Chemistry and biological activities of hetisine-type diterpenoid alkaloids

Design, synthesis, evaluation, pharmacophore modeling, and 3D-QSAR of lappaconitine analogs as potential analgesic agents

Alleviating pain is crucial for patients with various diseases. This study aimed to enhance the analgesic properties of lappaconitine, a natural drug, through structural modifications. Specifically, carbamate analgesic active fragments were innovatively introduced at multiple sites on the benzene ring of lappaconitine. A total of 53 lappaconitine analogs were synthesized and evaluated. Compounds 5a, 5c, 5e, 6, and 15j addressed the narrow therapeutic window of lappaconitine, enhancing drug safety. Notably, carbamate analogs exhibited significantly enhanced analgesic activity, with compounds 5a and 5c having ED50 values of 1.2 and 1.6 mg/kg, respectively, indicating higher potency than lappaconitine (3.5 mg/kg). A metabolic analysis of compound 5e was conducted in mice, revealing its primary metabolic processes and metabolites, and providing preliminary exploration for the druggability. Given the multiple analgesic targets of lappaconitine, its analgesic mechanism remains inconclusive. This study, for the first time, analyzed the pharmacological activity characteristics of the lappaconitine analogs using a pharmacophore model and established a three-dimensional quantitative structure-activity relationship (3D-QSAR) to elucidate the quantitative relationship between the structures of the synthesized compounds and their analgesic activities. These findings provide valuable guidance for future structural modification and optimization of analgesic drugs.

The expression of AcIDI1 reveals diterpenoid alkaloids' allocation strategies in the roots of Aconitum carmichaelii Debx

Isopentenyl diphosphate isomerase (IDI), a key enzyme in the biosynthetic pathway of diterpenoid alkaloids (DAs), plays an essential regulatory role in the synthesis and accumulation of DAs. In this study, the coding sequence (CDS) of AcIDI1 was isolated from the mother roots of Aconitum carmichaelii Debx. (GeneBank accession number OR915879). Bioinformatics analysis showed that the CDS of AcIDI1 was 894 bp, encoding a protein with 297 amino acids and the putative protein localized in the chloroplast. AcIDI1 exhibited significant homology with sequences encoding IDI in other species, and was most closely related to Aconitum vilmorinianum. Furthermore, the fusion protein has been successfully expressed in Escherichia coli (E. coli), providing a basis for future functional studies of AcIDI1. The expression pattern of AcIDI1 was analyzed by real-time quantitative PCR (qPCR), which demonstrates that AcIDI1 is a tissue-specific gene in the roots of A. carmichaelii and exhibits high expression in both daughter and mother roots. By comparing the expression levels of AcIDI1 in three tissues of the roots of A. carmichaelii at different growth stages, we propose that the mother roots (MRs) are the centers of resources allocation. The roots of A. carmichaelii continuously absorb the energy from external environment, while resources transfer behavior from MRs to both daughter roots (DRs) and axillary buds (ABs) occurs as the plant grows. This study establishes a foundation for applying the IDI gene to regulate the biosynthesis and accumulation of DAs in A. carmichaelii.

Diterpenoid and C20 diterpenoid alkaloid as a potent inhibitor of SARS-CoV-2 main protease (Mpro): from Piper barberi Gamble, an endemic and endangered species of Southern Western Ghats

The present study investigated the phytochemicals and in silico anti-nCoV properties of Piper barberi, an endangered and endemic species of Southern Western Ghats. Using conventional soxhlet extraction method, the leaf and stem were extracted separately with methanol (PBLM and PBSM). The bioactive compounds from the extracts were identified using HR-LCMS/MS-qTOF analysis. These compounds were subjected to various in silico analyses to identify potential drug candidates against nCoV. The HR LCMS/MS analysis of PBLM and PBSM revealed the presence of phenols, flavonoids, alkaloids, and terpenoids in it and this is the first report of the phytoconstituents present in the species P. barberi. All the identified bioactive compounds were subjected to predict ADMET. Out of 49 identified compounds, only 31 passed drug-likeness properties and toxicity tests. Molecular interaction studies were conducted using the AutoDockTools 4.2.6., which showed that only 13 compounds exhibited acceptable binding affinity with the nCoV target Mpro. Structural stability and binding free energy analyses of the five compounds with the higher binding affinity indicated that the bioactive compounds Hetisine and Ajaconine are stable with both hydrogen bonds and hydrophobic interactions. Hetisine shows stable binding among these two compounds with two hydrogen bond interactions with the crucial catalytic dyad residue (His41). Thus, this study concludes that these compounds might potentially be used as an alternative drug candidate for managing nCoV. However, further experimental validation, including in vitro and in vivo assays, is required to substantiate the results.Communicated by Ramaswamy H. Sarma.

