Eva Alonso

Marine natural products have exhibited uncommon chemical structures with relevant antitumor properties highlighting their potential to inspire the development of new anticancer agents. The goal of this work was to study the antitumor activities of the brominated diterpene sphaerodactylomelol, a rare example of the dactylomelane family. Cytotoxicity (10–100 µM; 24 h) was evaluated on tumor cells (A549, CACO-2, HCT-15, MCF-7, NCI-H226, PC-3, SH-SY5Y, SK-ML-28) and the effects estimated by MTT assay. Hydrogen peroxide (H₂O₂) levels and apoptosis biomarkers (membrane translocation of phosphatidylserine, depolarization of mitochondrial membrane potential, Caspase-9 activity, and DNA condensation and/or fragmentation) were studied in the breast adenocarcinoma cellular model (MCF-7) and its genotoxicity on mouse fibroblasts (L929). Sphaerodactylomelol displayed an IC₅₀ range between 33.04 and 89.41 µM without selective activity for a specific tumor tissue. The cells’ viability decrease was accompanied by an increase on H₂O₂ production, a depolarization of mitochondrial membrane potential and an increase of Caspase-9 activity and DNA fragmentation. However, the DNA damage studies in L929 non-malignant cell line suggested that this compound is not genotoxic for normal fibroblasts. Overall, the results suggest that the cytotoxicity of sphaerodactylomelol seems to be mediated by an increase of H₂O₂ levels and downstream apoptosis.

The oceans harbor a great reservoir of molecules with unknown bioactivities, which could be useful for the treatment of illnesses that nowadays have no cure, such as neurodegenerative diseases. In this work, we evaluated the neuroprotective potential of the marine Fijian compounds tavarua deoxyriboside A and jasplakinolide against oxidative stress and neuroinflammation, crucial mechanisms in neurodegeneration. Both metabolites protected SH-SY5Y human neuroblastoma cells from H₂O₂ damage, improving mitochondrial function and activating the antioxidant systems of cells. These effects were mediated by their ability of inducing Nrf2 translocation. In BV2 microglial cells activated with lipopolysaccharide, Fijian metabolites also displayed promising results, decreasing the release of proinflammatory mediators (ROS, NO, cytokines) through the reduction of gp91 and NFkB–p65 expression. Finally, we performed a coculture among both cell lines, in which treatment with compounds protected SH-SY5Y cells from activated microglia, corroborating their neuroprotective effects. These results suggest that tavarua deoxyriboside A and jasplakinolide could be used as candidate molecules for further studies against neurodegeneration.

Laxaphycins are a family of non-ribosomal lipopeptides that have been isolated from several cyanobacteria. Some of these compounds have presented cytotoxic activities, but their mechanism of action is poorly understood. In this work, the already described laxaphycins B and B3, and acyclolaxaphycins B and B3 were isolated from the marine cyanobacteria Anabaena torulosa. Moreover, two new acyclic compounds, [des-(Ala⁴-Hle⁵)] acyclolaxaphycins B and B3, were purified from the herviborous gastropod Stylocheilus striatus, with this being the first description of biotransformed laxaphycins. The structure of these new compounds was elucidated, together with the absolute configuration of acyclolaxaphycins B and B3. The bioactivities of the six peptides were determined in SH-SY5Y human neuroblastoma cells. Laxaphycins B and B3 were cytotoxic (IC₅₀: 1.8 and 0.8 µM, respectively) through the induction of apoptosis. In comparison, acyclic laxaphycins did not show cytotoxicity but affected mitochondrial functioning, so their effect on autophagy-related protein expression was analyzed, finding that acyclic peptides affected this process by increasing AMPK phosphorylation and inhibiting mTOR. This work confirms the pro-apoptotic properties of cyclic laxaphycins B and is the first report indicating the effects on autophagy of their acyclic analogs. Moreover, gastropod-derived compounds presented ring opening and amino-acids deletion, a biotransformation that had not been previously described.

Scope: Fruit‐derived drinks consumption is considered beneficial due to the antioxidant and neuroprotective effects of polyphenols separately, but studies including their total constituents are scarce. In this work, the antioxidant and anti‐inflammatory neuroprotective effects of apple‐derived beverages are determined in a mouse model of lipopolysaccharide (LPS)‐induced inflammation.Methods and results: Preliminary antioxidant and neuroinflammatory experiments are carried out with 15 drink polyphenolic extracts in SH‐SY5Y and BV2 cells, using H₂O₂ as pro‐oxidant and LPS as pro‐inflammatory stimulus, respectively. Extracts improve antioxidant systems functioning and present neuroprotective mitochondrial‐related effects. In microglia, extracts reduce reactive oxygen species and modulate cytokine release. To better mimic human consumption, four concentrated dealcoholized apple‐derived drinks (three ciders and apple juice) are supplied to mice for 7 days in substitution of drinking water. Mice treated with beverages present reduced brain oxidative stress and inflammatory markers after LPS injection. Interestingly, genetic expression of antioxidant enzymes and glutathione levels are also greatly augmented after drink intake.Conclusion: The results confirm the antioxidant and anti‐inflammatory‐mediated neuroprotective properties of apple‐derived drinks, suggesting that their consumption could be a good approach for prevention of neurodegenerative disorders. To the authors’ knowledge, this is the first description of cider neuroprotective effects.

