First-time Isolation of Flavonoids and Cytotoxic Potential of the Amazonian Shrub Ptychopetalum olacoides Benth

In the present study, three flavonoids, 3-O-methylquercetin (1), 3,4'-O-dimethylquercetin (2) and 3,7-O-dimethylquercetin (3) were isolated and characterized for the first time from a methanol extract obtained from the species Ptychopetalum olacoides. The structures of compounds were identified by spectroscopic methods (1D-, 2D-NMR, MS and UV) and confirmed by comparison with the respective literature data. The cytotoxic effect of crude extract was evaluated in vitro against three human cancer cell lines. The results showed a mild cytotoxic activity (IC50 = 45.16 mu g/mL) against breast cancer (MCF-7). However, crude extract did not exhibit any cytotoxic effect against normal cell human fibroblast (MRC-5).FAPERJCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Univ Fed Fluminense, Inst Quim, Dept Quim Organ, Campus Valonguinho, BR-24020141 Niteroi, RJ, BrazilUniv Fed Para, Inst Ciencias Biol, BR-66075110 Belem, Para, BrazilUniv Fed Sao Paulo, Dept Ciencias Mar, BR-11070100 Santos, SP, BrazilUniv Fed Rural Rio de Janeiro, Dept Quim, BR-23897000 Seropedica, RJ, BrazilUniv Fed Sao Paulo, Dept Ciencias Mar, BR-11070100 Santos, SP, BrazilWeb of Scienc

Avaliação da atividade antimicrobiana da esponja marinha Ectyoplasia ferox de Fernando de Noronha / Evaluation of antimicrobial activity of Ectyoplasia ferox marine sponge from Fernando de Noronha

Os oceanos cobrem mais de 70% da superfície terrestre e por isso são reservatórios de inúmeras espécies e estruturas químicas que podem ser potencialmente bioativas. Nos últimos anos o ambiente marinho recebeu maior atenção das indústrias farmacêuticas e biotecnológicas devido à diversidade de novas substâncias que podem ser descobertas. Estudos já demostraram que esponjas marinhas possuem algum tipo de defesa contra infecções microbianas em seu habitat. Nesse sentido esses organismos são uma fonte promissora de substâncias com potencial antibiótico que devem ser investigadas como alternativas terapêuticas para a problemática da resistência aos fármacos atuais.  Nesse trabalho avaliamos a atividade antimicrobiana de amostras da esponja Ectyoplasia ferox coletadas em diferentes locais do arquipélago de Fernando de Noronha (PE/Brasil). O ensaio antimicrobiano dos seis extratos brutos obtidos foi realizado através do método de micro diluição em caldo para determinar a Concentração Inibitória Mínima (CIM) contra Staphylococcus aureus HU25, Staphylococcus epidermidis ATCC 12228, e Escherichia coli ATCC 11775. Dois extratos demonstraram atividade moderada: FN98-009 coletada na região da Ressureta (S. aureus: CIM = 64 µg/mL; S. epidermidis: CIM = 128 µg/mL) e FN98-063 coletada na região de Pedras Secas (S. epidermidis: CIM = 128 µg/mL). A partição por gradiente de polaridade da amostra com menor CIM (FN98-009) forneceu uma fração butanólica com atividade menor que seu extrato bruto, levando à hipótese de sinergismo entre as substâncias das diferentes frações. Como estratégia para investigar o possível efeito sinérgico e restaurar a atividade, as quatro frações foram combinadas duas a duas, originando seis amostras. Nenhuma das combinações demonstrou atividade até 512 µg/mL. Dessa forma, acredita-se que a atividade observada no extrato bruto esteja relacionada ao conjunto da maioria de seus constituintes em um efeito sinérgico e que um fracionamento biomonitorado do extrato não permitirá identificar as substâncias mais ativas, mas o potencial do extrato deve ser considerado para maiores estudos

Pushing the boundaries of VCD spectroscopy in natural product chemistry

Vibrational circular dichroism (VCD) is one of the most powerful techniques to assess the stereochemistry of chiral molecules in solution state. The need for quantum chemical calculations to interpret experimental data, however, has precluded its widespread use by non-experts. Herein, we propose the search and validation of IR and VCD spectral markers to circumvent the requirement of DFT calculations allowing for absolute configuration assignments even in complex mixtures. To that end, a combination of visual inspection and machine learning based methods is used. Monoterpene mixtures are selected for this proof-of-concept study.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)2019/22319-

Plakilactone J: Structure and absolute configuration

The chemical investigation of the Brazilian marine sponge Plakortis angulospiculatus led to the isolation of the new peroxide-derived polyketide plakilactone J (1). The structure of (-)-1 was established by means of HRMS and NMR analysis, while its absolute configuration was unambiguously determined as (4R,6R) by vibrational circular dichroism spectroscopy and density functional theory calculations.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)88887.313278/2019-00APQ1E26/210.249/20212019/22319-

Vibrational circular dichroism for the assignment of absolute configuration of natural products in Brazil

The determination of the absolute configuration of chiral bioactive natural products is a crucial step in their structural characterization. Several well-established techniques, such as X-ray crystallography, stereo-controlled organic synthesis, NMR, and chiroptical spectroscopy, are commonly used to this end. However, even today, the configurational analysis of natural products remains a challenge, with a significant number of reassignments being reported every year. Among chiroptical methods, vibrational circular dichroism (VCD) has emerged as an excellent tool for the assignment of the absolute configuration of structurally diverse chiral natural products directly in solution. This review covers the use of VCD spectroscopy to elucidate the absolute stereochemistry of natural products in Brazil over the last 20 years. Although the number of VCD investigations on secondary metabolites has increased, VCD can still be considered under-explored in Brazil. Therefore, herein, we aim to demonstrate the unparalleled stereochemical discriminatory power of VCD to assign both conformation and absolute configuration of natural products in conditions not commonly accessible to other techniques.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)2019/22319-5431978/2018-2211.319-201