In vitro cytotoxic activity of phenanthroindolizidine alkaloids from Cynanchum vincetoxicum and Tylophora tanakae against drug-sensitive and multidrug-resistant cancer cells

Cynanchum atratum Bunge and Cynanchum versicolor Bunge for Baiwei: An updated review of their botany, phytochemistry, traditional uses and pharmacological activities

Cynanchum atratum Bunge (C. atratum) and Cynanchum versicolor Bunge (C. versicolor) are two related species that have been used as "Baiwei" (Cynanchi Atrati Radix Et Rhizoma) in traditional medicine in China and other Asian countries for a long time. However, to date, no comprehensive review of C. atratum and C. versicolor has been published. This review provides a comprehensive summary on the botany, phytochemistry, traditional uses and pharmacology of Baiwei; The authors focus especially on the revision of errors in previous articles and reviews, updating information and providing a comparison of C. atratum and C. versicolor. Furthermore, current research reveals significant disparities in the chemical composition and pharmacological effects between C. atratum and C. versicolor. Up to November 2023, 178 compounds have been isolated from C. atratum and C. versicolor, including C21 steroids, acetophenones, alkaloids and volatile oils. These compounds and extracts have been proven to exhibit significant pharmacological activities, including anti-inflammatory, anti-tumor, anti-virus, anti-fungal, memory-enhancing and anti-pyretic action, immune modulatory effects, reducing blood lipid, inhibition of melanin production, and anti-parasitic effects. Therefore, this review presents new insights into these two herbs used as "Baiwei" and further study is warranted to enhance their clinical application. Please cite this article as: Xie W, Liu XY, Li X, Jin YS. Cynanchum atratum Bunge and Cynanchum versicolor Bunge for Baiwei: An updated review of their botany, phytochemistry, traditional uses and pharmacological activities. J Integr Med. 2025; Epub ahead of print.

Phenol (bio)isosteres in drug design and development

Due to their versatile properties, phenolic compounds are integral to various biologically active molecules, including many pharmaceuticals. However, their application in drug design is often hindered by issues such as poor oral bioavailability, rapid metabolism, and potential toxicity. This review explores the use of phenol bioisosteres-structurally similar compounds that can mimic the biological activity of phenols while potentially offering improved drug-like properties. We provide an extensive analysis of various phenol bioisosteres, including benzimidazolones, benzoxazolones, indoles, quinolinones, and pyridones, highlighting their impact on the pharmacokinetic and pharmacodynamic profiles of drugs. Case studies illustrate the successful application of these bioisosteres in enhancing metabolic stability, receptor selectivity, and overall therapeutic efficacy. Additionally, the review addresses the challenges associated with phenol bioisosterism, such as maintaining potency and avoiding undesirable side effects. By offering a detailed examination of current strategies and potential future directions, this review serves as a valuable resource for medicinal chemists seeking to optimize phenolic scaffolds in drug development. The insights provided herein aim to facilitate the design of more effective and safer therapeutic agents through strategic bioisosteric modifications.

Palladium-Catalyzed Synthesis of Substituted Phenanthrenes via a C-H Annulation of 2-Biaryl Triflates with Alkynes

A new palladium-catalyzed efficient method for the synthesis of substituted 9,10-phenanthrenes from 2-biaryl triflates with alkynes has been developed. This method provides a great opportunity to prepare various symmetrical and unsymmetrical phenanthrene derivatives in good yields. This reaction proceeds via C-OTf bond cleavage and alkyne insertion followed by C-H annulation.

Potential applications of antofine and its synthetic derivatives in cancer therapy: structural and molecular insights

Cancer is a major global health challenge, being the second leading cause of morbidity and mortality after cardiovascular disease. The growing economic burden and profound psychosocial impact on patients and their families make it urgent to find innovative and effective anticancer solutions. For this reason, interest in using natural compounds to develop new cancer treatments has grown. In this respect, antofine, an alkaloid class found in Apocynaceae, Lauraceae, and Moraceae family plants, exhibits promising biological properties, including anti-inflammatory, anticancer, antiviral, and antifungal activities. Several molecular mechanisms have been identified underlying antofine anti-cancerous effects, including the inhibition of nuclear factor κB (NF-κB) and AKT/mTOR signaling pathways, epigenetic inhibition of protein synthesis, ribosomal targeting, induction of apoptosis, inhibition of DNA synthesis, and cell cycle arrest. This study discusses the molecular structure, sources, photochemistry, and anticancer properties of antofine in relation to its structure-activity relationship and molecular targets. Then, examine in vitro and in vivo studies and analyze the mechanisms of action underpinning antofine efficacy against cancer cells. This review also discusses multidrug resistance in human cancer and the potential of antofine in this context. Safety and toxicity concerns are also addressed as well as current challenges in antofine research, including the need for clinical trials and bioavailability optimization. This review aims to provide comprehensive information for more effective natural compound-based cancer treatments.

