Antifungal activity of the termite alkaloid norharmane against the mycelial growth of Metarhizium anisopliae and Aspergillus nomius

Antifungal activity of norharmane, a β-carboline alkaloid found in termites (Isoptera, Rhinotermitidae) was tested against two entomopathogenic fungi, Metarhizium anisopliae and Aspergillus nomius. It was determined that, at physiological concentration (10 μg ml⁻¹), norharmane had no significant effect on A. nomius mycelial growth rate but reduced M. anisopliae growth rate by 11.9%. Contrary to previous findings, we suggest that norharmane has a limited role in disease resistance against fungal pathogens in individual subterranean termites, and we discuss the potential role of this chemical at a colony level.     

Alkaloids from Oriciopsis glaberrima Engl. (Rutaceae)

Two alkaloid derivatives, oriciacridone A and B, were isolated from the stem bark of Oriciopsis glaberrima (Rutaceae). The structures were elucidated by a detailed spectroscopic analysis. The extract exhibited in vitro significant antimicrobial activity against a range of micro-organisms.     

Indolomonoterpenic alkaloids from Strychnos icaja roots

In the course of our search for new antiplasmodial alkaloids from Strychnos icaja, we have isolated five alkaloids: three monomers, protostrychnine and genostrychnine, previously described in Strychnos nux-vomica, pseudostrychnine, already found in the leaves of the plant, a new bisindolic alkaloid, named strychnogucine C, and the first naturally occurring trimeric indolomonoterpenic alkaloid: strychnohexamine. This latter trimeric alkaloid presented an antiplasmodial activity against the FCA Plasmodium falciparum line near 1 microM.     

Dioncophylline E from Dioncophyllum thollonii,the first 7,3'-coupled dioncophyllaceous naphthylisoquinoline alkaloid

The isolation and structural elucidation of dioncophylline E, a novel naphthylisoquinoline alkaloid from the rare West African liana Dioncophyllum thollonii, is described. The alkaloid displays an unusual 7,3'-linkage between the naphthalene and the isoquinoline portions. Due to the resulting medium degree of steric hindrance exerted by the ortho-substituents next to the biaryl axis, the compound undergoes slow rotation about the axis at room temperature and thus is the first such alkaloid that occurs as a mixture of two configurationally semi-stable atropo-diastereomers. Dioncophylline E exhibits good antimalarial activity against both chloroquine-sensitive and -resistant strains of Plasmodium falciparum while its antitrypanosomal activity against Trypanosoma cruzi is weak and that against T. brucei rhodesiense is moderate. Furthermore, four additional naphthylisoquinoline alkaloids previously known from the related plant species Triphyophyllum peltatum, have been identified in D. thollonii.     

Ancistrolikokine D,a 5,8'-coupled naphthylisoquinoline alkaloid,and related natural products from Ancistrocladus likoko

A new naphthylisoquinoline alkaloid, ancistrolikokine D, and the likewise 5,8'-coupled alkaloid ancistroealaine A, as well as two further, biosynthetically related, but nitrogen-free natural products, ancistronaphthoic acid B and cis-isoshinanolone, have been isolated from Ancistrocladus likoko J. LEACUTE;ONARD (Ancistrocladaceae). The 5,8'-coupling of the new alkaloids and of the alkaloids isolated earlier hints at a close phylogenetic relationship of A. likoko to other Central African Ancistrocladus species. The compounds show moderate activities against Leishmania donovani, Trypanosoma cruzi, and Trypanosoma brucei rhodesiense.     

Ancistroheynine B and two further 7,3'-coupled naphthylisoquinoline alkaloids from Ancistrocladus heyneanus Wall

A new axially chiral naphthylisoquinoline alkaloid, ancistroheynine B (7), has been isolated from the leaves of the Indian liana Ancistrocladus heyneanus Wall., along with two known related alkaloids, ancistrocladidine (3) and ancistrotanzanine C (6), which are 7,3'-coupled, too. The structural elucidation was achieved by chemical, spectroscopic, and chiroptical methods. Biological activities of ancistroheynine B against the pathogens of malaria, leishmaniasis, Chagas' disease, and African sleeping sickness were evaluated.     

An unusual quinolinone alkaloid from Waltheria douradinha

The chemical investigation of the methanolic extract of the root bark of Waltheria douradinha (Sterculiaceae) afforded an unusual quinolinone alkaloid named waltherione-A (1). Its structure was determined mainly by NMR spectroscopic methods. The antibacterial activity of waltherione-A (1) and the corresponding O-methylated derivative (2) was tested against three gram-negative and three gram-positive bacteria, with only (2) having moderate activity.     

