Ipecac alkaloids from Cephaelis acuminata

Structurally diverse isoquinoline alkaloids from the barks of Alangium salviifolium (L. f.) Wangerin and their cytotoxicity

Eleven undescribed isoquinoline alkaloids (1-8, 14, 15, and 24), along with 19 analogues (9-13, 16-23, and 25-30) were isolated from the barks of Alangium salviifolium. The structures of the undescribed compounds were elucidated through the analysis of their HR-ESI-MS, 1D and 2D NMR, IR, UV, and X-ray diffraction. The absolute configuration of 8 was established via the ECD calculation. Notably, compounds 1/2 and 3/4 were two pairs of C-14 epimers. The isolated alkaloids were evaluated for their cytotoxicity against various cancer cell lines, including SGC-7901, HeLa, K562, A549, BEL-7402, HepG2, and B16, β-carboline-benzoquinolizidine (14-22) and cepheline-type (24-28) alkaloids exhibited remarkable cytotoxicity, with IC50 values ranging from 0.01 to 48.12 μM. Remarkably, compounds 17 and 21 demonstrated greater cytotoxicity than the positive control doxorubicin hydrochloride. Furthermore, a significant proportion of these bioactive alkaloids possess a C-1' epimer configuration. The exploration of their structure-activity relationship holds promise for directing future investigations into alkaloids derived from Alangium, potentially leading to novel insights and therapeutic advancements.

1-Amino-1-deoxy-d-fructose ("fructosamine") and its derivatives

Fructosamine has long been considered as a key intermediate of the Maillard reaction, which to a large extent is responsible for specific aroma, taste, and color formation in thermally processed or dehydrated foods. Since the 1980s, however, as a product of the Amadori rearrangement reaction between glucose and biologically significant amines such as proteins, fructosamine has experienced a boom in biomedical research, mainly due to its relevance to pathologies in diabetes and aging. In this chapter, we assess the scope of the knowledge on and applications of fructosamine-related molecules in chemistry, food, and health sciences, as reflected mostly in publications within the past decade. Methods of fructosamine synthesis and analysis, its chemical, and biological properties, and degradation reactions, together with fructosamine-modifying and -recognizing proteins are surveyed.

Homologation of aryl ketones to long-chain ketones and aldehydes via C-C bond cleavage

Transition metal-catalyzed C-C bond cleavage is a powerful tool for the reconstruction of a molecular skeleton. We report herein the multi-carbon homologation of aryl ketones to long-chain ketones and aldehydes via ligand-promoted Ar-C(O) bond cleavage and subsequent cross coupling with alkenols. Various (hetero)aryl ketones are compatible in the reaction, affording the corresponding products wtih good to excellent yields with high regioselectivity. Further applications in the late-stage diversification of biologically important molecules demonstrate the synthetic utility of this protocol. Mechanistic studies indicate that the ligand plays an important role in both C-C bond cleavage and the asymmetric migration-insertion process.

Multi-Step In Silico Discovery of Natural Drugs against COVID-19 Targeting Main Protease

In continuation of our antecedent work against COVID-19, three natural compounds, namely, Luteoside C (130), Kahalalide E (184), and Streptovaricin B (278) were determined as the most promising SARS-CoV-2 main protease (Mpro) inhibitors among 310 naturally originated antiviral compounds. This was performed via a multi-step in silico method. At first, a molecular structure similarity study was done with PRD_002214, the co-crystallized ligand of Mpro (PDB ID: 6LU7), and favored thirty compounds. Subsequently, the fingerprint study performed with respect to PRD_002214 resulted in the election of sixteen compounds (7, 128, 130, 156, 157, 158, 180, 184, 203, 204, 210, 237, 264, 276, 277, and 278). Then, results of molecular docking versus Mpro PDB ID: 6LU7 favored eight compounds (128, 130, 156, 180, 184, 203, 204, and 278) based on their binding affinities. Then, in silico toxicity studies were performed for the promising compounds and revealed that all of them have good toxicity profiles. Finally, molecular dynamic (MD) simulation experiments were carried out for compounds 130, 184, and 278, which exhibited the best binding modes against Mpro. MD tests revealed that luteoside C (130) has the greatest potential to inhibit SARS-CoV-2 main protease.

