Hygroline derivatives from Schizanthus tricolor and their anti-trypanosomatid and antiplasmodial activities.

Chemical investigation of the alkaloid extract of the aerial parts of Schizanthus tricolor led to the targeted isolation of 26 hygroline derivatives of which 20 were fully characterized. They have not yet been described in the literature and their structures were established by 1D and 2D NMR, UV and IR spectroscopy, and HRESIMS. The configuration was determined by Gauge-Independent Atomic Orbital NMR chemical shift calculations supported by the advanced statistical method DP4 plus, vibrational circular dichroism, and measurement of optical rotation. Their anti-trypanosomatid, antiplasmodial and cytotoxic activities were measured. Several compounds exhibited low micromolar activity against Plasmodium falciparum. None of the identified molecules was cytotoxic.

Phytochemistry and biological properties of Drimys winteri JR et G. Forster var chilensis (DC) A / Fitoquímica y propiedades biológicas de Drimys winteri JR et G. Forster var chilensis (DC) A

Drimys winteri JR et G. Forster var chilensis (DC) A. is a tree native to central and southern Chile. Also it found in part of Argentina. It is abundant in wet swampy localities from sea level to an altitude of 1700 m. This tree is sacred for the Mapuche culture; it is used in folk medicine in such as inflammatory and painful processes. Phytochemical studies have demonstrated that this plant contains mainly sesquiterpenes of the drimane type, flavonoids, essential oils, phytosterols and some lignans. These drimanes have attracted interest because of their antifeedant, plant growth regulation, cytotoxic, antimicrobial and insecticidal properties. The objective of this review is to establish clearly the phytochemistry and biological activity of Drimys winteri JR et G. Forster var chilensis (DC) A. Articles based on other varieties are not considered.

Drimys winteri JR et G. Forster var chilensis (DC) A. es un árbol nativo del centro y sur de Chile. También se encuentra en parte de Argentina. Es abundante en localidades pantanosas y húmedas desde el nivel del mar hasta una altitud de 1700 m. Este árbol es sagrado para la cultura mapuche. Se utiliza en la medicina popular para tratar enfermedades como procesos inflamatorios y dolorosos. Los estudios fitoquímicos han demostrado que esta planta contiene principalmente sesquiterpenos del tipo drimano, flavonoides, aceites esenciales, fitoesteroles y algunos lignanos. Estos drimanos han despertado interés debido a sus propiedades antialimentarias, regulación del crecimiento de las plantas, propiedades citotóxicas, antimicrobianas e insecticidas. El objetivo de este examen es establecer claramente la fitoquímica y la actividad biológica de Drimys winteri JR et G. Forster var chilensis (DC) A. No se consideran los artículos basados en otras variedades D. winteri var winteri.

The Origins of Coca: Museum Genomics Reveals Multiple Independent Domestications from Progenitor Erythroxylum gracilipes.

Coca is the natural source of cocaine as well as a sacred and medicinal plant farmed by South American Amerindians and mestizos. The coca crop comprises four closely related varieties classified into two species (Amazonian and Huánuco varieties within Erythroxylum coca Lam., and Colombian and Trujillo varieties within Erythroxylum novogranatense (D. Morris) Hieron.) but our understanding of the domestication and evolutionary history of these taxa is nominal. In this study, we use genomic data from natural history collections to estimate the geographic origins and genetic diversity of this economically and culturally important crop in the context of its wild relatives. Our phylogeographic analyses clearly demonstrate the four varieties of coca comprise two or three exclusive groups nested within the diverse lineages of the widespread, wild species Erythroxylum gracilipes; establishing a new and robust hypothesis of domestication wherein coca originated two or three times from this wild progenitor. The Colombian and Trujillo coca varieties are descended from a single, ancient domestication event in northwestern South America. Huánuco coca was domesticated more recently, possibly in southeastern Peru. Amazonian coca either shares a common domesticated ancestor with Huánuco coca, or it was the product of a third and most recent independent domestication event in the western Amazon basin. This chronology of coca domestication reveals different Holocene peoples in South America were able to independently transform the same natural resource to serve their needs; in this case, a workaday stimulant. [Erythroxylum; Erythroxylaceae; Holocene; Museomics; Neotropics; phylogeography; plant domestication; target-sequence capture.].

