Objective
The present report describes the enzymatic acylation of umbelliferone with different vinyl esters as acyl donors biocatalyzed by the commercial lipase Novozym® 435, and the investigation ...for their antibacterial activity against ATCC and clinical strains isolated from hospital infection sites.
Results
The umbelliferone esters (
1
–
5
) were synthesized through the acylation reaction of 7-hydroxy-2
H
-chromen-2-one with different long chain vinyl esters catalyzed by the lipase Novozym 435. The reaction conditions were: 10% Novozym 435; tetrahydrofuran:acetone (3:1) for the reactions with acetate, propionate and butyrate vinyl esters 50–90% conversion, and (9:1) for decanoate and laurate vinyl esters 10–15% conversion; acyl donor/umbelliferone molar ratio of 10:1 and 60 °C. All the umbelliferone esters were characterized NMR and (HRMS). The antibacterial activity of the products were tested using the broth microdilution method in order to determine the minimum inhibitory concentration (MIC). The results displayed by 7-laurate and 7-decanoate-umbelliferone esters showed the highest antibacterial potential, with 1 mM inhibitory activity for ATCC 33591, a methicillin and oxacillin resistant
Staphylococcus aureus
strain. They were also able to inhibit gram-negative bacterial strains, such as
Pseudomonas aeruginosa
(MIC 0.5 mM) and
Klebsiella pneumoniae
(MIC 1 mM). In addition, 7-laurate- and 7-decanoate-umbelliferone esters were able to inhibit all clinical strains (MIC 1 mM; except 7-laurate-umbelliferone in which MIC 0.5 mM against 55a).
Conclusions
This is the first study performing the biocatalysis of umbelliferone followed by the purification of the products and the antibacterial evaluation.
The rapid annotation and identification by mass spectrometry techniques of flavonoids remains a challenge, due to their structural diversity and the limited availability of reference standards. This ...study applies a workflow to characterize two isoflavonoids, the orobol‐C‐glycosides analogs, using high‐energy collisional dissociation (HCD)‐ and collision‐induced dissociation (CID)‐type fragmentation patterns, and also to evaluate the antioxidant effects of these compounds by ferric reducing antioxidant power (FRAP), 2,2′‐azino‐bis(3‐ethylbenzothiazolin acid) 6‐sulfonic acid (ABTS), and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) methods. By the CID‐type fragmentation, in positive mode and at all high‐resolution mass spectrometry (HRMS) multiple stage, there were shown differences in the annotation of the compounds, mainly concerning some ratios of relative abundance. At CID‐MS2 20 eV, the compounds could be efficiently characterized, because they present distinct base peaks M + H+ and M + H–H2O+ for the orobol‐8‐C‐ and orobol‐6‐C‐glycoside, respectively. Similarly, by the HCD‐type fragmentation, in HRMS2 stage, differences between orobol analogs in both mode of ionization were observed. However, the HR HCD‐MS2 at 80 eV, in positive mode, generated more ions and each isomer presented different base peaks ions, 0,2X+ for the orobol‐8‐C‐glycoside and 0,3X+ for the orobol‐6‐C‐glycoside. By the DPPH, the 8‐C‐derivative showed a very close value compared with the standard rutin and, in the ABTS method, a higher radical‐scavenging activity. In both methods, the EC50 of orobol‐8‐C‐glycoside was almost twice better compared with orobol‐6‐C‐glycoside. In FRAP, both C‐glycosides showed a good capacity as Fe+3 reducing agents. We could realize that combined MS techniques, highlighting the positive mode of ionization, can be used to evaluate the isoflavones analogs being useful to differentiate between the isomeric flavones; therefore, these data are important to mass spectrometry dereplication studies become more efficient.
Highlights
The MS2, in positive mode of ionization, at low CID energies (15 and 20 eV) and at high HCD energies (50 eV), was suitable to characterize orobol 8 and 6‐C‐derivatives.