Different Aspects of Emetine's Capabilities as a Highly Potent SARS-CoV-2 Inhibitor against COVID-19

In the global movement to find the appropriate agents to fight the coronavirus disease of 2019 (COVID-19), emetine is one of the strongest anti-SARS-CoV-2 compounds with sub-micromolar EC50 values, identified in several studies and high-throughput screening efforts. The reported anti-SARS-CoV-2 mechanisms indicate the effect of this compound on both virus-based and host-based targets. In addition to having excellent antiviral effects, emetine can relieve COVID-19 patients by reducing inflammation through inhibitory activity against NF-κB by the mechanism of IκBα phosphorylation inhibition; it can also limit the lipopolysaccharide-induced expression of pro-inflammatory cytokines TNFα, IL-1β, and IL-6. Emetine also can well reduce pulmonary arterial hypertension as an important COVID-19 complication by modulating a variety of cellular processes such as the Rho-kinase/CyPA/Bsg signaling pathway. The therapeutic value of emetine for combating COVID-19 was highlighted when in vivo pharmacokinetic studies showed that the concentration of this compound in the lungs increases significantly higher than the EC50 of the drug. Despite its valuable therapeutic effects, emetine has some cardiotoxic effects that limit its use in high doses. However, high therapeutic capabilities make emetine a valuable lead compound that can be used for the design and development of less toxic anti-COVID-19 agents in the future. This Review provides a collection of information on the capabilities of emetine and its potential for the treatment of COVID-19, along with structural analysis which could be used for further research in the future.

Targeting HSF1 as a Therapeutic Strategy for Multiple Mechanisms of EGFR Inhibitor Resistance in EGFR Mutant Non-Small-Cell Lung Cancer

Simple Summary

We attempted to identify target proteins and compounds that can be used to overcome EGFR-TKI resistance in NSCLC. To accomplish this, we generated EGFR inhibitor erlotinib-resistant HCC827-ErlR cells and obtained a list of differentially expressed genes. Then, we performed connectivity map analysis and identified heat shock factor 1 (HSF1) as a potential target protein to overcome erlotinib resistance. Using specific HSF1 shRNAs and KRIBB11 (N²-(1H-Indazol-5-yl)-N⁶-methyl-3-nitropyridine-2,6-diamine), we proved the effectiveness of HSF1 inhibition for overcoming erlotinib resistance in vitro. In addition, we proved the efficacy of emetine in inhibiting HSF1 activity and the tumor growth of erlotinib-resistant PC9-ErlR cells in a mouse model.

Abstract

Although EGFR-TKI treatment of NSCLC (non-small-cell lung cancer) patients often achieves profound initial responses, the efficacy is transient due to acquired resistance. Multiple receptor tyrosine kinase (RTK) pathways contribute to the resistance of NSCLC to first- and third-generation EGFR-TKIs, such as erlotinib and osimertinib. To identify potential targets for overcoming EGFR-TKI resistance, we performed a gene expression signature-based strategy using connectivity map (CMap) analysis. We generated erlotinib-resistant HCC827-ErlR cells, which showed resistance to erlotinib, gefitinib, osimertinib, and doxorubicin. A list of differentially expressed genes (DEGs) in HCC827-ErlR cells was generated and queried using CMap analysis. Analysis of the top 4 compounds from the CMap list suggested HSF1 as a potential target to overcome EGFR-TKI resistance. HSF1 inhibition by using HSF1 shRNAs or KRIBB11 decreased the expression of HSF1 downstream proteins, such as HSP70 and HSP27, and also decreased the expression of HSP90/HSP70/BAG3 client proteins, such as BCL2, MCL1, EGFR, MET, and AXL, causing apoptosis of EGFR-TKI-resistant cancer cells. Finally, we demonstrated the efficacy of the HSF1 inhibitor on PC9-ErlR cells expressing mutant EGFR (T790M) in vivo. Collectively, these findings support a targetable HSF1-(HSP90/HSP70/BAG3)-(BCL2/MCL1/EGFR/MET/AXL) pathway to overcome multiple mechanisms of EGFR-TKI resistance.