Erythroxylum in Focus: An Interdisciplinary Review of an Overlooked Genus.

The genus Erythroxylum contains species used by indigenous people of South America long before the domestication of plants. Two species, E. coca and E. novogranatense, have been utilized for thousands of years specifically for their tropane alkaloid content. While abuse of the narcotic cocaine has impacted society on many levels, these species and their wild relatives contain untapped resources for the benefit of mankind in the form of foods, pharmaceuticals, phytotherapeutic products, and other high-value plant-derived metabolites. In this review, we describe the current state of knowledge of members within the genus and the recent advances in the realm of molecular biology and biochemistry.

Stable-bond polymeric reversed-phase/weak anion-exchange mixed-mode stationary phases obtained by simultaneous functionalization and crosslinking of a poly(3-mercaptopropyl)methylsiloxane-film on vinyl silica via thiol-ene double click reaction.

A polymeric reversed-phase/weak anion exchange (Poly-RP/WAX) mixed-mode stationary phase has been prepared by coating of a poly(3-mercaptopropyl)methylsiloxane film on vinyl-modified silica (100 Å, 5 µm) and simultaneous in situ functionalization with N-(10-undecenoyl)-3-aminoquinuclidine as well as crosslinking to the vinyl silica surface by solventless thiol-ene double click reaction. Such bonding chemistry showed greatly enhanced stability compared to brush-type analogs with bifunctional siloxane bonding to silica. Solid-state 29Si-CP/MAS NMR confirmed the immobilization of the siloxane layer. pH-Dependent ζ-potential determinations revealed a high anion-exchange capacity over the entire pH range with a maximum around pH 5. Oxidation of residual thiols yielded a zwitterionic Poly-RP/WAX/SCX mixed-mode phase with sulfonic acid endcapping and shifted the still net positive surface charge to lower ζ-potentials. It allowed a faster elution of strongly retained anionic species in particular of multiply negatively charged analytes such as oligonucleotides. Chromatographic tests under RPLC and HILIC elution mode with various test substances documented the multimodal utility and complementarity in retention profiles compared to RP, HILIC and commercial mixed-mode phases.

N-Propyl-N'-2-pyridylurea-modified silica as mixed-mode stationary phase with moderate weak anion exchange capacity and pH-dependent surface charge reversal.

Herein, we present a novel silica-based stationary phase modified with N-propyl-N'-2-pyridylurea selector. Due to the weakly basic properties of the pyridine selector and the presence of residual silanols after selector immobilization, a zwitterionic surface with a pI observed at approximately pH 5.5 was measured by electrophoretic light scattering in pH-dependent ζ-potential determinations. The capability of the new N-propyl-N'-2-pyridylurea-modified silica to serve as mixed-mode stationary phase was investigated. For this purpose, it was characterized under RP and HILIC conditions using test mixtures. Subsequent classification of this stationary phase in comparison to in-house and commercial benchmarks was carried by principal component analysis of resultant retention factors from chromatographic tests. The results show a relatively unique mixed-mode character amongst the tested stationary phases. The chromatographic retention characteristics of acidic compounds matched well the ζ-potential determinations. The application of anion-exchange at low pH values (e.g. pH 5) and ion exclusion chromatography at pH 7 for the separation of uridine 5'-mono-, di- and triphosphate demonstrated a pH-dependent umpolung of the stationary phase surface. The combination of these separation principles in a pH gradient from 5 to 7 gave rise to weak anion-exchange selectivity with a charge-inducted elution due to repulsive interactions at higher pH and resulted in a significant faster separation with improved peak shape under mild elution conditions.

Surface-anchored counterions on weak chiral anion-exchangers accelerate separations and improve their compatibility for mass-spectrometry-hyphenation.

