The C19-Diterpenoid Alkaloids

Glancing at the birth of a galaxy of scientists from Rikō Majima

Rikō Majima published seven papers in this journal, and seeing these papers and their surrounding contexts allows us to glance at the birth of a galaxy of scientists.

Kamaonensine A-G: Lycaconitine-type C19-diterpenoid alkaloids with anti-inflammatory activities from Delphinium kamaonense Huth

Delphinium kamaonense Huth is a sort of folkloric plant resource which is cultivated and planted with great ornamental and medicinal values. In this work, seven undescribed lycaconitine-type C19-diterpenoid alkaloids, especially a rare skeleton with -CH=N and N-oxide moieties, along with ten known compounds, were isolated from D. kamaonense, of which the structures were determined by various spectroscopic data, combined with calculated electronic circular dichroism (ECD) and single-crystal X-ray diffraction analysis. In vitro nitric oxide inhibitory activities assay of these compounds indicated that lycaconitine-type C19-diterpenoid alkaloids had significant anti-inflammatory inhibitory activities, with kamaonensine E being the most potent (0.9 ± 0.2 μM) stronger than positive (9.0 ± 1.3 μM). In the network pharmacology studies, binding three key targets mitogen-activated protein kinase 8 (MAPK8), mitogen-activated protein kinase 14 (MAPK14), and heat shock protein HSP 90-alpha (HSP90α), the anti-inflammatory mechanism might be related to MAPK signaling pathways. Furthermore, the molecular docking results revealed that the uncommon amides and methylenedioxy groups might be the most two promising pharmacophores for lycaconitine-type C19-diterpenoid alkaloids.

Multi-omics analysis reveals the evolutionary origin of diterpenoid alkaloid biosynthesis pathways in Aconitum

Diterpenoid alkaloids (DAs) have been often utilized in clinical practice due to their analgesic and anti-inflammatory properties. Natural DAs are prevalent in the family Ranunculaceae, notably in the Aconitum genus. Nevertheless, the evolutionary origin of the biosynthesis pathway responsible for DA production remains unknown. In this study, we successfully assembled a high-quality, pseudochromosome-level genome of the DA-rich species Aconitum vilmorinianum (A. vilmorinianum) (5.76 Gb). An A. vilmorinianum-specific whole-genome duplication event was discovered using comparative genomic analysis, which may aid in the evolution of the DA biosynthesis pathway. We identified several genes involved in DA biosynthesis via integrated genomic, transcriptomic, and metabolomic analyses. These genes included enzymes encoding target ent-kaurene oxidases and aminotransferases, which facilitated the activation of diterpenes and insertion of nitrogen atoms into diterpene skeletons, thereby mediating the transformation of diterpenes into DAs. The divergence periods of these genes in A. vilmorinianum were further assessed, and it was shown that two major types of genes were involved in the establishment of the DA biosynthesis pathway. Our integrated analysis offers fresh insights into the evolutionary origin of DAs in A. vilmorinianum as well as suggestions for engineering the biosynthetic pathways to obtain desired DAs.

Multi-conformers caused by conformational change of A-ring in the C18- and C19-N-dealkyl diterpenoid alkaloids

This paper describes a rare phenomenon of multi-conformers caused by conformational change of A-ring in the C18- and C19- N-dealkyl diterpenoid alkaloids. The possible reasons for the generation of multiple conformational isomers are complex, which could be affected by the substituents at C-1, C-3, C-13, C-14, and C-15, pH, solvents, the intramolecular hydrogen bond between 1α-OCH3/1α-OH and N-H groups, acid-base treatment, preparation methods, and work-up procedures.

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.

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.

