Solvents Of Different Polarity Research Articles

Pyrrole-type compounds from the flowers of Calotropis gigantea

Calotropis gigantea, a large shrub, has been used in traditional folk medicines for the treatment of fever, cough, swellings, bronchitis or dyspepsia. Previous studies on C. gigantea reported that its main constituents, specifically cardenolides and pregnanes, had cytotoxic activity against A549 human lung, Hela human cervical cancer cell lines and K562 human chronic myelogenous leukemia. This paper presents the isolation of chemical constituents from the flowers of C. gigantea (Apocynaceae) in order to provide more information about its chemical compounds to the database on medical plants in Vietnam. By using silica gel column chromatography, preparative TLC and eluting with organic solvents of different polarity, results showed that five pyrroles, including pollenopyrroside B (1), epi-acortatarin A (2), shensongine A (3), 5-methoxymethyl-1H-pyrrole-2-carbaldehyde (4), 1-[2-(furan-2-yl)-2-oxoethyl]pyrrolidin-2-one (5), were isolated from the CHCl3 extract of the flowers of C. gigantea (Apocynaceae), collected at Binh Thuan province in March, 2020. Their chemical structures were elucidated by HR-MS and 1D, 2D NMR spectra analysis and comparison with published data. All compounds were the first reported from C. gigantea.

Correlation of temperature dependence of hydride kinetic isotope effects with donor-acceptor distances in two solvents of different polarities.

Recently observed nearly temperature (T)-independent kinetic isotope effects (KIEs) in wild-type enzymes and T-dependent KIEs in variants were used to suggest that H-tunneling in enzymes is assisted by the fast protein vibrations that help sample short donor-acceptor distances (DADs). This supports the recently proposed role of protein vibrations in DAD sampling catalysis. However, use of T-dependence of KIEs to suggest DAD sampling associated with protein vibrations is debated. We have formulated a hypothesis regarding the correlation and designed experiments in solution to investigate it. The hypothesis is, a more rigid system with shorter DADTRS's at the tunneling ready states (TRSs) gives rise to a weaker T-dependence of KIEs, i.e., a smaller ΔEa (= EaD - EaH). In a former work, the solvent effects of acetonitrile versus chloroform on the ΔEa of NADH/NAD+ model reactions were determined, and the DADPRC's of the productive reactant complexes (PRCs) were computed to substitute the DADTRS for the DADTRS-ΔEa correlation study. A smaller ΔEa was found in the more polar acetonitrile where the positively charged PRC is better solvated and has a shorter DADPRC, indirectly supporting the hypothesis. In this work, the TRS structures of different DADTRS's for the hydride tunneling reaction from 1,3-dimethyl-2-phenylimidazoline to 10-methylacridinium were computed. The N-CH3/CD3 secondary KIEs on both reactants were calculated and fitted to the observed values to find the DADTRS order in both solutions. It was found that the equilibrium DADTRS is shorter in acetonitrile than in chloroform. Results directly support the DADTRS-ΔEa correlation hypothesis as well as the explanation that links T-dependence of KIEs to DAD sampling catalysis in enzymes.

Deciphering the ultrafast dynamics of a new tetraphenylethylene derivative in solutions: charge separation, phenyl ring rotation and CC bond twisting.

Tetraphenylethylene (TPE) derivatives are one of the fundamental units for developing aggregation induced emission (AIE) scaffolds. However, the underlying mechanisms implicated in the relaxation of the excited TPE remain a topic of ongoing discussion, while the effect of bulky substituents on its photobehaviour is still under scrutiny. Here, we report a detailed study of the photophysical properties of a new symmetrical and bulky TPE derivative with terphenyl groups (TTECOOBu) in solvents of different polarities and viscosities. Using femto- to nanosecond (fs-ns) time-resolved absorption and emission techniques, we elucidated the role of the phenyl group rotations and core ethylene bond twisting in its behaviour. We demonstrate that TTECOOBu in DCM solutions undergoes a 600 fs charge separation along the ethylene bond leading to a resonance structure with a lifetime of ∼1 ns. The latter relaxes via two consecutive events: a twisting of the ethylene bond (∼ 9 ps) and a rotation of the phenyl rings (∼ 30 ps) leading to conformationally-relaxed species with a largely Stokes-shifted emission (∼ 12 500 cm-1). The formation of the red-emitting species clearly depends on the solvent viscosity and rigidity of the medium. Contrary to the photobehavior in the highly viscous triacetin or rigid polymer matrix of PMMA, a reversible mechanism was observed in DCM and DMF solutions. These results provide new findings on the ultrafast mechanisms of excited TPE derivatives and should help in the development of new molecular rotors with interesting AIE properties for photonic applications.

