Classification, Toxicity and Bioactivity of Natural Diterpenoid Alkaloids

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.

Anticancer diterpenes of African natural products: Mechanistic pathways and preclinical developments

BACKGROUND

The African continent is home to five biodiversity hotspots, boasting an immense wealth of medicinal flora, fungi and marine life. Diterpenes extracted from such natural products have compelling cytotoxic activities that warrant further exploration for the drug market, particularly in cancer therapy, where mortality rates remain elevated worldwide.

PURPOSE

To demonstrate the potential of African natural products on the global stage for cancer therapy development and provide an in-depth analysis of the current literature on the activity of cancer cytotoxic diterpenes from African natural sources (to our knowledge, the first of its kind); not only to reveal the most promising candidates for clinical development, but to demonstrate the importance of preserving the threatened ecosystems of Africa.

METHODS

A comprehensive search by means of the PRISMA strategy was conducted using electronic databases, namely Web of Science, PubMed, Google Scholar and ScienceDirect. The search terms employed were 'diterpene & mechanism & cancer' and 'diterpene & clinical & cancer'. The selection process involved assessing titles in English, Portuguese and Spanish, adhering to predefined eligibility criteria. The timeframe for inclusion spanned from 2010 to 2023, resulting in 218 relevant papers. Chemical structures were visualized using ChemDraw 21.0, PubChem was utilized to search for CID numbers.

RESULTS

Despite being one of the richest biodiverse zones in the world, African natural products are proportionally underreported compared to Asian countries or otherwise. The diterpenes andrographolide (Andrographis paniculata), forskolin (Coleus forskohlii), ent-kauranes from Isodon spp., euphosorophane A (Euphorbia sororia), cafestol & kahweol (Coffea spp.), macrocylic jolkinol D derivatives (Euphorbia piscatoria) and cyathane erinacine A (Hericium erinaceus) illustrated the most encouraging data for further cancer therapy exploration and development.

CONCLUSIONS

Diterpenes from African natural products have the potential to be economically significant active pharmaceutical and medicinal ingredients, specifically focussed on anticancer therapeutics.

New diterpenoid alkaloids from Delphinium pachycentrum Hemsl

Six diterpenoid alkaloids, namely, pachycentine (1), deacetylswinanine A (2), siwanine A (3), tatsiensine (4), deacetyltatsiensine (5), and 6-deoxydeltamine (6), were isolated from a China-specific Delphinium plant (family Ranunculaceae), Delphinium pachycentrum Hemsl. Their structures were established via detailed spectroscopic analyses, including IR, HR-ESI-MS, 1D and 2D NMR techniques. Pachycentine (1) is a previously undescribed hetisine-type C20-diterpenoid alkaloid, and compounds 5 and 6 were synthetic intermediates newly identified as natural products. In addition, compounds 2-4 were isolated from this species for the first time. The chemotaxonomic significance of all the isolates was summarized. Moreover, the new compound was evaluated for its potential anti-inflammatory effect using LPS-stimulated RAW 264.7 macrophages.

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.

A toxicological review of alkaloids

Alkaloids are naturally occurring compounds with complex structures found in natural plants. To further improve the understanding of plant alkaloids, this review focuses on the classification, toxicity and mechanisms of action, providing insight into the occurrence of alkaloid-poisoning events and guiding the safe use of alkaloids in food, supplements and clinical applications. Based on their chemical structure, alkaloids can be divided into organic amines, diterpenoids, pyridines, isoquinolines, indoles, pyrrolidines, steroids, imidazoles and purines. The mechanisms of toxicity of alkaloids, including neurotoxicity, hepatoxicity, nephrotoxicity, cardiotoxicity and cytotoxicity, have also been reviewed. Some cases of alkaloid poisoning have been introduced when used as food or clinically, including accidental food poisoning, excessive consumption, and poisoning caused by the improper use of alkaloids in a clinical setting, and the importance of safety evaluation was illustrated. This review summarizes the toxicity and mechanism of action of alkaloids and provides evidence for the need for the safe use of alkaloids in food, supplements and clinical applications.