Advances on pharmacology and toxicology of aconitine

Aconitum alkaloids are considered to be the characteristic bioactive ingredients of Aconitum species, which are widely applied to the treatment of diverse diseases, and aconitine (AC) is found in most Aconitum plants. Research evidence shows that low-dose AC has a good therapeutic potential in heart failure, myocardial infarction, neuroinflammatory diseases, rheumatic diseases, and tumors, which has become one of the hotspots in global research in recent years. However, the cardiotoxicity and neurotoxicity of AC have also attracted extensive attention. Excessive use of AC always induces ventricular tachyarrhythmia and heart arrest, even can be potentially lethal. Therefore, AC cannot simply be regarded as a good medicine or a toxicant, but its underlying curative and toxic properties remained chaos. In order to dig the unique pharmacological value of AC while preventing its toxicity, the pharmacological activities and toxic effects of AC were summarized in this paper, providing new insight into the safe and effective use of AC in clinical practice.

Phytochemical Screening, Antioxidant and Antifungal Activities of Aconitum chasmanthum Stapf ex Holmes Wild Rhizome Extracts

Aconitum chasmanthum Stapf ex Holmes, an essential and critically endangered medicinal plant from Kashmir Himalayas, was studied for its antioxidant and antifungal properties. The shade-dried powdered rhizome was extracted sequentially with hexane, ethyl acetate, and methanol. These subsequent fractions were evaluated for total phenolic content (TPC); total flavonoid content (TFC); antioxidant assays, such as 1,1-diphenyl 1-2-picryl-hydrazyl (DPPH); ferric-reducing antioxidant power (FRAP); superoxide radical scavenging (SOR); hydroxyl radical scavenging (OH) and antifungal activity using the poisoned food technique. Highest TPC (5.26 ± 0.01 mg/g) and TFC (2.92 ± 0.04 mg/g) were reported from methanolic extracts. The highest values of radical scavenging activities were also observed in methanolic extracts with IC₅₀ values of 163.71 ± 2.69 μg/mL in DPPH, 173.69 ± 4.91 μg/mL in SOR and 159.64 ± 2.43 μg/mL in OH. The chemical profile of ethyl acetate extract was tested using HR-LCMS. Methanolic extracts also showed a promising inhibition against Aspergillus niger (66.18 ± 1.03), Aspergillus flavus (78.91 ± 1.19) and Penicillium notatum (83.14 ± 0.97) at a 15% culture filtrate concentration with minimum inhibitory concentration (MIC) values of 230 μg/mL, 200 μg/mL and 190 μg/mL, respectively. Overall, the methanolic fractions showed significant biological potential, and its pure isolates might be used to construct a potential new medicinal source.

Isolation, identification, and activity evaluation of diterpenoid alkaloids from Aconitum sinomontanum

A phytochemical study led to the isolation of 25 diterpenoid alkaloids from Aconitum sinomontanum, of which six were described for the first time. Among them compounds 1-3 are anhydrolycoctonine derivatives, rare rearranged aconitine-type C₁₉-diterpenoid alkaloids. To our best knowledge, less than ten of this type of alkaloids were isolated just from the genus Aconitum. The structures of these unreported compounds were elucidated by extensive analysis of NMR spectroscopic data and X-ray diffraction. The biological activities of compounds 1-3, 5-9, and 12-25 were evaluated. Among the tested compounds, compounds 2 and 17 showed potent inhibitory effect on the capsaicin (selective TRPV1 agonist) mediated activation of transient receptor potential vanilloid 1 (TRPV1) channels expressed in HEK-293 cells with inhibition rate of 31.78% and 30.94% at the concentration of 10 μM. Compounds 1-3, 5-9, 13, and 18-25 exhibited weak cytotoxic activity against human tumor cell lines NCI-H226 and MDA-MB-231 with inhibition rate over 10% at the concentration of 10 μM. Compound 16 showed most inhibitory effect on the expression of Nrf2 (NF-E2-related factor-2)-regulated gene with inhibition rate of 25% at the concentration of 20 μM.

Asymmetric Total Synthesis of Hetidine-Type C20-Diterpenoid Alkaloids: (+)-Talassimidine and (+)-Talassamine

Here, we report the first asymmetric total synthesis of (+)-talassimidine and (+)-talassamine, two hetidine-type C₂₀-diterpenoid alkaloids. A highly regio- and diastereoselective 1,3-dipolar cycloaddition of an azomethine ylide yielded a chiral tetracyclic intermediate in high enantiopurity, thus providing the structural basis for asymmetric assembly of the hexacyclic hetidine skeleton. In this key step, the introduction of a single chiral center induces four new continuous chiral centers. Another key transformation is the dearomative cyclopropanation of the benzene ring and subsequent S_N2-like ring opening of the resultant cyclopropane ring with water as a nucleophile, which not only establishes the B ring but also precisely installs the difficult-to-achieve equatorial C7-OH group.