New indolizidine- and pyrrolidine-type alkaloids with anti-angiogenic activities from Anisodus tanguticus

Eleven alkaloids, including five previously undescribed indolizidine alkaloids (1, 2a, 2b, 3a, and 3b) and four new pyrrolidine alkaloids (5-8), were isolated from the roots of Anisodus tanguticus. Of these, two new pairs of enantiomeric alkaloids (2a/2b and 3a/3b) are the first examples of alkaloids containing both indolizidine and pyrrolidine structural fragments. The one-carbon bridge connections with two pyrrolidine rings (6) or with a pyrrolidine ring and a pyridine ring (8) are the first reported from nature. Extensive spectroscopic techniques were used to elucidate their structures, and NMR and ECD calculations were used to determine the absolute configurations. The viability of human umbilical vein endothelial cells (HUVECs) was inhibited by compounds 2a, 2b, 3a, 4b, and 5, and compound 2b exhibited a potential anti-angiogenic effect by inhibiting the proliferation, migration, and tube formation of HUVECs. A chorioallantoic membrane assay also demonstrated the anti-angiogenic activity of 2b. In addition, compounds 2a, 2b, 3a, and 4b exhibited moderate cytotoxicity against A2780 cells.

Rapid entry to phenanthroindolizidine alkaloids via an acid-catalysed acyliminium ion-electrocyclization cascade

A rapid total synthesis of seco-phenanthroindolizidine alkaloids was achieved involving a one-pot acid catalyzed deprotection- condensation-electrocyclization strategy. This synthetic route provided a concise synthesis of (±)-seco-antofine and (±)-septicine in only 4 steps with an overall yield of 22% and 17%, respectively.

Annulation of O-silyl N,O-ketene acetals with alkynes for the synthesis of dihydropyridinones and its application in concise total synthesis of phenanthroindolizidine alkaloids

The formation of N-heterocycles with multiple substituents is important in organic synthesis. Herein, we report a novel method for the construction of functionalized dihydropyridinone rings through the annulation of an amide α-carbon with a tethered alkyne moiety. The reaction of the amide with the alkyne was achieved via O-silyl N,O-ketene acetal formation and silver-mediated addition. Furthermore, the developed method was applied for the total synthesis of phenanthroindolizidine and phenanthroquinolizidine alkaloids. By varying the coupling partners, a concise and collective total synthesis of these alkaloids was achieved.

Emerging roles of hnRNP A2B1 in cancer and inflammation

Heterogeneous nuclear ribonucleoproteins (hnRNPs) are a group of RNA-binding proteins with important roles in multiple aspects of nucleic acid metabolism, including the packaging of nascent transcripts, alternative splicing, transactivation of gene expression, and regulation of protein translation. As a core component of the hnRNP complex in mammalian cells, heterogeneous nuclear ribonucleoprotein A2B1 (hnRNP A2B1) participates in and coordinates various molecular events. Given its regulatory role in inflammation and cancer progression, hnRNP A2B1 has become a novel player in immune response, inflammation, and cancer development. Concomitant with these new roles, a surprising number of mechanisms deemed to regulate hnRNP A2B1 functions have been identified, including post-translational modifications, changes in subcellular localization, direct interactions with multiple DNAs, RNAs, and proteins or the formation of complexes with them, which have gradually made hnRNP A2B1 a molecular target for multiple drugs. In light of the rising interest in the intersection between cancer and inflammation, this review will focus on recent knowledge of the biological roles of hnRNP A2B1 in cancer, immune response, and inflammation.

What Goes in Must Come Out? The Metabolic Profile of Plants and Caterpillars, Frass, And Adults of Asota (Erebidae: Aganainae) Feeding on Ficus (Moraceae) in New Guinea

Insect herbivores have evolved a broad spectrum of adaptations in response to the diversity of chemical defences employed by plants. Here we focus on two species of New Guinean Asota and determine how these specialist moths deal with the leaf alkaloids of their fig (Ficus) hosts. As each focal Asota species is restricted to one of three chemically distinct species of Ficus, we also test whether these specialized interactions lead to similar alkaloid profiles in both Asota species. We reared Asota caterpillars on their respective Ficus hosts in natural conditions and analyzed the alkaloid profiles of leaf, frass, caterpillar, and adult moth samples using UHPLC-MS/MS analyses. We identified 43 alkaloids in our samples. Leaf alkaloids showed various fates. Some were excreted in frass or found in caterpillars and adult moths. We also found two apparently novel indole alkaloids-likely synthesized de novo by the moths or their microbiota-in both caterpillar and adult tissue but not in leaves or frass. Overall, alkaloids unique or largely restricted to insect tissue were shared across moth species despite feeding on different hosts. This indicates that a limited number of plant compounds have a direct ecological function that is conserved among the studied species. Our results provide evidence for the importance of phytochemistry and metabolic strategies in the formation of plant-insect interactions and food webs in general. Furthermore, we provide a new potential example of insects acquiring chemicals for their benefit in an ecologically relevant insect genus.

Improved Total Synthesis of Indolizidine and Quinolizidine Alkaloids via Nickel-Catalyzed (4 + 2) Cycloaddition

A Ni-catalyzed (4 + 2) cycloaddition of bicyclic 3-azetidinones and alkynes was developed to access indolizidine and quinolizidine alkaloids. A key element was the development of a diazomethylation procedure that allows the efficient synthesis of bicyclic azetidinones from pyroglutamic and 6-oxopiperidine-2-carboxylic acid. A ligand screening led to improved regioselectivity and enantiopurity during the Ni-catalyzed (4 + 2) cycloaddition. This straightforward methodology was leveraged to synthesize (+)-ipalbidine, (+)-septicine, (+)-seco-antofine, and (+)-7-methoxy-julandine.

