Solvents Of Different Polarity Research Articles

Scavenging Capacity of Extracts of Arrabidaea chica Leaves from the Amazonia against ROS and RNS of Physiological and Food Relevance.

Arrabidaea chica, a medicinal plant found in the Amazon rainforest, is a promising source of bioactive compounds which can be used to inhibit oxidative damage in both food and biological systems. In this study, the in vitro scavenging capacity of characterized extracts of A. chica leaves, obtained with green solvents of different polarities [water, ethanol, and ethanol/water (1:1, v/v)] through ultrasound-assisted extraction, was investigated against reactive oxygen (ROS) and nitrogen (RNS) species, namely superoxide anion radicals (O2•−), hydrogen peroxide (H2O2), hypochlorous acid (HOCl), and peroxynitrite anion (ONOO−). The extract obtained with ethanol–water presented about three times more phenolic compound contents (11.8 mg/g) than ethanol and water extracts (3.8 and 3.6 mg/g, respectively), with scutellarein being the major compound (6.76 mg/g). All extracts showed high scavenging efficiency against the tested ROS and RNS, in a concentration-dependent manner with low IC50 values, and the ethanol–water extract was the most effective one. In addition, all the extracts were five times more efficient against ROO• than Trolox. Therefore, the extracts from A. chica leaves exhibited high promising antioxidant potential to be used against oxidative damage in food and physiological systems.

Efficient one-pot synthesis, characterization and  DFT study of solvents polarity effects on the structural, energetic and thermodynamic proprieties of (a-methylamino-ethyl)-phosphonic acid dimethyl ester

In this work, an efficient procedure has been described for synthesis of (α-Methylamino-ethyl)-phosphonic acid dimethyl ester (MPDE) via Kabachnik-Fields reaction under green condition, using free solvent and free catalyst by employing microwave irradiation. The designed product is obtained with excellent yield (∼92%) in short reaction time (5–8 min), and confirmed by spectroscopy analyses. Results confirm the successful synthesis of MPDE with high purity. Through appropriate quantum chemical approaches, by the density functional theory (DFT) method, at B3LYP/6–31G* level of theory, we have performed a systematic investigation of the polarity solvent effects on the energetic, structural and thermodynamic proprieties of MPDE in gas phase and in a series of seven solvents of different polarity (water, DMSO, acetonitrile, methanol, ethanol, acetone, and diethylether). The polarizable continuum model (PCM) has been used to obtain the properties in the solvent environment. Results revealed that the participation of the solvent is fundamental for a series of effects concerning the stability and reactivity of the title compound.

Optimization of triphenylamine-based polyimide structure towards molecular sensors for selective detection of heavy/transition metal ions

A series of well-defined triphenylamine (TPA)-based polyimides having a stiff core or different flexible/kinking linkages in the main chains and pendant bipyridylamine (biPyA) ligands were developed with the aim to test them as chemosensors for selective detection of heavy/transition metal ions. Besides a detailed structural characterization by NMR/ FTIR spectroscopies, gel permeation chromatography and solubility tests, the chemosensors were investigated with regard to their thermal, photo-optical and electrochemical properties to anticipate their behavior in the ion sensing studies. The synergism between the main structural elements in these polymers proved to be beneficial towards developing materials that may withstand elevated temperatures and with optical behaviour depending on the chemical structure and macromolecular surrounding environment. With the support of DFT simulation, both localized and intramolecular charge transfer states were identified, which were responsible for the variable fluorescence signature of the polymers in solvents of different polarities. The TPA and imide units endowed these polymers with significant electroactivity, which was further exploited to evidence the metal ion detection capability of the chemosensors. For the first time, these unknown polyimides functionalized with biPyA receptor were explored in the detection of metal ions by three complementary methods, namely UV–vis absorption, fluorescence and electrochemistry. The polyimide with flexible ether bridges experienced selective turn-on fluorescence response to Zn2+ ion over a variety of other competing cations that had no or little influence on its fluorescence change. Whereas, complete fluorescence quenching was triggered by Fe3+ ions when progressively loaded to the solution of the analogous more rigid polyimide containing carbonyl bridged group. This demonstrates that the modulation of chelating ability of biPyA receptor through the macromolecular design is an appropriate tool to achieve high sensitivity towards a specific metal ion.