Phenolic analogs of the N,C-coupled naphthylisoquinoline alkaloid ancistrocladinium A, from Ancistrocladus cochinchinensis (Ancistrocladaceae), with improved antiprotozoal activities

The first N,8′-coupled naphthylisoquinoline alkaloids with free phenolic OH groups, 4′-O-demethylancistrocladinium A and 6,4′-O-didemethylancistrocladinium A, have been isolated from the leaves and bark of the Vietnamese liana Ancistrocladus cochinchinensis, along with its known, non-phenolic parent compound, ancistrocladinium A, and four C,C-coupled representatives. The structure elucidation was achieved by chemical, spectroscopic, and chiroptical methods. The mono-phenolic alkaloid showed excellent activities in particular against the pathogen causing Chagas’ disease, Trypanosoma cruzi.     

Caffeine biosynthesis and adenine metabolism in transgenic Coffea canephora plants with reduced expression of N-methyltransferase genes

In anti-sense and RNA interference transgenic plants of Coffea canephora in which the expression of CaMXMT1 was suppressed, caffeine biosynthesis from [8-(14)C]adenine was investigated, together with the overall metabolism of [8-(14)C]adenine. Compared with wild type control plants, total purine alkaloid biosynthesis from adenine and conversion of theobromine to caffeine were both reduced in the transgenic plants. As found previously, [8-(14)C]adenine was metabolised to salvage products (nucleotides and RNA), to degradation products (ureides and CO(2)) and to purine alkaloids (theobromine and caffeine). In the transgenic plants, metabolism of [8-(14)C]adenine shifted from purine alkaloid synthesis to purine catabolism or salvage for nucleotides. HPLC analysis revealed a significantly reduced caffeine content in the transgenic plants. A small quantity (less than 20 nmol g(-1) fresh weight) of xanthosine had accumulated in at least one of the transgenic plants.     

Testing chemical defence based on pyrrolizidine alkaloids

Pyrrolizidine alkaloids are considered the primary defence mechanism in aposematic ithomiine butterflies and arctiid moths. Despite evidence that pyrrolizidine alkaloids are effective against some invertebrate predators, proof for a protective function of pyrrolizidine alkaloids against vertebrate predators is fragmented. The present work shows that the pyrrolizidine alkaloid monocrot-aline is unpalatable to the pileated finch,Coryphospingus pileatusand that the unpalatability is learned through association with a specific colour pattern (blue stripes). In a series of trials, using mealworms as model prey, birds rejected those to which pyrrolizidine alkaloid solution had been applied topically but accepted prey devoid of the alkaloid. Subsequent offerings of prey with pyrrolizidine alkaloid and a painted blue-striped pattern led to consistent rejections by the experimental birds. Birds were then offered blue-striped painted larvae without pyrrolizidine alkaloids (‘mimics’), which were rejected at levels similar to the previous trial. The predators learned to recognize the prey as unpalatable items based on their experience in the previous encounters. These results provide evidence for the protective capacity of the pyrrolizidine alkaloid against a vertebrate predator and supports the role of these chemicals in aposematism in the Lepidoptera.     

Potential role for saccharopine reductase in swainsonine metabolism in endophytic fungus, Undifilum oxytropis

Locoweed plants in the southwestern United States often harbour a slow-growing endophytic fungus, Undifilum oxytropis (Phylum: Ascomycota; Order: Pleosporales), which produces a toxic alkaloid, swainsonine. Consumption of U. oxytropis by grazing animals induces a neurological disorder called locoism for which the toxic alkaloid swainsonine has been reported to be the causal agent. Little is known about the biosynthetic pathway of swainsonine in endophytic fungi, but previous studies on non-endophytic ascomycetous fungi indicate that pipecolic acid and saccharopine are key intermediates. We have used degenerate primers, Rapid amplification of cDNA ends (RACE)-PCR and inverse PCR to identify the gene sequence of U. oxytropis saccharopine reductase. To investigate the role of this gene product in swainsonine metabolism, we have developed a gene deletion system for this slow-growing endophyte based on our recently established transformation protocol. A strain of U. oxytropis lacking saccharopine reductase had decreased levels of saccharopine and lysine along with increased accumulation of pipecolic acid and swainsonine. Thus, saccharopine reductase influences the accumulation of swainsonine and its precursor, pipecolic acid, in U. oxytropis.     