Positive mode of ionization was effective to rapid annotation of each orobol C‐glycoside.
The orobol C‐derivatives showed high radical scavenging effects. Orobol‐8‐C‐glycoside showed higher antioxidant capacity.
A rare dihydoxyflavan-epicatechin proanthocyanidin, entcassiflavan-(4β→8)-epicatechin, was isolated from
, a plant widely used by traditional people from the Amazon to treat urinary tract infections. ...The constitution and relative configuration of the compound were elucidated by HR-MS and detailed 1D- and 2D-NMR measurements. By comparing the experimental electronic circular dichroism (ECD) spectrum with the calculated ECD spectra of all 16 possible isomers, the absolute configuration, the interflavan linkage, and the atropisomers could be determined.
Flavonoids are one of the most important and diversified phenolic groups among products of natural origin. An important property of this metabolite class is the antioxidant action. This study ...evaluated the antioxidant and cytotoxic activities and oxidative stress of transesterification products of the flavonoid rutin, catalyzed by Novozym® 435. The presence of monoacetate and diacetate was confirmed by quantitative evaluation of the retention times (rutin, 15.68 min; rutin monoacetate, 18.14 min; and rutin diacetate, 18.57 min) and by the data from LC-MS and NMR 1H and 13C. The experiment showed excellent conversion values of 96% in total acetates (rutin monoacetate and diacetate). These results confirmed that rutin derivatives have antioxidant potential, as evaluated by the ORAC method (rutin standard: 0.53 ± 0.08 μM Trolox/g and rutin derivatives: 2.33 ± 1.08 μM Trolox/g) and also show low cytotoxicity in human and animal cells. Rutin derivatives reduced the production of reactive oxygen species in RAW macrophages as well. Many qualities attributed to rutin derivatives make them promising potential candidates for use as nutraceuticals, including their high amounts of antioxidants, biological potential and low toxicity, which contribute to the reduction of oxidative stress.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Red algae of the genus Laurencia J. V. Lamouroux are found in tropical and subtropical regions throughout the world and are an extremely rich source of active secondary metabolites with diverse ...structural features. In the present study, 6 sesquiterpenes (obtusol, (−)‐elatol, dendoidiol, debrome‐elatol, triquinane, and obtusane) isolated from Laurencia dendroidea were investigated for their cytotoxicity, using 4 cancer cell lines (U937, Jurkat, B16F10, and Colo‐205). Among all sesquiterpenes tested, obtusol and (−)‐elatol showed a promising activity in the treatment of Colo‐205 strain, with IC50 of 1.2 ± 1.4 and 2.5 ± 1.3 μg/ml, respectively. In addition, fluorescence microscopy results indicated that, at 100 μg/ml, obtusol induced apoptosis at 79% and (−)‐elatol at 95%. Activation of Caspases 2, 4, 6, and 8 showed to be involved in (−)‐elatol activity and only Caspase 6 in obtusol activity. These data demonstrated the effective apoptosis‐inducing activity of the sesquiterpene (−)‐elatol and obtusol in the treatment of Colo‐205 strain. Therefore, more studies should be done so that the sesquiterpenes (−)‐elatol and obtusol might become promising chemotherapy.
Staphylococci are one of the most common causes of biofilm-related infections. Such infections are hard to treat with conventional antimicrobials, which often lead to bacterial resistance, thus being ...associated with higher mortality rates while imposing a heavy economic burden on the healthcare system. Investigating antibiofilm strategies is an area of interest in the fight against biofilm-associated infections. Previously, a cell-free supernatant from marine-sponge-associated
sp. inhibited staphylococcal biofilm formation and dissociated the mature biofilm. This study aimed to identify the chemical components responsible for the antibiofilm activity of
sp. Scanning electron microscopy confirmed that the aqueous extract at the concentration of 32 μg/mL could dissociate the mature biofilm. Liquid chromatography coupled with high-resolution mass spectrometry revealed seven potential compounds in the aqueous extract, including alkaloids, macrolides, steroids, and triterpenes. This study also suggests a possible mode of action on staphylococcal biofilms and supports the potential of sponge-derived
as a source of antibiofilm compounds.