A systematic review on the chemical constituents of the genus Consolida (Ranunculaceae) and their biological activities

For centuries, species of the genus Consolida (Ranunculaceae) have been extensively utilized for their extremely high ornamental and medicinal values. Phytochemical investigations of Consolida species have revealed the presence of multiple active ingredients, including diterpenoid alkaloids, flavonoids, phenolic acids, phytosterols, fatty acids, and volatile constituents. These chemical constituents are of great research significance due to their novel structures and broad biological activities. This review addresses, for the first time, the chemical constituents of Consolida plants and the biological activities of these compounds to facilitate future research.

Application of The Dess-Martin Oxidation in Total Synthesis of Natural Products

Dess-Martin periodinane (DMP), a commercially available chemical, is frequently utilized as a mild oxidative agent for the selective oxidation of primary and secondary alcohols to their corresponding aldehydes and ketones, respectively. DMP shows several merits over other common oxidative agents such as chromiumand DMSO-based oxidants; thus, it is habitually employed in the total synthesis of natural products. In this review, we try to underscore the applications of DMP as an effective oxidant in an appropriate step (steps) in the multi-step total synthesis of natural products.

Synthesis, in vitro and in vivo biological evaluation of novel lappaconitine derivatives as potential anti-inflammatory agents

Lappaconitine (LA), a natural compound with a novel C18-diterpenoid alkaloid skeleton, displayed extensive biological profile. Recent research on LA is focused mainly on its anti-tumor and analgesic effects, and therefore we aimed to investigate its anti-inflammatory potential. A series of novel LA derivatives with various substituents on the 20-N position was designed and synthesized. In the initial screening of LA derivatives against NO production, all the target compounds, except compound E2, exhibited excellent inhibitory ability relative to that of LA. Particularly, compound A4 exhibited the most potent inhibition with IC₅₀ of 12.91 μmol/L. The elementary structure-activity relationships (SARs) of NO inhibitory activity indicated that replacement of the benzene ring with an electron donating group could improve the anti-inflammatory efficacy. Furthermore, compound A4 shows an anti-inflammatory mechanism by inhibiting NO, PGE2, and TNF-α generation via the suppression of NF-κB and MAPK signaling pathways. Notably, compound A4 could exert a significant therapeutic effect on LPS-induced acute lung injury (ALI) in vivo. Based on the above research, we further investigated the preliminary pharmacokinetic property of A4 in rats. Therefore, compound A4 could be a promising candidate for the development of anti-inflammatory agents in the future.

Cytotoxic Effects of Diterpenoid Alkaloids Against Human Cancer Cells

Diterpenoid alkaloids are isolated from plants of the genera Aconitum, Delphinium, and Garrya (Ranunculaceae) and classified according to their chemical structures as C18-, C19- or C20-diterpenoid alkaloids. The extreme toxicity of certain compounds, e.g., aconitine, has prompted a thorough investigation of how structural features affect their bioactivities. Therefore, natural diterpenoid alkaloids and semi-synthetic alkaloid derivatives were evaluated for cytotoxic effects against human tumor cells [A549 (lung carcinoma), DU145 (prostate carcinoma), MDA-MB-231 (triple-negative breast cancer), MCF-7 (estrogen receptor-positive, HER2-negative breast cancer), KB (identical to cervical carcinoma HeLa derived AV-3 cell line), and multidrug-resistant (MDR) subline KB-VIN]. Among the tested alkaloids, C19-diterpenoid (e.g., lipojesaconitine, delcosine and delpheline derivatives) and C20-diterpenoid (e.g., kobusine and pseudokobusine derivatives) alkaloids exhibited significant cytotoxic activity and, thus, provide promising new leads for further development as antitumor agents. Notably, several diterpenoid alkaloids were more potent against MDR subline KB-VIN cells than the parental drug-sensitive KB cells.