Intraspecific variability in the alkaloid metabolism of Galanthus elwesii

Alkaloid pattern of individuals from 16 Bulgarian Galanthus elwesii populations was investigated by GC/MS and TLC. Twenty-one Amaryllidaceae alkaloids were detected and 14 of them were identified. Crinane type alkaloids, haemanthamine or crinine, dominated alkaloid metabolism in most of the populations. With exception of one population, where the separate individuals showed variable alkaloid profiles (dominated by crinine or haemanthamine) the individuals of the rest of populations have identical and characteristic alkaloid profiles. Some populations showed remarkable differences in respect to their alkaloid pattern-type of biosynthesis, main alkaloids and number of alkaloids. Populations dominated by galanthamine type alkaloids were found as well. These data demonstrate that like the morphological features, the alkaloid metabolism of G. elwesii is also variable.     

Pathogen resistance of transgenic tobacco plants producing caffeine

Caffeine (1,3,7-trimethylxanthine) is a typical purine alkaloid, and produced by a variety of plants such as coffee and tea. Its physiological function, however, is not completely understood, but chemical defense against pathogens and herbivores, and allelopathic effects against competing plant species have been proposed. Previously, we constructed transgenic tobacco plants, which produced caffeine up to 5 microg per gram fresh weight of leaves, and showed them to repel caterpillars of tobacco cutworms (Spodoptera litura). In the present study, we found that these transgenic plants constitutively expressed defense-related genes encoding pathogenesis-related (PR)-1a and proteinase inhibitor II under non-stressed conditions. We also found that they were highly resistant against pathogens, tobacco mosaic virus and Pseudomonas syringae. Expression of PR-1a and PR-2 was higher in transgenic plants than in wild-type plants during infection. Exogenously applied caffeine to wild-type tobacco leaves exhibited the similar resistant activity. These results suggested that caffeine stimulated endogenous defense system of host plants through directly or indirectly activating gene expression. This assumption is essentially consistent with the idea of chemical defense, in which caffeine may act as one of signaling molecules to activate defense response. It is thus conceivable that the effect of caffeine is bifunctional; direct interference with pest metabolic pathways, and activation of host defense systems.     

Combination chemotherapy of Rauscher leukemia and ascites tumors by narcissus alkaloid with standard drugs and effect on cellular immunity.

The therapeutic activity of the narcissus residual alkaloid A-2 against Rauscher leukemia has been compared with 10 standard anticancer drugs, and synergistic or additive combination pairs have been selected using a viral leukemia and two transplantable tumor systems. An increased beneficial effect has been demonstrated by a combination of the alkylating and DNA-binding agents and the alkaloid against the three malignant tumors, while a beneficial effect by combining the alkaloid and the antimetabolites (either 6-MP or 5-azacytidine) was seen only against the viral leukemia. The alkaloid has no suppressive activity against cellular immunity as tested by PHA reactivity and allogeneic tumor rejection systems.     

Angustilobine and andranginine type indole alkaloids and an uleine-secovallesamine bisindole alkaloid from Alstonia angustiloba

A total of 20 alkaloids were isolated from the leaf and stem-bark extracts of Alstonia angustiloba, of which two are hitherto unknown. One is an alkaloid of the angustilobine type (angustilobine C), while the other is a bisindole alkaloid angustiphylline, derived from the union of uleine and secovallesamine moieties. The structures of these alkaloids were established using NMR and MS analysis. Angustilobine C showed moderate cytotoxicity towards KB cells.     

Extract screening by HPLC coupled to MS-MS,NMR, and CD: a dimeric and three monomeric naphthylisoquinoline alkaloids from Ancistrocladus griffithii

Three new monomeric naphthylisoquinoline alkaloids, ancistrogriffines A, B, and C, and the first dimer of a 7,8'-coupled naphthylisoquinoline, ancistrogriffithine A, have been detected by phytochemical online screening of plant extracts of Ancistrocladus griffithii, using the analytical 'triad' HPLC-MS/MS, HPLC-NMR, and HPLC-CD. Ancistrogriffithine A, as well as ancistrogriffines A and C, were structurally completely assigned (including the absolute configuration) right from the extract, without previous isolation. Furthermore, two related, but known alkaloids, ancistrocladine and hamatine, were identified. Except for ancistrogriffine B, which occurs in trace quantities only, all new alkaloids were then isolated preparatively and the initial assignments were fully confirmed by conventional offline methods. Of particular interest is the constitutionally and configurationally unprecedented structure of ancistrogriffithine A, which is simultaneously the first dimeric naphthylisoquinoline alkaloid from an Asian Ancistrocladus species. Ancistrogriffithine A and ancistrogriffine A are active against Plasmodium falciparum. Furthermore, the latter compound shows good activity against Leishmania donovani. The results demonstrate the ability of modern online methods like HPLC-NMR, -MS/MS, and -CD to serve as powerful tools for the reliable structural elucidation of even complex structures of trace compounds in crude biological matrices.     

