive spectroscopic data. The inhibitory activities of these isolates on Cav3.1 low voltage-gated Ca2+ channel, NO production in LPS-activated RAW264.7cells, five human tumor cell lines, as well as acetylcholinesterase (AChE) were tested.

A Recent Look into Natural Products that have Potential to Inhibit Cholinesterases and Monoamine Oxidase B: Update for 2010-2019

With respect to the unknowns of pathophysiology of Alzheimer's Disease (AD)-, and Parkinson's Disease (PD)-like neurodegenerative disorders, natural product research is still one of the valid tools in order to provide alternative and/or better treatment options. At one hand, various extracts of herbals provide a combination of actions targeting multiple receptors, on the other hand, the discovery of active natural products (i.e., secondary metabolites) generally offers alternative chemical structures either ready to be employed in clinical studies or available to be utilized as important scaffolds for the design of novel agents. Regarding the importance of certain enzymes (e.g. cholinesterase and monoamine oxidase B), for the treatment of AD and PD, we have surveyed the natural product research within this area in the last decade. Particularly novel natural agents discovered within this period, concomitant to novel biological activities displayed for known natural products, are harmonized within the present study.

Natural Products as Potential Anti-Alzheimer Agents

Medicinal plants have curative properties due to the presence of various complex chemical substances of different composition, which are found as secondary metabolites in one or more parts of the plant. The diverse secondary metabolites play an important role in the prevention and cure of various diseases including neurodegenerative diseases like Alzheimer's disease. Naturally occurring compounds such as flavonoids, polyphenols, alkaloids, and glycosides found in various parts of the plant and/or marine sources may potentially protect neurodegeneration as well as improve memory and cognitive function. Many natural compounds show anti-Alzheimer activity through specific pharmacological mechanisms like targeting β-amyloid, Beta-secretase 1 and Acetylcholinesterase. In this review, we have compiled more than 130 natural products with a broad diversity in the class of compounds, which were isolated from different sources showing anti- Alzheimer properties.

Plants with Anti-Addictive Potential

Drug addiction is prevalent among individuals of modern society, being a major cause of disability and premature loss of life. Although the drug addiction have profound social, economical and health impact in the world population, its management remains a challenge as available pharmacological treatments remains ineffective for most people. The limited efficacy and adverse effects have led to a search for alternative therapies to treat drug addiction. In this context, natural products are an important source for new chemical substances with a potential therapeutic applicability. Therefore, this chapter will present data obtained after an extensive literature search regarding the use of medicinal plants as a pharmacological alternative for drug addiction treatment.

Macrocyclic sulfone derivatives: Synthesis, characterization, in vitro biological evaluation and molecular docking

An artificial series of macrocycles based on 4,4'-sulfonyldiphenol intermediate was synthesized using a multistep procedure involving oxidation of bisphenol sulfide, etherification of phenolic hydroxyl groups, and final ring closure with different diamines. Different chemical species having aromatic, heteroaromatic, and aliphatic characters were incorporated into macrocyclic frameworks in the final step of ring closure. This simple and easily executable synthetic strategy was applied to synthesize 15 macrocycles (5a-o) in excellent yields. Characterization of the synthesized products was achieved through well-known modern spectroscopic techniques such as IR, NMR, and Mass. Macrocycles 5m and 5n were found to show significant AChE inhibition with IC₅₀ values of 76.9 ± 0.24 and 71.2 ± 0.77 μM, respectively. Macrocycle 5n was also found to be an active inhibitor of butyrylcholinesterase (BChE) with IC₅₀ score of 55.3 ± 0.54 μM. Among others, macrocycle 5l cyclized with o-phenylenediamine demonstrated moderate inhibition with IC₅₀ value of 81.1 ± 0.54 μM. Increasing interest in studying interactions of macrocycles with different enzymatic targets compelled us to design and synthesize sulfone-based macrocycles that might prove as highly potent class of biologically active compounds.

Synthesis of N-phenylsulfonamide derivatives and investigation of some esterase enzymes inhibiting properties

In this study, synthesis of nine N-phenylsulfonamide derivatives was designed by starting from aniline, which is the simplest aromatic amine. These compounds were obtained in yields between 69 and 95%. Inhibitory properties of synthesized compounds on carbonic anhydrase I (CA I), CA II isoenzymes, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes were investigated. Inhibitors of CA isoenzymes are important therapeutic targets, particularly due to their preventive/activation potential in the treatment of diseases such as edema, glaucoma, cancer and osteoporosis. Cholinesterase inhibitors are valuable compounds that can be used in many different therapeutic applications, including Alzheimer's disease. The compound 8 for CA I, AChE and BChE, 2 for CA II showed a very active inhibition profile (K_I 45.7 ± 0.46 for CA I, 33.5 ± 0.38 nM for CA II, 31.5 ± 0.33 nM for AChE and 24.4 ± 0.29 nM for BChE). The results indicate that these N-phenyl-sulfonamide derivatives are potent CA and cholinesterases and new potential drugs.

