Gouregine, an α-Gem-Dimethyltetradehydrocularine Alkaloid, and Other Aporphinoid Alkaloids from the Bark of Guatteria olivacea (Annonaceae) and Their In Vitro Cytotoxic Activities.

Guatteria olivacea R.E. Fries is an Amazonian species known as 'envira-bobó' and 'envira-fofa' and is common in the states of Amazonas, Acre, and Pará. Recently, the essential oil from the leaves of this species has shown promising antitumor activity both in vitro and in vivo. The presence of isoquinoline-derived alkaloids, including aporphinoids and tetrahydroprotoberberine alkaloids, has also been previously reported. In our ongoing search for bioactive compounds from Annonaceae Amazonian plants, the bark of G. olivacea was investigated via classical chromatography techniques, which revealed nine compounds, eight isoquinoline-derived alkaloids, a rare alkaloid with a α-gem-dimethyltetradehydrocularine structure known as gouregine, seven known aporphinoid alkaloids: isopiline, O-methylisopiline, melosmine, 9-hydroxyiguattescine, dihydromelosmine, lysicamine, and guattouregidine, and one known pimaradiene diterpene: acanthoic acid. All the isolated compounds were described for the first time in the bark of G. olivacea, and their structures were elucidated by extensive analyses of their 1D and 2D NMR spectra in combination with MS data. The NMR data of the alkaloids isopiline, O-methylisopiline, melosmine, dihydromelosmine, and guattouregidine were revised due to incomplete data in the literature and some ambiguities. The in vitro cytotoxic activities of the isolated compounds were evaluated against human cancer (HepG2, KG-1a, and HCT116) and noncancerous (MRC-5) cell lines via the Alamar blue assay after 72 h of incubation. Among the compounds evaluated against human cancer cell lines, the most active was the oxoaporphine alkaloid lysicamine, which has strong activity against HCT116 cells, with an IC50 value of 6.64 µg/mL (22.79 µmol/L). Melosmine had a moderate effect on HCT116 cells, with an IC50 value of 16.77 µg/mL (49.70 µmol/L), whereas acanthoic acid had moderate effects on HepG2 and HCT116 cells, with IC50 values of 14.63 µg/mL (48.37 µmol/L) and 21.25 µg/mL (70.25 µmol/L), respectively.

DFT, ADME studies and evaluation of the binding with HSA and MAO-B inhibitory potential of protoberberine alkaloids from Guatteria friesiana: theoretical insights of promising candidates for the treatment of Parkinson's disease.

CONTEXT: Parkinson's disease is a chronic neurodegenerative condition that has no cure, characterized by the progressive degeneration of specific brain cells responsible for producing dopamine, a crucial neurotransmitter for controlling movement and muscle coordination. Parkinson's disease is estimated to affect around 1% of the world's population over the age of 60, but it can be diagnosed at younger ages. One of the treatment strategies for Parkinson's disease involves the use of drugs that aim to increase dopamine levels or simulate the action of dopamine in the brain. A class of commonly prescribed drugs are the so-called monoamine oxidase B (MAO-B) inhibitors due to the fact that this enzyme is responsible for metabolizing dopamine, thus reducing its levels in the brain. Studies have shown that berberine-derived alkaloids have the ability to selectively inhibit MAO-B activity, resulting in increased dopamine availability in the brain. In this context, berberine derivatives 13-hydroxy-discretinine and 7,8-dihydro-8-hydroxypalmatine, isolated from Guatteria friesiana, were evaluated via density functional theory followed by ADME studies, docking and molecular dynamic simulations with MAO-B, aiming to evaluate their anti-Parkinson potential, which have not been reported yet. Docking simulations with HSA were carried out aiming to evaluate the transport of these molecules through the circulatory system. METHODS: The 3D structures of the berberine-derived alkaloids were modeled via the DFT approach at B3LYP-D3(BJ)/6-311 + + G(2df, 2pd) theory level using Gaussian 09 software. Solvation free energies were determined through Truhlar's solvation model. MEP and ALIE maps were generated with Multiwfn software. Autodock Vina software was used for molecular docking simulations and analysis of the interactions in the binding sites. The 3D structure of MAO-B was obtained from the Protein Data Bank website under PDB code 2V5Z. For the interaction of studied alkaloids with human serum albumin (HSA) drug sites, 3D structures with PDB codes 2BXD, 2BXG, and 4L9K were used. Molecular dynamics simulations were carried out using GROMACS 2019.4 software, with the GROMOS 53A6 force field at 100 ns simulation time. The estimation of the ligand's binding free energies was obtained via molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method.