TICT compounds by design: comparison of two naphthalimide-π-dimethylaniline conjugates of different lengths and ground state geometries.

Two new twisted intramolecular charge transfer (TICT) donor-π-acceptor compounds were designed by combining a well-known electron acceptor naphthalimide unit with a classic electron donor dimethylaniline through two types of different rigid linkers. The combined steady-state and time-resolved spectroscopy of molecules in solvents of different polarities in comparison to solid-state solvation experiments of doped polymer matrixes of different polarities allowed distinguishing between solvation and conformation determined processes. The photophysical measurements revealed that non-polar solutions possess high fluorescence quantum yields of up to 70% which is a property of pre-twisted/planar molecules in the excited charge transfer (CT) states. The increase of polarity allows tuning the Stokes shift through all the visible wavelength range up to 8601 cm-1 which is accompanied by a three orders of magnitude drop of fluorescence quantum yields. This is a result of the emerged TICT states as dimethylaniline twists to a perpendicular position against the naphthalimide core. The TICT reaction of molecules enables an additional non-radiative excitation decay channel, which is not present if the twisting is forbidden in a rigid polymer matrix. Transient absorption spectroscopy was employed to visualize the excited state dynamics and to obtain the excited state reaction constants, revealing that TICT may occur from both the Franck-Condon region and the solvated pre-twisted/planar CT states. Both molecules undergo the same photophysical processes, however, a longer linker and thus a higher excited state dipole moment determines the faster excited state reactions.

Essential oil and extracts from Lavandula angustifolia Mill. cultivated in Bosnia and Herzegovina: Antioxidant activity and acetylcholinesterase inhibition

Lavender (Lavandula angustifolia Mill.) is a perennial, aromatic, medicinal, and decorative plant widespread in the Mediterranean. Due to the high content of essential oil and numerous beneficial properties, it is an extremely valued plant species. In Bosnia and Herzegovina, lavender is cultivated mainly for the needs of the cosmetic and pharmaceutical industries. In this research, the antioxidant activity and acetylcholinesterase inhibition of essential oil (EO) and extracts isolated from lavender were evaluated. L. angustifolia EO was isolated using whole plant material in the flowering period by steam distillation and analyzed by gas chromatography (GC) with flame-ionization (FID) and mass spectrometric (MS) detection. Extracts were prepared by ultrasonic extraction in solvents of different polarities. Total phenolic content in extracts was determined using Folin–Ciocalteu reagent. The antioxidant activity of EO and extracts was examined by two methods, 2,2-diphenyl-1-picrylhydrazil (DPPH) radical scavenging activities and ferric reducing/antioxidant power (FRAP), while the acetylcholinesterase (AChE) inhibitory potential was determined using modified Ellman’s method. The EO was high in content of linalool (27.72%) and linalyl acetate (22.82%), followed by α-pinene (9.82%), lavandulol acetate (7.32%), trans-caryophyllene (5.70%), and others. In total, 24 components were identified. Total phenol content was highest in water and ethanol extracts (45.3 and 14.40 mg gallic acid equivalent (GAE)/g dry extract). Polar extracts indicate good antioxidant power according to both methods, while EO can be considered as good inhibitor of AChE.