Natural Products: Key Prototypes to Drug Discovery Against Neglected Diseases Caused by Trypanosomatids

BACKGROUND

Neglected tropical diseases are a group of infections caused by microorganisms and viruses that affect mainly poor regions of the world. In addition, most available drugs are associated with long periods of treatment and high toxicity which limits the application and patient compliance. Investment in research and development is not seen as an attractive deal by the pharmaceutical industry since the final product must ideally be cheap, not returning the amount invested. Natural products have always been an important source for bioactive compounds and are advantageous over synthetic compounds when considering the unique structural variety and biological activities. On the other hand, isolation difficulties and low yields, environmental impact and high cost usually limit their application as drug per se.

OBJECTIVE

In this review, the use of natural products as prototypes for the semi-synthesis or total synthesis, as well as natural products as promising hits is covered, specifically regarding compounds with activities against trypanosomatids such as Trypanosoma spp. and Leishmania spp.

METHODS

Selected reports from literature with this approach were retrieved.

CONCLUSION

As summary, it can be concluded that natural products are an underestimated source for designing novel agents against these parasites.

The Trans Golgi Region is a Labile Intracellular Ca2+ Store Sensitive to Emetine

The Golgi apparatus (GA) is a bona fide Ca²⁺ store; however, there is a lack of GA-specific Ca²⁺ mobilizing agents. Here, we report that emetine specifically releases Ca²⁺ from GA in HeLa and HL-1 atrial myocytes. Additionally, it has become evident that the trans-Golgi is a labile Ca²⁺ store that requires a continuous source of Ca²⁺ from either the external milieu or from the ER, to enable it to produce a detectable transient increase in cytosolic Ca²⁺. Our data indicates that the emetine-sensitive Ca²⁺ mobilizing mechanism is different from the two classical Ca²⁺ release mechanisms, i.e. IP₃ and ryanodine receptors. This newly discovered ability of emetine to release Ca²⁺ from the GA may explain why chronic consumption of ipecac syrup has muscle side effects.

Evaluation of Alangium lamarckii Bark for Antiplasmodial and Cytotoxic Constituents and Isolation of a Novel Tubulosine Analogue

Alangium lamarkii is traditionally used in India for the treatment of malaria. Partial activity guided-fractionation of the basic chloroform fraction of the methanolic extract of the bark led to the isolation of a novel tubulosine analogue, 10-demethyl-9'- N-methyltubulosine (1), for which the trivial name tubulosatine is suggested. In addition, the known A. lamarkii constituents, tubulosine (2), cephaeline and emetine were isolated as potent antiplasmodial and cytotoxic constituents, but 1 was up to 1000-fold less potent than the former alkaloids against both malaria parasites and human cancer cell lines. The compounds were active against both chloroquine-sensitive and chloroquine-resistant malaria parasites, but no selective toxicity was observed towards malaria parasites compared with cancer cells with any of the alkaloids. Further work to explore the basis for the relatively weak biological activities of 1 would be worthwhile. Betulinic acid, stigmasterol and its 3- O-glucoside were isolated from the neutral chloroform fraction of the methanolic extract.