Chemical Evaluation, Phytotoxic Potential, and In Silico Study of Essential Oils from Leaves of Guatteria schomburgkiana Mart. and Xylopia frutescens Aubl. (Annonaceae) from the Brazilian Amazon.

The essential oils (EOs) of Guatteria schomburgkiana (Gsch) and Xylopia frutescens (Xfru) (Annonaceae) were obtained by hydrodistillation, and their chemical composition was evaluated by gas chromatography-mass spectrometry (GC/MS). Herbicide activity was measured by analyzing the seed germination percentage and root and hypocotyl elongation of two invasive species: Mimosa pudica and Senna obtusifolia. The highest yield was obtained for the EO of Xfru (1.06%). The chemical composition of Gsch was characterized by the presence of the oxygenated sesquiterpenes spathulenol (22.40%) and caryophyllene oxide (14.70%). Regarding the EO of Xfru, the hydrocarbon monoterpenes α-pinene (35.73%) and ß-pinene (18.90%) were the components identified with the highest concentrations. The germination of seeds of S. obtusifolia (13.33 ± 5.77%) showed higher resistance than that of seeds of M. pudica (86.67 ± 5.77%). S. obtusifolia was also more sensitive to the EO of Xfru in terms of radicle (55.22 ± 2.72%) and hypocotyl (71.12 ± 3.80%) elongation, while M. pudica showed greater sensitivity to the EO of Gsch. To screen the herbicidal activity, the molecular docking study of the major and potent compounds was performed against 4-hydroxyphenylpyruvate dioxygenase (HPPD) protein. Results showed good binding affinities and attributed the strongest inhibitory activity to δ-cadinene for the target protein. This work contributes to the study of the herbicidal properties of the EOs of species of Annonaceae from the Amazon region.

A novel eudesmol derivative from the leaf essential oil of Guatteria friesiana (Annonaceae) and evaluation of the antinociceptive activity.

In the present study, it was evaluated the chemical composition and the antinociceptive activity of the essential oil obtained from the leaves of Guatteria friesiana. Seven compounds corresponding to 96.2% of the crude essential oil were identified. The main components identified were the mixture of ß-eudesmol and α-eudesmol (58.1%), and γ-eudesmol (16.8%). A new α-eudesmol derivative, named 5-hydroxy-α-eudesmol, was isolated together with the known compounds ß-eudesmol and a mixture of α-eudesmol, ß-eudesmol and γ-eudesmol of the essential oil. The chemical structures were determined by 1D and 2D NMR, and MS experiments. Essential oil has significant antinociceptive properties, which are related probably with the involvement of the opioid receptors and K+-ATP channels.

Antitumor Effect of Guatteria olivacea R. E. Fr. (Annonaceae) Leaf Essential Oil in Liver Cancer.

Guatteria olivacea R. E. Fries (synonym Guatteria punctata (Aubl.) R.A. Howard) is a tree of 10-27 m tall popularly known as "envira-bobó", "envira-fofa", "envireira", "embira", "embira-branca", "embira-preta", envira-branca", and "envira-preta", which can be found in the Brazilian Amazon biome. In this study, we evaluated the cytotoxic and antitumor effects of the essential oil (EO) obtained from the leaves of G. olivacea against liver cancer using HepG2 cells as a model. EO was obtained using a hydrodistillation Clevenger-type apparatus and was qualitatively and quantitatively characterized using GC-MS and GC-FID, respectively. The alamar blue assay was used to assess the cytotoxic potential of EO in a panel of human cancer cell lines and human non-cancerous cells. In HepG2 cells treated with EO, YO-PRO-1/propidium iodide staining, cell cycle distribution, and reactive oxygen species (ROS) were examined. In C.B-17 SCID mice with HepG2 cell xenografts, the efficacy of the EO (20 and 40 mg/kg) was tested in vivo. GC-MS and GC-FID analyses showed germacrene D (17.65%), 1-epi-cubenol (13.21%), caryophyllene oxide (12.03%), spathulenol (11.26%), (E)-caryophyllene (7.26%), bicyclogermacrene (5.87%), and δ-elemene (4.95%) as the major constituents of G. olivacea leaf EO. In vitro cytotoxicity of EO was observed, including anti-liver cancer action with an IC50 value of 30.82 µg/mL for HepG2 cells. In HepG2 cells, EO treatment increased apoptotic cells and DNA fragmentation, without changes in ROS levels. Furthermore, the EO inhibited tumor mass in vivo by 32.8-57.9%. These findings suggest that G. olivacea leaf EO has anti-liver cancer potential.