In Vitro Antimicrobial Potential of Impatiens Balsamina Flower Against Staphylococcus Aureus, Escherichia Coli and Candida Albicans

The search for new drugs to treat cases of infection continues. This is because the microorganisms that cause infection continue to mutate as a form of self-defense which causes resistance to antibiotics. One strategy for finding new drugs is through the exploration of active ingredients derived from plants that have been used empirically by the community. Impatiens balsamina is a plant that has been shown to have antibacterial, antifungal, antipruritic, and anti-allergic characteristics. The ethanol extract of the Impatiens balsamina flower contains secondary metabolites such as naphthoquinones, coumarin derivatives, flavonoids, steroids, quinones, and saponins. This study aimed to obtain the active ingredient of the Impatiens balsamina flower which is used as an herbal medicine in the treatment of infection. A multilevel extraction process was carried out using solvents of different polarity, so that fractions containing nonpolar compounds, semipolar compounds, and polar compounds were obtained. Then, each fraction was tested for antimicrobial potency. Antimicrobial testing in vitro was carried out using the disc diffusion method. The results showed that the secondary metabolites contained in the hexane fraction were terpenoids, flavonoids, polyphenols, and anthraquinone compounds. Secondary metabolites contained in the ethyl acetate fraction were alkaloids, terpenoids, flavonoids, polyphenols, and anthraquinone compounds. Secondary metabolites contained in the ethanol fraction were terpenoids, flavonoids, polyphenols, and anthraquinone compounds. The hexane fraction had the best percentage of inhibition and percentage of effectiveness against Staphylococcus aureus, Escherichia coli, and Candida albicans.
 Keywords: antimicrobial, fractionation, Impatiens balsamina L flower, disc diffusion

Impact of an ortho-cyano group on photophysical properties and performance of OLEDs based on D-A–A type pyrazine push-pull system

A series of novel D–A–A push-pull systems based on a 2-cyanopyrazine acceptor core bearing various electron-donating fragments are synthesized and investigated. The effect of the cyano group on the spectral-luminescent properties of molecules in solvents of different polarities and films obtained by thermal vacuum deposition has been investigated. Fast and delayed luminescence was studied at room temperature and 77K. The energy gap between the S1 and T1 states is estimated. The reasons for the weak thermally activated delayed fluorescence are discussed. It has been found that increasing the efficiency of light-emitting organic diodes up to 20 times took place when a cyano group introduces into fluorophores.

Antimalarial Activity of Extract and Fractions of Sauropus androgynus (L.) Merr.

Sauropus androgynus (L.) Merr., in the Indonesian local name known as “Katuk,” is a tropical shrub plant of the family Euphorbiaceae. Based on genus and chemotaxonomic approaches, as well as in vitro testing of Plasmodium falciparum, leaves of S. androgynus are presumed to have an active compound content as an antimalarial. The current study aims to investigate the antimalarial activity of 96% ethanol extract and fractions of S. androgynus leaves. The ethanolic extract was fractionated using the vacuum liquid chromatography (VLC) method with three solvents of different polarities (n-hexane, chloroform, and 96% ethanol). The fraction obtained was then evaluated for antimalarial activity against P. falciparum 3D7 strain. The ethanolic extract was evaluated for antimalarial suppressive and prophylactic activity against P. berghei-infected mice, as well as inhibitory activity against the heme detoxification process in vitro. Fractionation of ethanolic extract resulted in seven combined fractions, with the most active fraction being FV (50% inhibitory concentration (IC50) = 2.042 µg/mL). The ethanolic extract showed good parasitic suppressive (therapeutic) activity with a median effective dose (ED50) value of 15.35 mg/kg body weight. In a prophylactic test, ethanolic extract showed parasite growth inhibitory activity of 67.74 ± 9.21% after the administration of 400 mg/kg body weight for 4 days before infection, and 65.30 ± 10.44% after the administration of 200 mg/kg body weight for 8 consecutive days (4 days before and after infection). The ethanolic extract also showed an effect in inhibiting the formation of β-hematin of about 26.87–79.36% at a concentration of 0.1–4 mg/mL and an IC50 value of 0.479 mg/mL. The S. androgynus leaves were shown to have antimalarial activity in vitro and in vivo, where ethanolic extract were more active compared with the fraction obtained. The antimalarial properties of the extract showed a higher suppressive activity than prophylactic activity.