In the present work we propose new variants of chiral stationary phases (CSP) with tert-butylcarbamoylquinine (tBuCQN) as chiral selector molecule. Four tBuCQN-CSPs with distinct bonding chemistries are compared in terms of their pH-dependent surface charge by ζ-potential determinations, by achiral and chiral liquid chromatographic tests and LC-ESI-MS hyphenation. In one embodiment tBuCQN was immobilized on 3-mercaptopropylmethylsilyl-modified silica by thiol-ene click reaction (brush type CSP with selector coverage of 0.38mmol/g). In another embodiment, poly-(3-mercaptopropyl)-methylsiloxane was coated onto vinylized silica particles in presence of tBuCQN and radical initiator. The tBuCQN selector was then immobilized onto the polysiloxane film which in turn was crosslinked to the vinyl-surface in a simultaneous double click reaction leading to a CSP with enhanced stability due to multiple linkages (0.29mmol/g tBuCQN). Aliquots of each of the two CSPs were further modified by oxidation of free residual thiol groups to sulfonic acid functionalities to obtain strongly acidic endcapping groups which act as immobilized counterions of the chiral WAX CSPs (0.2mmol/g sulfonic acid co-ligands for brush type CSP). This caused secondary repulsive interactions, hence balanced interactions of the target analytes (chiral acids) at the WAX site and decreased non-specific interactions. Furthermore, this rendered possible the use of milder elution conditions, i.e. lower ionic strength, for acidic compounds. Separation performance was maintained and slightly improved, respectively, when using polar organic or reversed-phase type elution mode in chiral separations which were significantly accelerated (isoeluotropic conditions could be achieved with ca. factor 40 lower counterion concentration in the mobile phase). Thus, LC-ESI-MS enantiomer separations could be readily performed at very low ionic strength conditions (10mM acetate) which is favorable due to less ion suppression. In addition to this the newly developed stationary phases showed complementary retention profiles in RP- and HILIC-mode which make these type of stationary phases also promising tools for achiral applications in pharmaceutical analysis, especially as orthogonal separation principle e.g. in 2D-LC and impurity profiling.

Two New Hygroline and Tropane Alkaloids Isolated from Schizanthus hookeri and S. tricolor (Solanaceae).

Two new hygroline and tropane alkaloids, 4-hydroxybenzenepropanoylhygroline (1) and 3α,4ß-dihydroxy-6ß-angeloyoxytropane (2) have been isolated from the aerial parts of Schizanthus hookeri and S. tricolor, respectively, two plants indigenous from Chile. Their structures were elucidated by spectroscopic methods and high resolution mass spectrometry. Their antiparasitic activity and cytotoxicity were measured.

Surface charge fine tuning of reversed-phase/weak anion-exchange type mixed-mode stationary phases for milder elution conditions.

A series of new mixed-mode reversed-phase/weak anion-exchange (RP/WAX) phases have been synthesized by immobilization of N-undecenyl-3-α-aminotropane onto thiol-modified silica gel by thiol-ene click chemistry and subsequent introduction of acidic thiol-endcapping functionalities of different type and surface densities. Click chemistry allowed to adjust a controlled surface concentration of the RP/WAX ligand in such a way that a sufficient quantity of residual thiols remained unmodified which have been capped by thiol click with either 3-butenoic acid or allylsulfonic acid as co-ligands. In another embodiment, performic acid oxidation of N-undecenyl-3-α-aminotropane-derivatized thiol-modified silica gave a RP/WAX phase with high density of sulfonic acid end-capping groups. ζ-Potential determinations confirmed the fine-tuned pI of these mixed-mode stationary phases which was shifted from 9.5 to 8.2, 7.8, and 6.5 with 3-butenoic acid and allylsulfonic acid end-capping as well as performic acid oxidation. For acidic solutes, the co-ionic endcapping leads to strongly reduced retention times and clearly allowed elution of these analytes under lower ionic strength thus milder elution conditions. In spite of the acidic endcapping, the new mixed-mode phases maintained their hydrophobic and anion-exchange selectivity as well as their multimodal nature featuring RP and HILIC elution domains at acetonitrile percentages below and above 50%, respectively. Column classification by principal component analysis of an extended retention map in comparison to a set of polar commercial and in-house synthesized stationary phases confirmed complementarity of the new mixed-mode phases with respect to HILIC, polar RP, amino and commercial mixed-mode phases.

Direct observation of nanometer-scale pores of melittin in supported lipid monolayers.