Overview of the chemistry and biological activities of natural atisine-type diterpenoid alkaloids

Atisine-type C20-diterpenoid alkaloids (DAs) are a very important class of diterpenoid alkaloids, which play an important role in the biosynthesis of DAs. To date, 87 atisine-type DAs and 11 bis-DAs containing an atisine unit have been reported from five genera in two families. The genus Spiraea in Rosaceae family could be regarded as the richest resource for atisine-type DAs, followed by the genera Delphinium and Aconitum in the Ranunculaceae family. Among the reported atisine-type DAs, several possess unprecedented skeletons. Natural atisine-type DAs have a wide range of biological activities, including antitumor, antiplatelet aggregation, biological control, and anti-inflammatory, analgesic, antiarrhythmic, and cholinesterase inhibitory effects, which are closely related to their structures. In particular, the antiparasitic effect of atisine-type DAs is more prominent than that of other types of DAs, which highlights their potential in antiparasite drug discovery. In summary, the high chemical and biological diversity of atisine-type DAs indicates their great potential as a vast resource for drug discovery.

Exploring the Biomedical Potential of Terpenoid Alkaloids: Sources, Structures, and Activities

Terpenoid alkaloids are recognized as a class of compounds with limited numbers but potent biological activities, primarily derived from plants, with a minor proportion originating from animals and microorganisms. These alkaloids are synthesized from the same prenyl unit that forms the terpene skeleton, with the nitrogen atom introduced through β-aminoethanol, ethylamine, or methylamine, leading to a range of complex and diverse structures. Based on their skeleton type, they can be categorized into monoterpenes, sesquiterpenes, diterpenes, and triterpene alkaloids. To date, 289 natural terpenoid alkaloids, excluding triterpene alkaloids, have been identified in studies published between 2019 and 2024. These compounds demonstrate a spectrum of biological activities, including anti-inflammatory, antitumor, antibacterial, analgesic, and cardioprotective effects, making them promising candidates for further development. This review provides an overview of the sources, chemical structures, and biological activities of natural terpenoid alkaloids, serving as a reference for future research and applications in this area.

The Chemical Ecology of Plant Natural Products

Plants are excellent chemists with an impressive capability of biosynthesizing a large variety of natural products (also known as secondary or specialized metabolites) to resist various biotic and abiotic stresses. In this chapter, 989 plant natural products and their ecological functions in plant-herbivore, plant-microorganism, and plant-plant interactions are reviewed. These compounds include terpenoids, phenols, alkaloids, and other structural types. Terpenoids usually provide direct or indirect defense functions for plants, while phenolic compounds play important roles in regulating the interactions between plants and other organisms. Alkaloids are frequently toxic to herbivores and microorganisms, and can therefore also provide defense functions. The information presented should provide the basis for in-depth research of these plant natural products and their natural functions, and also for their further development and utilization.

A new C19-diterpenoid alkaloid in Aconitum georgei Comber

Nine diterpenoid alkaloids were isolated from Aconitum georgei Comber belonging to the genus Aconitum in Ranunculaceae family. Their structures were determinated by using HR-ESI-MS and 1 D/2D NMR spectra as geordine (1), yunaconitine (2), chasmanine (3), crassicauline A (4), forestine (5), pseudaconine (6), 14-acetylalatisamine (7), austroconitine B (8), and talatisamine (9). Among them, compound 1 is a previously undescribed aconitine-type C19-diterpenoid alkaloid, and compounds 3, and 5-9 have not previously been isolated from this species. The results of in vitro experiments indicated that new compound 1 possesses mild anti-inflammatory activity, which inhibited the production of NO in LPS-activated RAW 264.7 cells with an inhibition ratio of 29.75% at 50 μM.

Network pharmacology combined with molecular docking and in vitro verification reveals the therapeutic potential of Delphinium roylei munz constituents on breast carcinoma

Delphinium roylei Munz is an indigenous medicinal plant to India where its activity against cancer has not been previously investigated, and its specific interactions of bioactive compounds with vulnerable breast cancer drug targets remain largely unknown. Therefore, in the current study, we aimed to evaluate the anti-breast cancer activity of different extracts of D. roylei against breast cancer and deciphering the molecular mechanism by Network Pharmacology combined with Molecular Docking and in vitro verification. The experimental plant was extracted with various organic solvents according to their polarity index. Phytocompounds were identified by High resolution-liquid chromatography-mass spectrometry (HR-LC/MS) technique, and SwissADME programme evaluated their physicochemical properties. Next, target(s) associated with the obtained bioactives or breast cancer-related targets were retrieved by public databases, and the Venn diagram selected the overlapping targets. The networks between overlapping targets and bioactive were visualized, constructed, and analyzed by STRING programme and Cytoscape software. Finally, we implemented a molecular docking test (MDT) using AutoDock Vina to explore key target(s) and compound(s). HR-LC/MS detected hundreds of phytocompounds, and few were accepted by Lipinski's rules after virtual screening and therefore classified as drug-like compounds (DLCs). A total of 464 potential target genes were attained for the nine quantitative phytocompounds and using Gene Cards, OMIM and DisGeNET platforms, 12063 disease targets linked to breast cancer were retrieved. With Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment, a total of 20 signalling pathways were manifested, and a hub signalling pathway (PI3K-Akt signalling pathway), a key target (Akt1), and a key compound (8-Hydroxycoumarin) were selected among the 20 signalling pathways via molecular docking studies. The molecular docking investigation revealed that among the nine phytoconstituents, 8-hydroxycoumarin showed the best binding energy (-9.2 kcal/mol) with the Akt1 breast cancer target. 8-hydroxycoumarin followed all the ADME property prediction using SwissADME, and 100 nanoseconds (ns) MD simulations of 8-hydroxycoumarin complexes with Akt1 were found to be stable. Furthermore, D. roylei extracts also showed significant antioxidant and anticancer activity through in vitro studies. Our findings indicated for the first time that D. roylei extracts could be used in the treatment of BC.