The search for compounds capable of targeting early pathological changes of Alzheimer̀s disease (AD), such as oxidative stress and neuroinflammation, is an important challenge. Gracilin A derivatives were recently synthesized, using a pharmacophore-directed retrosynthesis (PDR) strategy, and found to possess potent neuroprotective effects. In this work, the previously described derivatives 1–7 which demonstrated mitochondrial-mediated, antioxidant effects were chosen for further study. The ability of compounds to modulate the expression of antioxidant genes (CAT, GPx, SODs, and Nrf2) was determined in SH-SY5Y cells, and the simplified derivatives 2 and 3 were found to be the most effective. The anti-neuroinflammatory properties of all derivatives were assessed in BV2 microglial cells activated with lipopolysaccharide (LPS). Several derivatives decreased the release of cytokines (Il-1β, IL-6, GM-CSF, and TNF-α) and other damaging molecules (ROS, NO) and also regulated the translocation of Nrf2 and NFκB, and reduced p38 activation. These protective effects were confirmed in a trans-well coculture with BV2 and SH-SY5Y cells and several derivatives increased SH-SY5Y survival. This present work demonstrates the neuroprotective properties of gracilin A derivatives, making them promising candidate drugs for AD. Particularly, derivatives 2 and 3 showed the greatest potential as lead compounds for further development.

Cyclophilins (Cyps) are ubiquitous proteins that belong to the immunophilins family consistently associated with inflammatory and cardiovascular diseases. While levels of CypA have been extensively studied, less data are available for other Cyps. The purpose of this case-control study was to determine the relationship of Cyps (A, B, C and D) with coronary artery disease (CAD) and eight inflammation markers. Serum levels of Cyps, interleukins and metalloproteinases were measured in serum collected from 84 subjects. Participants were divided into two sub-groups based on CAD diagnosis: 40 CAD patients and 44 control volunteers. Serum levels of CypA, CypB and CypC, IL-1β and IL-6 were significantly higher in CAD patients. Bivariate correlation analysis revealed a significant positive correlation between Cyps and several blood and biochemical parameters. When the ability of Cyps levels for CAD diagnosis was evaluated, higher sensitivity and selectivity values were obtained with CypC (c-statistic 0.891, p < 0.001) indicating that it is a good marker of CAD disease, while less conclusive results were obtained with CypA (c-statistic 0.748, p < 0.001) and CypB (c-statistic 0.655, p < 0.014). In addition, significant correlations of traditional CAD risk factors and CypC were observed. In summary, high levels of CypC are a risk factor for CAD and therefore it can be proposed as a new biomarker for this disease.

The architecture and bioactivity of natural products frequently serve as embarkation points for the exploration of biologically relevant chemical space. Total synthesis followed by derivative synthesis has historically enabled a deeper understanding of structure–activity relationships. However, synthetic strategies towards a natural product are not always guided by hypotheses regarding the structural features required for bioactivity. Here, we report an approach to natural product total synthesis that we term ‘pharmacophore-directed retrosynthesis’. A hypothesized, pharmacophore of a natural product is selected as an early synthetic target and this dictates the retrosynthetic analysis. In an ideal application, sequential increases in the structural complexity of this minimal structure enable development of a structure–activity relationship profile throughout the course of the total synthesis effort. This approach enables the identification of simpler congeners retaining bioactivity at a much earlier stage of a synthetic effort, as demonstrated here for the spongiane diterpenoid, gracilin A, leading to simplified derivatives with potent neuroprotective and immunosuppressive activity.

The macrolide caniferolide A was isolated from extracts of a culture of the marine-derived actinomycete Streptomyces caniferus and its ability to ameliorate Alzheimer’s disease (AD) hallmarks was determined. The compound reduced neuroinflammatory markers in BV2 microglial cells activated with lipopolysaccharide (LPS), being able to block NFκB-p65 translocation to the nucleus and to activate Nrf2 pathway. It also produced a decrease in pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α), reactive oxygen species (ROS) and nitric oxide release, and inhibited iNOS, JNK and p38 MAPK activities. Moreover, the compound blocked BACE1 activity and attenuated Aβ-activation of microglia by drastically diminishing ROS levels. The phosphorylated state of tau protein was evaluated in SH-SY5Y tau441 cells. Caniferolide A reduced Thr212 and Ser214 phosphorylation by targeting JNK and p38 MAPK kinases. On the other side, the antioxidant properties of the macrolide were determined in an oxidative stress model with SH-SY5Y cells treated with H₂O₂. The compound diminished ROS levels and increased cell viability and GSH content by activating the nuclear factor Nrf2. Finally, the neuroprotective properties of the compound were confirmed in two trans-well co-culture systems with activated BV2 cells (both with LPS and Aβ) and wild type and transfected SH-SY5Y cells. The addition of caniferolide A to microglial cells produced a significant increase in the survival of neuroblastoma in both cases. These results indicate that the compound is able to target many pathological markers of AD, suggesting that caniferolide A could be an interesting drug lead for a polypharmacological approach to the illness.

The chemical investigation of marine invertebrates from the deep Northeastern Atlantic revealed new lipoglycotripeptides named characellides isolated from the tetractinellid sponge Characella pachastrelloides. This new family of natural products features a central tripeptide linked to a rare sugar unit and a long alkyl chain ending with a 2,3-dimethyltetrahydropyran. The configurations of all 13 chiral centers were determined by extensive use of NMR data and circular dichroism spectra combined with calculations.