The specie Ocotea notata (Nees & Mart). Mez is a tree with 5 meters high, that can be found in restinga regions in the Brazilian coast. This study describes a phytochemical investigation, total ...phenolic content and the antioxidant activity of extracts and fractions by DPPH and ORAC. Phenolic content revealed equivalent concentration between evaluated samples, similar to found in the leave extract (66.4 mEq GA/g). By DPPH, extracts and fractions showed effective concentration (EC
50
) lower than the standards Ginkgo biloba 761
®
(23.60 ± 0.64 µg/ml) and quercetin (6.06 ± 0, 92 µg/mL); for the ORAC method, ethyl acetate partition showed a value of 2.06 mmol Trolox equivalent g
−1
better than obtained in Ginkgo biloba (1.03 ± 0.25 mmol.Trolox equivalent g
−1
. The butanol partition (0.52 mmol.Trolox equivalent g
−1
) and the aqueous residue (0.74 mmol Trolox equivalent g
−1
) have a lesser ORAC potential than ethyl acetate partition. The butanolic partition, investigated by LC-DAD-MS/MS and QTOF-MS, revealed six major compounds: miquelianin (1), isoquercitrin (2), quercitrin (3), kaempferol-3-O-pentose (4), afzelin (5) and isorhamnetin-glucuronide (6).
Bacterial infections represent one of the leading causes of mortality in the world. Among causative pathogens, S. aureus is prominently known as the underlying cause of many multidrug resistant ...infections that are often treated with the first-line choice antibiotic vancomycin (VCM). Loading antibiotics into polymeric nanoparticles (Np) displays promise as an alternative method to deliver therapy due to the greater access and accumulation of the antibiotic at the site of the infection as well as reducing toxicity, irritation and degradation. The aim of this work was to prepare, characterize and evaluate VCM-loaded nanoparticles (VNp) for use against S. aureus strains. Moreover, conjugation of Nps with holo-transferrin (h-Tf) was investigated as an approach for improving targeted drug delivery. VNp were prepared by double emulsion solvent evaporation method using PLGA and PVA or DMAB as surfactants. The particles were characterized for size distribution, Zeta Potential, morphology by transmission electron microscopy, encapsulation yield and protein conjugation efficiency. Process yield and drug loading were also investigated along with an in vitro evaluation of VNp antimicrobial effects against S. aureus strains. Results showed that Np were spontaneously formed with a mean diameter lower than 300 nm in a narrow size distribution that presented a spherical shape. The bioconjugation with h-Tf did not appear to increase the antimicrobial effect of VNp. However, non-bioconjugated Np presented a minimal inhibitory concentration lower than free VCM against a MRSA (Methicillin-resistant S. aureus) strain, and slightly higher against a VISA (VCM intermediate S. aureus) strain. VNp without h-Tf showed potential to assist in the development of new therapies against S. aureus infections.
