Evaluation of in vivo solid phase microextraction for minimally invasive analysis of nonvolatile phytochemicals in Amazonian plants

Introduction

Although solid phase microextraction (SPME) has been used extensively for fingerprinting volatile compounds emitted by plants, there are very few such reports for direct insertion SPME. In this research, direct contact of SPME probes with the interstitial fluid of plants was investigated as a method for phytochemical analysis.

Objective

Medicinal plants from the Amazon have been the source of numerous drugs used in western medicine. However, a large number of species used in traditional medicine have not been characterized chemically, partly due to the difficulty of field work. In this project, the phytochemical composition of plants from several genera was fingerprinted by combining convenient field sampling by solid phase microextraction (SPME) with laboratory analysis by LC-MS. The new method was compared with classical sampling followed by liquid extraction (LE).

Methodology

SPME probes were prepared by coating stainless steel wires with a mixture of polyacrylonitrile and either RP-amide or HS-F5 silica particles. Sampling was performed by inserting the microextraction probes into various tissues of living plants in their natural environment. After in vivo extraction, the probes were sealed under vacuum and refrigerated until analyzed. The probes were desorbed in mobile phase and analyzed on a Waters Acquity UPLC with triple quadrupole mass spectrometer in positive ion mode.

Results

Twenty Amazonian plant species were sampled and unique metabolomic fingerprints were obtained. In addition, quantitative analysis was performed for previously identified compounds in three species. Comparison of the fingerprints obtained by in vivo SPME with those obtained by LE showed that 27% of the chromatographic features were unique to SPME, 57% were unique to LE, and 16% were common to both methods.

Conclusion

In vivo SPME caused minimal damage to the plants, was much faster than traditional liquid extraction, and provided unique fingerprints for all investigated plants. SPME revealed unique chromatographic features, undetected by traditional extraction, although it produced only half as many peaks as ethanol extraction.     

Z-Join Spectra of Z-Supercompactly Generated Lattices

The main result of this paper is a generalization of the classical equivalence between the category of continuous posets and the category of completely distributive lattices, based on the fact that the continuous posets are precisely the spectra of completely distributive lattices. Here we show that for so-called hereditary and union complete subset selections Z, the category of Z-continuous posets is equivalent (via a suitable spectrum functor) to the category of Z-supercompactly generated lattices; these are completely distributive lattices with a join-dense subset of certain Z-hypercompact elements. By appropriate change of the morphisms, these equivalences turn into dualities. We present two different approaches: the first one directly uses the Z-join ideal completion and the Z-below relation; the other combines two known equivalence theorems, namely a topological representation of Z-continuous posets and a general lattice theoretical representation of closure spaces.     

Metabolic Profiling of Inga Species with Antitumor Activity

This work evaluated the metabolic profiling of Inga species with antitumor potential. In addition, we described the antigenotoxicity of polyphenols isolated from I. laurina and a proteomic approach using HepG2 cells after treatment with these metabolites. The in vitro cytotoxic activity against HepG2, HT-29 and T98G cancer cell lines was investigated. The assessment of genotoxic damage was carried out through the comet assay. The ethanolic extract from I. laurina seeds was subjected to bioassay-guided fractionation and the most active fractions were characterized. One bioactive fraction with high cytotoxicity against HT-29 human colon cancer cells (IC₅₀ = 4.0 µg mL⁻¹) was found, and it was characterized as a mixture of p-hydroxybenzoic acid and 4-vinyl-phenol. The I. edulis fruit peel (IC₅₀ = 18.6 µg mL⁻¹) and I. laurina seed (IC₅₀ = 15.2 µg mL⁻¹) extracts had cytotoxic activity against the cell line T98G, and its chemical composition showed a variety of phenolic acids. The chemical composition of this species indicated a wide variety of aromatic acids, flavonoids, tannins, and carotenoids. The high concentration (ranging from 5% to 30%) of these polyphenols in the bioactive extract may be responsible for the antitumor potential. Regarding the proteomic approach, we detected proteins directly related to the elimination of ROS, DNA repair, expression of tumor proteins, and apoptosis.     