In vitro and in vivo growth inhibition of human acute promyelocytic leukemia HL-60 cells by Guatteria megalophylla Diels (Annonaceae) leaf essential oil.

Guatteria megalophylla Diels (Annonaceae) is an 8-10 m tall tree that grows near streams and is widely spread throughout Colombian, Ecuadorian, Peruvian, Brazilian and Guianese Amazon rainforest. Herein, we investigated for the first time the chemical composition and in vitro and in vivo anti-leukemia potential of G. megalophylla leaf essential oil (EO) using human promyelocytic leukemia HL-60 cells as model. EO was obtained by a hydrodistillation clevenger-type apparatus and characterized quali- and quantitatively by GC-MS and GC-FID, respectively. In vitro cytotoxic potential of EO was evaluated in human cancer cell lines (HL-60, MCF-7 CAL27, HSC-3, HepG2 and HCT116) and in human non-cancer cell line (MRC-5) by Alamar blue method. Annexin V/propidium iodide staining, cell cycle distribution and reactive oxygen species (ROS) were assessed by flow cytometry for HL-60 cells treated with EO. In vivo efficacy of EO (50 and 100 mg/kg) was evaluated in C.B-17 SCID mice with HL-60 cell xenografts. Chemical composition analyses showed spathulenol, γ-muurolene, bicyclogermacrene, ß-elemene and δ-elemene as main constituents of assayed sample. EO displayed in vitro cytotoxicity, including anti-leukemia effect with IC50 value of 12.51 µg/mL for HL-60 cells. EO treatment caused augment of phosphatidylserine externalization and DNA fragmentation without increasing of ROS in HL-60 cells. In vivo tumor mass inhibition rates of EO was 16.6-48.8 %. These data indicate anti-leukemia potential of G. megalophylla leaf EO.

Guaianolide sesquiterpene lactones and aporphine alkaloids from the stem bark of Guatteria friesiana.

Three guaianolide sesquiterpenes, denoted guatterfriesols A-C, and four aporphine alkaloid derivatives were isolated from the stem bark of the Amazonian plant Guatteria friesiana. Thus far, sesquiterpene lactones have not been described in Annonaceae. Structures of the previously undescribed compounds were established by using 1D and 2D NMR spectroscopy in combination with MS. The absolute stereochemistry was assigned via NOE NMR experiments, ECD spectroscopy, and theoretical calculations using the TDDFT approach. Among the isolated compounds, the alkaloid guatterfriesidine showed anti-glycation activity by inhibiting the formation of advanced glycation end-products (AGEs) through the prevention of oxidation in both BSA/methylglyoxal and BSA/fructose systems.

In vitro Antiproliferative and Antibacterial Activities of Essential Oils from Four Species of Guatteria.

The essential oils (EOs) extracted from four species of the genus Guatteria, G. australis, G. ferruginea, G. latifolia, and G. sellowiana were analyzed. A total of 24, 22, 25, and 19 constituents of the oils from four species, respectively, were identified by GC/MS. These oils showed qualitative and quantitative differences. All the oils contained the oxygenated sesquiterpenes spathulenol (11.04 - 40.29%) and caryophyllene oxide (7.74 - 40.13%) as predominant constituents. Evaluation of antiproliferative activity of the EOs showed strong selectivity (1.1 - 4.1 µg/ml) against the tumor cell line OVCAR-03 (ovarian cancer), i.e., more active than the positive control doxorubicin (11.7 µg/ml). All EOs showed strong antibacterial activity (minimum inhibitory concentrations of 0.062 - 0.25 mg/ml) against strains of Rhodococcus equi.

Leishmanicidal activity of the alkaloid-rich fraction from Guatteria latifolia.