An imidazole-derived polarity sensitive probe for lipid droplet target and in vivo tumor imaging

Accurate differentiation of tumor cells from normal cells is a fundamental and critical challenge for the early diagnosis of cancer. The intrinsic low-polarity and increased numbers of lipid droplets can be utilized as potential biomarkers for tumor cells. Therefore, we synthesized and screened the polar fluorescent probe (PI-CHO), which exhibiting notable fluorescence color change and spectral shift in solvents of different polarities. PI-CHO has a high sensitivity to polarity changes in the linear range of ET(30) = 37.4–63.1, with a fluorescence enhancement of more than 474-folds. Intracellular imaging experiments showed that PI-CHO has low cytotoxicity, excellent lipid droplet-targeted performance and discernibility between tumor and normal cells. Ex vivo imaging of the tumors and major organs demonstrated the great reliability and sensitive responsiveness of PI-CHO towards tumors. Moreover, the proposed probe was successfully applied to detect tumors in living mice, exhibiting the potential to become a powerful tool in early cancer diagnosis.

One‐Pot Transition‐Metal‐Free Synthesis of Polysubstituted Fused Benzene Derivatives from Methyl Enol Ethers and Alkynes

A one-pot synthesis of polysubstituted fused benzene derivatives from methyl enol ethers and alkynes is reported. A wide variety of diversely functionalized naphthalene and phenanthrene derivatives were obtained in good to excellent yields. Due to the fluorescent nature of naphthalene, selected compounds were screened for the solvatochromism study.

UHPLC-HRMS Method for the Simultaneous Screening of 235 Drugs in Capillary Blood for Doping Control Purpose: Comparative Evaluation of Volumetric and Non-volumetric Dried Blood Spotting Devices.

We present a quick and simple multi-targeted analytical workflow based on ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry for the screening in dried blood spots and dried plasma spots of a wide variety of drugs with different chemical properties. Seven different microsampling devices were evaluated in view of their application for the detection of the selected target analytes in the framework of doping control analysis. The extraction of the analytes was optimized by assessing the efficacy of protocols based on ultrasonication with aqueous buffers and/or organic solvents of different polarities. Optimal recoveries were obtained by using pure methanol or mixtures of methanol/acetonitrile and methanol/isopropanol, depending on both the device and the target analytes. The method was fully validated according to both ISO17025 and the requirements of the World Anti-Doping Agency: all the analytes were clearly distinguishable from the matrix, with limits of detection in the range of 0.1–3.0 ng mL–1. Stability studies simulating the storage of samples before the analysis and in view of a possible re-analysis showed that most of the analytes were stable for at least 24 h at 50 °C and for at least 3 weeks at 25 and at 4 °C. The real applicability of the method was assessed by analyzing the samples collected after the administration of two model drugs, acetazolamide and deflazacort. The performance of the method was confirmed to be fit for purpose, and data obtained in blood can also be used to complement those available in urine, allowing to refine the knowledge concerning the pharmacokinetic profiles.