Structure-activity relationships and evaluation of esterified diterpenoid alkaloid derivatives as antiproliferative agents

Diterpenoid alkaloids with remarkable chemical properties and biological activities are frequently found in plants of the genera Aconitum, Delphinium, and Garrya. However, little information has been reported on the antiproliferative effects of the diterpenoid alkaloid constituents of Aconitum and Delphinium plants. C-1 and 14 esterifications of delcosine (1) were carried out to provide 39 new diterpenoid alkaloid derivatives (3-14, 16-29, 3a-7a, 9a, 13a, 13b, 14a, 14b, 16a, 17a, 24a, 35a). Selected compounds (3-14, 16-29, 3a-7a, 9a, 13a, 13b, 14a, 14b, 16a, 17a, 24a, 35a) were evaluated for antiproliferative activity against three to five human tumor cell lines including triple-negative breast cancer (TNBC) and P-glycoprotein (P-gp) overexpressing multidrug-resistant (MDR) subline. Several newly synthesized delcosine derivatives (6, 7, 13, 13a, 13b) showed substantial suppressive effects against all human tumor cell lines tested. In contrast, the natural alkaloids (1, 31, 33) showed no effect. Most of the active compounds were delcosine derivatives with two specific substitution patterns-C-1 and C-1,14. In particular, 1-acyldelcosine derivative (5-7) displayed more potency than 1,14-diacyldelcosine derivatives (5a-7a). These acylated alkaloid derivatives caused accumulation of TNBC cells at sub-G1 within 24 h. 1-Acylation of 1 appears to be critical for producing antiproliferative activity in this alkaloid class and a means to provide promising new leads for further development into antitumor agents.

A Copper-Mediated Conjugate Addition Approach to Analogues of Aconitine-Type Diterpenoid Alkaloids

A copper-mediated conjugate addition of electron-rich aryl groups into a complex vinyl nitrile using arylmagnesium bromides is reported. The conjugate addition adducts were advanced toward the synthesis of designed aconitine-type analogues. The variation in oxygenation patterns on the arene coupling partner, introduced through the current conjugate addition approach, may ultimately provide insight into structure-activity relationships of the diterpenoid alkaloids.

Integration of non-targeted metabolomics and automated determination of elemental compositions for comprehensive alkaloid profiling in plants

Plants produce a large array of specialized metabolites to protect themselves. Among these allelochemicals, alkaloids display highly diverse and complex structures that are directly related to their biological activities. Plant alkaloid profiling traditionally requires extensive and time-consuming sample preparation and analysis. Herein, we developed a rapid and efficient approach for the comprehensive profiling of alkaloids in plants using ultrahigh performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS)-based metabolomics. Using automated compound extraction and elemental composition assignment, our method achieved >83% correct alkaloid identification and even >90% for medium to high intensity peaks. This represented a significant improvement in identification rate compared to generic methods used for EC determination with no a priori, such as in untargeted metabolomics studies. The developed approach was then applied to identify specific alkaloids of Aconitum lycoctonum L. and A. napellus L. (Ranunculaceae) using different parts of the plant (leaf, perianth and pollen). Significant differences in alkaloid profiles between the two species were highlighted and discussed under taxonomic and evolutionary perspectives. Taken together, the presented approach constitutes a valuable chemotaxonomic tool in the search for known and unknown alkaloids from plants.

Synthesis of Cardiopetaline via a Wagner-Meerwein Rearrangement without Preactivation of the Pivotal Hydroxy Group

A synthesis of cardiopetaline has been accomplished via a Wagner-Meerwein rearrangement of a diol having the denudatine skeleton. The Wagner-Meerwein rearrangement could be facilitated simply by heating the diol with p-toluenesulfonic acid in pivalic acid, without preactivating the pivotal hydroxy group. This strategy does not require differentiation of several hydroxy groups in the substrate for the Wagner-Meerwein rearrangement and could be applied to the synthesis of more highly oxygenated aconitine-type diterpenoid alkaloids.

