Publications

Using a series of standardized sampling plots within forest ecosystems in remote oceanic islands, we reveal fundamental differences between the structuring of aboveground and belowground arthropod biodiversity that are likely due to large-scale species introductions by humans. Species of beetle and spider were sampled almost exclusively from single islands, while soil-dwelling Collembola exhibited more than tenfold higher species sharing among islands. Comparison of Collembola mitochondrial metagenomic data to a database of more than 80 000 Collembola barcode sequences revealed almost 30% of sampled island species are genetically identical, or near identical, to individuals sampled from often very distant geographic regions of the world. Patterns of mtDNA relatedness among Collembola implicate human-mediated species introductions, with minimum estimates for the proportion of introduced species on the sampled islands ranging from 45% to 88%. Our results call for more attention to soil mesofauna to understand the global extent and ecological consequences of species introductions.

In Alzheimer’s disease, the microtubule-associated protein tau forms intracellular neurofibrillary tangles (NFTs). A critical step in the formation of NFTs is the conversion of soluble tau into insoluble filaments. Accordingly, a current therapeutic strategy in clinical trials is aimed at preventing tau aggregation. Here, we assessed altenusin, a bioactive polyphenolic compound, for its potential to inhibit tau aggregation. Altenusin inhibits aggregation of tau protein into paired helical filaments in vitro. This was associated with stabilization of tau dimers and other oligomers into globular structures as revealed by atomic force microscopy. Moreover, altenusin reduced tau phosphorylation in cells expressing pathogenic tau, and prevented neuritic tau pathology induced by incubation of primary neurons with tau fibrils. However, treatment of tau transgenic mice did not improve neuropathology and functional deficits. Taken together, altenusin prevents tau fibrillization in vitro and induced tau pathology in neurons.

A phytochemical study of an extract from transformed root cultures of Nepeta teydea, induced by Agrobacterium rhizogenes, led to the isolation of the following new compounds: the sesquiterpene (-)-cinalbicol, the diterpene teydeadione (6,11,14-trihydroxy-12-methoxy-abieta-5,8,11,13,15-penten-7-one), a degraded C23-triterpene (teydealdehyde) and three fatty acid esters of lanosta-7,24-dien-3β-ol. The propyl ester of rosmarinic acid was also isolated for the first time from a natural source. In addition, two dehydroabietane diterpenes, eight triterpenes and eighteen known phenolic compounds were obtained. The antifeedant, cytotoxic and phytotoxic activities of the isolated compounds have also been investigated.

A highly efficient, diastereoselective, iron(III)‐catalyzed intramolecular hydroamination/cyclization reaction involving α‐substituted amino alkenes is described. Thus, enantiopure trans‐2,5‐disubstituted pyrrolidines and trans‐5‐substituted proline derivatives were synthesized by means of a combination of enantiopure starting materials, easily available from l‐α‐amino acids, with sustainable metal catalysts such as iron(III) salts. The scope of this methodology is highlighted in an enantiodivergent approach to the synthesis of both (+)‐ and (−)‐pyrrolidine 197B alkaloids from l‐glutamic acid. In addition, a computational study was carried out to gain insight into the complete diastereoselectivity of the transformation.

Observations that unequivocally link seismicity and wastewater injection are scarce. Here we show that wastewater injection in eastern Texas causes uplift, detectable in radar interferometric data up to >8 kilometers from the wells. Using measurements of uplift, reported injection data, and a poroelastic model, we computed the crustal strain and pore pressure. We infer that an increase of >1 megapascal in pore pressure in rocks with low compressibility triggers earthquakes, including the 4.8–moment magnitude event that occurred on 17 May 2012, the largest earthquake recorded in eastern Texas. Seismic activity increased even while injection rates declined, owing to diffusion of pore pressure from earlier periods with higher injection rates. Induced seismicity potential is suppressed where tight confining formations prevent pore pressure from propagating into crystalline basement rocks.

Resolving changes in topography through time using accurate high‐resolution digital elevation models (DEMs) is key to understanding active volcanic processes. For the first time in a volcanic environment, we utilize very high‐resolution tri‐stereo optical imagery acquired by the Pleiades‐1 satellite constellation and generate a 1 m resolution DEM of Fogo Volcano, Cape Verde—the most active volcano in the Eastern Atlantic region. Point cloud density is increased by a factor of 6.5 compared to conventional stereo imagery, and the number of 1 m2 pixels with no height measurements is reduced by 43%. We use the DEM to quantify topographic changes associated with the 2014–2015 eruption at Fogo. Height differences between the posteruptive Pleiades‐1 DEM and the preeruptive topography from TanDEM‐X give a lava flow volume of 45.83 ± 0.02 × 106 m3, emplaced over an area of 4.8 km2 at a mean rate of 6.8 m3 s−1.