Does the change in the length of the alkyl chain bring us closer to the compounds with the expected photophysical and biological properties? – Studies based on D-π-D-A imidazole-phenothiazine system

The novel imidazole-based phenothiazine derivatives 3a-3e differing in the length of the alkyl chain at the imidazole substituents were effectively designed and synthesized. The effect of the alkyl chain on the photophysical properties of novel compounds was systematically investigated and supported by TD/DFT calculations. The photophysical characterization of 3a-3e compounds was performed in a series of solvents. Both absorption and fluorescence spectra exhibited positive solvatochromism. Phenothiazine derivatives 3a-3e have a noteworthy emission from blue to yellow region 450–600 nm, high quantum yields 41–93%, lifetimes in nanosecond scale (4.01–7.55 ns), and Stokes shifts in the range of 5688–7021 cm−1 in solvents of different polarity. The noticeable positive solvatochromism indicates the good charge separation in compounds. This work presents the variability of photophysical properties associated with a simple modification of the alkyl chain at the imidazole unit in 3a-3e compounds. Additionally, the ability of the novel compounds 3a-3e for cellular staining, and their cytotoxicity was investigated. Comparative lack of toxicity and appealing photophysical properties make them useful as molecular fluorescent dyes in biological applications.

Phytochemical screening of leaves and flower extracts of Sesbania grandiflora (L.) Pers. and its antimicrobial activity against fish pathogens

Antibiotic-resistant fish pathogens have emerged as a serious concern in the field of aquafarming. As commonly employed antibiotics are becoming increasingly ineffective, conventional medicinal herbs have been identified as a potential drug source that can combat microbial antibiotic resistance. The current work aims to scrutinize the antibacterial potential of a nutritional and conventional medicinal herb i.e., S. grandiflora extracts against predominant fish pathogens. The leaves and flowers were extracted consecutively by solvents of different polarities (hexane, chloroform, ethyl acetate, and methanol) and the presence of potential phytoconstituents was examined qualitatively. Alkaloids, flavonoids, and steroids were identified in both leaves and flower extracts whereas saponins and phenols were present only in flower and leaves, respectively. Agar well diffusion method was employed for determining the antimicrobial activities of different extracts. The hexane, chloroform, ethyl acetate, and methanolic fractions of both leaves and flowers showed an acceptable inhibition for all the fish pathogens except V. harveyi. The methanolic flower extract shows a maximum inhibitory activity against V. alginolyticus (33 mm). In conclusion, the extracts of S. grandiflora contain potential secondary metabolites, that can be used as antimicrobial agents for predominant fish pathogens and also the flower extracts possess higher inhibitory activity compared to that of the leaves.

The association of extracts of Achyrocline satureioides and the fungus Beauveria bassiana against the tick Rhipicephalus microplus

The tick Rhipicephalus microplus (Canestrini) is a major economic hurdle to the global livestock industry. The incorrect and indiscriminate control carried out by synthetic chemical compounds has contributed to the emergence of parasite resistance present today to many products available in the veterinary market. Effective, economically viable and potentially safe alternatives need to be investigated, including herbal medicine and biological control by entomopathogenic fungi. In this study, extracts from Achyrocline satureioides (Lam.) DC. obtained by extraction with solvents of different polarities associated and not associated with the entomopathogenic fungus Beauveria bassiana (Balsamo-Crivelli) Vuillemin were evaluated on different stages of the life cycle of R. microplus. The activity of plant extracts, fungus and their associations in ticks was analyzed in vitro through the adult immersion test, larval packet test and larval immersion test. The highest efficacy on engorged females (43.3%) was reached by the hexanic partition (ASh) at 5mg/mL + fungus, reducing larval hatchability. ASh associated with B. bassiana also caused high mortality of larvae, reaching LC50 of 6.23 and 2.65mg/mL in the packet and immersion tests, respectively. The results obtained showed that extracts, when used in combination with the fungus, have their action enhanced, reaching 100% mortality of larvae. Among the evaluated methodologies, it was observed that the larval immersion test allows better assessment, due to the time of contact with the larvae. The results obtained with A. satureioides associated with the fungus are considered promising and open new perspectives for future product development.

Full relaxation dynamics recovery from ultrafast fluorescence experiments by means of the stochastic model: Does the solvent response dynamics depend on the fluorophore nature?

