Toxicity assessment of gelsenicine and the search for effective antidotes.

BACKGROUND: Gelsenicine, one of the most toxic alkaloids of Gelsemium elegans Benth (G. elegans), causes severe respiratory depression. However, its toxicity mechanisms are yet to be elucidated and no effective antidotes are available. OBJECTIVE: This study aimed to analyse the toxicity characteristics of gelsenicine. METHODS: Both acute and sub-acute toxicities were evaluated. Gelsenicine distribution and elimination in the central nervous system (CNS) and blood were observed. Effective antidotes for gelsenicine poisoning were screened. RESULTS: In the acute toxicity study, gelsenicine was highly toxic, and female rats exhibited greater sensitivity to gelsenicine than male rats (LD50 0.520 mg/kg vs 0.996 mg/kg, respectively). Death was primarily caused by respiratory failure. However, in the sub-acute toxicity study, no significant organ damage was observed. Gelsenicine was easily absorbed from the gastrointestinal tract and penetrated the blood-brain barrier, reaching peak concentrations in the CNS within 15 min and rapidly decreasing thereafter. Flumazenil or diazepam combined with epinephrine reversed gelsenicine toxicity and significantly improved survival rate in mice. CONCLUSIONS: Gelsenicine is a highly toxic substance that affects nerve conduction without causing damage; the potential toxic mechanism is possibly associated with GABAA receptors. Our findings provide insights into the clinical treatment of gelsenicine-related poisoning and its toxicity mechanisms.

Bioactivity and cytotoxicity profiling of vincosamide and strictosamide, anthelmintic epimers from Sarcocephalus latifolius (Smith) Bruce leaf.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaf of Sarcocephalus latifolius is known to be used traditionally by the Fulanis in Nigeria to deworm animals. As helminthosis remains a major constraint to profitable livestock production worldwide, a precarious situation aggravated by the advent of resistant parasites, the discovery of new anthelmintics is a priority, necessitating exploration of medicinal plants for their anthelmintic principles. AIM OF THE STUDY: To identify and characterise compounds with anthelmintic activity from the leaf of Sarcocephalus latifolius. MATERIALS AND METHODS: Powdered S. latifolius leaves were extracted by successive maceration with n-hexane, chloroform and acetone. The dried extracts were evaluated for anthelmintic activity against Haemonchus placei adult worms, and the most active extract was subjected to bioassay-guided chromatographic separations. The isolated compounds were evaluated for cytotoxicity against the mammalian HeLa and MC3T3-E1 cell lines, using alamar blue and CellTitreGloTM to quantify cell viability. LC50 values were computed from the in vitro anthelmintic activity data by fitting to a non-linear regression equation (variable slope). Isolated compounds were characterized using spectroscopic and mass spectrometric analyses. RESULTS: Anthelmintic activity LC50 values for n-hexane, chloroform and acetone extracts were 47.85, 35.76 and 5.72 (mg/mL), respectively. Chromatographic separation of acetone extract afforded two bioactive epimers, identified as vincosamide (LC50 14.7 mg/mL) and strictosamide (LC50 12.8 mg/mL). Cytotoxicity evaluation showed that, below 200 µg/mL (400 µM), neither compound was toxic to the HeLa or MC3T3-E1 cells. CONCLUSION: Vincosamide and strictosamide could serve as novel scaffolds for the development of anthelmintic derivatives with improved potency and helminth selectivity.

Assessment of toxicity and differential antimicrobial activity of methanol extract of rhizome of Simaba ferruginea A. St.-Hil. and its isolate canthin-6-one.