C19-Diterpenoid alkaloid arabinosides from an aqueous extract of the lateral root of Aconitum carmichaelii and their analgesic activities

Eight new C₁₉-diterpenoid alkaloid arabinosides, named aconicarmichosides E–L (1–8), were isolated from an aqueous extract of the lateral roots of Aconitum carmichaelii (Fu Zi). Their structures were determined by spectroscopic and chemical methods including 2D NMR experiments and acid hydrolysis. Compounds 1–8, together with the previously reported four neoline 14-O-arabinosides from the same plant, represent the only examples of glycosidic diterpenoid alkaloids so far. At a dose of 1.0 mg/kg (i.p.), as compared with the black control, compounds 1, 2, and 4–6 exhibited analgesic effects with >65.6% inhibitions against acetic acid-induced writhing of mice. Structure–activity relationship was also discussed.

Four new diterpenoid alkaloids from Aconitum japonicum subsp. subcuneatum

Diterpenoid alkaloids with remarkable chemical properties and biological activities are frequently found in plants of the genera Aconitum, Delphinium, and Garrya. Accordingly, several diterpenoid alkaloid constituents of Aconitum and Delphinium plants as well as their derivatives exhibited cytotoxic activity against lung, prostate, nasopharyngeal, and vincristine-resistant nasopharyngeal cancer cell lines. Four new C₁₉-diterpenoid alkaloids, 14-anisoyllasianine (1), 14-anisoyl-N-deethylaconine (2), N-deethylaljesaconitine A (3), and N-deethylnevadensine (4), together with 17 known C₁₉- and C₂₀-diterpenoid alkaloids, were isolated in a phytochemical investigation of rhizoma of Aconitum japonicum THUNB. subsp. subcuneatum (NAKAI) KADOTA. Their structures were elucidated by extensive spectroscopic methods including NMR (1D and 2D), IR, and MS (HRMS). Eight known diterpenoid alkaloids, lipoaconitine, lipomesaconitine, aconine, nevadenine, talatisamine, nevadensine, ryosenamine, and dehydrolucidusculine, were isolated the first time from A. japonicum subsp. subcuneatum. Three of the new C₁₉-diterpenoid alkaloids (1, 3, 4) and six of the known diterpenoid alkaloids were evaluated for cytotoxic activity against five human tumor cell lines.

A Unifying Synthesis Approach to the C18-, C19-, and C20-Diterpenoid Alkaloids

The secondary metabolites that comprise the diterpenoid alkaloids are categorized into C18, C19, and C20 families depending on the number of contiguous carbon atoms that constitute their central framework. Herein, we detail our efforts to prepare these molecules by chemical synthesis, including a photochemical approach, and ultimately a bioinspired strategy that has resulted in the development of a unifying synthesis of one C18 (weisaconitine D), one C19 (liljestrandinine), and three C20 (cochlearenine, paniculamine, and N-ethyl-1α-hydroxy-17-veratroyldictyzine) natural products from a common intermediate.

Anticancer Activities of C18-, C19-, C20-, and Bis-Diterpenoid Alkaloids Derived from Genus Aconitum

Cancer is one of the most common lethal diseases, and natural products have been extensively studied as anticancer agents considering their availability, low toxicity, and economic affordability. Plants belonging to the genus Aconitum have been widely used medically in many Asian countries since ancient times. These plants have been proven effective for treating several types of cancer, such as lung, stomach, and liver cancers. The main effective components of Aconitum plants are diterpenoid alkaloids—which are divided into C₁₈-, C₁₉-, C₂₀-, and bis-diterpenoid alkaloids—are reportedly some of the most promising, naturally abundant compounds for treating cancer. This review focuses on the progress of diterpenoid alkaloids with different structures derived from Aconitum plants and some of their derivatives with potential anticancer activities. We hope that this work can serve as a reference for further developing Aconitum diterpenoid alkaloids as anticancer agents.