[Diversity of Secondary Metabolites from Some Medicinal Plants and Cultivated Lichen Mycobionts]

 Studies on the structural determination, biosynthesis, and biological activities of secondary metabolites from natural sources are significant in the field of natural products chemistry. This review focuses on diverse secondary metabolites isolated from medicinal plants and cultivated mycobionts of lichens in our laboratory. Monoterpene-tetrahydroisoquinoline glycosides and alkaloids isolated from Cephaelis acuminata and Alangium lamarckii gave important information on the biosynthesis of ipecac alkaloids. A variety of glycosides linked with a secologanin unit and indole alkaloids were obtained from medicinal plants belonging to the families of Rubiaceae, Apocynaceae, and Loganiaceae. Plant species of the four genera Fraxinus, Syringa, Jasminum, and Ligustrum of the family Oleaceae were chemically investigated to provide several types of secoiridoid and iridoid glucosides. The biosynthetic pathway leading from protopine to benzophenanthridine alkaloids in suspension cell cultures of Eschscholtzia californica was elucidated. The structures and biological activities of the bisbenzylisoquinoline alkaloids of Stephania cepharantha and Nelumbo nucifera were also investigated. In addition, the mycobionts of lichens were cultivated to afford various types of metabolites that differ from the lichen substances of intact lichens but are structurally similar to fungal metabolites. The biosynthetic origins of some metabolites were also studied. These findings suggest that cultures of lichen mycobionts could be sources of new bioactive compounds and good systems for investigating secondary metabolism in lichens.

A Cyclopeptide and a Tetrahydroisoquinoline Alkaloid from Ophiorrhiza nutans

A new cyclopeptide, ophiorrhisine A (1), a new tetrahydroisoquinoline alkaloid, 7',10-dide-O-methylcephaeline (2), two known β-carboline alkaloids, and four known tetrahydroisoquinoline alkaloids were isolated from Ophiorrhiza nutans (Rubiaceae). Compound 1 is a tetrapeptide possessing a 14-membered paracyclophane ring and a novel N,N,N-trimethyltyrosine residue in the side chain. The stereochemistry at the aryl-alkyl ether bond was different from that of other known 14-membered paracyclophanes. The structure of 2 was established by spectroscopic analysis and semisynthesis.

13C-NMR Spectral Data of Alkaloids Isolated from Psychotria Species (Rubiaceae)

The genus Psychotria (Rubiaceae) comprises more than 2000 species, mainly found in tropical and subtropical forests. Several studies have been conducted concerning their chemical compositions, showing that this genus is a potential source of alkaloids. At least 70 indole alkaloids have been identified from this genus so far. This review aimed to compile ¹³C-NMR data of alkaloids isolated from the genus Psychotria as well as describe the main spectral features of different skeletons.

Secondary metabolites from Rubiaceae species

This study describes some characteristics of the Rubiaceae family pertaining to the occurrence and distribution of secondary metabolites in the main genera of this family. It reports the review of phytochemical studies addressing all species of Rubiaceae, published between 1990 and 2014. Iridoids, anthraquinones, triterpenes, indole alkaloids as well as other varying alkaloid subclasses, have shown to be the most common. These compounds have been mostly isolated from the genera Uncaria, Psychotria, Hedyotis, Ophiorrhiza and Morinda. The occurrence and distribution of iridoids, alkaloids and anthraquinones point out their chemotaxonomic correlation among tribes and subfamilies. From an evolutionary point of view, Rubioideae is the most ancient subfamily, followed by Ixoroideae and finally Cinchonoideae. The chemical biosynthetic pathway, which is not so specific in Rubioideae, can explain this and large amounts of both iridoids and indole alkaloids are produced. In Ixoroideae, the most active biosysthetic pathway is the one that produces iridoids; while in Cinchonoideae, it produces indole alkaloids together with other alkaloids. The chemical biosynthetic pathway now supports this botanical conclusion.

