Zaira Domínguez

Antibacterial and free‐radical scavenging activities of Sonoran propolis

Aims:  To evaluate the antibacterial and free‐radical scavenging (FRS) activities of propolis collected from three different areas of Sonoran Desert in northwestern Mexico [Pueblo de Alamos (PAP), Ures (UP) and Caborca (CP)].

Electrochemical Oxidation of Caffeic and Ferulic Acid Derivatives in Aprotic Medium

O comportamento eletroquimico em funcao da estrutura de uma serie de derivados dos acidos cafeico e ferulico, assim como de seus precursores catecol e guaiacol, eletroquimicamente ativos, foi avaliado por voltametria ciclica. Os resultados revelaram que as condicoes experimentais sao a chave para as mudancas no mecanismo de oxidacao do guaiacol e acido ferulico. A oxidacao eletroquimica dos derivados amida do acido ferulico revelou que o atomo de nitrogenio desempenha um papel importante na derivatizacao da superficie do eletrodo. Alem disso, a atividade sequestradora de radicais dos compostos, avaliada atraves da porcentagem de inibicao do radical 2,2’-difenil-1picril-hidrazila, mostrou uma boa correlacao com os potenciais de oxidacao. We studied the electrochemical behaviour as a function of the structure of a series of caffeic and ferulic acids derivatives as well as their corresponding redox moieties catechol and guaiacol by cyclic voltammetry. Results revealed that the medium is key for changes in the oxidation mechanism of guaiacol and ferulic acid. Electrochemical oxidation of the ferulic acid amide derivatives revealed that the nitrogen atom plays an important role in the derivatization of the electrode surface. In addition, radical scavenging activity of the compounds evaluated through the percentage of inhibition of the 2,2’-diphenyl-1-picrylhidrazyl radical showed a good relationship with the oxidation potentials.

Conformational analysis of highly hindered thiophosphoramidates

Abstract The conformational analyses in solution and in solid state of the highly crowded mobile systems, 2-dicyclohexylamino-2-thio-1,3,2λ 5 -dioxaphosphinane ( 1 ), 2-dicyclohexylamino-2-thio- trans -4,6-dimethyl-1,3,2λ 5 -dioxaphosphinane ( trans - 2 ) and their anancomeric analogs, ax -2-dicyclohexylamino-2-thio- cis -4,6-dimethyl-1,3,2λ 5 -dioxaphosphinane ( ax - cis - 2 ) and eq -2-dicyclohexylamino-2-thio- cis -4,6-dimethyl-1,3,2λ 5 -dioxaphosphinane ( eq - cis - 2 ) are informed. In accordance with proton–proton and proton–phosphorus coupling constants, the dioxaphosphinane ring adopts a chair conformation in all compounds except in the case of trans - 2 , which was found in a twisted conformation. Solid state structural analyses suggest that only the synaxial Me/NR 2 or Me/S interactions in trans - 2 , force the heterocycle ring to remain as a mixture of twisted boat and half-chair (chaise loungue) conformers.

Antibacterial activity of Sonoran propolis and some of its constituents against clinically significant Vibrio species.

The aim of the present study was to evaluate the anti-Vibrio activity of propolis collected from three different areas of the Sonoran Desert in northwestern, Mexico [Pueblo de Alamos (PAP), Ures (UP), and Caborca (CP)]. The anti-Vibrio spp. activity of Sonoran propolis was determined by the broth microdilution method. UP propolis showed the highest antibacterial activity [minimal inhibitory concentration (MIC(50))<50 μg mL(-1)] against Vibrio spp. (UP>CP>PAP). UP propolis significantly inhibited the growth of Vibrio cholerae O1 serotype Inaba (MIC(50)<50 μg mL(-1)), V. cholerae non-O1 (MIC(50)<50 μg mL(-1)), V. vulnificus (MIC(50)<50 μg mL(-1)), and V. cholerae O1 serotype Ogawa (MIC(50) 100 μg mL(-1)), in a concentration-dependent manner. The UP propolis constituents, galangin and caffeic acid phenethyl ester (CAPE), exhibited a potent growth inhibitory activity (MIC(50) 0.05-0.1 mmol l(-1)) against V. cholerae strains (non-O1 and serotype Ogawa). The strong anti-Vibrio activity of Sonoran propolis and some of its chemical constituents (galangin and CAPE) support further studies on the clinical applications of this natural bee product against different Vibrio spp., mainly V. cholerae.