Syntheses of Denudatine Diterpenoid Alkaloids: Cochlearenine, N-Ethyl-1α-hydroxy-17-veratroyldictyzine, and Paniculamine

The denudatine-type diterpenoid alkaloids cochlearenine, N-ethyl-1α-hydroxy-17-veratroyldictyzine, and paniculamine have been synthesized for the first time (25, 26, and 26 steps from 16, respectively). These syntheses take advantage of a common intermediate (8) that we have previously employed in preparing aconitine-type natural products. The syntheses reported herein complete the realization of a unified strategy for the preparation of C20, C19, and C18 diterpenoid alkaloids.

Identification of Oxygenated Fatty Acid as a Side Chain of Lipo-Alkaloids in Aconitum carmichaelii by UHPLC-Q-TOF-MS and a Database

Lipo-alkaloid is a kind of C19-norditerpenoid alkaloid usually found in Aconitum species. Structurally, they contain an aconitane skeleton and one or two fatty acid moieties of 3–25 carbon chains with 1–6 unsaturated degrees. Analysis of the lipo-alkaloids in roots of Aconitum carmichaelii resulted in the isolation of six known pure lipo-alkaloids (A1–A6) and a lipo-alkaloid mixture (A7). The mixture shared the same aconitane skeleton of 14-benzoylmesaconine, but their side chains were determined to be 9-hydroxy-octadecadienoic acid, 13-hydroxy-octadecadienoic acid and 10-hydroxy-octadecadienoic acid, respectively, by MS/MS analysis after alkaline hydrolysis. To our knowledge, this is the first time of the reporting of the oxygenated fatty acids as the side chains in naturally-occurring lipo-alkaloids. In order to identify more lipo-alkaloids, a compound database was established based on various combinations between the aconitane skeleton and the fatty acid chain, and then, the identification of lipo-alkaloids was conducted using the database, UHPLC-Q-TOF-MS and MS/MS. Finally, 148 lipo-alkaloids were identified from A. carmichaelii after intensive MS/MS analysis, including 93 potential new compounds and 38 compounds with oxygenated fatty acid moieties.

Epoxide Opening of a 7,17-Seco–7,8-Epoxy-C19-Diterpenoid Alkaloid

A new and effective approach toward epoxide opening of a 7,17- seco–7,8-epoxy-C19-diterpenoid alkaloid is herein described. The starting epoxide was prepared from naturally occurring yunnaconitine via a nine-step transformation. Treatment of this epoxide with trifluoroacetic anhydride in dioxane at 110oC followed by reduction with sodium boron hydride generated two epoxide opening compounds 7 and 8. Each of their structures is characteristic of a Δ8,15 bridgehead double bond and a 7β-oxygen-substituted group.

Majusine D: A New C19-diterpenoid Alkaloid from Delphinium majus

A new C19-diterpenoid alkaloid, designated as majusine D (1), has been isolated from Delphnium majus W. T. Wang. The structure was elucidated by detailed NMR-spectroscopic studies.

Atropurpuran - Missing Biosynthetic Link Leading to the Hetidine and Arcutine C20-Diterpenoid Alkaloids or an Oxidative Degradation Product?

A possible biosynthetic link between atropurpuran, the hetidine diterpenoid alkaloids and the alkaloid arcutine and congeners is proposed. The feasibility of aspects of this biosynthesis, especially key 1,2-rearrangements, have been examined computationally.

Evaluation of Aconitum diterpenoid alkaloids as antiproliferative agents

Little information has been reported on the antitumor effects of the diterpenoid alkaloid constituents of Aconitum plants, used in the herbal drug 'bushi'. This study was aimed at determining the antitumor activities of Aconitum C19-and C20-diterpenoid alkaloids and synthetic derivatives against lung (A549), prostate (DU145), nasopharyngeal (KB), and vincristine-resistant nasopharyngeal (KB-VIN) cancer cell lines. Newly synthesized C20-diterpenoid alkaloid derivatives showed substantial suppressive effects against all human tumor cell lines tested. In contrast, natural and derivatized C19-diterpenoid alkaloids showed only a slight or no effect. Most of the active compounds were hetisine-type C20-diterpenoid alkaloids, specifically kobusine and pseudokobusine analogs with two different substitution patterns, C-11 and C-11,15. Notably, several C20-diterpenoid alkaloids were more potent against multidrug-resistant KB subline KB-VIN cells. Pseudokobusine 11-3'-trifluoromethylbenzoate (94) is a possible promising new lead meriting additional evaluation against multidrug-resistant tumors.