Melittin is the most studied membrane-active peptide and archetype within a large and diverse group of pore formers. However, the molecular characteristics of melittin pores remain largely unknown. Herein, we show by atomic force microscopy (AFM) that lipid monolayers in the presence of melittin are decorated with numerous regularly shaped circular pores that can be distinguished from nonspecific monolayer defects. The specificity of these pores is reinforced through a statistical evaluation of depressions found in Langmuir-Blodgett monolayers in the presence and absence of melittin, which eventually allows characterization of the melittin-induced pores at a quantitative low-resolution level. We observed that the large majority of pores exhibit near-circular symmetry and a Gaussian distribution in size, with a mean diameter of ∼8.7 nm. A distinctive feature is a ring of material found around the pores, made by, on average, three positive peaks, with a height over the level of the lipidic background of ∼0.23 nm. This protruding rim is most likely due to the presence of melittin near the pore border. Although the current resolution of the AFM images in the {x, y} plane does not allow distinction of the specific organization of the peptide molecules, these results provide an unprecedented view of melittin pores formed in lipidic interfaces and open new perspectives for future structural investigations of these and other pore-forming peptides and proteins using supported monolayers.

Medicinal plants of Chile: evaluation of their anti-Trypanosoma cruzi activity.

The extracts of several plants of Central Chile exhibited anti-Trypanosoma cruzi trypomastigotes activity. Most active extracts were those obtained from Podanthus ovatifolius, Berberis microphylla, Kageneckia oblonga, and Drimys winteri. The active extract of Drimys winteri (IC50 51.2 microg/mL) was purified and three drimane sesquiterpenes were obtained: polygodial, drimenol, and isodrimenin. Isodrimenin and drimenol were found to be active against the trypomastigote form of T. cruzi with IC50 values of 27.9 and 25.1 microM, respectively.

Inhibition of cholinergic contractions of rat ileum by tkopane-type alkaloids present in Schizanthus hookeri.

The relative lack of specificity of atropine as a competitive antagonist of muscarinic receptors is a frequent cause of undesirable parasympathetic side effects. Consequently, new tropane alkaloids with potentially greater selectivity are usually seen with real interest. The cholinergic antagonistic effects of a purified mixture of tropane alkaloids extracted from Schizanthus hookeri were evaluated in rat ileum. For this purpose, ileal segments were obtained from randomly selected male Sprague-Dawley rats, and the effect of 1 x 10(-4), 1 x 10(-3), and 1 x 10(-2) mg/mL of the purified mixture of alkaloids on the contractile response of the ileum induced with increasing doses of carbachol (5 x 10(-8) - 10(-4) M) was determined. The results were compared with those obtained in the presence of 3.46 x 10(-7), 3.46 x 10(-6), and 3.46 x 10(-5) mg/mL atropine as an agonist. Tropane alkaloids extracted from Schizanthus hookeri competitively antagonized acetylcholine muscarinic receptors.

Canonical azimuthal rotations and flanking residues constrain the orientation of transmembrane helices.

In biological membranes the alignment of embedded proteins provides crucial structural information. The transmembrane (TM) parts have well-defined secondary structures, in most cases α-helices and their orientation is given by a tilt angle and an azimuthal rotation angle around the main axis. The tilt angle is readily visualized and has been found to be functionally relevant. However, there exist no general concepts on the corresponding azimuthal rotation. Here, we show that TM helices prefer discrete rotation angles. They arise from a combination of intrinsic properties of the helix geometry plus the influence of the position and type of flanking residues at both ends of the hydrophobic core. The helical geometry gives rise to canonical azimuthal angles for which the side chains of residues from the two ends of the TM helix tend to have maximum or minimum immersion within the membrane. This affects the preferential position of residues that fall near hydrophobic/polar interfaces of the membrane, depending on their hydrophobicity and capacity to form specific anchoring interactions. On this basis, we can explain the orientation and dynamics of TM helices and make accurate predictions, which correspond well to the experimental values of several model peptides (including dimers), and TM segments of polytopic membrane proteins.

Grahamines A-E, cyclobutane-centered tropane alkaloids from the aerial parts of Schizanthus grahamii.