Lead Optimization: Synthesis and Biological Evaluation of PBT-1 Derivatives as Novel Antitumor Agents

Phenanthrene-based tylophorine-1 (PBT-1) was identified previously as a lead compound in an anticancer drug discovery effort based on natural Tylophora alkaloids. An expanded structural optimization using a new more efficient synthetic route provided 14 PBT-derivatives. Eleven compounds displayed obvious antiproliferative activities in cellular assays (GI₅₀ 0.55-9.32 μM). The most potent compounds 9c, 9g, and 9h (GI₅₀ < 1 μM) contained a 7-hydroxy group on the phenanthrene B-ring in addition to a pendant piperidine E-ring with different 4-substituents. Compound 9h with NH₂ as the piperidine substituent was at least 4-fold more potent against triple-negative breast cancer MDA-MB-231 than estrogen-responsible breast cancer MCF-7 cell growth. In further biological evaluations, the new active compounds induced cell cycle accumulation in the late S and G2/M phase without interfering with microtubule formation or cell morphology. These results on the optimization of the B- and E-rings of PBT-1 should benefit further development of novel antitumor agents.

Bioinspired triangular ZnO nanoclusters synthesized by Argyreia nervosa nascent leaf extract for the efficient electrochemical determination of vitamin C

This work deals with the synthesis of bioinspired triangular ZnO nanoclusters (bT-ZnO NCs) from Argyreia nervosa nascent leaf extract for their effective antibacterial activity and further utilization as a platform for the electrocatalytic determination of ascorbic acid (AA; vitamin C) for applications in the agricultural domain. The structural, optical, and morphological characteristics of the synthesized bT-ZnO NCs were analyzed by UV-vis, FT-IR, XRD, AFM, SEM, TEM, HR-TEM, and EDX techniques. After this, bT-ZnO NCs were electrophoretically deposited onto an indium-tin-oxide (ITO) glass substrate and assessed for the electro-oxidation of AA by cyclic voltammetry (CV), and from this it was proven that bT-ZnO NCs had a very high electrochemical sensitivity of 29.88 μA cm⁻² toward AA and a low limit of detection of 0.5321 mM under the optimized experimental conditions. Thus, it provides a potential sensing platform for electrochemical studies to detect AA. Moreover, bT-ZnO NCs were preliminarily investigated for their antibacterial activity, and the obtained results showed that the bT-ZnO NCs have potency as an antibacterial agent.

This study reports the synthesis of bioinspired triangular ZnO nanoclusters (bT-ZnO NCs) from Argyreia nervosa nascent leaf extract and their use in the agricultural domain for the label-free detection of vitamin C and its antibacterial efficiency.

A Concise Total Synthesis of Dehydroantofine and Its Antimalarial Activity against Chloroquine-Resistant Plasmodium falciparum

The total synthesis of dehydroantofine was achieved by employing a novel, regioselective, azahetero Diels-Alder reaction of easily accessible 3,5-dichloro-2H-1,4-oxazin-2-one with 14 a as a key step. Furthermore, it is demonstrated that dehydroantofine is a promising candidate as a new antimalarial agent in a biological assay with chloroquine-resistant Plasmodium falciparum.

Biologically active indolizidine alkaloids

Indolizidine alkaloids are chemical constituents isolated from various marine and terrestrial plants and animals, including but not limited to trees, fungi, ants, and frogs, with a myriad of important biological activities. In this review, we discuss the biological activity and pharmacological effects of indolizidine alkaloids and offer new avenues toward the discovery of new and better drugs based on these naturally occurring compounds.

Molecular networking based dereplication of AChE inhibitory compounds from the medicinal plant Vincetoxicum funebre (Boiss. & Kotschy)

Alzheimer's disease (AD) is a devastating neurodegenerative disease affecting 47 million people worldwide. While acetylcholinesterase (AChE) inhibitors such as donepezil and galantamine are leading drugs in the symptomatic treatment of AD, new AChE inhibitors continue to be explored for improved potency and selectivity. Herein, a molecular networking approach using high resolution (HR-MS) and tandem mass spectrometry (MS²) has been used for rapid chemical profiling of an extract of the medicinal plant Vincetoxicum funebre Boiss. & Kotschy (Apocynaceae family) that was active against AChE. A total of 44 compounds were identified by combining the MN with traditional natural product methods, including the isolation and identification of five known compounds (13, 41-44) and a novel C₁₃-norisoprenoid (40). In addition, the potential inhibitory activity of all 44 compounds was evaluated against the AChE enzyme via molecular docking to provide further support to the proposed structures. The glycosylated flavonoid querciturone (31) exhibited the highest affinity with a docking score value of -13.43 kJ/mol. Another five compounds showed stronger docking scores against AChE than the clinically used donepezil including the most active isolated compound daucosterol (44), with a binding affinity of -10.11 kJ/mol towards AChE. These findings broaden our understanding of Vincetoxicum metabolites and highlight the potential of glycosylated flavonoids as AChE inhibitors.Communicated by Ramaswamy H. Sarma.