ETHNOPHARMACOLOGICAL RELEVANCE: Simaba ferruginea A. St.-Hil., Simaroubaceae, popularly known as "calunga" is a typical subtropical shrub used in Central Brazil mainly for infection, anti-inflammatory, analgesic and gastric duodenal-ulcers. It presents in its composition the alkaloid canthin-6-one, an alkaloid indole ß-carboxylic. AIM: This study aims to investigate the toxicity, antimicrobial activities of methanol extract of Simaba ferruginea (MESf) and canthin-6-one by using different experimental models. METHODS: The present study evaluated the phytochemical analysis by high performance liquid chromatography (HPLC), toxicological potential of MESf and canthin-6-one, using the cytotoxicity, genotoxicity assays with CHO-K1 cells and in vivo acute test in mice. Antimicrobial activity was evaluated by the broth microdilution assays, while the antimicrobial mechanism of action was also assessed using different in vitro bacterial and fungal models. RESULTS: The HPLC analysis of MESf revealed the presence of canthin-6-one, kaempferol and morin. Differential in vitro toxicities were observed between MESf and canthin-6-one. In the cytotoxicity assay, MESf presented toxicity against CHO-K1, while canthin-6-one did not. In the case of in vitro genotoxicity, both showed to be potentially genotoxic. In the in vivo toxicity study, both MESf (up to 1000 mg/kg) and cantin-6-one (up to 100 mg/kg) caused no toxicologically relevant alterations and are thus considered not to be toxic. MESf was shown to be relatively safe with NOAEL (100 mg/kg) when administrate in mice. Both MESf and canthin-6-one also showed differential antimicrobial activities. On one hand, MESf demonstrated good spectrum of antibacterial action against Staphylococcus aureus (MIC 12.5 µg/mL) and Escherichia coli (MIC 25 µg/mL) and moderate activity against Enterococcus faecalis and Shigella flexneri (MIC 200 µg/mL) but no antifungal effect. On the hand, canthin-6-one showed no antibacterial activity, except against Staphylococcus aureus (100 µg/mL), but potent in vitro fungicidal activity against clinically important Aspergillus niger and Candida species at MFC intervals ranging from 3.12 to 25 µg/mL. Both MESf and canthin-6-one were bacteriostatic in action. MESf antimicrobial mechanism of actions are associated with changes in the permeability of bacterial membranes, evidenced by the increased entry of hydrophobic antibiotic in Shigella flexneri, intense K+ efflux (Shigella flexneri, Staphylococcus aureus) and nucleotides leakage (Staphylococcus aureus). In the antifungal mode of action, canthin-6-one inhibited Saccharomyces cerevisiae growth and including alteration in the cell membrane of Neurospora crassa. CONCLUSION: The results of this work demonstrated the differential antimicrobial activities of MESf and its alkaloid isolate, canthin-6-one with antibacterial and antifungal activities, respectively. The present study support the popular use of Simaba ferruginea in combatting afflictions related to bacterial infections, and demonstrate that canthin-6-one as a promising antifungal agent. Both MESf and canthin-6-one are considered non-toxic based on the in vitro toxicological study.

Mesembrine alkaloids: Review of their occurrence, chemistry, and pharmacology.

ETHNOPHARMACOLOGICAL RELEVANCE: Mesembrine alkaloids are considered to be the primary active constituents of the South African medicinal plant Sceletium tortuosum (L.) N.E.Br. (Aizoaceae), and it is used as the dried or fermented aerial material from the plant, which is known as kanna (aka, channa, kougoed). Traditional regional use ranged from relieving thirst, mild analgesia, and alteration of mood. Current interest has focused primarily on the antidepressant action of preparations based on the plant and commercialization is expanding the recognition and availability of these preparations. MATERIALS AND METHODS: Searches for the keywords "Sceletium or mesembrine" were performed in "PubMed-NCBI", "Chemical Abstracts SciFinder" and "Thomson Reuters Web of Science" databases in addition to the inclusion of references cited within prior reviews and scientific reports. Additionally the "SciFinder" database was searched using 3a-phenyl-cis-octahydroindole in the SciFinder Substructure Module (SSM). Plant taxonomy was validated by the database "The Plant List". RESULTS: This review focuses on the chemistry, analysis, and pharmacology of the mesembrine alkaloids. Despite a long history of medicinal used and research investigation, there has been a renewed interest in the pharmacological properties of the mesembrine alkaloids and much of the pharmacology has only recently been published. The two major active alkaloids mesembrine and mesembrenone are still in the process of being more fully characterized pharmacologically. They are serotonin reuptake inhibitors, which provides a rationale for the plant's traditional use as an antidepressant, but other actions are beginning to appear in the literature. Additionally, mesembrenone has reasonably potent PDE4 inhibitory activity. This review intends to provide an overview of the available literature, summarize the current findings, and put them in perspective with earlier studies and reviews.