Brunonianines A-C, C20-diterpenoid alkaloids with cyano group from Delphinium brunonianum Royle

Cyano tends to have better biological activity, but it is rarely reported in natural products, especially in the C20-diterpene alkaloids. Herein, three unprecedented C20-diterpenoid alkaloids, brunonianines A-C (1-3), possessing rare cyano functional group as well as an atisine backbone constructed from a phenethyl substituent and a tetrahydropyran ring, along with four C19-alkaloids (4-7) and one amide alkaloids (8), were isolated from the whole plant of Delphinium brunonianum Royle. Compounds 1-3 are also the first atisine type diterpenoid alkaloids with cyano group obtained from nature. The structures of the previously undescribed compounds were elucidated by HR-ESI-MS, 1D/2D NMR spectroscopic data and electronic circular dichroism calculations and single-crystal X-ray diffraction. Reasonable speculations have also been made regarding the biogenic synthetic pathways of compounds 1-3. In addition, the inhibitory activity of all compounds was also tested against four tumor lines: A549, Caco-2, H460 and Skov-3, where compound 2 (IC50 2.20 ± 0.21 μM) showed better inhibitory activity against Skov-3 cells than the hydroxycamptothecin. Using flow cytometry, cell staining, migration and invasion analysis, and Western blot, compound 2 was found to arrest cells in the G2/M phase and was able to effectively inhibit cell motility to achieve potent anti-tumor effects. In addition, compound 2 can effectively induce apoptosis by activating the Bax/Bcl-2/Caspase-3 signaling pathway.

Diterpenoid Alkaloids from Delphinium ajacis and Their Anti-inflammatory Activity

Three novel diterpenoid alkaloids, comprising two C19 -diterpenoid alkaloids (1 and 2) and one C20 -diterpenoid alkaloid (3), were isolated from Delphinium ajacis, alongside the six known compounds (4-9). Their structures were elucidated by spectroscopic methods (MS, UV, IR, 1D and 2D NMR) and chemical properties. Simultaneously, the anti-inflammatory properties of all compounds (1-9) was conducted, focusing on nitric oxide (NO) production in LPS-induced BV-2 cells. The results indicated compounds 1-3, 7, and 8 have potential anti-inflammatory activity.

Zanthoxylum armatum DC fruit ethyl acetate extract site induced hepatotoxicity by activating endoplasmic reticulum stress and inhibiting autophagy in BRL-3A models

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum armatum DC (Z. armatum) is renowned not only as a culinary spice but also as a staple in traditional ethnic medicine, predominantly in Southeast Asia and various other regions. Recent research has unveiled its multifaceted pharmacological properties, including anti-inflammatory, antibacterial, and toothache relief effects. Nonetheless, some studies have reported the potential toxicity of Z. armatum, emphasizing the need to further explore its toxicity mechanisms for safer application.

AIM OF THE STUDY

This study investigated the effect and mechanism of hepatotoxicity in BRL-3A cells induced by Z. armatum.

MATERIALS AND METHODS

The compounds of the ethyl acetate extract of Z. armatum (ZADC-EA) were identified by ultrahigh performance liquid chromatography coupled with quadrupole-orbitrap high resolution mass spectrometry (UPLC-Q-Orbitrap HRMS). The hepatotoxicity of the extract was evaluated by detecting cell viability, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) activity, and apoptosis. Endoplasmic reticulum stress, autophagy, and apoptosis were detected by Ad-mCherry-GFP-LC3B, flow cytometry, and Western blot to explore the mechanism of hepatotoxicity induced by ZADC-EA.

RESULTS

UPLC-Q-Orbitrap HRMS analysis revealed the presence of compounds belonging to flavonoids, terpenoids, and alkaloids. The IC50 value of ZADC-EA was 62.43 μg/mL, the cell viability of BRL-3A decreased in a time-dose dependent manner, and the levels of AST, ALT, and LDH were upregulated. In addition, ZADC-EA-induced increased expression of eIF2α-ATF4-CHOP pathway proteins, inhibited autophagy, and promoted apoptosis.