Leishmaniasis is caused by protozoan parasites belonging to the genus Leishmania and includes cutaneous, mucocutaneous and visceral clinical forms. The drugs currently available for leishmaniasis treatment are pentavalent antimonials, amphotericin B and miltefosine, which present high toxicity, elevated cost and development of parasite resistance. The natural products constitute an important source of substances with leishmanicidal potential. Here we evaluated in vitro the anti-Leishmania amazonensis activity of crude extracts of branches, leaves and fruits of Guatteria latifolia. The branch extract (GCE) exhibited promising leishmanicidal activity against promastigotes (IC50 51.7 µg/ml), and was submitted to fractionation guided by in vitro assays. Among the seven subfractions obtained, GF1 and GF2 were the most actives against promastigotes with IC50 25.6 and 16 µg/ml, respectively. Since GCE, GF1 and GF2 were not toxic for macrophages, next, we tested their effect on intracellular amastigotes, and the IC50 values obtained were, respectively 30.5, 10.4 and 7.4 µg/ml, after 24 h treatment. The selectivity index for GCE, GF1 and GF2 were >6.5, >19.2 and > 27, respectively. Additionally, GCE, GF1 and GF2 affected the division pattern of the promastigotes by increasing 6.7, 9.4 and 7-fold the cells in Sub-G0/G1 phase, and decreasing 1.6, 2.5 and 1.8-fold the cells in G0/G1 phase, respectively. To assess the GCE and GFs capacity to modulate microbicidal mechanisms of macrophages, nitric oxide (NO) and TNF-α production were tested. Our results indicated that at the IC50s GCE, GF1 and GF2 decreased NO production of infected macrophages stimulated with IFN-γ and LPS, besides, only GF1 decreased the production of TNF-α. Our data warrant further studies of GCE, GF1 and GF2 to identify active compounds against Leishmania parasites.

7,7-Dimethylaporphine and Other Alkaloids from the Bark of Guatteria friesiana.

Phytochemical investigation of the bark of Guatteria friesiana afforded 12 new aporphines (1-12), along with nine known alkaloids (13-21). The structures of the new alkaloids were determined on the basis of spectroscopic data interpretation. The cytotoxic activity of the isolated compounds against a small panel of tumor cell lines was assessed using the Alamar blue assay.

Antimicrobial photodynamic effect of extracts and oxoaporphine alkaloid isomoschatoline from Guatteria blepharophylla.

Photodynamic Therapy, a tumor therapy idealized at the beginning of the last century, emerges nowadays as a promising treatment alternative against infectious diseases. In this study we report a bioguided study of Guatteria blepharophylla phytoderivatives for antimicrobial PDT. Crude extracts and fraction from the species bark were obtained and further fractionated for substances isolation. All samples were evaluated in relation to their photophysical (absorbance and fluorescence) and photochemical properties (1,3-DPBF bleaching method). Then, bioassays were conducted using as biological models bacteria and yeast strains and a diode laser as a light source. Phytochemical analyses lead to the isolation of 5 isoquinoline alkaloids from oxoaporphine subclass, denominated GB1 to GB5. Photophysical and photochemical analysis showed that extracts, fraction and GB1 (isomoschatoline) presented absorption profile with bands at 600-700nm and were positive for singlet oxygen production. Photobiological assays indicate that these samples presented photodynamic antimicrobial activity against both gram-positive and gram-negative bacterial and some Candida ssp. yeast strains at sub-inhibitory concentrations. The susceptibility of gram-negative bacteria was significantly enhanced when CaCl2 or MgCl2 were employed. Greater energy doses and double sample's dosage also decreased microbial survival. It is suggested that GB1 photodynamic activity happens through both types I and II photochemical mechanisms, but with a predominance of the latter. Phytoderivatives of G. blepharophylla promoted antimicrobial effect, however more detailed study concerning chemical composition of the crude extracts and fractions as also photophysical and photochemical characteristics of GB1 are necessary to ensure their potential as photosensitizers at antimicrobial photodynamic inactivation.

Alkaloids of the Annonaceae: occurrence and a compilation of their biological activities.

This chapter presents an overview of the chemistry and pharmacology of the alkaloids found in species of the Annonaceae family. The occurrence of alkaloids from Annonaceae species, as well as their chemical structures and pharmacological activities are summarized in informative and easy-to-understand tables. Within the Annonaceae family, the genera Annona, Duguetia, and Guatteria have led to many important publications. Valuable and comprehensive information about the structure of these alkaloids is provided. The alkaloids of the aporphine type represent the predominant group in this family. Many of the isolated alkaloids exhibit unique structures. In addition to the chemical structures, the pharmacological activities of some alkaloids are also presented in this chapter. Thus, the leishmanicidal, antimicrobial, antitumor, cytotoxic, and antimalarial activities observed for these alkaloids are highlighted. The chapter is presented as a contribution for the scientific community, mainly to enable the search for alkaloids in species belonging to the Annonaceae family.