Genotoxicity and cytotoxicity of oxindole alkaloids from Uncaria tomentosa (cat's claw): Chemotype relevance.

ETHNOPHARMACOLOGICAL RELEVANCE: Uncaria tomentosa (Willdenow ex Roemer & Schultes) DC. (Rubiaceae) or cat's claw is a climber vine from the South American rainforest used in folk medicine for cancer treatment. Its antitumor activity has been mostly ascribed to pentacyclic oxindole alkaloids (POA) from stem bark and leaves while the activity of tetracyclic oxindole alkaloids (TOA) remains unknown. In recent times, the occurrence of three chemotypes based on its oxindole alkaloid profile was noticed in U. tomentosa, namely, chemotype I (POA cis D/E ring junction); chemotype II (POA trans D/E ring junction) or chemotype III (TOA). Consequently, the relationship between the chemotype and cytotoxic and genotoxic activities deserves attention. AIM OF THE STUDY: To evaluate the influence of cat's claw chemotypes on genotoxicity and cytotoxicity against non malignant and malignant human cell line models. MATERIAL AND METHODS: Four authentic stem bark cat's claw samples (SI-SIV) and two leaf samples (LII and LIII) were analyzed by HPLC-PDA, properly extracted and fractioned by ion-exchange to obtain oxindole alkaloid purified fractions (OAPFs). The freeze-dried fractions were assayed for genotoxicity and cytotoxicity against human leukocytes (non malignant cell line) by the micronuclei frequency method and the alkaline comet DNA assay, and the trypan blue method, respectively. Moreover, the cytotoxicity of each OAPF was evaluated against a human bladder cancer cell line (T24) and human glioblastoma cell line (U-251-MG) by MTT method (malignant cell lines). Additionally, the isomerization of oxindole alkaloids throughout the course of cell incubation was monitored by HPLC-PDA. RESULTS: Based on HPLC-PDA analyses, sample SI was characterized as chemotype I, while samples SII and LII were characterized as chemotype II, and samples SIII, SIV and LIII as chemotype III. The chemotypes showed comparable cytotoxic activity toward malignant cell lines (T24 and U-251-MG) unlike human leukocytes (non malignant cell line), where this activity was clearly distinct. Chemotype II (POA trans D/E ring junction) showed a higher selectivity index (SI) against malignant cells (SI=1.11-3.04) than chemotype I (SI=0.10-0.19) and III (SI=0.21-0.57). No important genotoxic potential was found by micronuclei frequency and alkaline comet DNA assays. Despite the isomerization of oxindole alkaloids during the cell incubation, the chemotype of the cat's claw samples remained unchanged. CONCLUSION: Cat's claw chemotypes showed different selectivity against human malignant cells, so that the correct identification of each chemotype seems to be important to better understand its antitumor potential.

Identification of anti-cancer chemical compounds using Xenopus embryos.

Cancer tissues have biological characteristics similar to those observed in embryos during development. Many types of cancer cells acquire pro-invasive ability through epithelial-mesenchymal transition (EMT). Similar processes (gastrulation and migration of cranial neural crest cells [CNCC]) are observed in the early stages of embryonic development in Xenopus during which cells that originate from epithelial sheets through EMT migrate to their final destinations. The present study examined Xenopus embryonic tissues to identify anti-cancer compounds that prevent cancer invasion. From the initial test of known anti-cancer drugs, AMD3100 (an inhibitor of CXCR4) and paclitaxel (a cytoskeletal drug targeting microtubules) effectively prevented migration during gastrulation or CNCC development. Blind-screening of 100 synthesized chemical compounds was performed, and nine candidates that inhibited migration of these embryonic tissues without embryonic lethality were selected. Of these, C-157 (an analog of podophyllotoxin) and D-572 (which is an indole alkaroid) prevented cancer cell invasion through disruption of interphase microtubules. In addition, these compounds affected progression of mitotic phase and induced apoptosis of SAS oral cancer cells. SAS tumors were reduced in size after intratumoral injection of C-157, and peritoneal dissemination of melanoma cells and intracranial invasion of glioma cells were inhibited by C-157 and D-572. When the other analogues of these chemicals were compared, those with subtle effect on embryos were not tumor suppressive. These results suggest that a novel chemical-screening approach based on Xenopus embryos is an effective method for isolating anti-cancer drugs and, in particular, targeting cancer cell invasion and proliferation.