Influence of plant resistance traits in selectiveness and species strength in a tropical plant-herbivore network

PREMISE OF THE STUDY Plant-herbivore networks are highly specialized in their interactions, yet they are highly variable with regard to the relative importance of specific host species for herbivores. How host species traits determine specialization and species strength in this antagonistic network is still an unanswered question that we addressed in this study. METHODS We assessed plant cover and antiherbivore resistance traits to assess the extent to which they accounted for the variation in specialization and strength of interactions among species in a plant-herbivore network. We studied a tropical antagonistic network including a diverse herbivore-host plant assemblages in different habitat types and climatic seasons, including host plants with different life histories. KEY RESULTS Particular combinations of leaf toughness, trichome density, and phenolic compounds influenced herbivore specialization and host species strength, but with a significant spatiotemporal variation among plant life histories. Conversely, plant-herbivore network parameters were not influenced by plant cover. CONCLUSIONS Our study highlights the importance of species-specific resistance traits of plants to understand the ecological and evolutionary consequences of plant-herbivore interaction networks. The novelty of our research lies in the use of a trait-based approach to understand the variation observed in diverse plant-herbivore networks.

The formation of open-chain thioesters in the reaction of 2-lithio-2-methyl- and 2-lithio-2-phenyl-1,3-dithiane with chlorodiphenylphosphane followed by oxidation ☆

The unexpected formation of open-chain thioesters (3) and (6) from the reaction of 2-lithio-r-2-t-4-t-6-trimethyl (1-Li) and 2-lithio-r-2-phenyl-t-4-t-6-dimethyl-1,3-dithiane (4-Li), respectively, with chlorodiphenylphosphane followed by oxidation was observed instead of the anticipated gem-derivatives. The X-ray diffraction analysis of (6) and the trapped intermediate (10) confirmed the structure and the proposed mechanism of formation of the open-chain products.

Substituent Effects on 31P NMR Chemical Shifts and 1JP–Se of triarylselenophosphates

The effect of electron-withdrawing (EW) and electron-releasing (ER) substituents on the 31P NMR chemical shifts and the structural parameters of a series of tris-(p-X-aryl)selenophosphates is reported in this article. Similarly to O-aryl phosphates and O-aryl thiophosphates, EW groups attached to aromatic rings induce a shielding effect on the 31P NMR signal. After a detailed experimental and theoretical analysis, we confirmed that the selenium atom is the main part responsible for the charge density transfer toward phosphorus through a back-bonding effect. The obtained 1JP-Se values for the complete series agree with this observation. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Mesoscopic Modeling of the Encapsulation of Capsaicin by Lecithin/Chitosan Liposomal Nanoparticles

The transport of hydrophobic drugs in the human body exhibits complications due to the low solubility of these compounds. With the purpose of enhancing the bioavailability and biodistribution of such drugs, recent studies have reported the use of amphiphilic molecules, such as phospholipids, for the synthesis of nanoparticles or nanocapsules. Given that phospholipids can self-assemble in liposomes or micellar structures, they are ideal candidates to function as vehicles of hydrophobic molecules. In this work, we report mesoscopic simulations of nanoliposomes, constituted by lecithin and coated with a shell of chitosan. The stability of such structures and the efficiency of the encapsulation of capsaicin, as well as the internal and superficial distribution of capsaicin and chitosan inside the nanoliposome, were analyzed. The characterization of the system was carried out through density maps and the potentials of mean force for the lecithin-capsaicin, lecithin-chitosan, and capsaicin-chitosan interactions. The results of these simulations show that chitosan is deposited on the surface of the nanoliposome, as has been reported in some experimental works. It was also observed that a nanoliposome of approximately 18 nm in diameter is stable during the simulation. The deposition behavior was found to be influenced by a pattern of N-acetylation of chitosan.

Seasonal Effect on the Biological Activities of Litsea glaucescens Kunth Extracts

This study shows the seasonal effect on the antioxidant, antiproliferative, and antimicrobial activities of L. glaucescens Kunth (LG) leaves extracts. Their antioxidant activity was evaluated through the DPPH, FRAP, and ORAC assays. Their phenolic content (PC) was determined by means of the Folin-Ciocalteu method, and the main phenolic compounds were identified through a HPLC-DAD analysis. Antiproliferative activity was determined by MTT assay against HeLa, LS 180, M12.C3.F6, and ARPE cell lines. Antimicrobial potential was evaluated against Staphylococcus aureus and Escherichia coli using a microdilution method. All the LG extracts presented high antioxidant activity and PC, with quercitrin and epicatechin being the most abundant. Antioxidant activity and PC were affected by the season; particularly autumn (ALGE) and summer (SULGE) extracts exhibited the highest values (p < 0.05). All extracts presented moderate antiproliferative activity against the cell lines evaluated, HeLa being the most susceptible of them. However, ALGE and SULGE were the most active too. About antimicrobial activity, SULGE (MIC90 < 800 μg/mL; MIC50 < 400 μg/mL), and SLGE (MIC50 < 1000 μg/mL) showed a moderate inhibitory effect against S. aureus. These findings provide new information about the seasonal effect on the PC and biological properties of LG extracts. Clearly, antioxidant activity was the most important with respect to the other two.