A new C₁₉-diterpenoid alkaloid from the roots of Aconitum duclouxii

Antibacterial Activity and Antifungal Activity of Monomeric Alkaloids

Scientists are becoming alarmed by the rise in drug-resistant bacterial and fungal strains, which makes it more costly, time-consuming, and difficult to create new antimicrobials from unique chemical entities. Chemicals with pharmacological qualities, such as antibacterial and antifungal elements, can be found in plants. Alkaloids are a class of chemical compounds found in nature that mostly consist of basic nitrogen atoms. Biomedical science relies heavily on alkaloid compounds. Based on 241 papers published in peer-reviewed scientific publications within the last ten years (2014-2024), we examined 248 natural or synthesized monomeric alkaloids that have antifungal and antibacterial activity against Gram-positive and Gram-negative microorganisms. Based on their chemical structure, the chosen alkaloids were divided into four groups: polyamine alkaloids, alkaloids with nitrogen in the side chain, alkaloids with nitrogen heterocycles, and pseudoalkaloids. With MIC values of less than 1 µg/mL, compounds 91, 124, 125, 136-138, 163, 164, 191, 193, 195, 205 and 206 shown strong antibacterial activity. However, with MIC values of below 1 µg/mL, compounds 124, 125, 163, 164, 207, and 224 demonstrated strong antifungal activity. Given the rise in antibiotic resistance, these alkaloids are highly significant in regard to their potential to create novel antimicrobial drugs.

Two New C19 -Diterpenoid Alkaloids from Delphinium shawurense

Shawurenine C (1a) and D (1b), a new pair of regioisomeric C₁₉ -diterpenoid alkaloids, and five known C₁₉ -diterpenoid alkaloids (2-6) were isolated from the aerial part of Delphinium shawurense W. T. Wang. The chemical structures of new compounds were established based on spectroscopic analyses: HR-ESI-MS, and 1D, 2D NMR spectroscopic data. The anti-inflammatory and cytotoxic activities of these diterpenoid alkaloids were also evaluated.

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.

Structural diversity, bioactivities, and biosynthesis of natural diterpenoid alkaloids

Covering: 2009 to 2018. Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, are a diverse class of compounds having complex structural features with many stereocenters. The important pharmacological activities and structural complexity of the diterpenoid alkaloids have long interested scientists due to their medicinal uses, infamous toxicity, and unique biosynthesis. Since 2009, 373 diterpenoid alkaloids, assigned to 46 skeletons, have been isolated and identified from plants mostly in the Ranunculaceae family. The names, classes, molecular weight, molecular formula, NMR data, and plant sources of these diterpene alkaloids are collated here. This review will be a detailed update of the naturally occurring diterpene alkaloids reported from the plant kingdom from 2009-2018, providing an in-depth discussion of their diversity, biological activities, pharmacokinetics, toxicity, application, evolution, and biosynthesis.

Classification, Toxicity and Bioactivity of Natural Diterpenoid Alkaloids

Diterpenoid alkaloids are natural compounds having complex structural features with many stereo-centres originating from the amination of natural tetracyclic diterpenes and produced primarily from plants in the Aconitum, Delphinium, Consolida genera. Corals, Xenia, Okinawan/Clavularia, Alcyonacea (soft corals) and marine sponges are rich sources of diterpenoids, despite the difficulty to access them and the lack of availability. Researchers have long been concerned with the potential beneficial or harmful effects of diterpenoid alkaloids due to their structural complexity, which accounts for their use as pharmaceuticals as well as their lousy reputation as toxic substances. Compounds belonging to this unique and fascinating family of natural products exhibit a broad spectrum of biological activities. Some of these compounds are on the list of clinical drugs, while others act as incredibly potent neurotoxins. Despite numerous attempts to prepare synthetic products, this review only introduces the natural diterpenoid alkaloids, describing 'compounds' structures and classifications and their toxicity and bioactivity. The purpose of the review is to highlight some existing relationships between the presence of substituents in the structure of such molecules and their recognised bioactivity.

A systematic review of pharmacological activities, toxicological mechanisms and pharmacokinetic studies on Aconitum alkaloids

The tubers and roots of Aconitum (Ranunculaceae) are widely used as heart medicine or analgesic agents for the treatment of coronary heart disease, chronic heart failure, rheumatoid arthritis and neuropathic pain since ancient times. As a type of natural products mainly extracted from Aconitum plants, Aconitum alkaloids have complex chemical structures and exert remarkable biological activity, which are mainly responsible for significant effects of Aconitum plants. The present review is to summarize the progress of the pharmacological, toxicological, and pharmacokinetic studies of Aconitum alkaloids, so as to provide evidence for better clinical application. Research data concerning pharmacological, toxicological and pharmacokinetic studies of Aconitum alkaloids were collected from different scientific databases (PubMed, CNKI, Google Scholar, Baidu Scholar, and Web of Science) using the phrase Aconitum alkaloids, as well as generic synonyms. Aconitum alkaloids are both bioactive compounds and toxic ingredients in Aconitum plants. They produce a wide range of pharmacological activities, including protecting the cardiovascular system, nervous system, and immune system and anti-cancer effects. Notably, Aconitum alkaloids also exert strong cardiac toxicity, neurotoxicity and liver toxicity, which are supported by clinical studies. Finally, pharmacokinetic studies indicated that cytochrome P450 proteins (CYPs) and efflux transporters (ETs) are closely related to the low bioavailability of Aconitum alkaloids and play an important role in their metabolism and detoxification in vivo.