Over the past twenty-five years, isothermal titration calorimetry (ITC) has become a potent tool for the study a great variety of molecular interactions. This technique is able to provide a complete thermodynamic profile of an interaction process in a single experiment, with a series of advantages in comparison to other comparable techniques, such as less amount of sample or no need of chemical modification or labelling. It is thus not surprising that ITC has been applied to study the manifold types of interactions of natural products to get new insights into the molecular key factors implied in the complexation process of this type of compounds. This review provides an overview over the applications of ITC as a potent tool to investigate interactions of natural products with proteins, nucleic acids, oligosaccharides, and other types of receptors. The examples have been selected depending on the impact that this technique had during the investigation and revision of the interactions involved in the bioactivity of a compound, lead optimization or technical applications.

Investigation of the aerial parts of two Spanish members of the Asteriscus alliance, Asteriscus graveolens subsp. stenophyllus and Asteriscus schultzii, afforded four new sesquiterpene lactones containing a humulene skeleton (1–4) and one new sesquiterpene lactone of the asteriscanolide type (5). Their chemical structures were determined on the basis of the HRMS and from 1D and 2D NMR spectroscopic studies. Both species showed different profiles of sesquiterpenoid constituents. A. schultzii did not show humulene or asteriscane sesquiterpenes, suggesting a resemblance to the genus Pallenis, another member of the Asteriscus alliance. A literature review on chemical isolates from the Asteriscus alliance supported the placement of A. schultzii in the genus Pallenis. The isolated components (1–5) were assessed for cytotoxicity against the HL-60 and MOLT-3 leukemia cell lines, with compound 1 showing activity in both biological assays (IC50 value range 4.1–5.4 μM).

During the last years, we have been involved in the development of a diversity-oriented synthetic strategy aimed at transforming simple, linear, and densely functionalized molecular platforms into collections of topologically diverse scaffolds incorporating biologically relevant structural motifs such as N- and O- heterocycles, multifunctionalized aromatic rings, fused macrocycles, etc. The strategy merges the concepts of pluripotency (the property of an array of chemical functionalities to express different chemical outcomes under different chemical environments) and domino chemistry (chemistry based on processes involving two or more bond-forming transformations that take place while the initial reaction conditions are maintained, with the subsequent reaction resulting as a consequence of the functionality installed in the previous one) to transform common multifunctional substrates into complex and diverse molecular frameworks. This design concept constitutes the ethos of the so-called branching cascade strategy, a branch of diversity-oriented synthesis focused on scaffold diversity generation. Two pluripotent molecular platforms have been extensively studied under this merging (branching) paradigm: C4–O–C3 propargyl vinyl ethers (PVEs) and C7 tertiary skipped diynes (TSDs). These are conveniently constructed from simple and commercially available raw materials (alkyl propiolates, ketones, aldehydes, acid chlorides) through multicomponent manifolds (ABB′ three-component reaction for PVEs; A2BB′ four-component reaction for TSDs) or a simple two-step procedure (for PVEs). Their modular origin facilitates their structural/functional diversification without increasing the number of synthetic steps for their assembly. These two pluripotent molecular platforms accommodate a well-defined and dense array of through-bond/through-space interrelated functionalities on their structures, which defines their primary reactivity principles and establishes the reactivity profile. The PVEs are defined by the presence of an alkyne (alkynoate) function and a conjugated enol moiety and their mutual through-bond/through-space connectivity. This functional array accommodates a number of domino reactions launched either by a Michael addition on the alkynoate moiety (conjugated alkynes) or by a [3,3]-propargyl Claisen rearrangement (conjugated and nonconjugated alkynes). The reactivity profile of the TSDs is defined by the two connected alkynoate moieties (Michael addition) and the bispropargylic ester group ([3,3]-sigmatropic rearrangement). Using these first reactivity principles, each platform selectively delivers one unique and different skeleton (topology) from each domino transformation. Thus, through the use of 11 instrumentally simple and scalable domino reactions, we have transformed these two linear (rod-symmetric) pluripotent molecular platforms into 16 different scaffolds incorporating important structural motifs and multifunctional decorative patterns. The generated scaffolds entail carbocycles, heterocycles, aromatics, β,γ-unsaturated esters and acids, and fused polycycles. They can be transformed into more elaborated molecular skeletons by the use of chemical handles generated in their own domino reactions or by appending different functionalities to the pluripotent molecular platform (secondary reactivity principles).

Eighteen new oxysterols have been isolated from a previously undescribed octocoral collected from the eastern Pacific of Panama. Their structures were determined based on spectroscopic evidence. The absolute configuration was established by derivatization with (R)- and (S)-MPA. Antimicrobial and antileishmanial effects were evaluated.