Spin-coating of Graphene Oxide as Counter Electrode for Dye-sensitized Solar Cells in Various Dispersing Solvents

Platinum (Pt) is the most commonly used counter electrode material for DSSCs. However, as Pt is a noble metal and expensive, researchers have tried to replace the Pt counter electrode with a variety of materials. In this study, graphene oxide (GO) powders were added to solvents of different polarities as precursor solutions for the counter electrode. The solvents were deionized water, dimethylformamide, isopropanol, and chlorobenzene in descending order of polarity. The prepared GO precursor solutions were coated on the Florine doped Tin Oxide (FTO) glass substrate via spin coating, then coated substrate subjected to thermal reduction reaction to obtain reduced graphene oxide, which was used as the counter electrode of the DSSC. The photoelectric conversion efficiency (PCE) of DSSC using deionized water as the dispersing solvent was 2.70%, which was five times higher than that of DSSC using chlorobenzene.

Component Composition and Antimicrobial Activity of Fractions from the Aerial Part of Common Toadflax (<i>Linaria vulgaris</i> Mill.)

Introduction. Natural biologically active substances (BAS) are distinguished by different polarity, which determines their physicochemical properties, including solubility. When using solvents of different polarity, it is possible to influence the spectrum of BAS extracted from plants, achieving their division into groups, and further achieving isolation in an individual form. Тhe aerial part of Linaria vulgaris Mill. (common toadflax) contains both lipophilic and hydrophilic substances. The herb L. vulgaris is widely used in folk medicine for treatment of angina, conjunctivitis, dermatomycosis, periodontitis and other diseases. Bacterial factors play an important role in the pathogenesis of these diseases.Aim. To study the effect of solvents of different polarity on the component composition of extracted BAS and to study the antimicrobial activity of fractions from the herb L. vulgaris.Materials and methods. The aerial part of L. vulgaris was collected at the flowering stage – at the beginning of fruiting stage in July 2021 in the Perm region. The fractions were obtained by sequential exhaustive liquid-liquid extraction of an alcoholic extract from the herb L. vulgaris with hexane, dichloromethane, and n-butanol. Detection of BAS was carried out by HPLC and planar chromatography on paper. Antimicrobial activity was studied against Escherichia coli, Staphylococcus aureus and Candida albicans.Results and discussion. Using solvents of different polarity four fractions were obtained from the alcohol extract of L. vulgaris: hexane, dichloromethane, n-butanol and water. These fractions have differences in the composition of BAS. The number of polyphenolic substances in the fractions increases with increasing of solvent polarity: hexane (14), dichloromethane (55), butanol (61). The dichloromethane and n-butanol fractions have a similar composition, represented by polyphenolic compounds and iridoids. The main groups of compounds in these fractions are phenolic acids and flavonoids. Iridoids are found in trace amounts. In the hexane fraction, the smallest number of substances was found, iridoids are completely absent, and phenolic acids were found in trace amounts. The water fraction is characterized by the content of the entire BAS complex. The highest antibacterial activity against Escherichia coli and Staphylococcus aureus was found for the aqueous fraction, while the highest antifungal activity was found for the hexane and dichloromethane fractions.Conclusion. Using solvents of different polarity, fractions containing a diverse set of BAS were obtained from the alcoholic extract of L. vulgaris. Fractions exhibiting different polarities from L. vulgaris have antimicrobial activity against Staphylococcus aureus and Escherichia coli, as well as against pathogenic fungi from the genus Candida.

Qualitative Phytochemical Screening and Antimicrobial Activities of n-Hexane, Chloroform, Ethyl Acetate and Methanol Extracts of Ficus capensis Stem Bark