Possible pharmaceutical applications can be developed from naturally occurring phenanthroindolizidine and phenanthroquinolizidine alkaloids

Naturally occurring phenanthroindolizidine and phenanthroquinolizidine alkaloids (PIAs and PQAs) are two small groups of herbal metabolites sharing a similar pentacyclic structure with a highly oxygenated phenanthrene moiety fused with a saturated or an unsaturated N-heterocycle (indolizidine/quinolizidine moieties). Natural PIAs and PQAs only could be obtained from finite plant families (such as Asclepiadaceae, Lauraceae and Urticaceae families, etc.). Up to date, more than one hundred natural PIAs, while only nine natural PQAs had been described. PIA and PQA analogues have been applied to the development of potent anticancer agents all along because of their excellent cytotoxic activity. However, in the last two decades, other great biological properties, such as anti-inflammatory and antiviral activities were revealed successively by different pharmacological assays. Especially because of their potent antiviral activity against coronavirus (TGEV, SARS CoV and MHV) and tobacco mosaic virus, PIA and PQA analogues have attracted much pharmaceutical attention again, some of them have been used to present interesting targets for total or semi synthesis, and structure-activity relationship (SAR) study for the development of antiviral agents. In this review, natural PIA and PQA analogues obtained in the last two decades with their herbal origins, key spectroscopic characteristics for structural identification, biological activity with possible SARs and application prospects were systematically summarized. We hope this paper can stimulate further investigations on PIA and PQA analogues as an important source for potential drug discovery.

Design, Synthesis and in Vitro Evaluation of Tylophorine Derivatives as Possible Antitumor Agents

Structural simplification and modification of natural products are always very important resources to antitumor drugs. By introducing various aminomethyl groups and amide groups into the phenanthrene ring of tylophorine, a novel series of tylophorine derivatives have been designed and synthesized, and their antiproliferative activities against MCF-7, A549 and HepG-2 cells have been evaluated, too. The results indicated that most of the prepared compounds exhibited good antitumor activities. Especially, one compound with an {ethyl[2-(morpholin-4-yl)ethyl]amino}methyl group at the side chain exhibited the most significant cytotoxic effects.

Design, synthesis and antitumour evaluation of pyrrolo[1,2-f]-phenanthridine and dibenzo[f,h]pyrrolo[1,2-b]isoquinoline derivatives

A series of 1,2-bis(hydroxymethyl)pyrrolo[1,2-f]phenanthridine derivatives and their alkyl (ethyl and isopropyl) carbamates and 12,13-bis(hydroxymethyl)-9,14-dihydro-dibenzo[f,h]pyrrolo[1,2-b]isoquinoline derivatives were synthesized for antiproliferative evaluation. The preliminary antitumour studies revealed that these two types of bis(hydroxymethyl) derivatives showed significant antitumour activities and were able to inhibit the growth of various human tumour cell lines in vitro. Several of the derivatives were demonstrated to cause DNA interstrand cross-links by an alkaline agarose gel shifting assay. These conjugates were cytotoxic to a variety of cancer cell lines by inducing DNA damage, delaying cell cycle progression in the G2/M phase and triggering apoptosis. Compound 21a, dissolved in a vehicle suitable for intravenous administration, was selected for antitumour studies in animal models. We demonstrated that at a dose that did not cause body weight loss in mice, compound 21a could significantly suppress the growth of tumour xenografts of human lung cancer H460 and colorectal cancer HCT-116 cells in nude mice. Our present results confirm the antitumour activities of these conjugates.

Vincetoxicum arnottianum ameliorate inflammation by suppressing oxidative stress and pro-inflammatory mediators in rat

ETHNOPHARMACOLOGICAL RELEVANCE

Aerial parts of Vincetoxicum arnottianum (Wight) Wight (Family Apocynaceae) are used by local communities for inflammation, healing of wound and injuries and also for urticaria.

AIM OF STUDY

Extract/fractions of V. arnottianum were evaluated for potential anti-inflammatory activity in rat.

METHODS

Methanol extract of aerial parts of V. arnottianum (VAM) was partitioned on polarity for n-hexane (VAH), ethyl acetate (VAE), butanol (VAB) and aqueous (VAA) fractions. The extract/fractions were evaluated during in vitro assay for protection against heat induced protein denaturation and Carrageenan induced paw inflammation in rat. VAM and VAE were evaluated for anti-inflammatory potential against formalin and Freund's complete adjuvant (FCA) induced inflammation in paw of rat while croton oil induced inflammation in ear of rat, respectively. The level of inflammatory mediators; IL-17, IL-1β, IL-6, TNF-α and nitric oxide (NO) was estimated in serum of rat.

RESULTS

All the extract/fractions used in this study exhibited anti-inflammatory activity. However, VAE (300 mg/kg) exhibited potential anti-inflammatory activity in carrageenan (78.06 ± 4.6%), formalin (54.71 ± 0.34%) and croton oil (73.12 ± 1.9%) induced edema in rat. In FCA induced inflammation model VAM and VAE showed admiring proficiencies against alteration of body weight and organ weight indices, paw edema and histological studies. In serum increased level of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-17) and NO during adjuvant-induced inflammation were more efficiently restored with VAE treatment to rat. Presence of polyphenolics; rutin, gallic acid, caffeic acid, apigenin, myricetin and quercetin was indicated in VAE.