Finding activity through rigidity: syntheses of natural products containing tricyclic bridgehead carbon centers

Covering: up to 2022Tricyclic bridgehead carbon centers (TBCCs) are a synthetically challenging substructure found in many complex natural products. Here we review the syntheses of ten representative families of TBCC-containing isolates, with the goal of outlining the strategies and tactics used to install these centers, including a discussion of the evolution of the successful synthetic design. We provide a summary of common strategies to inform future synthetic endeavors.

Diterpenoid alkaloids from two species of Delphinium

Four new compounds (1-4) were isolated from the whole plants of two species of Delphinium, including two C₂₀-diterpenoid alkaloids, umbrodines A and B (1 and 2), and a dibenzoxazepinone, umbrolide A (3) from Delphinium umbrosum Hand.-Mazz. and a C₂₀-diterpenoid alkaloid, kingiadine (4) from Delphinium kingianum Bruhl. ex Huth. Ten known diterpenoid alkaloids were also isolated. Their structures were elucidated via HR-ESIMS, IR, and NMR data. Lycoctonine (11) and delectinine (12) exhibited appreciable cardiac activity. Furthermore, 11 and 12 showed cardioprotective effects against doxorubicin-induced toxicity in H9c2 cells, with the maximum protection rates of 61.63% and 51.18%, respectively.

Antiplasmodial diterpenoid alkaloid from Aconitum heterophyllum Wall. ex Royle: Isolation, characterization, and UHPLC-DAD based quantification

ETHNOPHARMACOLOGICAL RELEVANCE

Aconitum heterophyllum Wall. ex Royle is a traditionally important medicinal plant having numerous therapeutic actions as documented in Ayurveda. This plant is traditionally known for combating worm infestation, fever, respiratory tract disease, vomiting, diarrhoea, diabetes, skin disorders, anaemia, and joint disorders. Further, it has been used alone and in combination with other plants to prepare various anti-malarial formulations. However, there is no report on the assessment of its anti-plasmodial activity, and the metabolite(s) responsible for this activity.

AIM OF THE STUDY

The main aim of this study was to conduct phytochemical investigation of A. heterophyllum roots for the preparation of extract, fractions, and isolation of pure molecules to identify active fractions/molecules responsible for the anti-plasmodial activity, and development of UHPLC-DAD based analytical method which can be used for the quantification of marker compounds in the extracts and fractions.

MATERIALS AND METHODS

Hydroalcoholic extract (1:1 v/v) and fractions (n-hexane, chloroform, ethyl acetate, n-butanol, and water) were prepared from the dried powdered roots of A. heterophyllum. Fractions were further subjected to silica gel column chromatography to isolate pure specialized secondary metabolites from this plant. All extracts, fractions, and pure molecules were evaluated against the chloroquine resistant Pf INDO and chloroquine sensitive Pf3D7 strains in culture for calculating their IC₅₀ values. UHPLC-DAD based analytical method was also developed for the first time for the quantification of marker compounds and quality assessment of this commercially important Himalayan medicinal plant.

RESULTS

Phytochemical investigation of A. heterophyllum root led to the isolation of six specialized metabolites viz. 2-O-cinnamoyl hetisine (1), atisinium (2), 4-oxabicyclo [3.2.2] nona-1(7),5,8-triene (3), atisinium cinnamate (4), aconitic acid (5), and atisinium formate (6). Compound 1 is a new hetisine type diterpenoid alkaloid, compounds 4 and 6 are new counter ionic forms observed with atisinium ion, and compound 3 is being reported for the first time from this genus. Chloroform fraction was found to be the most active with IC₅₀ (μg/mL) 1.01 (Pf INDO) and 1.32 (Pf3D7). The molecule 2-O-cinnamoyl hetisine (1), a new diterpenoid alkaloid isolated from chloroform fraction, showed promising antiplasmodial activities with IC₅₀ (μM) 1.92 (Pf INDO) and 10.8 (Pf 3D7). The activity of chloroform fraction was further validated by the developed UHPLC-DAD based method as the quantity of 2-O-cinnamoyl hetisine (1) was higher in the chloroform fraction (≅200 mg/g) than in all other fractions (<7 mg/g). Atisinium (2) and 2-O-cinnamoyl hetisine (1) were found to be the main marker compounds of this plant based on quantity and antiplasmodial activity, respectively.

CONCLUSION

This study provides the scientific rationale for the traditional use of this plant in treating malaria. Further, this study revealed that the anti-malarial potential of this plant might be due to the presence of diterpenoid alkaloids.