• The model of non-stationary charge-transfer dye fluorescence spectrum is presented. • The solvation dynamics depend on fluorophore. • The contribution of intramolecular vibrations in FLUPS is separated. • The solvent relaxation function of hexane is determined. An approach to analysing time-resolved fluorescence spectra has been developed for dyes with non-parabolic free energy curves of the excited and ground states. It incorporates the description of the solvent relaxation and redistribution/relaxation of intramolecular high-frequency vibrations proceeding in parallel with the pumping. The approach has been applied to simulate spectra of covalently linked perylene-dimethylaniline (PD) in a series of solvents of different polarity. The developed approach combined with the achieved temporal resolution of the modern fluorescence upconversion spectroscopy is shown to provide a possibility to disentangle the relaxation of high-frequency vibrations and the dynamics of the solvent. In this compound the reorganization of both intramolecular vibrations and the solvent strongly affects the absorption and fluorescence spectra so that their influence on spectral dynamics is highly entangled. The comparison of fluorescence spectral dynamics of two dyes, coumarin 153 and PD, shows that the solvation dynamics depend on the fluorophore. The fitting of simulated fluorescence spectral dynamics of PD to the experimental data enables us to determine the solvent relaxation function of hexane.

Solvent effects on the vibrational modes of (R)-3-methylcyclohexanone conformers

• DFT calculations of IR spectra are reported for ( R )-3-methylcyclohexanone ( R 3MCH) conformers in 11 solvents. • Solvent effects on IR spectra of R 3MCH conformers are investigated. • DFT calculations of the dipole moment components and magnitude of R 3MCH conformers were performed in 11 solvents. • A weak linear correlation was observed between the EQ and AX enthalpy difference as a function of solvent polarity. Quantum chemical calculations of the IR spectra, dipole moments, and enthalpies for the optimized geometries of dominant Equatorial (EQ) and Axial (AX) conformers of R-(+)-3-methylcyclohexanone (R3MCH) were performed in 11 common solvents of different polarity and nature, in the framework of polarizable continuum model (PCM). Density Functional Theory (DFT) involving exchange–correlation functional B3LYP and aug-cc-pVTZ basis set were used. The IR calculations of the individual conformers of R3MCH in CCl 4 yielded two distinct vibrational modes at 1086.13 cm −1 and 1030.86 cm −1 that were identified as unique markers of the EQ and AX conformers, respectively. By monitoring the calculated peaks of these two markers in 11 different solvents, a linear correlation between the EQ and AX markers’ intensities and frequencies with solvent polarity was observed. This correlation was directly related to the dipole moment orientation of each conformer. Upon increasing solvent polarity, the mode frequency of the EQ and AX markers experienced hypsochromic (blue) and bathochromic (red) shifts, respectively. A weak linear correlation was observed between the EQ and AX enthalpy difference as a function of solvent polarity.

Phytochemical Composition, Antioxidant, Antibacterial, and Enzyme Inhibitory Activities of Various Organic Extracts from Apocynum hendersonii (Hook.f.) Woodson.

Apocynum hendersonii is a traditional medicinal plant used primarily as tea. It has a potential health benefit from its rich bioactive substances. This study investigated the reactivity of solvents of different polarities (ethanol, ethyl acetate, n-hexane, methanol, and water) extracts of the A. hendersonii leaf. The phytochemical composition of the extracts was evaluated using a Fourier Transform Infrared spectrophotometer (FT-IR), Gas Chromatography-Mass Spectrometry (GC-MS), UHPLC-MS, and Higher Performance Liquid Chromatography (HPLC). The result revealed the presence of medicinally important bioactive constituents, including phenols, flavonoids, and polysaccharides. Methanol extracts exhibited the highest flavonoid contents (20.11 ± 0.85 mg QE/g DW) and the second-highest in terms of phenolic (9.25 ± 0.03 mg GAE/g DW) and polysaccharide (119.66 ± 2.65 mg GE/g DW). It also had the highest antioxidant capacity with 60.30 ± 0.52% and 4.60 ± 0.02 µmol Fe2+ per g DW based on a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and ferric reducing antioxidant power (FRAP), respectively. Ethanol extract displayed the maximum antibacterial action against Gram-negative and Gram-positive bacteria and the highest inhibition activity against the enzymes tyrosinase and acetylcholinesterase, followed by methanol extract. The principal component analysis revealed a positive correlation between the constituents, bioactivities, and extracts. The overall result showed A. hendersonii as a rich natural source of antimicrobial and antioxidant bioactive compounds and may be used for future applications in pharmaceuticals and food industries.

