Polycyclic aromatic hydrocarbon derivatives onto polar microplastics of polyurethane: equilibrium, thermodynamics, and kinetics of monolayer-multilayer adsorption.

The study of the adsorption of polycyclic aromatic hydrocarbons on microplastics (MPs) has attracted much attention as to how microplastics can act as carriers of these pollutants. Polyurethane (PU) is one of the MPs found in aquatic environments, containing different functional groups it can interact with polar and nonpolar molecules. PAH derivatives (dPAHs) present different properties and thus can be adsorbed by different interactions; thus, this study investigated the adsorption of fluorene (FLN), dibenzothiophene (DBT), dibenzofuran (DBF), and carbazole (CBZ) onto PU MP. The Langmuir, Freundlich, and BET isotherm models were examined, and the BET model best fitted. The adsorption was a nonspontaneous process, exothermic for mono- and multilayer formation for FLN, DBT, and CBZ, and endothermic for DBF monolayer formation. The adsorption monolayer was formed by van der Waals forces, H─bonding, and π─π interactions, while the formation of the multilayer can be explained by π─π and hydrophobic interactions. The pseudo-second-order model proved to be more consistent for the adsorption of dPAHs. The adsorption in artificial seawater shows no significant differences for the monolayer but favored the adsorption multilayer due to the salting-out effect. Due to the existence of several adsorption mechanisms, PU MP interacts with dPAHs in greater quantities when compared to a MP with a simpler structure.

Adsorption of naphthalene and its derivatives onto high-density polyethylene microplastic: Computational, isotherm, thermodynamic, and kinetic study.

Microplastics (MP) have received great attention due to the mass-produced residues discharged into the environment. MP are ideal for adhering to organic pollutants that can be easily dispersed, thus posing risks to human health. Furthermore, little has been reported on how different functional groups in polycyclic aromatic hydrocarbons (PAH) derivatives influence the adsorption behavior on MP. To better understand this process, groups methyl (-CH3) and hydroxyl (-OH) were selected and commercial and waste high-density polyethylene (HDPE, ≤ 1 mm) were used as adsorbents, and Naphthalene (Nap), 1-Methyl-Naphthalene (Me-Nap) and α-Naphthol as adsorbates. The results showed different behaviors for nonpolar and polar adsorbates. Dispersion forces were the main type of interaction between HDPE and Nap/Me-Nap, while dipole-induced dipole forces and H-bonding were the chief interactions involving MP and polar compounds. Regardless the HDPE source, Nap and Me-Nap have a Type III isotherm, and α-Naphthol presents a Type II isotherm. Nap and Me-Nap fitted to Freundlich isotherm of an unfavorable process (n = 2.12 and 1.11; 1.87 and 1.31, respectively), with positive values of ΔH° (50 and 77.17; 66 and 64.63 kJ mol-1) and ΔS° (0.070 and 0.0145; 0.122 and 0.103 kJ mol-1) for commercial and waste MP, respectively. Besides, the adsorption isotherm of α-Naphthol on commercial and waste HDPE fitted to the Langmuir model (Qmax = 42.5 and 27.2 µmol g-1, respectively), presenting negative values of ΔH° (-43.71 and -44.10 kJ mol-1) and ΔS° (-0.037 and -0.025 kJ mol-1). The adsorption kinetic study presents a nonlinear pseudo-second-order model for all cases. The K2 values follow the order Me-Nap > Nap > α-Naphthol in both MP. Therefore, this experimental study provides new insights into the affinity of PAH derivatives for a specific class of MP, helping to understand the environmental fate of residual MP and organic pollutants.

Reviewing variables and their implications affecting adsorption of Cr(VI) onto activated carbon: an in-depth statistical case study.