Antifungal Indole Alkaloids from Winchia calophylla.

Ten indole alkaloids (1-10) were obtained from an antifungal extract of Winchia calophylla, of which two (2 and 4) were new. N(4)-Methyl-10-hydroxyl-desacetylakuammilin (2) was an akuammiline-type indole alkaloid. N(1)-Methyl-echitaminic acid (4) was an unusual zwitterion with a basic vincorine-type skeleton. This is the first report of 10 in W. calophylla. The structures of all of the compounds were determined based on spectroscopic data, and their bioactivities were assessed. Compound 1 showed potent activity against the plant pathogenic fungi of Penicillium italicum and Fusarium oxysporum f.sp cubens with IC50 s of 10.4 and 11.5 µM, respectively, and 3 inhibited Rhizoctonia solani with an IC50 of 11.7 µM. Compounds 2 and 4 showed weak cytotoxicity against the human leukemic cell line HL-60 in vitro with IC50 s of 51.4 and 75.3 µM, respectively. Compounds 1 and 2 displayed weak activity against acetylcholinesterase with IC50 s around 61.3 and 52.6 µM, respectively.

GC-MS, LC-MS(n), LC-high resolution-MS(n), and NMR studies on the metabolism and toxicological detection of mesembrine and mesembrenone, the main alkaloids of the legal high "Kanna" isolated from Sceletium tortuosum.

Mesembrine and mesembrenone are the main alkaloids of Sceletium tortuosum, a plant species that was used for sedation and analgesia by the KhoiSan, previously known as Hottentots, a tribe in South Africa. After fermentation, the obtained preparation called "Kanna" or "Kougoed" was used by chewing, smoking, or sniffing. Today, Kanna gains popularity by drug users as legal high. For monitoring such consumption, metabolism studies are mandatory because the metabolites are mostly the analytical targets, especially in urine. Therefore, the metabolism of both alkaloids was investigated in rat urine and pooled human liver preparations after several sample work-up procedures. As both alkaloids were not commercially available, they were isolated from plant material by Soxhlet extraction, and their identity confirmed by NMR. The metabolites were identified using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography coupled to linear ion trap high resolution mass spectrometry (LC-HR-MS(n)). Both alkaloids were O- and N-demethylated, dihydrated, and/or hydroxylated at different positions. The phenolic metabolites were partly excreted as glucuronides and/or sulfates. Most of the phase I metabolites identified in rat urine could be detected also in the human liver preparations. After a common user's low dose application of mesembrine, mainly the O- and N demethyl-dihydro, hydroxy, and bis-demethyl-dihydro metabolites, and in case of mesembrenone only the N-demethyl and the N-demethyl-dihydro metabolite could be detected in rat urine using the authors' standard urine screening approaches (SUSA) by GC-MS or LC-MS(n). Thus, it should be possible to monitor a consumption of mesembrine and/or mesembrenone assuming similar pharmacokinetics in humans.

Effects of Sceletium tortuosum in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Broad historical and current uses in addition to diverse activity on CNS targets may make Sceletium tortuosum a useful therapeutic in a variety of clinical settings. This study sought to more broadly characterize activity of Sceletium tortuosum and mesembrine in a number of common, rodent-based assays that model nociception, depression, anxiety, ataxia, and abuse liability. MATERIALS AND METHODS: Male Sprague-Dawley were administered Sceletium tortuosum extract products and behavioral responses were evaluated in the conditioned place preference (CPP), hot plate, forced swim, elevated plus, and rotarod tests. RESULTS AND CONCLUSIONS: Sceletium tortuosum does not cause preference or aversion in CPP. Mesembrine appears to have analgesic properties without abuse liabilities or ataxia. The Sceletium tortuosum fraction has antidepressant properties but does produce ataxia. The ataxia may limit its usefulness as an antidepressant unless the antidepressant activity is associated with one constituent and the ataxia is associated with a separate constituent.

