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Introduction. Combretum leprosum (Combretaceae) is commonly found in the Northeast Region of Brazil and is known for several bioactivities, including antimicrobial ones. Because of increasing bacterial antibiotic resistance, natural products from several plants have been studied as putative adjuvants to antibiotic activity, including products from C. leprosum. Aims. This study was carried out to investigate the structural properties, bactericidal activity and antibiotic modifying action of the lupane triterpene 3β,6β,16β-trihydroxylup-20(29)-ene (CLF1) isolated from C. leprosum Mart. leaves. Methods. The CLF1 was evaluated by the Fourier transform infrared spectroscopy method and the antibacterial activity of this compound was assayed alone and in association with antibiotics by microdilution assay. Results. Spectroscopic studies confirmed the molecular structure of the CLF1 and permitted assignment of the main infrared bands of this natural product. Microbiological assays showed that this lupane triterpene possesses antibacterial action with clinical relevance against Staphylococcus aureus . The CLF1 triterpene increased antimicrobial activity against the multidrug-resistant Escherichia coli 06 strain when associated with the antibiotics gentamicin and amikacin. Synergistic effects were observed against the S. aureus 10 strain in the presence of the CLF1 triterpene with the antibiotic gentamicin. Conclusion. In conclusion, the CLF1 compound may be useful in the development of antibacterial drugs against the aforementioned bacteria.

Staphylococcus aureus represents the most common etiologic agent of purulent infections, affecting humans and animals. Escherichia coli is one of the principal causes of infectious diseases, mainly diarrheal diseases due to enterotoxin action. There are many reports indicating that these bacteria are multidrug-resistant (MDR) pathogens.In this study, we investigated the antimicrobial and modulatory activities of 5-hydroxy-3,7,4'-trimethoxyflavone (VG.EF.CLII) against E. coli and S. aureus strains.5-Hydroxy-3,7,4'-trimethoxyflavone was isolated from Vitex gardneriana Schauer leaves and structurally characterized using nuclear magnetic resonance. The antibacterial effect of VG.EF.CLII and modulation of antibiotic activity, both determined by minimum inhibitory concentration, were assessed using microtiter plates.VG.EF.CLII showed bacterial growth inhibition at concentrations ≤512 μg/mL, and synergistic effects were observed for the modulation of two distinct antibiotic classes (the fluoroquinolone norfloxacin and the aminoglycoside gentamicin).5-Hydroxy-3,7,4'-trimethoxyflavone isolated from V. gardneriana showed promising antimicrobial activity against MDR bacterial strains S. aureus 358 and E. coli 27 when associated with the antibiotics norfloxacin and gentamicin. Therefore, this natural product can contribute to the control of bacterial resistance.

Chalcones are important intermediates in the biosynthesis of biologically active compounds such as flavonoids and their derivatives. In this paper, a new chalcone 2E-1-(2ʹ-Hydroxy-3ʹ,4ʹ,6ʹ-trimethoxyphenyl)-3-(phenyl)-prop-2-en-1-one (HYTPHENYL) was synthesized by the condensation reaction of Claisen-Schmidt in basic medium between the 2-hydroxy-3,4,6-trimethoxyacetophenone (HTMCX) and benzaldehyde. The molecular structure of this chalcone was determined by Nuclear Magnetic Resonance, and characterized by infrared and Raman spectroscopy, at room temperature. Its electrochemical behavior was also evaluated. Vibrational wavenumber and wavevector have been predicted using the Density Functional Theory (DFT) calculations and their normal modes were analyzed in terms of the potential energy distribution (PED). Furthermore, DFT calculations were carried out to obtain the molecular orbitals and the electrostatic surface map. Electronic absorption spectrum of HYTPHENYL was measured and compared with that obtained for the HTMCX compound. Additionally, analysis of the antimicrobial activity and antibiotic resistance modulation was carried out to evaluate the antibacterial potential of the HYTPHENYL chalcone.