CONCLUSION

The results suggest the presence of anti-inflammatory constituents in V. arnottianum.

Antimalarial alkaloid from Hypoestes forskaolii

Following on from previous studies, we brought further our quest for anti-malarial agents isolated from plants grown in the Saudi Arabian Peninsula. Methanolic extracts were prepared from eighteen Saudi plants and then tested in vitro to assess their anti-malarial effects on Plasmodium falciparum K1, (a chloroquine-resistant strain) as well as their cytotoxicity on MRC5 (human diploid embryonic lung cell line) cells. Moderate anti-malarial activity was observed in extracts prepared from Hypoestes forskaolii (Vahl) R. Br. (IC50 value of 5.5 μg/ml) and Rhus retinorrhaea (IC50: 7.71 μg/ml). The remaining sixteen plant extracts appeared to be inactive (IC50 > 12.5 μg/ml). A novel phenanthro-quinolizidine alkaloid, 15β-hydroxycryptopleurine-N-oxide, was isolated from H. forskaolii using bio-guided fractionation procedures. Chloroquine-resistant (K1) and chloroquine-sensitive (FCR3) strains of P. falciparum appeared very sensitive to the anti-malarial activity of 15β-hydroxycryptopleurine-N-oxide, giving IC50 of 6.11 and 5.13 nM respectively. It showed cytotoxicity against MRC5 "IC50 of 24.45 nM" with selectivity indices of 4.0 and 4.76 against K1 and FCR3 strains, respectively. It is our understanding that this is the first account on phenanthro-quinolizidine alkaloids anti-malarial activity on a chloroquine-resistant P. falciparum strain.

Spiro[3.5]nonenyl Meroterpenoid Lactones, Cryptolaevilactones G-L, an Ionone Derivative, and Total Synthesis of Cryptolaevilactone M from Cryptocarya laevigata

A CH3OH-CH2Cl2 (1:1) extract (N025439) of the leaves and twigs of Cryptocarya laevigata furnished eight new compounds, 1-8. Based on extensive 1D and 2D NMR spectroscopic data examination, the new δ-lactone derivatives 1-6 are monoterpene-polyketide hybrids containing a unique spiro[3.5]nonenyl moiety. Their trivial names, cryptolaevilactones G-L, follow those of the related known meroterpenoids cryptolaevilactones A-F. Cryptolaevilactone L (6) contains 11,12-cis-oriented substituents, while the other cryptolaevilactones contain trans-oriented groups. The structure of the linear δ-lactone 7, cryptolaevilactone M, was characterized from various spectroscopic data analysis, and the absolute configuration was determined by total synthesis through stereoselective allylation and Grubbs olefin metathesis. Compound 8 was elucidated to be an ionone derivative with a 3,4-syn-diol functionality.

Applications of Friedel-Crafts reactions in total synthesis of natural products

Over the years, Friedel-Crafts (FC) reactions have been acknowledged as the most useful and powerful synthetic tools for the construction of a special kind of carbon-carbon bond involving an aromatic moiety. Its stoichiometric and, more recently, its catalytic procedures have extensively been studied. This reaction in recent years has frequently been used as a key step (steps) in the total synthesis of natural products and targeted complex bioactive molecules. In this review, we try to underscore the applications of intermolecular and intramolecular FC reactions in the total syntheses of natural products and complex molecules, exhibiting diverse biological properties.

Ethnobotany, Phytochemistry and Pharmacological Effects of Plants in Genus Cynanchum Linn. (Asclepiadaceae)

Genus Cynanchum L. belongs to the family Asclepiadaceae, which comprise more than 200 species distributed worldwide. In Chinese medical practice, numerous drugs (such as tablets and powders) containing different parts of plants of this genus are used to treat snake bites, bruises, osteoblasts, rheumatoid arthritis and tumors. A search for original articles published on the cynanchum genus was performed by using several resources, including Flora of China Official Website and various scientific databases, such as PubMed, SciFinder, the Web of Science, Science Direct, and China Knowledge Resource Integrated (CNKI). Advances in the botanical, ethnomedicinal, phytochemical, and pharmacological studies of this genus are reviewed in this paper. Results showed that more than 440 compounds, including C21 steroids, steroidal saponins, alkaloids, flavonoids and terpene, have been isolated and identified from Cynanchum plants up to now. In vivo and in vitro studies have shown that plants possess an array of biological activities, including anti-tumor, neuroprotective and anti-fungal effects. Popular traditional prescription of Cynanchum sp. was also summed up in this paper. However, many Cynanchum species have received little or no attention. Moreover, few reports on the clinical use and toxic effects of Cynanchum sp. are available. Further attention should be focused on the study of these species to gather information on their respective toxicology data and relevant quality-control measures and clinical value of the crude extracts, active compounds, and bioactive metabolites from this genus. Further research on Cynanchum sp. should be conducted, and bioactivity-guided isolation strategies should be emphasized. In addition, systematic studies of the chemical composition of plants should be enhanced.