Steroidal alkaloid saponins and steroidal saponins from Solanum surattense

A rare 16β-H steroidal alkaloid saponin (1), an avenacoside-type saponin (2), two steroidal saponins (4, 5), one revised-structure steroidal saponin (3) and six known compounds (6-11) were isolated from aerial parts of Solanum surattense Burm. f. Their structures were established on the basis of physical data, as well as by using spectroscopic (HRESIMS, 1D and 2D NMR), and chemical analysis methods. Compounds 1 and 11 showed cytotoxicity against A549 cell line with IC₅₀ values of 20.3 and 15.7 μM, respectively.     

Meroterpenes from Penicillium sp found in association with Melia azedarach

A Penicillium sp was isolated from the root bark of Melia azedarach and cultivated over sterilized rice. After chromatographic procedures, two meroterpenes, named preaustinoid A and B, were obtained in addition to the known alkaloid verruculogen. Their structures were identified by extensive spectroscopic studies, and they exhibited moderate bacteriostatic effects on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus sp.     

Tissue distribution, core biosynthesis and diversification of pyrrolizidine alkaloids of the lycopsamine type in three Boraginaceae species

Three species of the Boraginaceae were studied: greenhouse-grown plants of Heliotropium indicum and Agrobacterium rhizogenes transformed roots cultures (hairy roots) of Cynoglossum officinale and Symphytum officinale. The species-specific pyrrolizidine alkaloid (PA) profiles of the three systems were established by GC-MS. All PAs are genuinely present as N-oxides. In H. indicum the tissue-specific PA distribution revealed the presence of PAs in all tissues with the highest levels in the inflorescences which in a flowering plant may account for more than 70% of total plant alkaloid. The sites of PA biosynthesis vary among species. In H. indicum PAs are synthesized in the shoot but not roots whereas they are only made in shoots for C. officinale and in roots of S. officinale. Classical tracer studies with radioactively labelled precursor amines (e.g., putrescine, spermidine and homospermidine) and various necine bases (trachelanthamidine, supinidine, retronecine, heliotridine) and potential ester alkaloid intermediates (e.g., trachelanthamine, supinine) were performed to evaluate the biosynthetic sequences. It was relevant to perform these comparative studies since the key enzyme of the core pathway, homospermidine synthase, evolved independently in the Boraginaceae and, for instance, in the Asteraceae [Reimann, A., Nurhayati, N., Backenkohler, A., Ober, D., 2004. Repeated evolution of the pyrrolizidine alkaloid-mediated defense system in separate angiosperm lineages. Plant Cell 16, 2772-2784.]. These studies showed that the core pathway for the formation of trachelanthamidine from putrescine and spermidine via homospermidine is common to the pathway in Senecio ssp. (Asteraceae). In both pathways homospermidine is further processed by a beta-hydroxyethylhydrazine sensitive diamine oxidase. Further steps of PA biosynthesis starting with trachelanthamidine as common precursor occur in two successive stages. Firstly, the necine bases are structurally modified and either before or after this modification are converted into their O(9)-esters by esterification with one of the stereoisomers of 2,3-dihydroxy-2-isopropylbutyric acid, the unique necic acid of PAs of the lycopsamine type. Secondly, the necine O(9)-esters may be further diversified by O(7)- and/or O(3')-acylation.     

Neopetrosiamine A,biologically active bis-piperidine alkaloid from the Caribbean sea sponge Neopetrosia proxima

A new tetracyclic bis-piperidine alkaloid, neopetrosiamine A (1), has been extracted from the marine sponge Neopetrosia proxima collected off the west coast of Puerto Rico. The structure of compound 1 was elucidated by analysis of spectroscopic data coupled with careful comparisons of its ¹H and ¹³C NMR data with those of a well-known 3-alkylbis-piperidine alkaloid model. The new alkaloid displayed strong in vitro cytotoxic activity against a panel of cancer cell lines as well as in vitro inhibitory activity against the pathogenic microbes Mycobacterium tuberculosis and Plasmodium falciparum.