CONCLUSIONS

This study provides insights into the hepatotoxicity mechanisms of ZADC-EA on BRL-3A cells. It was found that ZADC-EA could induce endoplasmic reticulum stress and inhibit autophagy, then intensify apoptosis, and endoplasmic reticulum stress could exacerbate autophagy inhibition.

Aconitine and its derivatives: bioactivities, structure-activity relationships and preliminary molecular mechanisms

Aconitine (AC), which is the primary bioactive diterpene alkaloid derived from Aconitum L plants, have attracted considerable interest due to its unique structural feature. Additionally, AC demonstrates a range of biological activities, such as its ability to enhance cardiac function, inhibit tumor growth, reduce inflammation, and provide analgesic effects. However, the structure-activity relationships of AC are remain unclear. A clear understanding of these relationships is indeed critical in developing effective biomedical applications with AC. In line with these challenges, this paper summarized the structural characteristics of AC and relevant functional and bioactive properties and the structure-activity relationships presented in biomedical applications. The primary temporal scope of this review was established as the period spanning from 2010 to 2023. Subsequently, the objective of this review was to provide a comprehensive understanding of the specific action mechanism of AC, while also exploring potential novel applications of AC derivatives in the biomedical field, drawing upon their structural characteristics. In conclusion, this review has provided a comprehensive analysis of the challenges and prospects associated with AC in the elucidation of structure-bioactivity relationships. Furthermore, the importance of exploring modern biotechnology approaches to enhance the potential biomedical applications of AC has been emphasized.

Stir Fry with a Side of Extracorporeal Membrane Oxygen: Management of Cardiogenic Shock Secondary to Unintentional Aconitine Ingestion

Plant exposures leading to systemic or topical toxicity are common presentations seen in the emergency department. While often nonfatal, certain highly toxic plants result in cardiovascular or respiratory failure requiring invasive management. We describe a 65-y-old patient who presented with a refractory ventricular dysrhythmia secondary to an unintentional ingestion of an aconitine-containing plant after incorrect identification. Despite aggressive treatment with vasopressors, intravenous fluids, antiarrhythmics, as well as electrolyte correction and multiple attempted synchronized cardioversions, the patient remained in a refractory dysrhythmia with cardiogenic shock. Venoarterial extracorporeal membrane oxygen (ECMO) therapy was initiated successfully and resulted in rapid resolution of the unstable dysrhythmia. The patient was weaned from ECMO in under 48 h and was discharged without neurological or cardiovascular sequelae. This case highlights management options available to clinicians who encounter toxicity associated with aconitine ingestion. Fatal consequences were averted, and caution is required with the use of plant-identifying applications and resources.

Production of secondary metabolites using tissue culture-based biotechnological applications

Plants are the sources of many bioactive secondary metabolites which are present in plant organs including leaves, stems, roots, and flowers. Although they provide advantages to the plants in many cases, they are not necessary for metabolisms related to growth, development, and reproduction. They are specific to plant species and are precursor substances, which can be modified for generations of various compounds in different plant species. Secondary metabolites are used in many industries, including dye, food processing and cosmetic industries, and in agricultural control as well as being used as pharmaceutical raw materials by humans. For this reason, the demand is high; therefore, they are needed to be obtained in large volumes and the large productions can be achieved using biotechnological methods in addition to production, being done with classical methods. For this, plant biotechnology can be put in action through using different methods. The most important of these methods include tissue culture and gene transfer. The genetically modified plants are agriculturally more productive and are commercially more effective and are valuable tools for industrial and medical purposes as well as being the sources of many secondary metabolites of therapeutic importance. With plant tissue culture applications, which are also the first step in obtaining transgenic plants with having desirable characteristics, it is possible to produce specific secondary metabolites in large-scale through using whole plants or using specific tissues of these plants in laboratory conditions. Currently, many studies are going on this subject, and some of them receiving attention are found to be taken place in plant biotechnology and having promising applications. In this work, particularly benefits of secondary metabolites, and their productions through tissue culture-based biotechnological applications are discussed using literature with presence of current studies.