Alkaloid Synthesis Using Organocatalysts

This chapter covers the literature since the advent, in the 21st century, of total syntheses of alkaloids using enantio- or diastereoselective organocatalytic reactions to construct the alkaloid scaffolds. The details of these alkaloid syntheses are described separately for each basic skeleton, including indole, indoline, oxindole, and piperidine alkaloids.

Expedient synthesis of 9,10-phenanthrenes via LiOPiv-promoted and palladium-catalysed aryne annulation by vinyl triflates

An expedient synthesis of 9,10-phenanthrenes via LiOPiv-promoted and palladium-catalysed aryne annulation by vinyl triflates.

A Bis-benzopyrroloisoquinoline Alkaloid Incorporating a Cyclobutane Core and a Chlorophenanthroindolizidine Alkaloid with Cytotoxic Activity from Ficus fistulosa var. tengerensis

Tengerensine (1), isolated as a racemate and constituted from a pair of bis-benzopyrroloisoquinoline enantiomers, and tengechlorenine (2), purified as a scalemic mixture and constituted from a pair of chlorinated phenanthroindolizidine enantiomers, were isolated from the leaves of Ficus fistulosa var. tengerensis, along with three other known alkaloids. The structures of 1 and 2 were determined by spectroscopic data interpretation and X-ray diffraction analysis. The enantiomers of 1 were separated by chiral-phase HPLC, and the absolute configurations of (+)-1 and (-)-1 were established via experimental and calculated ECD data. Compound 1 is notable in being a rare unsymmetrical cyclobutane adduct and is the first example of a dimeric benzopyrroloisoquinoline alkaloid, while compound 2 represents the first naturally occurring halogenated phenanthroindolizidine alkaloid. Compound (+)-1 displayed a selective in vitro cytotoxic effect against MDA-MB-468 cells (IC50 7.4 μM), while compound 2 showed pronounced in vitro cytotoxic activity against all three breast cancer cell lines tested (MDA-MB-468, MDA-MB-231, and MCF7; IC50 values of 0.038-0.91 μM).

Antofine suppresses endotoxin-induced inflammation and metabolic disorder via AMP-activated protein kinase

The inhibition of activated macrophages has been used to develop anti-inflammatory agents for therapeutic intervention to human diseases that cause excessive inflammatory responses. Antofine, a phenanthroindolizidine alkaloid, has a potent anti-inflammatory effect. However, the molecular mechanisms of its anti-inflammatory activity have not yet been fully detailed. In this study, we comprehensively explored the anti-inflammatory effects of antofine on endotoxin-induced inflammation in macrophages using cDNA microarray analysis, thereby elucidating the potential mechanism by which antofine suppresses inflammation. Antofine significantly suppressed the secretion of proinflammatory cytokines such as TNFα and IL-1β and the production of iNOS in LPS-activated Raw264.7 macrophage cells. In addition, antofine can suppress the expressions of several inflammation-related genes (such as ARG-1, IL1F9, IL-10, and IL-33) and extracellular matrix genes (such as TNC and HYAL1), as well as a vasopressor gene (EDN1) in activated macrophage cells, that are induced by LPS stimulation. The gene expression profiles analyzed by GeneMANIA software showed that antofine not only contributed anti-inflammatory activity but also modulated the cellular metabolism via AMPK. Furthermore, antofine also modulated the activation of AMPK and caspase-1, the key regulator in inflammasome-mediated IL-1β maturation, in activated macrophage cells. In conclusion, these data indicated that antofine potentially can not only contribute an anti-inflammatory effect but can also attenuate the metabolic disorders induced by inflammation via AMPK.

In vitro anticancer effects of two novel phenanthroindolizidine alkaloid compounds on human colon and liver cancer cells

Malignant cancer is one of the most serious diseases threatening the health of human beings. Natural plant alkaloids exhibit multiple biological functions, including inhibition of cell proliferation, and may have potential anticancer activity. However, most natural alkaloids may not be suitable for human therapies owing to instability, poor dissolubility and potential side effects. To improve their anticancer activity and drug effect, the present study aimed to develop new alkaloid derivatives, the phenanthroindolizidine alkaloid compounds, and evaluated their potential antitumor effects on human cancer cells in vitro. Among the several newly synthesized analogues of phenanthroindolizidine alkaloids (PAs), the compounds YS306 and YS206 exhibited an increased growth inhibition activity on HepG2 liver cancer cells and on HCT116 and HT29 colon cancer cells, with half‑maximal inhibitory concentrations in the micromolar range. YS206 and YS306 (5 µg/ml) both significantly induced cell cycle arrest at the G2/M phase and notably decreased cell distribution at the G0/G1 and S phase. In addition, these two molecules significantly inhibited cancer cell migration, as analyzed by the wound‑healing and Transwell assays. However, neither YS306 nor YS206 exhibited observable effects on apoptosis. Therefore, chemical structure modifications of natural PAs based on anticancer activity assessments may be feasible in the development of new cancer chemotherapeutic agents.

