Prenylated Flavanone Isolated from Dalea Species as a Potential Multitarget-Neuroprotector in an In Vitro Alzheimer's Disease Mice Model.

Alzheimer's disease (AD) involves a neurodegenerative process that has not yet been prevented, reversed, or stopped. Continuing with the search for natural pharmacological treatments, flavonoids are a family of compounds with proven neuroprotective effects and multi-targeting behavior. The American genus Dalea L. (Fabaceae) is an important source of bioactive flavonoids. In this opportunity, we tested the neuroprotective potential of three prenylated flavanones isolated from Dalea species in a new in vitro pre-clinical AD model previously developed by us. Our approach consisted in exposing neural cells to conditioned media (3xTg-AD ACM) from neurotoxic astrocytes derived from hippocampi and cortices of old 3xTg-AD mice, mimicking a local neurodegenerative microenvironment. Flavanone 1 and 3 showed a neuroprotective effect against 3xTg-AD ACM, being 1 more active than 3. The structural requirements to afford neuroprotective activity in this model are a 5'-dimethylallyl and 4'-hydroxy at the B ring. In order to search the mechanistic performance of the most active flavanone, we focus on the flavonoid-mediated regulation of GSK-3ß-mediated tau phosphorylation previously reported. Flavanone 1 treatment decreased the rise of hyperphosphorylated tau protein neuronal levels induced after 3xTg-AD ACM exposure and inhibited the activity of GSK-3ß. Finally, direct exposure of these neurotoxic 3xTg-AD astrocytes to flavanone 1 resulted in toxicity to these cells and reduced the neurotoxicity of 3xTg-AD ACM as well. Our results allow us to present compound 1 as a natural prenylated flavanone that could be used as a precursor to development and design of future drug therapies for AD.

Biologically synthesized silver nanoparticles, mediated by Bothriochloa laguroides, inhibit biofilm formation and eradicate mature biofilm of Yersinia enterocolitica and Staphylococcus aureus.

AIMS: To phytosynthesize silver nanoparticles (AgNPs) and determine their antibacterial and antibiofilm capacity against gram-positive and gram-negative bacterial strains. METHODS AND RESULTS: AgNPs were synthesized using Bothriochloa laguroides aqueous extract as reducing and stabilizing agent. After characterization, a phytochemical screening to the extract and the AgNPs was performed. Antibacterial activity, inhibition and eradication of biofilms against Staphylococcus aureus and Yersinia enterocolitica strains were tested. Spherical AgNPs with an average size of 8 nm were obtained. Tannins, flavonoids, carbohydrates, proanthocyanidins, anthocyanins and saponins were identified in aqueous extract; meanwhile, only carbohydrates were identified in AgNPs. The MIC and MBC were determined at pmol L-1  levels for all tested strains. Furthermore, AgNPs inhibited more than 90% of biofilms formation and eradicated more than 80% of mature biofilms at concentrations higher than MIC. CONCLUSIONS: The AgNPs obtained in this study inhibited planktonic and sessile growth, and eradicated mature biofilms of pathogenic bacterial strains at very low concentrations. SIGNIFICANCE AND IMPACT OF STUDY: The current study showed the promising potential of AgNPs as antibiofilm agents opening the way for the future development of a new class of antibacterial products.

Neuroprotective effects of prenylated flavanones isolated from Dalea species, in vitro and in silico studies.

Neurodegenerative diseases (NDs) represent a global problem on public health, with a growing incidence as human longevity increases. Currently, although there are palliative strategies available for most of these diseases, there is a lack of effective therapies for their cure. Flavonoids are extensively studied for their multi-target behavior. Among numerous biological activities, it has been reported that they act at the CNS level, presenting neuroprotective activity through different mechanisms of action. Dalea L. (Fabaceae) is an American genus, with about 172 species. Dalea elegans Gillies ex. Hook. & Arn and Dalea pazensis Rusby, both South American species, are the important source of natural compounds of the prenylated flavanones type. In the present study, five prenylated flavanones isolated from Dalea species were assayed for their neuroprotective activity in two in vitro models of neurodegeneration. Flavanones 1 and 2 exhibited neuroprotective effects against oxidative stress-induced death in both models, granular cerebellar neurons and (NGF)-differentiated PC12 cells. Structure-activity relationships were also reported. Our results indicated that an 8-prenyl group at the A-ring accompanied by an unsubstituted B-ring, or a 2',4'-dihydroxy-5'-dimethylallyl substitution, lead to the most potent flavanones. Furthermore, in silico studies were performed, and several putative targets in NDs were identified for compounds 1 and 2. Between them, the enzyme acetylcholinesterase was selected for its validation in vitro. The present in vitro and in silico results imply that prenylated flavanones 1 and 2 may be useful in the development and design of future strategies for the treatment of NDs diseases.

Melanogenic inhibitory effects of Triangularin in B16F0 melanoma cells, in vitro and molecular docking studies.

The lack of secure therapies for hyperpigmentation disorders, without serious adverse effects, and the latest reports relating melanogenic disorders with development of neurodegenerative diseases, encourage the continuing search for new drugs for the treatment of such disorders. In this sense, the plant kingdom is an important source of bioactive natural products with great potential for the research and development of new therapeutics. The present study evaluated the anti-melanogenic activity of the natural methoxylated chalcone, 2',6'-dihydroxy-4'-methoxy-3'-methylchalcone (Triangularin, T), on diphenolase activity from mushroom tyrosinase and on murine B16F0 melanoma cell model. In addition, molecular modelling studies were carried out in order to understand the inhibitory activity observed. T showed a potent anti-melanogenic activity being more active than kojic acid (KA) on tyrosinase isolated of both sources and on intracellular tyrosinase. Molecular docking studies displayed important interactions between T and the active site of tyrosinase. Our results suggest that T may be useful for the treatment of hyperpigmentary disorders.