Schizanthus grahamii is an endemic Chilean plant that is known to contain tropane alkaloids. Five new alkaloids, grahamines A-E (1-5), were isolated and characterized by extensive spectroscopic analysis. Their structures were determined to be 2-{[(3α-hydroxytropo-6ß-yl)oxy]carbonyl}-2-methyl-3-{[((6ß-angeloyloxy)-3α-yl)oxy]carbonyl}-4-phenylcyclobutanecarboxylic acid (1), 2-{[(3α-hydroxytropo-6ß-yl)oxy]carbonyl}-2-methyl-3-{[((6ß-tigloyloxy)-3α-yl)oxy]carbonyl}-4-phenylcyclobutanecarboxylic acid (2), 1-methyl-2-{[(3α-hydroxytropo-6ß-yl)oxy]carbonyl}-4-{[((6ß-angeloyloxy)-3α-yl)oxy]carbonyl}-3-phenylcyclobutanecarboxylic acid (3), 1,2-bis{[(3α-hydroxytropo-6ß-yl)oxy]carbonyl}-2-methyl-3-{[((6ß-angeloyloxy)-3α-yl)oxy]carbonyl}-4-phenylcyclobutanecarboxylate (4), and 1-{[(3α-mesaconyloxytropo-6ß-yl)oxy]carbonyl}-2-{[(3α-hydroxytropo-6ß-yl)oxy]carbonyl}-2-methyl-3-{[((6ß-angeloyloxy)-3α-yl)oxy]carbonyl}-4-phenylcyclobutanecarboxylate (5).

Comparison of the essential oils of leaves and stem bark from two different populations of Drimys winteri a Chilean herbal medicine.

The chemical composition of the essential oils obtained by hydrodistillation of stem bark and leaves of Drimys winteri J.R. et G. Foster var. chilensis /DC A. Gray (Winteraceae) from Chiloe Island (ID) and Continental Chile (Santiago) (CD) were studied by GC and GC/MS. Sesquiterpene hydrocarbons constituted the main chemical groups in the stem bark oils, with alpha-santalene, trans-beta-bergamotene and curcumenes as the major components. Monoterpenes constituted the main chemical groups in the leaves of Island plants with alpha-pinene (23.1%) beta-pinene (43.6%) and linalool (10.5%) as the main components whereas sesquiterpenes (germacrene D 17.6%) and phenylpropanoids (safrole 20.8%) are the most abundant in the leaves of Continental plants.

Chirality and numbering of substituted tropane alkaloids.

The strict application of IUPAC rules for the numbering of tropane alkaloids is not always applied by authors and there is hence a lot of confusion in the literature. In most cases, the notation of 3, 6/7-disubstituted derivatives has been chosen arbitrarily, based on NMR and MS data, without taking into account the absolute configuration of these two carbons. This paper discusses the problem and the relevance of CD and NMR to determine molecular configurations. We report on the use of (1)H-NMR anisochrony (Δδ) induced by the Mosher's chiral auxiliary reagents (R)-(-)- and (S)-(+)-α-methoxy-α-trifluoromethyl-phenylacetyl chlorides (MTPA-Cl), to determine the absolute configuration of (3R,6R)-3α-hydroxy-6ß-senecioyloxytropane, a disubstituted tropane alkaloid isolated from the aerial parts of Schizanthus grahamii (Solanaceae). These analytical tools should help future works in correctly assigning the configuration of additional 3, 6/7 disubstituted tropane derivatives.

Chemical study and anti-inflammatory, analgesic and antioxidant activities of the leaves of Aristotelia chilensis (Mol.) Stuntz, Elaeocarpaceae.