Chalcones and their derivatives are substances of great interest for medicinal chemistry due to their antibacterial activities. As the bacterial resistance to clinically available antibiotics has become a worldwide public health problem, it is essential to search for compounds capable of reverting the bacterial resistance. As a possibility, the chalcone class could be an interesting answer to this problem. The chalcones (2E)-1-(4'-aminophenyl)-3-(phenyl)‑prop-2-en-1-one (APCHAL), and (2E)-1-(4'-aminophenyl)-3-(4-chlorophenyl)‑prop-2-en-1-one (ACLOPHENYL) were synthesized by the Claisen-Schmidt condensation and characterized by 1H and 13C nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR), and mass spectrometry (MS), In addition, microbiological tests were performed to investigate the antibacterial activity, modulatory potential, and efflux pump inhibition against Staphylococcus aureus (S. aureus) multi-resistant strains. Regarding the S. aureus Gram-positive model, the APCHAL presented synergism with gentamicin and antagonism with penicillin. APCHAL reduced the Minimum inhibitory concentration (MIC) of gentamicin by almost 70%. When comparing the effects of the antibiotic modifying activity of ACLOPHENYL and APCHAL, a loss of synergism is noted with gentamicin due to the addition of a chlorine to the substance structure. For Escherichia coli (E. coli) a total lack of effect, synergistic or antagonistic, was observed between ACLOPHENYL and the antibiotics. In the evaluation of inhibition of the efflux pump, both chalcones presented a synergistic effect with norfloxacin and ciprofloxacin against S. aureus, although the effect is much less pronounced with ACLOPHENYL. The effect of APCHAL is particularly notable against the K2068 (MepA overexpresser) strain, with synergistic effects with both ciprofloxacin and ethidium bromide. The docking results also show that both compounds bind to roughly the same region of the binding site of 1199B (NorA overexpresser), and that this region overlaps with the preferred binding region of norfloxacin. The APCHAL chalcone may contribute to the prevention or treatment of infectious diseases caused by multidrug-resistant S. aureus.

Chalcones are α,β-unsaturated ketones containing the 1,3-diarylprop-2-en-1-one framework. This study aims to evaluate the potentiation of antibacterial activity by the chalcone (E)-1-(4-aminophenyl)-3-(furan-2-yl)-prop-2-en-1-one (C13H11NO2), hereafter named AFPO, against multi-resistant strains of Staphylococcus aureus and Escherichia coli. AFPO was synthesized using the Claisen-Schmidt condensation reaction, and the molecular structure was confirmed by nuclear magnetic resonance (NMR). The antibacterial and potentiating properties of AFPO were evaluated by measuring the minimum inhibitory concentration (MIC) using microdilution plates. The AFPO MIC was 1024 μg/mL for the S. aureus 10 strain, revealing synergy in combination with the following antibiotics: penicillin, norfloxacin, ampicillin/sulbactam, and gentamicin. The AFPO MIC was 256 μg/mL for the E. coli 06 strain, and synergy was observed with norfloxacin, gentamicin, and penicillin. The potentiation of antibacterial activity by AFPO was observed against the strains of S. aureus 10 and E. coli 06.

In this paper the isolation of 2-Hydroxy-3,4,6-trimethoxyacetophenone (C11O5H14) from the stem bark of Croton anisodontus Mull. Arg. (Euphorbiaceae) is presented and its structure is characterized using Nuclear Magnetic Resonance and single crystal X-ray diffraction. The crystalline structure of this natural compound, which presents potential antimicrobial activity, was determined at 100 K and 298 K. Additionally, the vibrational properties were characterized through infrared and Raman spectroscopy at room temperature in the spectral regions 400 cm−1 to 4000 cm−1 and 25 cm−1 to 4000 cm−1, respectively. Vibrational wavenumber and wavevector have been predicted using the Density Functional Theory calculations with the hybrid functional B3LYP and the basis set 6–31 G(d,p). Furthermore, the description of the normal modes was furnished in terms of the Potential Energy Distribution. Hirshfeld surface analysis is presented in order to investigate the interactions between the molecules in the crystals. Density Functional Theory calculations were carried out in order to obtain the molecular orbitals and other quantum chemical parameters. Experimental and theoretical UV absorption spectra of 2-Hydroxy-3,4,6-trimethoxyacetophenone are also evaluated from time-dependent density functional theory with the purpose to analyze the energies of the most important molecular orbitals and the transitions modes for this compound. Finally, the electrostatic surface potential map was also constructed to display the charge density distribution and the sites of chemical reactivity.