6-OH-Phenanthroquinolizidine Alkaloid and Its Derivatives Exert Potent Anticancer Activity by Delaying S Phase Progression

To discover new phenanthroindolizidine and phenanthroquinolizidine alkaloids as potential anticancer drug candidates, non-natural 6-O-desmethylcryptopleurine (2) and its derivatives were prepared. Most of the new compounds exhibited potent antiproliferative activity against A549 and BEL-7402 cells, with the lowest IC₅₀ being 3 nM. Optically pure 2-R was further evaluated against a panel of 30 cancer cell lines and found to inhibit the proliferation of all tested cell lines, including three multidrug-resistant cell lines, with an average IC₅₀ value of 2.1 nM, which is much lower than that of previously reported phenanthroindolizidine DCB-3503 (1, IC₅₀: 166.7 nM). A mechanistic evaluation showed that 2-R potently inhibited cell growth and colony formation, which are associated with a delay in S phase progression through the inhibition of DNA synthesis. These results along with further study on the safety profile of these compounds will facilitate the discovery of new phenanthroindolizidine and phenanthroquinolizidine alkaloids for use as anticancer drug candidates.

Anti-anaphylactic effects of Trichilia monadelpha (Thonn.) J. J. De Wilde extracts on rodent models of anaphylaxis

Effects of petroleum ether and ethanolic extracts of Trichilia monadelpha stem bark (PEE and EAE) on compound 48/80-induced systemic and passive anaphylaxis were determined. Survival rate, extravasation, degranulation of mast cells, and secretion of tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were measured after pre-treatment with extracts (10-100 mg/kg) and disodium chromoglycate (2.5-250 μg/kg) and induction of anaphylaxis in C57BL/6 mice or Sprague-Dawley rats with compound 48/80. Histopathological assessments were made from skin biopsies of rats. Data was analyzed by Kaplan-Meier Survival Log-Rank Analysis, or One-way ANOVA and Holm-Sidak’s post hoc test. PEE and EAE inhibited (P ≤ 0.0001) tremors in systemic anaphylaxis passive cutaneous anaphylactic reactions and extravasation, stabilized or prevented (P ≤ 0.001-0.0001) mast cell degranulation, and inhibited (P ≤ 0.001-0.0001) TNF-α and IL-6 secretion. Per the findings, PEE and EAE of T. monadelpha have exhibited substantial anti-anaphylactic and anti-inflammatory property (with PEE performing better) which substantiates its use traditionally in management of allergies and other inflammatory disorders.

Cholinesterase inhibitory activity of isoquinoline alkaloids from three Cryptocarya species (Lauraceae)

Alzheimer's disease is the most common form of dementia among older adults. Acetylcholinesterase and butyrylcholinesterase are two enzymes involved in the breaking down of the neurotransmitter acetylcholine. Inhibitors for these enzymes have potential to prolong the availability of acetylcholine. Hence, the search for such inhibitors especially from natural products is needed in developing potential drugs for Alzheimer's disease. The present study investigates the cholinesterase inhibitory activity of compounds isolated from three Cryptocarya species towards acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Nine alkaloids were isolated; (+)-nornantenine 1, (-)-desmethylsecoantofine 2, (+)-oridine 3, (+)-laurotetanine 4 from the leaves of Cryptocarya densiflora BI., atherosperminine 5, (+)-N-methylisococlaurine 6, (+)-N-methyllaurotetanine 7 from the bark of Cryptocarya infectoria Miq., 2-methoxyatherosperminine 8 and (+)-reticuline 9 from the bark of Cryptocarya griffithiana Wight. In general, most of the alkaloids showed higher inhibition towards BChE as compared to AChE. The phenanthrene type alkaloid; 2-methoxyatherosperminine 8, exhibited the most potent inhibition against BChE with IC50 value of 3.95μM. Analysis of the Lineweaver-Burk (LB) plot of BChE activity over a range of substrate concentration suggested that 2-methoxyatherosperminine 8 exhibited mixed-mode inhibition with an inhibition constant (Ki) of 6.72μM. Molecular docking studies revealed that 2-methoxyatherosperminine 8 docked well at the choline binding site and catalytic triad of hBChE (butyrylcholinesterase from Homo sapiens); hydrogen bonding with Tyr 128 and His 438 residues respectively.

Screening of promising chemotherapeutic candidates from plants extracts

Over the course of our studies investigating anti-proliferative properties of compounds originating from plants against human gastric adenocarcinoma (MK-1), human uterine carcinoma (HeLa), murine melanoma (B16F10), and two human T cell lymphotropic virus type 1 (HTLV-1)-infected T-cell lines (MT-1 and MT-2), we have screened 582 extracted samples obtained from a variety of parts from 370 plants. A few extracts showed anti-proliferative activity against all cell lines, but upon further investigation, toxicity toward selected cell lines was recognized. After activity-guided fractionation, isolation of the active principles was achieved. Structure–activity relationship studies identified the components and functionalities responsible for the specific selectivity against each cancer cell line. The effect of polyacetylenes against MK-1 cells was more potent than against HeLa and B16F10 cells. The compound having a 3,4-dihydroxyphenethyl group also showed an anti-proliferative effect against B16F10 cells. Some 6-methoxyflavone derivatives and 8-hydroxy furanocoumarins were good inhibitors of HeLa cell growth. The 17 compounds whose EC₅₀ values were less than 1 nM did not show specific cellular selectivity. Because the cytotoxic effect of 24, 25-dihydrowithanolide D toward control cells was observed at a concentration about 100 times higher than those for the cancer cell lines, withanolide was identified as the most promising chemotherapeutic candidate in our experiments.