Ultrasound-assisted extraction of total flavonoids from Aconitum gymnandrum

BACKGROUND

Aconitum gymnandrum is a Chinese traditional herb used as carminative and analgesic. In this study, A. gymnandrum was used as an experimental matrix.

MATERIALS AND METHODS

Optimized ultrasonic extraction technology of total flavonoids from the A. gymnandrum Maxim was studied by using the methodology of single factor and orthogonal design to study the effects of operation conditions, such as ethanol content, ultrasonic wave power, temperature, ultrasonic wave radiation time, and the ratio of sample weight to solvent volume.

RESULT

THROUGH THE ORTHOGONAL EXPERIMENT, THE OPTIMAL EXTRACTION CONDITIONS WERE DETERMINED AS FOLLOWS: Ultrasonic power 100 W, ultrasonic temperature 45°C, 60% ethyl alcohol, extraction time 30 min, and solid-liquid ratio 1:20.

CONCLUSION

Under the optimum parameters, the extraction ratio of total flavonoids from the A. gymnandrum Maxim is about 1.278%.

Total synthesis, relay synthesis, and structural confirmation of the C18-norditerpenoid alkaloid neofinaconitine

The first total synthesis of the C18-norditerpenoid aconitine alkaloid neofinaconitine and relay syntheses of neofinaconitine and 9-deoxylappaconitine from condelphine are reported. A modular, convergent synthetic approach involves initial Diels-Alder cycloaddition between two unstable components, cyclopropene 10 and cyclopentadiene 11. A second Diels-Alder reaction features the first use of an azepinone dienophile (8), with high diastereofacial selectivity achieved via rational design of siloxydiene component 36 with a sterically demanding bromine substituent. Subsequent Mannich-type N-acyliminium and radical cyclizations provide complete hexacyclic skeleton 33 of the aconitine alkaloids. Key endgame transformations include the installation of the C8-hydroxyl group via conjugate addition of water to a putative strained bridghead enone intermediate 45 and one-carbon oxidative truncation of the C4 side chain to afford racemic neofinaconitine. Complete structural confirmation was provided by a concise relay synthesis of (+)-neofinaconitine and (+)-9-deoxylappaconitine from condelphine, with X-ray crystallographic analysis of the former clarifying the NMR spectral discrepancy between neofinaconitine and delphicrispuline, which were previously assigned identical structures.

Unusual Reactions of a 7,17-seco-type C19-Diterpenoid Alkaloid Derived from Deltaline

Treatment of a 7,17- seco-type C19-diterpenoid alkaloid (3), prepared from deltaline (8), with triethylamine in either DMF or TEG (triethylene glycol) at 120°C provided two interesting compounds 6 and 7. The structures of compounds 3, 6, and 7 were established based on extensive interpretations of their 1D and 2D NMR data. Compound 6, a lycoctonine-type C19-diterpenoid alkaloid, can be transformed from alkaloid 3 via Grob fragmentation, Prins reaction, and intramolecular disproportionation. The mechanism of the formation of compound 6 was confirmed by deuteration experiments. Product 7 was formed through a pinacol-like rearrangement of alkaloid 3.

An O-to-N intramolecular acyl migration in C₁₉-diterpenoid alkaloids

The O-acyl group at C-1 of two C₁₉-diterpenoid alkaloids 2 and 5 was transferred to the secondary amine nitrogen to form amides 3 and 6 in the basic condition. This kind of O-to-N intramolecular acyl migration could be caused by the near distance between the nucleophilic nitrogen atom and the carbonyl group of the ester at C-1 in the C₁₉-diterpenoid alkaloids, which is consistent with the conformation of rings A and E in the C₁₉-diterpenoid alkaloids.