Synthesis, Pharmacological Evaluation, and Molecular Modeling of Lappaconitine-1,5-Benzodiazepine Hybrids

Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, have long interested scientists due to their medicinal uses and infamous toxicity which has limited the clinical application of the native compound. Alkaloid lappaconitine extracted from various Aconitum and Delphinium species has displayed extensive bioactivities and active ongoing research to reduce its adverse effects. A convenient route to construct hybrid molecules containing diterpenoid alkaloid lappaconitine and 3H-1,5-benzodiazepine fragments was proposed. The key stage involved the formation of 5'-alkynone-lappaconitines in situ by acyl Sonogashira coupling of 5'-ethynyllappaconitine, followed by cyclocondensation with o-phenylenediamine. New hybrid compounds showed low toxicity and outstanding analgesic activity in experimental pain models, which depended on the nature of the substituent in the benzodiazepine nucleus. An analogous dependence was also shown for the antiarrhythmic activity in the epinephrine arrhythmia test in vivo. Studies on the isolated atrium have shown that the mechanism of action of the new compounds is included the blockade of beta-adrenergic receptors and potassium channels. Molecular docking analysis was conducted to determine the binding potential of target molecules with the voltage-gated sodium channel NaV1.5. All obtained results provide a basis for future rational modifications of lappaconitine, reducing side effects, while retaining its therapeutic effects.

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.

Unification of medicines and excipients: The roles of natural excipients for promoting drug delivery

INTRODUCTION

Drug delivery systems (DDSs) formed by natural active compounds be instrumental in developing new green excipients and novel DDS from natural active compounds (NACs). 'Unification of medicines and excipients'(UME), the special inherent nature of the natural active compounds, provides the inspiration and conduction to achieve this goal.

AREAS COVERED

This review summarizes the typical types of NACs from herbal medicine, such as saponins, flavonoids, polysaccharides, etc. that act as excipients and their main application in DDS. The comparison of the drug delivery systems formed by NACs and common materials and the primary formation mechanisms of these NACs are also introduced to provide a deepened understanding of their performance in DDS.

EXPERT OPINION

Many natural bioactive compounds, such as saponins, polysaccharides, etc. have been used in DDS. Diversity of structure and pharmacological effects of NACs turn out the unique advantages in improving the performance of DDSs like targeting ability, adhesion, encapsulation efficiency(EE), etc. and enhancing the bioavailability of loaded drugs.

Neoline, fuziline, songorine and 10-OH mesaconitine are potential quality markers of Fuzi: In vitro and in vivo explorations as well as pharmacokinetics, efficacy and toxicity evaluations

ETHNOPHARMACOLOGICAL RELEVANCE

Fuzi, the lateral roots of Aconitum carmichaelii Debx, plays an irreplaceable role in treating Yang deficiency and cold coagulation syndromes. However, Fuzi has a narrow margin of safety since its pharmacological constituents, Aconitum alkaloids, have potential cardiotoxicity and neurotoxicity. The current quality markers (Q-markers) for the control of Fuzi's efficacy and toxicity are 3 monoester-diterpenoid alkaloids, namely, benzoylaconine (BAC), benzoylhypaconine and benzoylmesaconine (BMA) and 3 diester-diterpenoid alkaloids, namely, aconitine (AC), hypaconitine and mesaconitine (MA). However, mounting evidence indicates that the current 6 Q-markers may not be efficacy- or toxicity-specific enough for Fuzi.

AIM OF THE STUDY

The aim of this study was to explore and evaluate efficacy- or toxicity-specific potential quality markers (PQ-markers) of Fuzi.

MATERIALS AND METHODS

PQ-markers were explored by analyzing 30 medicinal samples and alkaloids exposed in mouse. Pharmacokinetics of PQ-markers on C57BL/6J mice were determined. Anti-inflammatory effects of PQ-markers were evaluated by λ-carrageenan-induced paw edema model and lipopolysaccharide-induced RAW264.7 cell inflammatory model, while analgesic effects were assessed by acetic acid-induced pain model and Hargreaves test. Cardiotoxicity and neurotoxicity of PQ-markers were assessed by histological and biochemical analyses, while acute toxicity was evaluated by modified Kirschner method.