Bioactivity and chemical composition of the essential oil from the leaves of Guatteria australis A.St.-Hil.

Essential oil from the leaves of Guatteria australis was obtained by hydrodistillation, analyzed by Gas Chromatography coupled to Mass Spectromery (GC-MS) and their antiproliferative, antileishmanial, antibacterial, antifungal and antioxidant activities were also evaluated. Twenty-three compounds were identified among which germacrene B (50.66%), germacrene D (22.22%) and (E)-caryophyllene (8.99%) were the main compounds. The highest antiproliferative activity was observed against NCI-ADR/RES (TGI = 31.08 µg/ml) and HT-29 (TGI = 32.81 µg/ml) cell lines. It also showed good antileishmanial activity against Leishmania infantum (IC50 = 30.71 µg/ml). On the other hand, the oil exhibited a small effect against Staphylococcus aureus ATCC 6538, S. aureus ATCC 14458 and Escherichia coli ATCC 10799 (MIC = 250 µg/ml), as well as small antioxidant activity (457 µmol TE/g) assessed through ORACFL assay. These results represent the first report regarding chemical composition and bioactivity of G. australis essential oil.

Antitumor effect of the essential oil from leaves of Guatteria pogonopus (Annonaceae).

Guatteria pogonopus Martius, a plant belonging to the Annonaceae family, is found in the remaining Brazilian Atlantic Forest. In this study, the chemical composition and antitumor effects of the essential oil isolated from leaves of G. pogonopus was investigated. The chemical composition of the oil was determined by GC-FID and GC/MS analyses. The in vitro cytotoxicity was evaluated against three different tumor cell lines (OVCAR-8, NCI-H358M, and PC-3M), and the in vivo antitumor activity was tested in mice bearing sarcoma 180 tumor. A total of 29 compounds was identified and quantified in the oil. The major compounds were γ-patchoulene (13.55%), (E)-caryophyllene (11.36%), ß-pinene (10.37%), germacrene D (6.72%), bicyclogermacrene (5.97%), α-pinene (5.33%), and germacrene B (4.69%). The essential oil, but neither (E)-caryophyllene nor ß-pinene, displayed in vitro cytotoxicity against all three tumor cell lines tested. The obtained average IC50 values ranged from 3.8 to 20.8 µg/ml. The lowest and highest values were obtained against the NCI-H358M and the OVCAR-8 cell lines, respectively. The in vivo tumor-growth-inhibition rates in the tumor-bearing mice treated with essential oil (50 and 100 mg/kg/d) were 25.3 and 42.6%, respectively. Hence, the essential oil showed significant in vitro and in vivo antitumor activity.

In vitro and in vivo antitumor effects of the essential oil from the leaves of Guatteria friesiana.

Guatteria friesiana (W. A. Rodrigues) Erkens & Maas (synonym Guatteriopsis friesiana W. A. Rodrigues), popularly known as "envireira", is a medicinal plant found in the Brazilian and Colombian Amazon basin that is used in traditional medicine for various purposes. Recent studies on this species have demonstrated antimicrobial activity. In this study, the antitumor activity of the essential oil from the leaves of G. friesiana (EOGF) and its main components ( α-, ß-, and γ-eudesmol) were determined using experimental models. In the in vitro study, EOGF and its components α-, ß-, and γ-eudesmol displayed cytotoxicity against tumor cell lines, showing IC50 values in the range of 1.7 to 9.4 µg/mL in the HCT-8 and HL-60 cell lines for EOGF, 5.7 to 19.4 µg/mL in the HL-60 and MDA-MB-435 cell lines for α-eudesmol, 24.1 to > 25 µg/mL in the SF-295 and MDA-MB-435 cell lines for ß-eudesmol, and 7.1 to 20.6 µg/mL in the SF-295 and MDA-MB-435 cell lines for γ-eudesmol, respectively. In the in vivo study, the antitumor effect of EOGF was evaluated in mice inoculated with sarcoma 180 tumor cells. Tumor growth inhibition rates were 43.4-54.2 % and 6.6-42.8 % for the EOGF treatment by intraperitoneal (50 and 100 mg/kg/day) and oral (100 and 200 mg/kg/day) administration, respectively. The treatment with EOGF did not significantly affect body mass, macroscopy of the organs, or blood leukocyte counts. Based on these results, we can conclude that EOGF possesses significant antitumor activity and has only low systemic toxicity. These effects could be assigned to its components α-, ß-, and γ-eudesmol.