Cardioactive C₁₉-diterpenoid alkaloids from the lateral roots of Aconitum carmichaeli "Fu Zi"

Bioassay-guided fractionation of an n-BuOH extract of the lateral roots of Aconitum carmichaeli. led to the isolation of 5 cardioactive C(19)-diterpenoid alkaloids: N-deethylaconine (1), beiwutinine (2), hypaconine (3), mesaconine (4), and 15α-hydroxyneoline (5). N-Deethylaconine and beiwutinine are new aconitine-type C(19)-diterpenoid alkaloids. Hypaconine was isolated from this species for the first time. Among them, mesaconine, hypaconine, and beiwutinine showed the strongest cardiac actions on the isolated perfused bullfrog heart. Furthermore, mesaconine has protective effects, including improved inotropic effect and left ventricular diastolic function, on myocardial ischemia-reperfusion injury in rat at a dose of 10(-9) mol/L. However, mesaconine has almost no effect on heart rate.

Studies on the relative reactivity of three hydroxyl groups in aconitine

The relative reactivity of three hydroxyl groups in aconitine toward acetylation, chlorination, sulfonylation, and oxidation has been studied in this paper. The reduction of C-3 ketone and C-15 ketone derivatives of aconitine was also investigated. It was found that (1) the relative reactivity of three hydroxyl groups toward acetylation, chlorination, and sulfonylation is 3-OH>13-OH>>15-OH; (2) 3-OH is much more reactive than 15-OH toward oxidation; and (3) reduction of the carbonyl group at C-3 with NaBH(4) generated a pair of C-3 epimers, while the reduction products of the carbonyl group at C-15 depend largely on the specific reducing agent and the absolute configuration of 16-OCH(3). When the substrate has 16β-OCH(3), its carbonyl group at C-15 can be reduced with NaBH(4) to yield exclusively the 15α-OH-containing product. Upon replacement of reducing agent NaBH(4) with LiAlH(4), the C-15 carbonyl group can be reduced to yield a pair of C-15 epimers. On the other hand, when the substrate has 16α-OCH(3), C-15 carbonyl group can only be reduced to generate 15α-OH-containing product.

Cytotoxic esterified diterpenoid alkaloid derivatives with increased selectivity against a drug-resistant cancer cell line

C-6 Esterifications of delpheline (1) were carried out to provide 20 new diterpenoid alkaloid derivatives (4-22, 24). Three natural alkaloids (1-3) and all synthesized compounds (4-25) were evaluated for cytotoxic activity against lung (A549), prostate (DU145), nasopharyngeal (KB), and vincristine-resistant nasopharyngeal (KB-VIN) cancer cell lines and interestingly, showed an improved drug resistance profile compared to paclitaxel. Particularly, 6-(4-fluoro-3-methylbenzoyl)delpheline (22) displayed 2.6-fold greater potency against KB-VIN cells compared with the parental non-drug resistant KB cells. 6-Acylation of 1 appears to be critical for producing cytotoxic activity in this alkaloid class and a means to provide promising new leads for further development into antitumor agents.

Conversional synthesis and cytotoxic evaluation of novel taxoid analogs

Four novel taxoid analogs were conversionally synthesized from the C(19)-diterpenoid alkaloid deltaline, and their cytotoxic activities were evaluated against a small panel of cancer cell lines.

Conversional studies towards taxoids from C(19)-diterpenoid alkaloids by the BAC sequence

The conversional synthesis of taxoids by the BAC sequence from the C(19)-diterpenoid alkaloids, 14-acetyltalatisamine (1), yunaconitine (12), and 14-acetylchasmanine (19), was designed and explored. Two aconane-type diterpenes 17 and 28, the advanced intermediates for our conversional synthesis, were synthesized. The key steps include the rupture of the C(7)-C(17) bond, the formation of imine, and the denitrogenation.

Two New C20-Diterpenoid Alkaloids from Delphinium anthriscifolium var. savatieri

Further phytochemical investigation of the whole herb of Delphinium anthriscifolium var. savatieri resulted in the isolation of two new C20-diterpenoid alkaloids, anthriscifolmines I (1) and J (2). The structures of the two new alkaloids were elucidated on the basis of spectral data, including 2D NMR and HRESIMS.