OBJECTIVES: Aristotelia chilensis leaves (Elaeocarpaceae) are used in Chilean folk medicine to treat pain and inflammation. A bioguided study was carried out on serial extracts (hexane, dichloromethane, methanol, aqueous extract (INFU) and a crude mixture of alkaloids (ALK-MIX). All extracts were evaluated for (1) topical administration against both arachidonic acid and 12-deoxyphorbol-13-decanoate (TPA)-induced inflammation in mice and (2) per-os administration against inflammation by λ-carrageenan-induced paw oedema in guinea-pigs and (3) topical analgesia in tail flick and formalin models and per-os writhing test in mice. METHODS: Greater anti-inflammatory effects were obtained against TPA with dichloromethane extract and methanol extract (63.9 and 66.0%, respectively). INFU showed the most potent effect (56.2%) against arachidonic acid. Greater effects were obtained in the writhing test with hexane and dichloromethane extracts (89.2% both). In the topical analgesia models, all the extracts and ALK-MIX were active with exception of the hexane extract in the formalin assay. In tail flick test, ALK-MIX and the methanol extract were the most active (58.2 and 55.2%, respectively). In relation to the tail formalin assay, the methanol extract (74.1%) was the most active. Concerning antioxidant activity, both INFU and the methanol extract were the most active either in the inhibition of xanthine oxidase (52.9 and 62.7%, respectively) or in the DPPH free radical scavenging activity (EC50 (concentration that produced 50% of activity) = 12.1 and 9.7 µg/ml, respectively). KEY FINDINGS: Aristoteline, aristone, serratoline and hobartinol were isolated from ALK-MIX. Ursolic acid, friedelin and quercetin 5,3'-dimethyl ether were present in the dichloromethane extract while quercetin 3-O-ß-D-glucoside and kaempferol were present in the methanol extract. From INFU were isolated protopine, aristoteline and caffeic and ferulic acids. CONCLUSIONS: The effects of A. chilensis are herein demonstrated, validating its use in traditional medicine. Protopine is reported for the first time in Elaeocarpaceae.

A lipocentric view of peptide-induced pores.

Although lipid membranes serve as effective sealing barriers for the passage of most polar solutes, nonmediated leakage is not completely improbable. A high activation energy normally keeps unassisted bilayer permeation at a very low frequency, but lipids are able to self-organize as pores even in peptide-free and protein-free membranes. The probability of leakage phenomena increases under conditions such as phase coexistence, external stress or perturbation associated to binding of nonlipidic molecules. Here, we argue that pore formation can be viewed as an intrinsic property of lipid bilayers, with strong similarities in the structure and mechanism between pores formed with participation of peptides, lipidic pores induced by different types of stress, and spontaneous transient bilayer defects driven by thermal fluctuations. Within such a lipocentric framework, amphipathic peptides are best described as pore-inducing rather than pore-forming elements. Active peptides bound to membranes can be understood as a source of internal surface tension which facilitates pore formation by diminishing the high activation energy barrier. This first or immediate action of the peptide has some resemblance to catalysis. However, the presence of membrane-active peptides has the additional effect of displacing the equilibrium towards the pore-open state, which is then maintained over long times, and reducing the size of initial individual pores. Thus, pore-inducing peptides, regardless of their sequence and oligomeric organization, can be assigned a double role of increasing the probability of pore formation in membranes to high levels as well as stabilizing these pores after they appear.

Switchable bactericidal effects from novel silica-coated silver nanoparticles mediated by light irradiation.

Here we report on the triggering of antibacterial activity by a new type of silver nanoparticle coated with porous silica, Ag@silica, irradiated at their surface plasmon resonant frequency. The nanoparticles are able to bind readily to the surface of bacterial cells, although this does not affect bacterial growth since the silica shell largely attenuates the intrinsic toxicity of silver. However, upon simultaneous exposure to light corresponding to the absorption band of the nanoparticles, bacterial death is enhanced selectively on the irradiated zone. Because of the low power density used for the treatments, we discard thermal effects as the cause of cell killing. Instead, we propose that the increase in toxicity is due to the enhanced electromagnetic field in the proximity of the nanoparticles, which indirectly, most likely through induced photochemical reactions, is able to cause cell death.

Schizanthines N, O, and P, tropane alkaloids from the aerial parts of Schizanthus tricolor.

Three tropane alkaloids, named schizanthines N, O, and P (1-3), have been isolated from the crude alkaloid extract of the endemic Chilean plant Schizanthus tricolor. On the basis of extensive NMR studies and MS fragmentation analysis, their structures were determined to be 3α-(E)-4-hydroxysenecioyloxy-6ß-angeloyloxytropane (1), 3α-(E)-4-hydroxysenecioyloxy-6ß-senecioyloxytropane (2), and 3α-mesaconyloxy-6ß-senecioyloxytropane (3). Compounds 1 and 2 are the first isomeric alkaloids in the tropane series possessing a hydroxysenecioyl substituent as an esterifying moiety.