Stereoselective synthesis of 3-substituted tetrahydropyrazinoisoquinolines via intramolecular cyclization of enantiomerically enriched dihydro-2H-pyrazines

The preparation of 3-substituted tetrahydropyrazinoisoquinolines using the tributyltin hydride mediated intramolecular radical cyclization of suitably protected 2-substituted 3,4-dihydropyrazines is reported. The compounds are obtained as single enantiomers, as the relative configuration of the new generated stereogenic center is driven by the stereochemistry of the 2-substituted carbon in the starting materials, which is in turn derived from naturally occurring amino acids.

Recent applications of the hetero Diels–Alder reaction in the total synthesis of natural products

The synthetic utility and potential power of the Diels–Alder (D–A) reaction in organic chemistry is evident.

Evaluation of Antioxidant Activity, Total Flavonoids, Tannins and Phenolic Compounds in Psychotria Leaf Extracts

The antioxidant activity of Psychotria carthagenensis, P. leiocarpa, P. capillacea and P. deflexa (Rubiaceae) extracts were investigated, and the concentrations of total phenolics, flavonoids, condensed tannins and flavonols were determined. The chemical compositions of the extracts were investigated using the high performance liquid chromatography (HPLC/PAD) method. We used 1,1-diphenyl-1-picrylhydrazyl free radical (DPPH), β-Carotene bleaching and 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cations to determine antioxidant activity. The ability to scavenge radical was measured in these experiments by the discoloration of the solution. Concentrations of constituents were measured spectrophotometrically. P. carthagenensis and P. capillacea exhibited the highest antioxidant activity, in the DPPH test, β-carotene bleaching and ABTS system. The highest phenolic, flavonoid, condensed tannin and flavonol concentration was found in P. carthagenensis and P. capillacea extracts. HPLC-PDA analysis of P. carthagenensis and P. capillacea revealed hydroxycinnamic acid (p-coumaric acid). This is the first report on the antioxidant properties and constituent analysis of these Psychotria extracts.

Angustinine – A New Benzopyridoquinolizine Alkaloid from Alangium lamarckii

A new benzopyridoquinolizine alkaloid, designated as angustinine (1), was isolated from the root bark of Alangium lamarckii Thwaites, along with the known ipecac alkaloid, emetine. Investigation of the stem bark of the same plant resulted in the isolation of another known ipecac alkaloid, cephaeline. The structure of the new alkaloid (1) was elucidated on the basis of 2D NMR spectral analysis.

Inhibition of Gastric H+, K+-ATPase Activity by Compounds from Medicinal Plants

H+, K+-ATPase enzyme is a therapeutic target for the treatment of gastric disturbances. Several medicinal plants and isolated compounds inhibit the acid gastric secretion through interaction with the proton pump. In order to add new properties to some natural constituents, five compounds, a benzylated derivative of vincoside, a diterpene (abietic acid) and three alkaloids (cephaeline, vinblastine and vindoline), were tested for their activities on gastric H+,K+-ATPase isolated from rabbit stomach. All the compounds inhibited H+, K+-ATPase activity with varied potency. The IC50value for benzylvincoside was 121 (50-293) μM, and for abietic acid 177 (148-211) μM. The alkaloids cephaeline, vinblastine and vindoline inhibited the H+,K+-ATPase activity with IC50values of 194, 761 and 846 μM, respectively. The results suggest that benzylvincoside, abietic acid and cephaeline can be important sources for the development of anti-secretor agents.

Three new O-methyltransferases are sufficient for all O-methylation reactions of ipecac alkaloid biosynthesis in root culture of Psychotria ipecacuanha