Permeability of rhynchophylline across human intestinal cell in vitro.

Rhynchophylline (Rhy) is the major component of Uncaria species, which is used in Chinese traditional medicine for the treatment of central nervous system disorders. However, its oral bioavailability has not been known. This study aims to investigate the intestinal permeability and related mechanisms of Rhy using cultured human epithelial Caco-2 cells. The cytotoxicity of Rhy on Caco-2 cells was evaluated with MTT assay. The effect of Rhy on the integrity of Caco-2 cell monolayer was assayed with transepithelial electrical resistance. The permeability of Rhy across cell monolayer was assayed by measuring Rhy quantity in received side with HPLC. The effect of Rhy on the expression of P-glycoprotein and MDR1 was detected with Western blot and flow cytometry, respectively. In the concentration of Rhy, which did not produce toxicity on cell viability and integrity of Caco-2 cell monolayer, Rhy crossed the monolayer with velocity 2.76~5.57×10^-6 cm/sec and 10.68~15.66×10^-6 cm/sec from apical to basolateral side and from basolateral to apical side, respectively. The permeability of Rhy was increased by verapamil, a P-glycoprotein inhibitor, or rhodamine123, a P-glycoprotein substrate. Rhy revealed an induction effect on P-glycoprotein expression in Caco-2 cells. These results demonstrate the low permeability of Rhy in intro, and suggest that P-glycoprotein may underlie the mechanism.

Anti-malarial activity of indole alkaloids isolated from Aspidosperma olivaceum.

BACKGROUND: Several species of Aspidosperma (Apocynaceae) are used as treatments for human diseases in the tropics. Aspidosperma olivaceum, which is used to treat fevers in some regions of Brazil, contains the monoterpenoid indole alkaloids (MIAs) aspidoscarpine, uleine, apparicine, and N-methyl-tetrahydrolivacine. Using bio-guided fractionation and cytotoxicity testing in a human hepatoma cell line, several plant fractions and compounds purified from the bark and leaves of the plant were characterized for specific therapeutic activity (and selectivity index, SI) in vitro against the blood forms of Plasmodium falciparum. METHODS: The activity of A. olivaceum extracts, fractions, and isolated compounds was evaluated against chloroquine (CQ)-resistant P. falciparum blood parasites by in vitro testing with radiolabelled [3H]-hypoxanthine and a monoclonal anti-histidine-rich protein (HRPII) antibody. The cytotoxicity of these fractions and compounds was evaluated in a human hepatoma cell line using a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, and the SI was calculated as the ratio between the toxicity and activity. Two leaf fractions were tested in mice with Plasmodium berghei. RESULTS: All six fractions from the bark and leaf extracts were active in vitro at low doses (IC50 < 5.0 µg/mL) using the anti-HRPII test, and only two (the neutral and basic bark fractions) were toxic to a human cell line (HepG2). The most promising fractions were the crude leaf extract and its basic residue, which had SIs above 50. Among the four pure compounds evaluated, aspidoscarpine in the bark and leaf extracts showed the highest SI at 56; this compound, therefore, represents a possible anti-malarial drug that requires further study. The acidic leaf fraction administered by gavage to mice with blood-induced malaria was also active. CONCLUSION: Using a bio-monitoring approach, it was possible to attribute the anti-P. falciparum activity of A. olivaceum to aspidoscarpine and, to a lesser extent, N-methyl-tetrahydrolivacine; other isolated MIA molecules were active but had lower SIs due to their higher toxicities. These results stood in contrast to previous work in which the anti-malarial activity of other Aspidosperma species was attributed to uleine.

Ultrasound/microwave-assisted extraction and comparative analysis of bioactive/toxic indole alkaloids in different medicinal parts of Gelsemium elegans Benth by ultra-high performance liquid chromatography with MS/MS.