Identification of oleamide in Guatteria recurvisepala by LC/MS-based Plasmodium falciparum thioredoxin reductase ligand binding method.

Our current research on applications of mass spectrometry to natural product drug discovery against malaria aims to screen plant extracts for new ligands to Plasmodium falciparum thioredoxin reductase (PfTrxR) followed by their identification and structure elucidation. PfTrxR is involved in the antioxidant defense and redox regulation of the parasite and is validated as a promising target for therapeutic intervention against malaria. In the present study, detannified methanol extracts from Guatteria recurvisepala, Licania kallunkiae, and Topobea watsonii were screened for ligands to PfTrxR using ultrafiltration and liquid chromatography/mass spectrometry-based binding experiments. The PfTrxR ligand identified in the extract of Guatteria recurvisepala displayed a relative binding affinity of 3.5-fold when incubated with 1 µM PfTrxR. The ligand corresponding to the protonated molecule m/z 282.2792 [M+ H]+ was eluted at a retention time of 17.95 min in a 20-min gradient of 95% B consisting of (A) 0.1%formic acid in 95% H2O-5% ACN, and (B) 0.1% formic acid in 95% ACN-5% H2O in an LC-QTOF-MS.Tandem MS of the protonated molecule m/z 282.2792 [M + H]+, C18H36NO (DBE: 2; error: 1.13 ppm) resulted in two daughter ions m/z 265.2516[M + H-NH3]+ (DBE: 3; error: 0.35 ppm) and m/z 247.2405 [M + H-NH3-H2O] +, (DBE: 4; error:2.26 ppm). The PfTrxR ligand was identified as oleamide and confirmed by comparison of the retention time, molecular formula, accurate mass,and double bond equivalence with the standard oleamide. This is the first report on the identification of oleamide as a PfTrxR ligand from Guatteria recurvisepala R. E. Fr. and the corresponding in vitro activity against P. falciparum strain K1 (IC50 4.29 µg/mL).

Alkaloids from the bark of Guatteria hispida and their evaluation as antioxidant and antimicrobial agents.

Phytochemical investigation of the bark of Guatteria hispida afforded three new alkaloids, 9-methoxy-O-methylmoschatoline (1), 9-methoxyisomoschatoline (2), and isocerasonine (3), along with 10 known alkaloids, 8-oxopseudopalmatine (4), O-methylmoschatoline (5), lysicamine (6), liriodenine (7), 10-methoxyliriodenine (8), nornuciferine (9), anonaine (10), xylopine (11), coreximine (12), and isocoreximine (13). The major compounds, 2, 6, 12, and 13, showed significant antioxidant capacity in the ORAC(FL) assay. Compounds 5, 6, and 7 were active against S. epidermidis and C. dubliniensis, with MIC values in the range 12.5-100 microg mL(-1).

Minor alkaloids from Guatteria dumetorum with antileishmanial activity.

Nine known alkaloids [(+)-isodomesticine (1), (+)-norisodomesticine (2), (+)-nantenine ( 3), (+)-neolitsine (4), (+)-lirioferine (5), (+)-N-methyllaurotetanine (6), (+)-norlirioferine (7), (+)-isoboldine (8) and (+)-reticuline (9)] were isolated from young leaves of Guatteria dumetorum. Their structures were confirmed by NMR, mass and UV spectral analysis and by comparison to literature data. The growth inhibitory activity of each alkaloid was determined against the parasite Leishmania mexicana. Compounds 1-4 all showed significant activity whereby potency increased when a methylenedioxy functionality was present, especially at the 1,2-positions.

Aporphine alkaloids from Guatteria spp. with leishmanicidal activity.

Fractionation of Guatteria amplifolia yielded the alkaloids xylopine (1), nornuciferine (4), lysicamine (6), and laudanosine (5). Fractionation of Guatteria dumetorum yielded the alkaloids cryptodorine (2) and nornantenine (3). Compounds 1-4 demonstrated significant activity against Leishmania mexicana and L. panamensis. Xylopine (1) was among the most active compounds (LD 50 = 3 microM) and showed a 37-fold higher toxicity towards L. mexicana than macrophages, the regular host cells of Leishmania spp.