Copper(II) Ion Promoted Reverse Solvatochromic Response of the Silatrane Probe to Spectral Shifts: Preferential Solvation and Computational Approach.

The unique solvatochromic attitude of an analyte owing to its coordination with metal ions in solvents of different polarities is challenging. Herein, we introduce two new solvatochromic 4-(pentan-3-yl) benzaldehyde-based triazolyl silatrane probes (5 and 6). The solvatochromic behavior of both probes 5 and 6 was studied using Reichardt's E (30) and the Kamlet-Taft empirical scale by UV-visible spectra in 14 solvents (hydrogen-bond donor (HBD) and non-HBD), and the results show that probes 5 and 6 exhibit reverse solvatochromism. Probe 5 witnessed an enhancement in this behavior upon coordination with the Cu2+ ion in MeCN/MeOH solvents due to the intramolecular charge transfer (ICT) process. Interestingly, the binding of probe 5 with Cu2+ ions resulted in an instant color change in MeCN and MeOH from pale yellow to light blue and brown-red, respectively, which can be easily detected by the "naked eye". A solvatochromic study of the complex 5-Cu2+ in binary mixtures of polar aprotic and polar protic solvents (MeCN/MeOH) discloses that the latter are more preferred over polar aprotic solvents in the solvation microsphere. The entire metal coordination process of probe 5 toward the Cu2+ ion can be visualized and was further evaluated by UV-vis/fluorescence spectral titrations, Fourier transform infrared (FT-IR) spectroscopy, and theoretical calculations employing density functional theory (DFT) and time-dependent-DFT (TD-DFT). The proposed analytical approach is believed to play a crucial role in the solvatochromic study of higher coordinated silicon compounds, which may be utilized to develop a solvent-dependent sensor.

A highly selective and sensitive fluorescent sensor based on a 1,8-naphthalimide with a Schiff base function for Hg2+ in aqueous media

Abstract A new fluorescent sensor, N-allyl-4-[(2-(3-methoxysalicylaldimino)ethylamino]-1,8-naphthalimide (HL), for Hg2+ has been developed where the Schiff base substituent acts as a recognition group. This sensor shows a large Stokes shift of 3535–4042 cm−1 and a general fluorescence quantum yield of 0.05, 249–0.11, 866 in organic solvents of different polarity as expected. It also exhibits highly selective and a sensitive response to Hg2+ (Ф Hg+HL/Ф HL = 2.28) over other metal ions (Na+, K+, Ca2+, Mg2+, Al3+, Pb2+, Fe3+, Ni2+, Zn2+, Cu2+, Ag+, Co2+, Cr3+, Mn2+ and Cd2+) in solution (DMF/Tris-HCl buffer, 1:1, v/v, pH = 7.2). The Hg2+-induced fluorescence enhancement at 526 nm is proportional to the concentration of Hg2+ in the range of 0.5–4.0 µm with a detection limit of 0.18 µm. Based on the fluorescence titration and a Job’s plot analysis, the metal-to-ligand ratio of the complex is 2:1 with a binding constant of 1.56 × 1012 m −1.

Solvent polarity‐dependent ESIPT behavior for 5‐(benzothiazole‐2‐yl)‐4‐hydroxyisophthalaldehyde fluorophore: A theoretical study