The medicinal plant Psychotria ipecacuanha produces ipecac alkaloids, a series of monoterpenoid-isoquinoline alkaloids such as emetine and cephaeline, whose biosynthesis derives from condensation of dopamine and secologanin. Here, we identified three cDNAs, IpeOMT1-IpeOMT3, encoding ipecac alkaloid O-methyltransferases (OMTs) from P. ipecacuanha. They were coordinately transcribed with the recently identified ipecac alkaloid beta-glucosidase Ipeglu1. Their amino acid sequences were closely related to each other and rather to the flavonoid OMTs than to the OMTs involved in benzylisoquinoline alkaloid biosynthesis. Characterization of the recombinant IpeOMT enzymes with integration of the enzymatic properties of the IpeGlu1 revealed that emetine biosynthesis branches off from N-deacetylisoipecoside through its 6-O-methylation by IpeOMT1, with a minor contribution by IpeOMT2, followed by deglucosylation by IpeGlu1. The 7-hydroxy group of the isoquinoline skeleton of the aglycon is methylated by IpeOMT3 prior to the formation of protoemetine that is condensed with a second dopamine molecule, followed by sequential O-methylations by IpeOMT2 and IpeOMT1 to form cephaeline and emetine, respectively. In addition to this central pathway of ipecac alkaloid biosynthesis, formation of all methyl derivatives of ipecac alkaloids in P. ipecacuanha could be explained by the enzymatic activities of IpeOMT1-IpeOMT3, indicating that they are sufficient for all O-methylation reactions of ipecac alkaloid biosynthesis.

Astonishing diversity of natural surfactants: 6. Biologically active marine and terrestrial alkaloid glycosides

This review article presents 209 alkaloid glycosides isolated and identified from plants, microorganisms, and marine invertebrates that demonstrate different biological activities. They are of great interest, especially for the medicinal and/or pharmaceutical industries. These biologically active glycosides have good potential for future chemical preparation of compounds useful as antioxidants, anticancer, antimicrobial, and antibacterial agents. These glycosidic compounds have been subdivided into several groups, including: acridone; aporphine; benzoxazinoid; ergot; indole; enediyne alkaloidal antibiotics; glycosidic lupine alkaloids; piperidine, pyridine, pyrrolidine, and pyrrolizidine alkaloid glycosides; glycosidic quinoline and isoquinoline alkaloids; steroidal glycoalkaloids; and miscellaneous alkaloid glycosides.

Cytotoxic Alangium alkaloids from Alangium longiflorum

Seven alkaloids (1-7) were isolated from the stem bark of Alangium longiflorum. Compound 1, (-)-10-O-demethylisocephaeline, was isolated for the first time as a naturally occurring product from a plant source. All structures were elucidated by detailed spectroscopic analysis. Biological evaluation showed that 2, 10-O-demethylcephaeline, exhibited potent cytotoxic activity against human lung carcinoma (A549) and breast adenocarcinoma (MCF-7) with ED(50) values of 0.013 and 0.062 microM, respectively. The stereoisomer 1 was less potent than 2, and related compounds with different hydroxy/methoxy substitution patterns were also less potent or inactive. Thus, compound 2 merits attention as a cytotoxic lead for further study.

Antiparasitic alkaloids from Psychotria klugii

Psychotria klugii yielded two new benzoquinolizidine alkaloids, klugine (1) and 7'-O-demethylisocephaeline (2), together with the previously known cephaeline (3), isocephaeline (4), and 7-O-methylipecoside (5). The structures and stereochemistry of 1 and 2 were determined by 1D and 2D NMR data and circular dichroism experiments. Cephaeline (3) demonstrated potent in vitro antileishmanial activity against Leishmania donavani (IC(50) 0.03 microg/mL) and was >20- and >5-fold more potent than pentamidine and amphotericin B, respectively, while klugine (1) (IC(50) 0.40 microg/mL) and isocephaeline (4) (IC(50) 0.45 microg/mL) were <13- and <15-fold less potent than 3. In addition, emetine (6) (IC(50) 0.03 microg/mL) was found to be as equally potent as 3, but was >12-fold more toxic than 3 against VERO cells (IC(50) 0.42 vs 5.3 microg/mL). Alkaloids 1 and 3 exhibited potent antimalarial activity against Plasmodium falciparum clones W2 and D6 (IC(50) 27.7-46.3 ng/mL). Compound 3 was cytotoxic to SK-MEL, KB, BT-549, and SK-OV-3 human cancer cells, while 1 was inactive.