Ficus capensis (farin baure) has wide application in traditional medicine especially in the Northan part of Nigeria in the treatment and management of diarrhoea and digestive distress. This is attributed to the presence of many biologically active compounds in their different parts. In this study, stem bark of F. capensis was extracted with four (4) solvents of different polarities ranging from non-polar, moderately polar to polar. Qualitative phytochemical screening of these extracts was conducted using standard laboratory procedures. The results revealed that only alkaloids, glycosides and carbohydrates were detected from the n-hexane (non-polar) extract of F. capensis while the chloroform and ethyl acetate (moderately polar solvents) and methanol (polar solvent) extracts showed the presence of tannins, saponins, alkaloids, carbohydrates, glycosides, flavonoids and proteins. But anthraquinones were not detected in all the extracts.
 Antimicrobial properties of the extracts were evaluated using clinical isolates of four different bacteria and fungi each. Different concentration of extracts was prepared and activity was measured using zone of inhibition in millimetres (mm). Methanol extracts showed activities against E. coli with the zone of inhibition 10 mm, 11 mm, 12 mm and 14 mm; B. subtilis with the zone of inhibition 10 mm, 11 mm, 13 mm and 15 mm all for 10, 20, 25 and 30% concentration of extracts respectively. Chloroform and ethyl acetate extracts showed antimicrobial activities against S. aureus (12 mm, 14 mm), E. coli (12 mm, 14 mm), P. aeruginosa (14 mm, 12 mm) and B. subtilis (12 mm, 16 mm) respectively for 20% concentration of the extracts. The methanol and ethyl acetate extracts showed considerable antifungal activities against Aspergillus flavus and Aspergillus fungatus. But the n-hexane extract did not show any reasonable antibacterial and no antifungal activities.

Metabolites of Moringa oleifera Activate Physio-Biochemical Pathways for an Accelerated Functional Recovery after Sciatic Nerve Crush Injury in Mice.

In this study, the functional metabolites of Moringa oleifera (MO) were screened to evaluate their possible role in accelerated functional retrieval after peripheral nerve injury (PNI). MO leaves were used for extract preparation using solvents of different polarities. Each dry extract was uniformly mixed in rodents' chow and supplemented daily at a dose rate of 2 g/kg body weight from the day of nerve crush until the completion of the trial. The sciatic functional index (SFI) and muscle grip strength were performed to assess the recovery of motor functions, whereas the hotplate test was performed to measure the regain of sensory functions. An optimal level of oxidative stress and a controlled glycemic level mediates a number of physio-biochemical pathways for the smooth progression of the regeneration process. Therefore, total oxidant status (TOS), total antioxidant capacity (TAC) and glycemic levels were analyzed in metabolite-enriched extract-treated groups compared to the control. The supplementation of polar extracts demonstrated a significantly high potential to induce the retrieval of sensory and motor functions. Further, they were highly effective in controlling oxidative stress, facilitating accelerated nerve generation. This study has highlighted MO as a sustainable source of nutritive metabolites and a valuable target for drug development.

Amphiphilic Silver Nanoparticles for Inkjet-Printable Conductive Inks.

The large-scale manufacturing of flexible electronics is nowadays based on inkjet printing technology using specially formulated conductive inks, but achieving adequate wetting of different surfaces remains a challenge. In this work, the development of a silver nanoparticle-based functional ink for printing on flexible paper and plastic substrates is demonstrated. Amphiphilic silver nanoparticles with narrow particle size distribution and good dispersibility were prepared via a two-step wet chemical synthesis procedure. First, silver nanoparticles capped with poly(acrylic acid) were prepared, followed by an amidation reaction with 3-morpholynopropylamine (MPA) to increase their lipophilicity. Density functional theory (DFT) calculations were performed to study the interactions between the particles and the dispersion medium in detail. The amphiphilic nanoparticles were dispersed in solvents of different polarity and their physicochemical and rheological properties were determined. A stable ink containing 10 wt% amphiphilic silver nanoparticles was formulated and inkjet-printed on different surfaces, followed by intense pulsed light (IPL) sintering. Low sheet resistances of 3.85 Ω sq-1, 0.57 Ω sq-1 and 19.7 Ω sq-1 were obtained for the paper, coated poly(ethylene terephthalate) (PET) and uncoated polyimide (PI) flexible substrates, respectively. Application of the nanoparticle ink for printed electronics was demonstrated via a simple flexible LED circuit.