RESULTS

After in vitro and in vivo explorations, 7 PQ-markers, namely, neoline (NE), fuziline (FE), songorine (SE), 10-OH mesaconitine (10-OH MA), talatizamine, isotalatizidine and 16β-OH cardiopetalline, were found. In the herbal medicines, NE, FE, SE and 10-OH MA were found in greater abundance than many other alkaloids. Specifically, the amounts of NE, FE and SE in the Fuzi samples were all far higher than that of BAC, and the contents of 10-OH MA in 56.67% of the samples were higher than that of AC. In mouse plasma and tissues, NE, FE, SE, talatizamine, isotalatizidine and 16β-OH cardiopetalline had higher contents than the other alkaloids, including the 6 current Q-markers. The pharmacokinetics, efficacy and toxicity of NE, FE, SE and 10-OH MA were further evaluated. The average oral bioavailabilities of NE (63.82%), FE (18.14%) and SE (49.51%) were higher than that of BMA (3.05%). Additionally, NE, FE and SE produced dose-dependent anti-inflammatory and analgesic effects, and their actions were greater than those of BMA. Concurrently, the toxicities of NE, FE and SE were lower than those of BMA, since no cardiotoxicity or neurotoxicity was found in mice after NE, FE and SE treatment, while BMA treatment notably increased the creatine kinase activity and matrix metalloproteinase 9 level in mice. The average oral bioavailability of 10-OH MA (7.02%) was higher than that of MA (1.88%). The median lethal dose (LD₅₀) of 10-OH MA in mice (0.11 mg/kg) after intravenous injection was close to that of MA (0.13 mg/kg). Moreover, 10-OH MA produced significant cardiotoxicity and neurotoxicity, and notable anti-inflammatory and analgesic effects that were comparable to those of MA.

CONCLUSIONS

Seven PQ-markers of Fuzi were found after in vitro and in vivo explorations. Among them, NE, FE and SE were found to be more efficacy-specific than BMA, and 10-OH MA was as toxicity-specific as MA.

Anti-inflammatory diterpenoid alkaloids from Aconitum tanguticum (Maxim.) Stapf

Fifteen undescribed diterpenoid alkaloids and seven known analogs were coisolated from the whole plant Aconitum tanguticum (Maxim.) Stapf. Their structures were elucidated based on spectroscopic methods. Among them, tangirine A was a heteratisine-hetidine-type bis-diterpenoid alkaloid, tanguticinines A-F were six hetidine-hetisine-type bis-diterpenoid alkaloids, tanguticinine G was one hetidine-atisine-type bis-diterpenoid alkaloid, and N-oxide anthoroidine B, 5-deoxyanthoridine B and N-oxide 5-deoxyanthoroidine B were three unusual hetidine-rearranged hetisine-type bis-diterpenoid alkaloids. In the bioassay, thirteen compounds showed some inhibitory effects on the secretion of NO and TNF-α in LPS-treated RAW 264.7 cells, with IC₅₀ values of 67.56 μM-683.436 μM.

Antifungal and Antibacterial Activities of Isolated Marine Compounds

To combat the ineffectiveness of currently available pharmaceutical medications, caused by the emergence of increasingly resistant bacterial and fungal strains, novel antibacterial and antifungal medications are urgently needed. Novel natural compounds with antimicrobial activities can be obtained by exploring underexplored habitats such as the world's oceans. The oceans represent the largest ecosystem on earth, with a high diversity of organisms. Oceans have received some attention in the past few years, and promising compounds with antimicrobial activities were isolated from marine organisms such as bacteria, fungi, algae, sea cucumbers, sea sponges, etc. This review covers 56 antifungal and 40 antibacterial compounds from marine organisms. These compounds are categorized according to their chemical structure groups, including polyketides, alkaloids, ribosomal peptides, and terpenes, and their organismal origin. The review provides the minimum inhibitory concentration MIC values and the bacterial/fungal strains against which these chemical compounds show activity. This study shows strong potential for witnessing the development of new novel antimicrobial drugs from these natural compounds isolated and evaluated for their antimicrobial activities.