Monoterpenes, such as beta-pinene, are secondary metabolites widely used in the flavors and fragrance industries and can have their structure altered to enhance their applicability, such as producing ...epoxides, which are used as intermediaries for pharmaceuticals. Epoxides are commonly synthesized by the use of inorganic acids as catalysts, although the acid medium induces epoxide degradation. To overcome these limitations biocatalysis is shown as an alternative. Related to, this work aimed to perform the synthesis of β-Pinene epoxide using Pseudozyma antarctica lipase B (Novozym®435) as a biocatalyst, while determining the independent variables that influence the reaction using experimental design tools. Different solvent systems were evaluated (cyclohexane, acetonitrile, ethyl acetate, and dichloromethane) until 72 h reaction time, from which ethyl acetate showed higher conversion into the epoxidized product (40% in 24 h). Under the other solvents systems, several oxidized by-products were obtained, such as ketones and aldehydes. Moreover, applying metrics of green chemistry, ethyl acetate was also corroborated as the most promising solvent, with a higher atom economy (66.8%) in comparison to the others (41.3%), and a smaller E-value (1.19). Ethyl acetate was the solvent/acyl donor of choice and had the molar ratio and percentage of biocatalyst increased, which resulted in 80% of the product after 3 h of reaction. To obtain an optimized model, four independent variables (temperature, stirring, molar ratio, percentage of biocatalyst) were evaluated using experimental design tools, Fractional Factorial Design and Central Composite Rotatable Design, with conversions ranging from 23 to 95% after 3 h. All the independent variables were statistically significant (p < 0.05) and had different degrees of impact on the conversion. Kinetic parameters of the reaction were determined using the Lineweaver–Burk model (results under 30.1 mmol for Km and 10.7 mmol.min
−1
for Vmax). In conclusion, the combination of two different tools of experimental design provided the development of an optimized model for beta-Pinene epoxidation, achieving high conversion to the epoxidized product after 3 h.
Abstract Tuberculosis (TB) still constitutes a threat to public health in various regions of the world. The existing treatment is long and has many side effects. The need to identify new anti-TB ...compounds and also adjuvants to control exacerbated inflammation in severe TB cases is relevant. Therefore, the objective of this study was to evaluate the anti-mycobacterial activity of extracts and fractions in vitro from plant species collected in the Restinga of Jurubatiba, in Rio de Janeiro state, Brazil. In addition, to verify their immunomodulatory action and cytotoxicity on macrophages. The dichloromethane fraction of Kielmeyera membranacea and Eremanthus crotonoides showed the lowest MIC50 against Mycobacterium bovis BCG (0.95 ± 1.08 and 2.17 ± 1.11 μg/mL, respectively) and M. tuberculosis H37Rv (4.38 ± 1.19 and 15.28 ± 1.21 μg/mL, respectively). They were also able to inhibit the NO and TNF-α production in LPS-stimulated macrophages, without being toxic to cells. Using gas chromatography analysis coupled with mass spectrometer it was possible to suggest the presence of fatty acids and terpenes in the most promising fractions. Those compounds have been described for their anti-mycobacterial activity. These results have enabled identifying Kielmeyera membranacea and Eremanthus crotonoides as the most promising studied species in searching for new anti-TB compounds with dual activity.
Resumo A tuberculose (TB) ainda representa um problema de Saúde Pública em várias regiões do mundo. O tratamento existente é longo e apresenta diversos efeitos adversos. Neste contexto, é relevante a necessidade de identificar novas substancias anti-TB e complementares ao controle do processo inflamatório exacerbado em quadros severos da doença pulmonar. O objetivo deste trabalho foi avaliar, in vitro, extratos e frações de espécies vegetais coletadas na Restinga de Jurubatiba, quanto a sua atividade antimicobacteriana, assim como verificar a ação imunomoduladora e citotóxica em macrófagos. As frações em diclorometano de Kielmeyera membranacea e Eremanthus crotonoides apresentaram os menores CIM50 contra Mycobacterium bovis BCG (0,95 ± 1,08 e 2,17 ± 1,11 μg/mL; respectivamente) e M. tuberculosis H37Rv (4,38 ± 1,19 e 15,28 ± 1,21 μg/mL; respectivamente). Essas também foram capazes de inibir a produção de NO e TNF-α em macrófagos estimulados por LPS, sem serem tóxicas para as células. Através de análise por cromatografia em fase gasosa acoplada ao espectrômetro de massas foi possível sugerir a presença de ácidos graxos e terpenos nas frações mais promissoras, substancias estas descritas por apresentarem atividade antimicobacteriana. Estes resultados permitiram a identificação de Kielmeyera membranacea e Eremanthus crotonoides como as espécies mais promissoras desse estudo, tendo em vista a busca de novos fármacos anti-TB com dupla atividade.
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