AbstractIn view of the potential applications of 5‐(benzothiazole‐2‐yl)‐4‐hydroxyisophthalaldehyde (BHI) in the rapid identification of cyanide, the mechanism of excited‐state intramolecular proton transfer (ESIPT) of BHI has been studied in this work. By exploring the geometric parameters of hydrogen bonding in aprotic solvents with different polarities, infrared (IR) vibrational spectroscopy can confirm that hydrogen bonding is enhanced in the first excited state (S1). It is worth mentioning that the enhancement of hydrogen bonding in the S1 state by polar solvents is particularly important. In light‐induced excitation, by comparing the energy gaps of the leading molecular orbitals and the charge recombination around the proton acceptor and donor in aprotic solvents of different polarities, it is further predicted that polar solvents can promote the ESIPT process of BHI. In order to clarify the detailed ESIPT mechanism, we constructed the potential energy curves, searched for the transition state (TS) form, and determined the ESIPT mechanism for BHI fluorophore. Herein, we not only elucidated the excited‐state behavior of BHI, but also proposed a mechanism for regulating ESIPT by solvent polarity.

Phytochemical study of the plant species Bidens pilosa L. (Asteraceae) and Croton floccosus (Euphorbiaceae).

Background: Given the chemical richness of medicinal plants ( Bidens pilosa L. and Croton floccosus) in Ecuador, they are considered the natural source of numerous medicines. Methods: The leaves were dried at 40°C and 50°C and the extracts were characterized by means of phytochemical screening, verifying the presence of secondary metabolites such as alkaloids, reducing sugars, phenols, flavonoids, tannins and saponins. Three extraction processes were carried out, with two solvents of different polarities: hexane and ethanol. The extraction methods that were applied to the leaves of the plants were Soxhlet, ultrasonic bath and maceration, the latter two at room temperature and Soxhlet at the boiling temperature of the solvent. Determination of the total content of phenols and flavonoids is carried out using the Follin-Ciocalteau colorimetric reaction, Quercetin standard, Aluminum Chloride solution measured with a UV-Vis spectrophotometer. The antioxidant activity was performed with the DPPH radical and measured with the same equipment. Results: The highest content of total phenols obtained by employing the Soxhlet method for extraction when the material was dried at 50°C was 48.609 ± 0.370 mg GAE/g of dry sample for Bidens pilosa L. while in the case of Croton floccosus it was 128.212 ± 0.601 mg GAE/g of dry sample obtained from the extraction by means of maceration. Finally, the antioxidant activity against the 1.1-diphenyl-2-picryl-hydrazyl radical was determined, and it was found that the Bidens pilosa L. species performed better and responded better to the test, with an IC 50 value of 239.33 µg/mL, than Croton floccosus (IC 50 of 644.125 µg/mL). Conclusions: The following preliminary phytochemical study of the Bidens pilosa L. and Croton floccosus plants provided important information on the content of secondary metabolites and response to the DPPH radical reported for the first time in Ecuador, which may be future use for medicinal application.

Amphiphilic Polymer Conetwork Gel Films Based on Tetra-Poly(ethylene Glycol) and Tetra-Poly(ε-Caprolactone).

The preparation and investigation of gel films from a model amphiphilic polymer conetwork (ACN) grant a deeper control and understanding of the structure–property relationship in the bulk phase and at the interface of materials with promising applications. In order to allow the simultaneous transport of hydrophilic and hydrophobic substances, polymeric networks with finely distributed hydrophilic and hydrophobic components are very suitable. When designing new soft materials such as coatings, in addition to the structure in the bulk phase, the structure at the interface plays a critical role. In this study, two alternating tetra-arm star polymers poly(ε-caprolactone) (tetra-PCL-Ox) and amino-terminated poly(ethylene glycol) (tetra-PEG-NH2) form an amphiphilic polymer conetwork. The correlation between different synthesis strategies for gel films of this ACN model system and their resulting properties will be described. Through various spin coating techniques, control over film thickness and roughness is achievable and highlights differences to macroscopic gel samples. Atomic force microscopy (AFM) measurements reveal the effect of solvents of different polarities on the swelling ability and surface structure. This correlates with AFM investigations of the mechanical properties on ACN gel films, demonstrating a strong effect on the resulting elastic modulus E, depending on the presence or absence of a good solvent during synthesis. Furthermore, a higher E modulus is obtained in the presence of the selective solvent water, compared to the non-selective solvent toluene. This observation is explained through selective swelling of the tetra-arm star polymers displaying a different hydrophobicity.