Natural-product-inspired bioactive alkaloids agglomerated with potential antioxidant activity: Recent advancements on structure-activity relationship studies and future perspectives

Alkaloids derived from natural sources have been shown to have substantial antioxidant activity, suggesting that these natural-product-inspired bioactive entities may have major beneficial influence on human health and food processing sector. The primary process intricates in the etiology of several disorders such as neurodegenerative, inflammatory cardiovascular, and other chronic diseases appear to be either oxidative injury or a cellular damage caused by reactive oxygen species (ROS) or free-radicals. The alkaloid class of bio-heterocycles have been divided into numerous groups based on their biosynthetic precursor and heterocyclic ring systems i.e., piperidine, imidazole, purine, pyrrolizidine, indole, quinolozidine, isoquinoline, tropane, and pyrrolidine alkaloids. Distinct biological properties have been attributed to various compounds belonging to this chemical groups, including antirheumatic, cardiovascular, antispasmodic, anti-ulcer, anti-inflammatory, antibacterial, antinociceptive etc. For many years, natural products and their analogs have been recognized as a possible source of medicinal agents. Recently, research has been concentrated on the synthesis, separation/purification, and identification of new alkaloids derived from a variety of natural sources. This book chapter aims to summarize on the latest developments on the current knowledge on the relationship between the structural features of promising class of bioactive alkaloids with their antioxidant activities.

Grandiflolines A–F, new anti-inflammatory diterpenoid alkaloids isolated from Delphinium grandiflorum

Delphinium grandiflorum L. (family Ranunculaceae), one of the most important and widely distributed Delphinium species, has received considerable interest due to its extremely high medicinal value. The discovery of novel metabolites from D. grandiflorum supported and broadened its application as an herbal medicine. In this study, the whole herb of D. grandiflorum was phytochemically investigated to obtain fourteen C₁₉-lycaconitine-type diterpenoid alkaloids (1–14), including six undescribed alkaloids, grandiflolines A–F (1–6). The structural elucidation of them was accomplished by detailed spectroscopic analyses, mainly including HR-MS, 1D and 2D NMR (¹H–¹H COSY, NOESY, HMBC and HSQC), and IR spectra. New alkaloids 1–3 and 5 possess a characteristic △^2,3 functional group in the A ring, while compounds 5 and 6 feature a rare OH-16 substituent. In addition, known compounds 7–12 were isolated from D. grandiflorum for the first time. Moreover, according to its medicinal use, new alkaloids 1–6 were estimated for their potential in vitro anti-inflammatory effects, and some of them exhibited inhibitory effects on NO production in LPS-activated RAW 264.7 macrophages. Our work enriched the chemical diversity of D. grandiflorum and the genus Delphinium and presented beneficial information for further investigations.

Design, synthesis and insecticidal activity and mechanism research of Chasmanthinine derivatives

Unrestricted reproduction and spread of pest had caused great damage to the quality and yield of crops in recent years. Besides the use of traditional chemical pesticides, natural products also make a huge contribution against pests. Chasmanthinine, a diterpenoid alkaloid isolated from Aconitum franchetii var. villosulum, shown extremely antifeedant activity against Spodoptera exigua. Therefore, a series of novel Chasmanthinine derivatives were synthesized and their biological activity was studied in this work. Compound 33 showed the strongest antifeedant activity (EC₅₀ = 0.10 mg/cm²) among all the test compounds. The mechanism research of 33 revealed that its antifeedant effect was related to the inhibition of carboxylesterase (CES), and proved the thiophene acyl group could form a strong binding effect with CES by molecular docking. Moreover, compound 10 exhibited the strongest cytotoxicity (IC₅₀ = 12.87 μM) against Sf9 cell line and moderate contact toxicity. The mechanism research indicated that compound 10 could induce Sf9 cells apoptosis. In summary, the results lay a foundation for the application of diterpene alkaloids in plant protection.