Quantification of 3,5,7,3'-4'-pentahydroxflavona of the aerial parts of p. Guajava

Psidium guajava is popularly known as guava. It is a very common species in South America, found most often in tropical climate. It is a plant known for its anti-inflammatory property, used in folk medicine for combating intestinal discomfort, colic, colitis, among others. The leaves of P. guajava present flavonoids in their composition, with emphasis on quercetin. The flavonoid class has antioxidant properties and acts on the central nervous system through oxidative inhibition of the endoplasmic reticulum. Thus, the objective of this study was to quantify the quercetin of the aerial parts of guava. Therefore, ethanol extraction was performed, followed by fractionation with solvents of different polarities, obtaining the hexanic, dichloromethane and ethyl acetate fractions. Then, quercetin was identified in the ethyl acetate fraction by Thin Layer Chromatography (CCD), the total flavonoid content was quantified by spectrophotometry and quercetin by High Efficiency Liquid Chromatography (HPLC). The qualitative analysis in CCD of the ethyl acetate fraction revealed the presence of flavonoids. Quantitative spectrophotometry analysis showed 46.2 mg of total flavonoids per g of the ethyl acetate fraction, being 816 μg g-1 of quercetin revealed by HPLC. With this study, it was possible to identify the presence of flavonoids, and about 2% correspond to the substance quercetin, present in the ethyl acetate fraction of P. guajava. Therefore, further studies can be carried out aiming at the isolation of quercetin for application in a pharmaceutical form acting on the central nervous system.

Evaluation of the antioxidant and cytotoxic activities of crude extracts from marine Chlorella sp.

The potential usage of Chlorella as an emerging source of novel and safe pharmacologically important compounds sparked scientists’ interest currently due to its numerous bioactive properties, like anticancer, antioxidant, anti-inflammatory, and anti-microbial. Bioactivities from freshwater Chlorella have been studied previously. However, those isolated from marine water have been poorly investigated. Therefore, this study was undertaken to explore the antioxidant activity and cytotoxicity of the marine Chlorella sp. extracts isolated from the Malaysian coastal area. The result showed that methanolic extract was found the most efficient one among seven solvents of different polarities, resulting in the highest extraction yield (41%), TPC (13.32 ± 0.93 mg GAE/g extract), and TFC (40.35 ± 1.26 mg QE/g extract). In terms of antioxidant activity, methanol extract showed the highest radical scavenging activity that was revealed through DPPH (44.98 ± 2.06 mg TAEC/g extract) and ABTS (33.15 ± 1.50 mg TAEC/g extract) assays. This crude methanolic extract also reduced the viability of (32.07 ± 4.54%) human breast cancer, MCF-7 cells at 100 μg/ml after 48 h of incubation. GC/MS analysis of methanolic extract disclosed the abundance of diterpene and fatty acid esters as the most prevailing metabolites, which are reported to have antioxidant and anticancer properties. This study advocates that marine Chlorella sp. has a promising antioxidant and cytotoxic activity, which could be used as pharmaceuticals and nutraceuticals.

B-doped graphene quantum dots array as fluorescent sensor platforms for plasticizers detection

Human health and environmental safety are imperceptibly disturbed by illegally used plasticizers. A fluorescence sensor array based on B-doped graphene quantum dots was designed to detect six plasticizers. Specifically, the dexterous design is the first to disperse B-doped graphene quantum dots in two solvents of different polarities (N,N-Dimethylformamide and Cyclohexane), select three characteristic fluorescence peaks of B-doped graphene quantum dots in the above two solvents, and construct a 3 × 2 array, with a total of 6 array points. The basis of the detection is that the plasticizers affect the dispersion of B-doped graphene quantum dots in different solutions, which are accompanied by the change of its fluorescence signals. Or the plasticizers affect the electron transfer process of B-doped graphene quantum dots in different solvents, resulting in fluorescence quenching. Fluorescence information output by the sensor array showed a good linear relationship with the concentrations of the six plasticizers. The quantitative detection capability can be specified as: the detection range is 100 ng/mL-195 mg/mL, and the detection limit is 1.05–11.58 ng/mL. The fluorescence sensor array also showed good analytical performance in real samples, with recoveries ranging from 95% to 106%. This method has satisfactory specificity, reproducibility, stability and practicality, making it potential for application.