Four new C19-diterpenoid alkaloids from Aconitum hemsleyanum var. circinatum

Four new C19-diterpenoid alkaloids, hemaconitines A-D (1-4), were isolated from the roots of Aconitum hemsleyanum var. circinatum. Their structures were elucidated as 19R-hydroxyl-secoyunnaconitine (1), (3R)-hydroxyl-liwaconitine (2), 14-anisoyl-leucanthumsine E (3), and 19R -acetonyl-8-O-methyltalatisamine (4) by extensive spectroscopic analysis (IR, UV, HR-ESI-MS, 1D, and 2D NMR).

Diterpenoid alkaloids from Aconitum brevicalcaratum as autophagy inducers

A new C19 diterpenoid alkaloid, brevicanine (1) and six known ones (2-7) were isolated from Aconitum brevicalcaratum (Finet et Gagnep.) Diels. Their structures were elucidated on the basis of extensive spectroscopic analyses. The cytotoxicity of those compounds was investigated against HCT116 human cancer cell line, which showed none of them possessing considerable anti-proliferative activities. To evaluate the autophagy effect of compounds 1-7, Western blot was used to detect the expression of autophagic marker by stimulating human cancer HCT116 cells. The results showed that compound 6 induced protective autophagy in HCT116 cells. Mechanistic insight showed that compound 6 induced protective autophagy through p53 activation, ERK1/2 and p38 MAPK signaling cascade.

New pyrazinoquinazoline alkaloids Isolated from a culture of Stenotrophomonas maltophilia QB-77

Two new pyrazinoquinazoline alkaloids, epi-fiscalin D (1) and epi-fiscalin E (2), as well as three known analogues, norquinadoline A (3), quinadoline A (4), and fiscalin C (5), were isolated from ethyl acetate extract of the fermentation broth of Stentrophomonas maltophilia QB-77. The structures of new compounds were elucidated on the basis of extensive spectroscopic data analysis including UV, HRESIMS, and 1D and 2D NMR experiments. All the isolated compounds were tested for their in vitro cytotoxicity against five human cancer cell lines (SMMC-7721, MCF-7, HL-60, SW480, and A-549) and antibacterial activities against Bacillus subtilis, Escherichia coli, and Staphylococcus aureus.

Diterpenoid alkaloids from the roots of Aconitum brachypodum Diels

A new diterpenoid alkaloid, named bullatine H (1), along with 10 known diterpenoid alkaloids were isolated from the roots of Aconitum brachypodum Diels (Ranunculaceae). The structure of 1 was elucidated by analysis of its spectroscopic data. It should be noted that compound 1 is the first example with 11, 13-dioxygenated denudatine-type diterpenoid alkaloid isolated from Aconitum brachypodum.

A new C20-diterpenoid alkaloid from the lateral roots of Aconitum carmichaeli

A new C₂₀-diterpenoid alkaloid carmichaedine (1) and six known alkaloids (2-7) were isolated from the lateral roots of Aconitum carmichaeli. Their structures were established on the basis of extensive spectroscopic analyses. Compound 1 exhibited potent antibacterial activity against Bacillus subtilis with minimum inhibitory concentration of 8 μg/mL.

A new C20-diterpenoid alkaloid from Aconitum soongaricum var. pubescens

A new denudatine-type C₂₀-diterpenoid alkaloid, pubesine (1), along with seven known diterpenoid alkaloids, altaconitine (2), 14-benzoylaconine (3), spicatine A (4), 14-benzoylaconine-8-palmitate (5), 14-O-acetylsenbusine A (6), senbusine A (7) and 14-acetylneoline (8) were isolated from the whole plant of Aconitum soongaricum var. pubescens. Their structures were elucidated by means of extensive spectroscopic analyses (NMR and HR-ESI-MS) and comparison with data reported in the literature. All compounds were evaluated for their cytotoxicity against H460, MCF-7 and Hep G2 human cancer cell lines.

Separation and purification of five alkaloids from Aconitum duclouxii by counter-current chromatography

C19 -diterpenoid alkaloids are the main components of Aconitum duclouxii Levl. The process of separation and purification of these compounds in previous studies was tedious and time consuming, requiring multiple chromatographic steps, thus resulted in low recovery and high cost. In the present work, five C19 -diterpenoid alkaloids, namely, benzoylaconine (1), N-deethylaconitine (2), aconitine (3), deoxyaconitine (4), and ducloudine A (5), were efficiently prepared from A. duclouxii Levl (Aconitum L.) by ethyl acetate extraction followed with counter-current chromatography. In the process of separation, the critical conditions of counter-current chromatography were optimized. The two-phase solvent system composed of n-hexane/ethyl acetate/methanol/water/NH3 ·H2 O (25%) (1:1:1:1:0.1, v/v) was selected and 148.2 mg of 1, 24.1 mg of 2, 250.6 mg of 3, 73.9 mg of 4, and 31.4 mg of 5 were obtained from 1 g total Aconitum alkaloids extract, respectively, in a single run within 4 h. Their purities were found to be 98.4, 97.2, 98.2, 96.8, and 96.6%, respectively, by ultra-high performance liquid chromatography analysis. The presented separation and purification method was simple, fast, and efficient, and the obtained highly pure alkaloids are suitable for biochemical and toxicological investigation.