Tetrahydroisoquinoline-monoterpene glycosides from Cephaelis acuminata

From the dried roots of Cephaelis acuminata, five tetrahydroisoquinoline-monoterpene glycosides, 2-O-beta-D-glucopyranosyldemethylalangiside, demethylisoalangiside, 6"-O-beta-D-glucopyranosylipecoside, 6"-O-alpha-D-glucopyranosylipecoside and (4R)-4-hydroxyipecoside, were isolated. The structures of these glycosides were determined by spectroscopic and chemical means.

High-performance liquid chromatographic assay with fluorescence detection for the determination of cephaeline and emetine in human plasma and urine

A high-performance liquid chromatographic assay method for the quantitation of ipecac alkaloids (cephaeline and emetine) in human plasma and urine is described. Human plasma or urine was extracted with diethylether under alkaline conditions following the addition of an internal standard. Concentrations of alkaloids and internal standard were determined by octadecylsilica chromatographic separation (Symmetry C18 columns, plasma analysis; 15 cmx4.6 mm I.D., 5 microm particle size, urine analysis; 7.5 cmx4.6 mm I.D., 5 microm particle size). The mobile phase consisted of buffer (20 mmol/l 1-heptanesulfonic acid sodium salt, adjusted to pH 4.0 with acetic acid)-methanol (51:49, v/v). Eluate fluorescence was monitored at 285/316 nm. The lowest quantitation limits of cephaeline and emetine were 1 and 2.5 ng/ml, respectively, in plasma, and 5 ng/ml in urine. Intra- and inter-day relative standard deviations were below 15%. The assay is sensitive, specific and applicable to pharmacokinetic studies in humans.

Metabolism of ipecac alkaloids cephaeline and emetine by human hepatic microsomal cytochrome P450s, and their inhibitory effects on P450 enzyme activities

In this study, we identified the metabolites and the CYP forms that are specifically involved in emetine O-demethylation in human liver microsomes, and cleared the inhibitory potential of cephaeline and emetine on the activity of the major drug-metabolizing CYP enzymes. Incubation of emetine with human liver microsomes yielded three metabolites identified by using HPLC by comparison of the retention time with the authentic sample of cephaeline, 9-O-demethylemetine and 10-O-demethylemetine. CYP3A4 and CYP2D6 were able to metabolize emetine to cephaeline and 9-O-demethylemetine, and CYP3A4 also participated in metabolizing emetine to 10-O-demethylemetine. Cephaeline and emetine inhibited probe substrates metabolism. IC50 for cephaeline against CYP2D6 and CYP3A4 were 121 and 1000 microM, respectively. For the emetine, CYP2D6 and CYP3A4 were 80 and 480 microM, respectively. Inhibition constants (Ki) for both compounds on the CYP2D6 and CYP3A4 activities were determined by graphic analysis of Dixon plots at various concentrations. The obtained Ki values of cephaeline for CYP2D6 and CYP3A4 were 54 and 355 microM, respectively, and the values of emetine were 43 and 232 microM, respectively. We concluded that these in vitro inhibitions of cephaeline and emetine would hardly increase plasma concentrations of co-administered drugs in clinical therapy.

Two Alangium alkaloids from Alangium lamarckii

Two new Alangium alkaloids, 1',2'-dehydrotubulosine (1) and alangine (2), were isolated from the dried fruits of Alangium lamarckii along with tubulosine (3), isotubulosine (4), deoxytubulosine, cephaeline, isocephaeline, psychotrine, neocephaeline, 10-O-demethylcephaeline, 2'-N-(1"-deoxy-1" -beta-D-fructopyranosyl)cephaeline, protoemetine, protoemetinol, salsoline, and alangiside. The structures of the new alkaloids (1 and 2) were determined by spectroscopic and chemical means.