SPECTRAL-LUMINESCENT PROPERTIES OF A NEW BENZETHIAZOLE POLYMETHINE DYE

The absorption and fluorescence spectra of a new styryl derivative of thioflavin T tosylate 2-{(1E,3E)-4-[4-(dimethylamino)-2,6-dimethylphenyl]buta-1,3-dien-1-yl}- 3-ethyl-1,3-benzothiazolium-3 (Th-C23) in solvents of different polarity and viscosity, as well as when it is incorporated into the structure of amyloid fibrils
 and bovine serum albumin are investigated. A characteristic feature of the dye is an extremely low fluorescence quantum yield in low-viscosity solvents (10–4 in water), which, however, increases significantly in viscous solutions and when incorporated into the structure of proteins or amyloid fibrils. In the latter case,
 the quantum yield increases by 8х103 times. Based on experimental studies and quantum chemical calculations,
 it is shown that Th-C23 exhibits molecular rotor properties. An increase in the fluorescence quantum yield in viscous solutions and upon incorporation into biopolymers is the result of limiting the torsion rotation of molecular fragments, leading to fluorescence quenching. The long-wavelength position of the absorption spectrum and the fluorescence spectrum of the new dye in the red region of the spectrum (520 and 600 nm)
 makes it possible to use it as a fluorescent marker sensitive to the viscosity (hardness) of the microenvironment not only in vitro, but also in vivo.

The Effects of Solvents Polarity on the Phenolic Contents and Ferric Reducing Antioxidant Power of <em>Cassytha filiformis, Commiphora schlechteri, Ochna natalitias</em> and <em>Pavetta assimilis</em>

In the present study, the levels of Total Phenols compounds (TPC) and the antioxidant capacity of different extracts from leaves of Cassytha filiformis (C. filiformis), Commiphora schlechteri (C. schlechterii), Ochna natalitias (O. natalitia) and Pavetta assimilis (P. assimilis) were evaluated by the Folin-Ciocalteu and ferric ion reduction methods, respectively. The extracts evaluated were prepared with solvents of different polarities (n-hexane, dichloromethane, ethyl acetate and aqueous methanol). The total phenols found in all samples increase with solvent polarity. The reduction power found was linearly proportional to the concentration and is greater the greater the content of total phenolics. All extracts of the species O. natalitia (DCM, EtAcO and MetOH) showed higher antioxidant capacity than the other species. Thus, the promising results found in the present study suggest a high potential of these species as a source for the development of therapeutically useful natural antioxidants.

The Influence of Solvent and Extraction Time on Yield and Chemical Selectivity of Cuticular Waxes from Quercus suber Leaves

The cuticular lipid compounds, usually named cuticular waxes, present in the cuticular layering of Quercus suber adult leaves were extracted with solvents of different polarities (n-hexane, dichloromethane and acetone) and analysed by GC–MS. Q. suber leaves have a substantial cuticular wax layer (2.8% of leaf mass and 239 μg/cm2), composed predominantly by terpenes (43–63% of all compounds), followed by aliphatic long chain molecules, mainly fatty acids, and by smaller amounts of aliphatic alcohols and n-alkanes. The major identified compound was lupeol (1.2% of leaves in n-hexane extract). The recovery and composition of cuticular lipids depended on the solvent and extraction time. The non-polar or weak polar solvents n-hexane and dichloromethane extracted similar lipid yields (77% and 86% of the total extract, respectively) while acetone solubilised other cellular compounds, namely sugars, with the lipid compounds representing 43% of the total extract. For cuticular lipids extraction, solvents with a low polarity such as n-hexane are the more suitable with an adequate extraction duration, e.g., n-hexane with a minimum extraction of 3 h.

Evaluation of the in vitro antioxidant and antitumor activity of extracts from Camellia fascicularis leaves.