Recent Advances in the Synthesis of Marine-Derived Alkaloids via Enzymatic Reactions

Alkaloids are a large and structurally diverse group of marine-derived natural products. Most marine-derived alkaloids are biologically active and show promising applications in modern (agro)chemical, pharmaceutical, and fine chemical industries. Different approaches have been established to access these marine-derived alkaloids. Among these employed methods, biotechnological approaches, namely, (chemo)enzymatic synthesis, have significant potential for playing a central role in alkaloid production on an industrial scale. In this review, we discuss research progress on marine-derived alkaloid synthesis via enzymatic reactions and note the advantages and disadvantages of their applications for industrial production, as well as green chemistry for marine natural product research.

Diterpenoid Alkaloids Isolated from Delphinium brunonianum and Their Inhibitory Effects on Hepatocytes Lipid Accumulation

This research aimed to excavate compounds with activity reducing hepatocytes lipid accumulation from Delphinium brunonianum. Four novel diterpenoid alkaloids, brunodelphinine B–E, were isolated from D. brunonianum together with eleven known diterpenoid alkaloids through a phytochemical investigation. Their structures were elucidated by comprehensive spectroscopy methods including HR-ESI-MS, NMR, IR, UV, CD, and single-crystal X-ray diffraction analysis. The inhibitory effects of a total of 15 diterpenoid alkaloids on hepatocytes lipid accumulation were evaluated using 0.5 mM FFA (oleate/palmitate 2:1 ratio) to induce buffalo rat liver (BRL) cells by measuring the levels of triglyceride (TG), total cholesterol (TC), alanine transaminase (ALT), aspartate transaminase (AST), and the staining of oil red O. The results show that five diterpenoid alkaloids—brunodelphinine E (4), delbruline (5), lycoctonine (7), delbrunine (8), and sharwuphinine A (12)—exhibited significant inhibitory effects on lipid accumulation in a dose-dependent manner and without cytotoxicity. Among them, sharwuphinine A (12) displayed the strongest inhibition of hepatocytes lipid accumulation in vitro. Our research increased the understanding on the chemical composition of D. brunonianum and provided experimental and theoretical evidence for the active ingredients screened from this herbal medicine in the treatment of the diseases related to lipid accumulation, such as non-alcoholic fatty liver disease and hyperlipidemia.

Ecological and Pharmacological Activities of Polybrominated Diphenyl Ethers (PBDEs) from the Indonesian Marine Sponge Lamellodysidea herbacea

Two known Polybrominated Diphenyl Ethers (PBDEs), 3,4,5-tribromo-2-(2′,4′-dibromophenoxy)phenol (1d) and 3,4,5,6-tetrabromo-2-(2′,4′-dibromophenoxy)phenol (2b), were isolated from the Indonesian marine sponge Lamellodysidea herbacea. The structure was confirmed using ¹³C chemical shift average deviation and was compared to the predicted structures and recorded chemical shifts in previous studies. We found a wide range of bioactivities from the organic crude extract, such as (1) a strong deterrence against the generalist pufferfish Canthigaster solandri, (2) potent inhibition against environmental and human pathogenic bacterial and fungal strains, and (3) the inhibition of the Hepatitis C Virus (HCV). The addition of a bromine atom into the A-ring of compound 2b resulted in higher fish feeding deterrence compared to compound 1d. On the contrary, compound 2b showed only more potent inhibition against the Gram-negative bacteria Rhodotorula glutinis (MIC 2.1 μg/mL), while compound 1d showed more powerful inhibition against the other human pathogenic bacteria and fungi. The first report of a chemical defense by compounds 1d and 2b against fish feeding and environmental relevant bacteria, especially pathogenic bacteria, might be one reason for the widespread occurrence of the shallow water sponge Lamellodysidea herbacea in Indonesia and the Indo-Pacific.