There has been a rapid increase in the incidence and prevalence of opportunistic bacterial infections. Inappropriate use of current antibiotics has continuously contributed to the emergence of resistance to conventional antibiotic therapy. Therefore, the search for natural molecules that are able to combat infections is of great public interest, and many of these compounds with antimicrobial properties can be obtained from phytochemical studies of medicinal plants. In this context, this study reports the isolation and characterization of the flavonoid, kaempferol 7-O-β-D-(6″-O-cumaroyl)-glucopyranoside, from Croton piauhiensis leaves. Additionally, the intrinsic antimicrobial action of the compound and its enhancement against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus strains were assessed. The minimum inhibitory concentration (MIC) of the compound was determined using broth microdilution assays. To evaluate the modulatory effect of the flavonoid, the MIC of antibiotics amikacin and gentamicin, belonging to the class aminoglycosides was assessed, with and without the compound in sterile microplates. The results of intrinsic antibacterial activity tests revealed that the compound had no antibacterial activity against strains tested at concentrations1024 μg/mL. The combination of the flavonoid at a concentration of 128 μg/mL with gentamicin presented synergistic effects against S. aureus 10 and E. coli 06, and also reduced the MIC from 16 μg/mL to 4 μg/mL and 8 μg/mL, respectively. Amikacin also showed synergistic effects against S. aureus 10 and E. coli 06. We also observed reduced MIC for both, from 128 μg/mL to 32 μg/mL; however, antagonism for P. aeruginosa increased the MIC from 16 μg/mL to 64 μg/mL. The combination of the flavonoid with the aminoglycosides may be an alternative to potentiate the expected results in treatment against S. aureus and E. coli, since their association leads to a synergistic effect, reducing the MIC of these drugs and decreasing the dose necessary for therapeutic success.

The chemical composition, vibrational spectroscopy and DFT studies of the essential oils from Lippia sidoides constituents were performed in this study. The harvesting time periods greatly affect the yields of the essential oil extracted from the leaves of the Lippia sidoides plant material. The chemical composition of the essential oil by gas chromatography coupled to mass spectrometry (GC MS) showed thymol as the main constituent of the essential oil. Through Fourier transform Raman (FT-Raman) and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy measurements exhibited a good agreement of the thymol component from the essential oil and the polycrystalline thymol. The Density Functional Theory (DFT) calculations were performed over the molecular structure of the thymol and predicted its Raman and infrared spectra. A good correlation between the experimental spectra of the essential oil and the thymol was observed. Complete assignments of the normal modes were presented for both Raman and infrared spectra of the thymol.

In this study, two 4′-aminochalcones with structural similarity were structurally characterized using the NMR technique of 1H and 13C. Polycrystalline samples of these chalcones were analyzed by FT-Raman and ATR-FTIR spectroscopy at room temperature in the regions 40-4000 cm-1 and 400-4000 cm-1, respectively. The DFT calculations using the B3LYP functional with 6-311 G(d,p) basis set were performed, revealing the optimized molecular geometry and the vibrational wavenumbers for these chalcones. Conformational analysis was done from the optimized structures to obtain different conformers. The calculated harmonic vibrational wavenumbers were scaled to improve the agreement between theoretical and experimental wavenumbers. A complete vibrational assignment using Potential Energy Distributions (PED) was provided for the observed Raman and infrared spectra. The scaled wavenumbers were found to be in good agreement with experimental wavenumbers. Furthermore, a comparative structural and vibrational analysis was performed. The structural analysis allowed us concluding that in addition to differences in the position 4′ – where one chalcone has a methoxy group and the other, an ethoxy group – the molecular conformation of them is significantly different, especially regarding the torsion angles linking the enone chains with the rings of these chalcones. The vibrational analysis allowed us to identify all Raman and infrared bands of the two chalcones, highlighting the main differences and correspondences between them.

In the present study, the natural product sonderianin diterpene (C 21 H 26 O 4 ), a diterpenoid isolated from Croton blanchetianus , with potential application in the drug industry, was characterized by nuclear magnetic resonance, infrared and Raman spectroscopy. Vibrational spectra were supported by Density Functional Theory calculations. Infrared and Raman spectra of sonderianin were recorded at ambient temperature in the regions from 400 cm −1 to 3600 cm −1 and from 40 cm −1 to 3500 cm −1 , respectively. DFT calculations with the hybrid functional B3LYP and the basis set 6–31 G(d,p) were performed with the purpose of obtaining information on the structural and vibrational properties of this organic compound. A comparison with experimental spectra allowed us to assign all of the normal modes of the crystal. The assignment of the normal modes was carried out by means of potential energy distribution.

The use of films or membranes to treat cutaneous lesions has become a standard therapeutic procedure in the last two decades. For this reason, many polymeric materials such as chitosan, collagen, alginate, and gelatin, have been investigated to better understand their physical, chemical and biological properties. This study addresses the preparation, structural and spectroscopic characterization of chitosan membranes, chitosan with glycerol and chitosan with glycerol plus allantoin as the active principle, using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Raman and Infrared spectroscopy techniques. The insertion of the active principle allantoin in the polymer matrix was also observed using the techniques mentioned above. The results from this study showed that the chitosan membranes containing the active principle allantoin in the polymer matrix present adequate characteristics for the use in medicine as a biodegradable drug vehicle.