Indole alkaloids are the main bioactive/toxic components in Gelsemium elegans Benth. To determine the distribution and contents of indole alkaloids in its different medicinal parts, a novel and rapid method using ultra-high performance LC (UPLC) with MS/MS has been established and validated with an optimized ultrasound/microwave-assisted extraction method. Four constituents, namely, humantenidine, humantenmine, gelsemine, and koumine, were simultaneously determined in 6 min. Chromatographic separation was achieved on an ultra-high performance LC BEH C18 column with a gradient mobile phase consisting of methanol and water (containing 0.1% formic acid both in methanol and water) at a flow rate of 0.3 mL/min. The detection was performed on a triple quadrupole electrospray MS/MS by positive ion multiple-reaction monitoring mode. All the analytes showed good linearity (r ≥ 0.9934) within a concentration range from 0.1-25 µg/mL with a LOQ of 25-50 ng/mL. The overall intra- and intervariations of four components were <4.7% with an accuracy of 97.3-101.3%. The analysis results showed that there were remarkable differences in the distribution and contents of four chemical markers in the roots, stems, and leaves of G. elegans Benth. The findings can provide necessary and meaningful information for the rational utilization of its resources.

Chemical composition of Aspidosperma ulei Markgr. and antiplasmodial activity of selected indole alkaloids.

A new indole alkaloid, 12-hydroxy-N-acetyl-21(N)-dehydroplumeran-18-oic acid (13), and 11 known indole alkaloids: 3,4,5,6-tetradehydro-ß-yohimbine (3), 19(E)-hunteracine (4), ß-yohimbine (5), yohimbine (6), 19,20-dehydro-17-α-yohimbine (7), uleine (10), 20-epi-dasycarpidone (11), olivacine (8), 20-epi-N-nor-dasycarpidone (14), N-demethyluleine (15) and 20(E)-nor-subincanadine E (12) and a boonein δ-lactone 9, ursolic acid (1) and 1D,1O-methyl-chiro-inositol (2) were isolated from the EtOH extracts of different parts of Aspidosperma ulei Markgr. (Apocynaceae). Identification and structural elucidation were based on IR, MS, ¹H- and ¹³C-NMR spectral data and comparison to literature data. The antiplasmodial and antimalarial activity of 1, 5, 6, 8, 10 and 15 has been previously evaluated and 1 and 10 have important in vitro and in vivo antimalarial properties according to patent and/or scientific literature. With the aim of discovering new antiplasmodial indole alkaloids, 3, 4, 11, 12 and 13 were evaluated for in vitro inhibition against the multi-drug resistant K1 strain of the human malaria parasite Plasmodium falciparum. IC50 values of 14.0 (39.9), 4.5 (16.7) and 14.5 (54.3) mg/mL (mM) were determined for 3, 11 and 12, respectively. Inhibitory activity of 3, 4, 11, 12 and 13 was evaluated against NIH3T3 murine fibroblasts. None of these compounds exhibited toxicity to fibroblasts (IC50 > 50 mg/mL). Of the five compounds screened for in vitro antiplasmodial activity, only 11 was active.

Acute toxicity, antinociceptive activity and indole alkaloids of aqueous extract from bark of Aspidosperma cuspa (Kunth) Blake.

UNLABELLED: ETNOPHARMACOLOGICAL RELEVANCE: Aspidosperma cuspa (Kunth) Blake (Apocynaceae) is popularly known as "amargosa" or "cuspa", and its bark is used in folk medicine primarily for pain. AIM OF THE STUDY: In the present study the acute toxicity, antinociceptive effect and alkaloids of the aqueous decoction extract of the Aspidosperma cuspa bark in mice was investigated. MATERIALS AND METHODS: Acute toxicity was tested using a variation of the method described by Lichfield and Wilcoxon. The antinociceptive activity was evaluated using the acetic acid induced writhing and tail-flick tests. The phytochemical analysis was performed. RESULTS AND CONCLUSION: Oral administration of the extract did not cause animal death (LD(50)>4 g/kg), and the histological analysis showed an absence of alterations in all organs examined. TD(50) of the extract was 0.5521 g/kg for male mice and 1.1565 g/kg for females. The aqueous extract at doses 276 mg/kg (p.o.) did not produce a significant inhibition of acetic acid-induced writhes, but showed a significant effect in tail-flick test. Naloxone, an opioid receptor antagonist, pretreatment inhibited significantly the antinociceptive activity of the extract. It is suggested that the aqueous decoction extract of the bark of Aspidosperma cuspa has an antinociceptive effect, and this may be mediated by opioid receptors. Three indole alkaloids (aspidocarpine, 11-methoxytubotaiwine and picraline) were isolated from the aqueous extract. The antinociceptive activity of the extract is presumed to be due to these compounds.