Triazolopyridopyrimidine: A New Scaffold for Dual-Target Small Molecules for Alzheimer's Disease Therapy

Alzheimer’s disease (AD) is multifactorial disease characterized by the accumulation of abnormal extracellular deposits of amyloid-beta (Aβ) peptide, and intracellular neurofibrillary tangles (NFTs), along with dramatic neuronal death and decreased levels of choline acetyltransferase. Given the limited therapeutic success of available drugs, it is urgent to explore all the opportunities available to combat this illness. Among them, the discovery of new heterocyclic scaffolds binding different receptors involved in AD should offer structural diversity and new therapeutic solutions. In this context, this work describes new triazolopyridopyrimidine easily prepared in good yields showing anticholinesterase inhibition and strong antioxidant power, particularly the most balanced: 6-amino-5-(4-methoxyphenyl)-2-phenyl-[1,2,4]triazolo[1′,5′:1,6] pyrido[2,3-d]pyrimidine-4-carbonitrile(3c) with IC₅₀ equal to 1.32 μM against AChE and oxygen radical absorbance capacity (ORAC) value equal to 4.01 Trolox equivalents (TE); thus representing a new and very promising hit-triazolopyridopyrimidine for AD therapy.

An overview of the chemical constituents from the genus Delphinium reported in the last four decades

Species of the genus Delphinium have been extensively used for different purposes by various civilizations worldwide since antiquity. Phytochemical investigations on Delphinium plants in the last four decades (1980–2019) have afforded a total of 453 new compounds, most of which are diterpenoid alkaloids. These constituents are of great research significance due to their novel structures and broad bioactivities. This review addresses, for the first time, the chemical constituents of Delphinium plants and the biological properties of these compounds to facilitate future research.

Multiple chemical constituents, mainly diterpenoid alkaloids, from Delphinium showed great research significance for their novel structures and broad bioactivities.

Effect of Salvia miltiorrhiza on acetylcholinesterase: Enzyme kinetics and interaction mechanism merging with molecular docking analysis

Acetylcholinesterase (AchE) serves as an important target for Alzheimer's disease. Salvia miltiorrhiza has been used to treat cardiovascular disease for hundreds of years. However, the interaction between S. miltiorrhiza and AchE is still inadequate. Herein, an integrated method including molecular docking and experimental studies was employed to investigate the interaction. Consequently, some components were screened as potent AchE inhibitors by in silico and in vitro. Among them, miltirone (MT) and salvianolic acid A (SAA) reversibly inhibited AchE in a mixed-competitive manner. Fluorescence data revealed that SAA and salvianolic acid C (SAC) strongly quenched the intrinsic fluorescence of AchE through a static quenching mechanism, and the binding was spontaneous and dominated by hydrophobic interaction inferred by the thermodynamic parameters. The synchronous and ANS-binding fluorescence spectra suggested that SAA and SAC could bind to the enzyme and induce its conformation changes of secondary structures, which was further confirmed by Fourier transform infrared spectra. Meanwhile, molecular docking presented the probable binding modes of inhibitors to AchE and highlighted the key role of hydrophobic interaction and hydrogen bonds for the stability of docking complex. These findings put more insights into understanding the interaction of S. miltiorrhiza chemicals and AchE, as well as Alzheimer's disease.

Cardiotoxicity of Consolida rugulosa, a poisonous weed in Western China

Poisonous weeds are a global problem since they not only hinder local economic development, but also cause ecological harm. Consolida rugulosa (family Ranunculaceae) is a weed that is widespread in Northwestern China and causes severe poisoning when ingested by livestock. In the present study, we purified the toxins in this plant and investigated their mechanism of action. Five natural diterpene alkaloids (compounds 1-5)-including two new compounds (1 and 2)-were isolated, and five semi-synthetic derivatives (6-10) were synthesised based on 4 or 5 for structure-activity analysis. The toxicity of the compounds was evaluated in vitro with lactate dehydrogenase (LDH) assay. All of the compounds-especially 1-stimulated LDH release in primary cultured rat myocardial cells, an effect that was blocked by the Na⁺ channel blocker lidocaine. Electrocardiography revealed that rats treated with 1 had severe arrhythmia, while heart Doppler echocardiography and analysis of serum biomarkers levels revealed that administration of 1 for 15 days induced changes in cardiac structure and myocardial enzyme levels. These effects were antagonised by lidocaine treatment. Thus, diterpene alkaloids are the main compounds responsible for the cardiotoxicity of C. rugulosa, which can be mitigated by co-administration of lidocaine.