Isolation, structure elucidation and biological activity of hederacine A and B, two unique alkaloids from Glechoma hederaceae

Preparative HPLC purification of a methanol extract of the aerial parts of Glechoma hederaceae has yielded two unique alkaloids, hederacine A (1) and hederacine B (2). The structures of these compounds were established unequivocally by UV, IR, MS and a series of 1D and 2D NMR analyses. These alkaloids were inactive against any of the 11 bacterial species at test concentrations, but showed prominent toxicity in the brine shrimp lethality assay (LC₅₀s=3.2, 14.0 and 2.7 μg/mL, respectively, for 1, 2 and the positive control, podophyllotoxin).     

Template-Assembled Synthetic Proteins (TASP). Cyclic Templates with Incorporated Turn-Inducing Mimics

The 8-amino-5,6,7,8-tetrahydronaphth-2-oic acid ( 1 ), 8-(aminomethyl)-5,6,7,8-tetrahydronaphth-2-oic acid ( 2 ), and 8-(aminomethyl)naphth-2-oic acid ( 3 ) were synthesized in their protected forms as turn-inducing dipeptide mimics. Two of them ( 2 and 3 ) were incorporated into a novel type of cyclic, peptide-based structures (see 21 and 34 – 36 ) designed as templates for the synthesis of TASP molecules.     

How Many Phosphoric Acid Units Are Required to Ensure Uniform Occlusion of Sterically Stabilized Nanoparticles within Calcite?

Polymerization‐induced self‐assembly (PISA) mediated by reversible addition–fragmentation chain transfer (RAFT) polymerization offers a platform technology for the efficient and versatile synthesis of well‐defined sterically stabilized block copolymer nanoparticles. Herein we synthesize a series of such nanoparticles with tunable anionic charge density within the stabilizer chains, which are prepared via statistical copolymerization of anionic 2‐(phosphonooxy)ethyl methacrylate (P) with non‐ionic glycerol monomethacrylate (G). Systematic variation of the P/G molar ratio enables elucidation of the minimum number of phosphate groups per copolymer chain required to promote nanoparticle occlusion within a model inorganic crystal (calcite). Moreover, the extent of nanoparticle occlusion correlates strongly with the phosphate content of the steric stabilizer chains. This study is the first to examine the effect of systemically varying the anionic charge density of nanoparticles on their occlusion efficiency and sheds new light on maximizing the loading of guest nanoparticles within calcite host crystals.     

A review of recent methods for the determination of ranges of feasible solutions resulting from soft modelling analyses of multivariate data

Soft modelling or multivariate curve resolution (MCR) are well-known methodologies for the analysis of multivariate data in many different application fields. Results obtained by soft modelling methods are very likely impaired by rotational and scaling ambiguities, i.e. a full range of feasible solutions can describe the data equally well while fulfilling the constraints of the system. These issues are severely limiting the applicability of these methods and therefore, they can be considered as the most challenging ones. The purpose of the current review is to describe and critically compare the available methods that attempt at determining the range of ambiguity for the case of 3-component systems. Theoretical and practical aspects are discussed, based on a collection of simulated examples containing noise-free and noisy data sets as well as an experimental example.     

C−H Activation Enables a Concise Total Synthesis of Quinine and Analogues with Enhanced Antimalarial Activity

We report a novel approach to the classical natural product quinine that is based on two stereoselective key steps, namely a C?H activation and an aldol reaction, to unite the two heterocyclic moieties of the target molecule. This straightforward and flexible strategy enables a concise synthesis of natural (?)‐quinine, the first synthesis of unnatural (+)‐quinine, and also provides access to unprecedented C3‐aryl analogues, which were prepared in only six steps. We additionally demonstrate that these structural analogues exhibit improved antimalarial activity compared with (?)‐quinine both in vitro and in mice infected with Plasmodium berghei.