Camellia fascicularis is a unique plant rich in bioactive components. However, the isolation of the active substances in C. fascicularis leaves via sequential extraction with solvents of different polarity and the determination of their antioxidant and antitumor activities have not been reported. In this study, the total methanol extract of C. fascicularis leaves was sequentially extracted with different polar solvents, and the corresponding petroleum ether extract (PEE), ethyl acetate extract (EAE), and water extract (WE) were analyzed for their contents in active substances such as flavonoids, polyphenols, polysaccharides, and saponins. The antioxidant ability of the polar extracts was investigated by determining their reducing power and the radical scavenging rate on 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and hydroxyl radicals, and CCK-8 and Annexin-FITC/propidium iodide staining assays were conducted to investigate their inhibitory effects on HCCLM6 and HGC27 tumor cells. The results showed that PEE had a high saponin content of 197.35 ± 16.21mgOAE/g, while EAE and WE exhibited a relatively higher polysaccharide content of 254.37 ± 1.99 and 373.27 ± 8.67mgGE/g, respectively. The EAE demonstrated the greatest reducing power and the strongest clearing abilities on ABTS and DPPH radicals with respective EC50 values of 343.45 ± 20.12 and 14.07 ± 0.06μg/ml. Moreover, the antitumor ability of the different polar extracts was dose-dependent, with WE showing the most potent inhibitory ability against HCCLM6 and HGC27 cells.

Push-Pull Structures Based on 2-Aryl/thienyl Substituted Quinazolin-4(3H)-ones and 4-Cyanoquinazolines.

Design and synthesis of 2-(aryl/thiophen-2-yl)quinazolin-4(3H)-ones and 4-cyano-2-arylquinazolines with Et2N-, Ph2N- or carbazol-9-yl- electron donating fragment are described. The key photophysical properties of these compounds have been studied by UV/Vis absorption and fluorescence spectroscopy in solvents of different polarity (toluene and MeCN). 2-(Aryl/thiophen-2-yl)quinazolin-4(3H)-ones show fluorescence in blue-green region in toluene solution with quantum yields up to 89% in the case of 2-(4'-N,N-diphenylamino[1,1'-biphenyl]-4-yl)-quinazolin-4(3H)-one. Moreover, triphenylamino derivative based on quinazolin-4(3H)-one with para-phenylene linker displays the highest quantum yield of 40% in powder. The fluorescence QY of Et2N and Ph2N derivatives decrease when going from toluene to MeCN solution, whereas carbazol-9-yl counterparts demonstrate strengthening of intensity that emphasizes the strong influence of donor fragment nature on photophysical properties. 4-Cyanoquinazolines are less emissive in both solvents, as well as, in solid state. The introduction of cyano group into position 4 leads to orange/red colored powder and dual emission bands. Some molecules demonstrate the increase in emission intensity upon addition of water to MeCN solution. According to frontier molecular orbitals (HOMO, LUMO) calculations, the energy gap of 4-cyanoquinazoline decreases by more than 1 eV compared to quinazolin-4-one, that is consistent with experimental data.

Evaluation of Hydrogen peroxide Scavenging and Antibacterial activity of successive extracts of Luisia tenuifolia Blume against skin and wound infections

Skin and wound infections might trigger severe secondary complications when left untreated. A proper balance between reactive oxygen species generation and antioxidant formation is necessary to achieve redox haemostasis. Luisia tenuifolia Blume (Orchidaceae) has been traditionally applied on cuts, boils and wounds in regions of Western Ghats. The present study was aimed to validate the antioxidant and antibacterial effect of the whole plants of Luisia tenuifolia against five pathogenic bacteria often responsible for skin and wound infections The whole plants of L.tenuifolia, after drying under shade, was pulverised, successively extracted with solvents of different polarity and evaporated to dryness. The hydrogen peroxide scavenging potential of all the four extracts was determined by H2O2 assay. The agar-well diffusion technique was employed for the preliminary screening of antibacterial activity. Further, the minimum inhibitory concentration was determined by broth-dilution assay. Among the four extracts, the ethanol extract of L. tenuifolia exhibited a strong antioxidant activity with an IC50 value of 42.61μg/mL compared to the standard Ascorbic acid (IC50 value of 21.56μg/mL). Moreover, the n-hexane extract was found to be more effective against Staphylococcus aureus whereas the ethanol extract exhibited highest antibacterial effect on Streptococcus oralis, Pseudomonas aeruginosa, Aeromonas hydrophila and Escherichia coli. Furthermore, the ethanol extract was found to be a promising antibacterial candidate with an MIC value of 0.312μg/mL against S.oralis and A.hydrophila. Thus the current study validate the antioxidant and antibacterial potential of L. tenuifolia whole plant extracts and further studies were aimed at identification of active components responsible for the activity.

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.