In vitro antiplasmodial activity of indole alkaloids from the stem bark of Geissospermum vellosii.

ETHNOPHARMACOLOGICAL RELEVANCE: The stem bark of Geissospermum vellosii has been traditionally used by the native population of northern South America to treat malaria. Indole alkaloids have been previously isolated from this plant, but the antiplasmodial constituents have not yet been described. As part of our ongoing investigations of new bioactive compounds with activity against malaria parasites, we tested the in vitro antiplasmodial activity of isolated fractions and purified alkaloids from Geissospermum vellosii. MATERIALS AND METHODS: Indole alkaloids were isolated and identified from a methanolic crude extract of Geissospermum vellosii bark using a combination of high performance counter current chromatography, mass spectrometry and nuclear magnetic resonance technologies. The methanolic extract, the crude alkaloid fractions and the purified compounds were tested for in vitro antiplasmodial activity against the chloroquine-sensitive strain of Plasmodium falciparum (D10). RESULTS: An indole alkaloid (4) along with four known indole alkaloids, geissolosimine (1), geissospermine (2), geissoschizoline (3), and vellosiminol (5) were isolated and structure elucidated. The antiplasmodial activity (IC(50)) of the methanolic crude extract was 2.22 µg/mL, while for the isolated compounds it ranged from 0.96 µM to 13.96 µM except for (5) which showed a low activity (157 µM). Geissolosimine (1) showed the highest antiplasmodial activity (0.96 µM). CONCLUSIONS: This study provides evidence to support the use of Geissospermum vellosii as an antimalarial agent, as used by the native populations. Geissolosimine (1) is a lead molecular structure for possible antimalarial drug development.

Uncaria tomentosa aqueous-ethanol extract triggers an immunomodulation toward a Th2 cytokine profile.

Uncaria tomentosa (Willd.) DC (Rubiaceae) is a large woody vine that is native to the Amazon and Central American rainforests and is used widely in traditional medicine for its immunomodulatory and antiinflammatory activities. The present work used in vivo immunotoxic and in vitro immunomodulatory experiments to investigate the effects of a pentacyclic oxindole alkaloid extract from U. tomentosa bark on lymphocyte phenotype, Th1/Th2 cytokine production, cellular proliferation and cytotoxicity. For the in vivo immunotoxicity testing, BALB/c male mice were treated once a day with 125, 500 or 1250 mg/kg of U. tomentosa extract for 28 days. For the in vitro protocol, lymphocytes were cultured with 10-500 µg/mg of the extract for 48 h. The extract increased the cellularity of splenic white pulp and the thymic medulla and increased the number of T helper lymphocytes and B lymphocytes. Also, a large stimulatory effect on lymphocyte viability was observed. However, mitogen-induced T lymphocyte proliferation was significantly inhibited at higher concentrations of U. tomentosa extract. Furthermore, an immunological polarization toward a Th2 cytokine profile was observed. These results suggest that the U. tomentosa aqueous-ethanol extract was not immunotoxic to mice and was able to modulate distinct patterns of the immune system in a dose-dependent manner.

Biologically active ibogan and vallesamine derivatives from Tabernaemontana divaricata.

Six new indole alkaloids, viz., (3S)-3-cyanocoronaridine (2), (3S)-3-cyanoisovoacangine (3), conolobine A (5), conolobine B (6), conolidine (7), and (3R/3S)-3-ethoxyvoacangine (8), in addition to 36 known ones, were obtained from the stem-bark extract of the Malayan Tabernaemontana divaricata. The structures were determined by NMR and MS analysis. The CN-substituted alkaloids showed appreciable cytotoxicity towards the KB human oral epidermoid carcinoma cell-line.