Production of Bioactive Peptides from Lactic Acid Bacteria: A Sustainable Approach for Healthier Foods.

Traditional fermented foods where lactic acid bacteria (LAB) are present have been associated with beneficial effects on human health, and some of those benefits are related to protein-derived products. Peptides produced by LAB have attracted the interest of food industries because of their diverse applications. These peptides include ribosomally produced (bacteriocins) and protein hydrolysates by-products (bioactive peptides), which can participate as natural preservatives and nutraceuticals, respectively. It is essential to understand the biochemical pathways and the effect of growth conditions for the production of bioactive peptides and bacteriocins by LAB, in order to suggest strategies for optimization. LAB is an important food-grade expression system that can be used in the simultaneous production of peptide-based products for the food, animal, cosmetic, and pharmaceutical industries. This review describes the multifunctional proteinaceous compounds generated by LAB metabolism and discusses a strategy to use a single-step production process, using an alternative protein-based media. This strategy will provide economic advantages in fermentation processes and will also provide an environmental alternative to industrial waste valorization. New technologies that can be used to improve production and bioactivity of LAB-derived peptides are also analyzed.

Chemical and bioactivity of flavanones obtained from roots of Dalea pazensis Rusby.

Two new prenylated flavanones, pazentin A (3',4'-dihydroxy-6,2'-diprenylpinocembrin, 1) and pazentin B [4'-hydroxy-2'-methoxy-5'-(1‴, 1‴-dimethylallyl)-6-prenylpinocembrin, 2] together with two known ones (3 and 4) previously isolated from other Dalea species were obtained from the benzene extract of Dalea pazensis Rusby roots. The compounds were evaluated in vitro for their inhibition on mushroom tyrosinase enzyme and in relation to their effect on melanogenesis in B16 murine melanoma cells, by using a spectrophotometric method. The information obtained could be relevant to the knowledge of the structure-activity relationship for these flavonoids with the aim to explore the rational design for skin-whitening agents.

Mass spectrometry studies of lycodine-type Lycopodium alkaloids: sauroxine and N-demethylsauroxine.

RATIONALE: Sauroxine and N-demethylsauroxine are lycodine-type Lycopodium alkaloids. In recent years, Lycopodium alkaloids have gained significant interest due to their unique skeletal characteristics as well as due to their acetylcholinesterase activity. It is known that drugs that inhibit acetylcholinesterase can be used to treat the early stages of Alzheimer's disease. METHODS: Sauroxine and N-demethylsauroxine were isolated from the aerial parts of Huperzia saururus (Lam.) Trevis. Electron ionization mass spectrometry (EI-MS) (low resolution) and collision-induced dissociation tandem mass spectrometry (CID-MS/MS) fragmentation was conducted using an ion trap, GCQ Plus mass spectrometer with MS/MS. Electron ionization high-resolution mass spectrometry (EI-HRMS) was performed in a magnetic sector mass spectrometer (Micromass VG). RESULTS: Using GC/EI-CID-MS/MS we obtained different fragmentation routes that connect all the ionic populations. In addition, the use of EI-HRMS allowed us to measure the exact masses of all the fragment ions, and, with all this information gathered, we tried to establish a fragmentation scheme concordant with the ascendant and descendant species. CONCLUSIONS: The mass spectrometry studies presented in this work complete our mass studies of Lycopodium alkaloids. The mass spectrometry work presented has been very useful to confirm the structures as well as to support the biogenetic relationships between the lycodine-type Lycopodium alkaloids: sauroxine and N-demethylsauroxine.

Inhibitory effect of quercetin on matrix metalloproteinase 9 activity molecular mechanism and structure-activity relationship of the flavonoid-enzyme interaction.

Epidemiological studies have demonstrated an inverse association between the consumption of flavonoid-rich diets and the risk of atherosclerosis. In addition, an increased activity of the matrix metalloproteinase 9 (MMP-9) has been implicated in the development and progression of atherosclerotic lesions. Even though the relationship between flavonoid chemical structure and the inhibitory property on MMP activity has been established, the molecular mechanisms of this inhibition are still unknown. Herein, we first evaluated the inhibitory effect of quercetin on MMP-9 activity by zymography and a fluorescent gelatin dequenching assay, secondly we determined the most probable sites and modes of quercetin interaction with the MMP-9 catalytic domain by using molecular modelling techniques, and finally, we investigated the structure-activity relationship of the inhibitory effect of flavonoids on MMP-9 activity. We show that quercetin inhibited MMP-9 activity with an IC(50) value of 22 microM. By using docking and molecular dynamics simulations, it was shown that quercetin interacted in the S1' subsite of the MMP-9 active site. Moreover, the structure-activity relationship analysis demonstrated that flavonoid R(3)(')-OH and R(4)(')-OH substitutions were relevant to the inhibitory property against MMP-9 activity. In conclusion, our data constitute the first evidence about the quercetin and MMP-9 interaction, suggesting a mechanism to explain the inhibitory effect of the flavonoid on the enzymatic activity of MMP-9, which provides an additional molecular target for the cardioprotective activity of quercetin.

Sauroine, an alkaloid from Huperzia saururus with activity in wistar rats in electrophysiological and behavioral assays related to memory retention.

The present study describes the effects of sauroine (1), the main alkaloid obtained from Huperzia saururus, on memory retention and learning. To evaluate this, electrophysiological experiments and behavioral tests (step down) were performed on male Wistar rats. The results showed that 1 improved memory retention in the step-down test, significantly increasing hippocampal plasticity. Thus, 1 seems to be a constituent responsible for the activity claimed in folk medicine for H. saururus in Argentina.