Cyclic enaminones. Part II: applications as versatile intermediates in alkaloid synthesis

Among many other strategies, the enaminone approach is an important strategy to construct and diversify the azacyclic core in various alkaloids syntheses. In this brief review we discuss the application of cyclic enaminones as building blocks, as well as potential intermediates in the total synthesis of selected alkaloids.

G-Quadruplex DNA-binding quaternary alkaloids from Tylophora atrofolliculata

Quaternary alkaloids from T. atrofolliculata with human telomeric DNA G-quadruplex binding capacity.

Phenanthroindolizidine alkaloids from Tylophora atrofolliculata with hypoxia-inducible factor-1 (HIF-1) inhibitory activity

Phenanthroindolizidine alkaloids from T. atrofolliculata with potent HIF-1 inhibitory effects.

The antibacterial, phytochemicals and antioxidants evaluation of the root extracts of Hydnora africanaThunb. used as antidysenteric in Eastern Cape Province, South Africa

Background

To determine the anti-dysenteric, phytochemicals and antioxidative properties of the root extracts of Hydnora africana. The use of plants for the treatment of dysentery and other diseases in traditional medicine has increased on the basis of these rich traditional medicine systems. Series of pharmacological tests are recommended since the aetiology of many diseases may be due to more than one factor.

Methods

The agar well diffusion method was used to determine the susceptibility of bacterial strains to crude extracts of the plant. The minimum inhibitory concentration was determined by the microdilution test. The presence of phytochemicals and antioxidant was also assessed using standard methods.

Results

The antimicrobial activity of H. africana against all the tested organisms demonstrated a mean zone diameter of inhibition ranging from 0 to 25 mm. The MIC of the extracts ranged from 0.071 to 5.0 mg/mL. Antioxidant activity showed lower ferric reducing activities, moderate nitric oxide, moderate DPPH and higher ABTS scavenging activities of the plant. Phytochemical assay revealed the presence and equivalent quantity of alkaloids, tannins, flavonoids, saponins and phenolic acid in the extracts. The water and methanol extracts were also shown as the best solvents of extraction for the phytochemicals.

Conclusions

The methanol and acetone extracts of H. africana exhibited a significant antibacterial and antioxidant activities, suggesting the presence of either good bioactive potency or the high concentration of the active principle in the extracts which may serve as a guide for selecting bio- medicinal substances of plant origin in antidysenteric drugs.

Phytochemical investigation of natural and in vitro raised Vṛddhadāruka plants

Background:

Argyreia nervosa commonly known as elephant creeper (English) and Vṛddhadāruka (Sanskrit) is a woody climber that belongs to the family Convolvulaceae. Seeds of this plant contain hallucinogens including ergot alkaloids and a naturally occurring lysergic acid amide. Traditionally the plant is used in the treatment of gonorrhea, strangury, chronic ulcers, diabetes, anemia and cerebral disorders. The plant is also used as appetitiser, brain tonic, cardiotonic, aphrodisiac. It possesses anti-inflammatory, immunomodulatory, antibacterial, antiviral and antifungal activities.

Objective:

To give an account of information on in vitro regeneration and phytochemical analysis of the plant.

Materials and Methods:

Nodal explants were selected for in vitro regeneration. Different aerial parts viz., seeds, natural and in vitro leaf, stem and callus were dried and extracted with different solvents and were subjected to various phytochemical analyses.

Results:

Different concentrations of 6-benzylaminopurine showed shoot and root initiation. The study of phytochemical screening of different extracts showed the presence of bioactive substances like flavonoids, alkaloids, terpenoids, etc.

Conclusion:

The study will provide an efficient in vitro protocol for micropropagation as an alternative method to conserve the plant and shows the presence of some important secondary metabolites in the nature grown and in vitro raised plants which can be useful for treatment of various diseases.

Antitumor activity of phenanthroindolizidine alkaloids is associated with negative regulation of Met endosomal signaling in renal cancer cells

Met is a receptor tyrosine kinase for hepatocyte growth factor. Met mutations have been considered as a major cause of primary resistance to Met tyrosine kinase inhibitors (TKIs). Mutated Met enhances its endosomal signaling, which includes internalization, signaling within endosomes, recycling to membrane, and sorting for degradation. These sequential events lead to a plausible mechanism for resistance. (-)-Antofine, a phenanthroindolizidine alkaloid, has exhibited potent antitumor activity but the precise underlying mechanism has been poorly understood. We found that (-)-antofine effectively inhibited the proliferation of Met-mutated Caki-1 cells, which were resistant to well-known Met TKIs. (-)-Antofine negatively regulated Met endosomal signaling and consequently inhibited the nuclear translocation of STAT3 both in vitro and in vivo. These findings emphasize the potential of Met endosomal signaling as a novel target for Met TKI-resistant cancers and (-)-antofine as a novel lead compound associated with the suppression of Met endosomal signaling.