Removal of Cr(VI) from the aqueous phase using numerous activated carbons (AC) has been broadly studied in the last decades. Nevertheless, the diversity of activation methods, AC properties, and adsorption conditions precludes the standardization of specific characteristics required to achieve better adsorption results. This work reviewed the pertinent literature on Cr(VI) adsorption onto AC published over the past four decades. Pearson's correlation matrix and principal component analysis (PCA) assisted in identifying the parameters and AC characteristics that have the greatest influence on the maximum adsorption capacity (qm). Two hundred thirty-six adsorption assays were found reporting data on 110 ACs and different parameters. Of these, 39.8% of the studies contemplated the variables qm, pH, temperature (T), surface area (SBET), micropore volume (Vmicro), and mesopore volume (Vmeso), and only 19.5% reported the point of zero charge (pHPZC). Statistical analysis disclosed that SBET and Vmicro have a strong positive correlation with qm, while Vmeso, T, and pH show little or no correlation. The difference between pH and pHPZC (PZCdiff) indicated a significant anticorrelation with qm, thus evidencing that lower PZCdiff values enhance adsorption. The findings are useful for all researchers that work with Cr(VI) adsorption on AC since they provide a start point concerning the required adsorbent characteristics and process conditions to be employed.

A critical examination of the DPPH method: Mistakes and inconsistencies in stoichiometry and IC50 determination by UV-Vis spectroscopy.

The DPPH method has been reported with misconceptions in a large number of studies, thus precluding comparison of results. Attention is drawn to a common mistake in the unit used to express the IC50 of ascorbic acid and other antioxidant substances. Concentration of the antioxidant is widely misused with a total disregard for the DPPH• concentration, while the molar ratio of antioxidant/DPPH• would be the correct choice. Data from 26 studies with widely varying IC50 values were renormalized according to reaction stoichiometry, resulting in values which are more coherent and closer to the ideal one of 0.25 for at least 15 of them. In addition, the model which is currently being used to calculate the DPPH• concentration can lead to an overestimation of around 7%, as it does not take into account the small contribution of the reaction product. In view of that, we present a mathematical model to correct the overestimation of the DPPH• concentration.

Application of multivariate analysis on naphthalene adsorption in aqueous solutions.

Naphthalene (NAP) is found as a pollutant in water, soil, and air, and adsorption is the most prominent removal process of this compound, among the methods studied. A study concerning the types of adsorbents and the parameters with the greatest influence on the adsorption process is interesting to direct future works on new adsorbents. The use of multivariate data analysis tools becomes an appealing way to compile data obtained from bibliographic reviews and to establish a behavior in NAP adsorption. This work aims to evaluate the parameters with greater influence on NAP adsorption process regarding adsorption capacity (qeexp) with the principal component analysis (PCA), and to group common NAP adsorbents by chemical characteristics through hierarchical cluster analysis (HCA). The variables qeexp, S, [NAP]0, T, CT, and [Ads] were used to perform PCA with correlation matrix. For the HCA, the variables S, [NAP]0, T, CT, and [Ads] with average linkage method (UPGMA) and Euclidean distance were used. Through PCA, it is possible to infer that S and [NAP]0 are the factors with greater influence in qeexp of NAP, while T, CT, and [Ads] have little correlation. PCA also shows that activated charcoal is the adsorbent with higher qeexp. HCA grouped the adsorbents into four groups by their chemical classes, except group A. Both PCA and HCA methods show themselves as potential tools to evaluate a data set of NAP adsorption processes.

Ultrasound-assisted extraction of bioactive compounds from palm pressed fiber with high antioxidant and photoprotective activities.

This work is focused on the optimization of the ultrasound-assisted extraction of antioxidant compounds with photoprotective effect from palm pressed fiber. The influence of ultrasound intensity and pulse cycle was investigated by means of a central composite rotational design. The optimized condition was ultrasound intensity of 120W.cm-2 and pulse factor of 0.4, yielding 3.24wt%. Compounds such as fatty acids, ß-sitosterol, α-tocopherol, squalene, total phenolics and carotene were identified. The extract presented antioxidant activity towards synthetic (2,2-diphenyl-1-picrylhydrazyl - DPPH, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) - ABTS) and biological radicals (Hydroxyl - OH), besides a sun protection factor of 15.01. Polar extracts from palm pressed fiber are promising candidates for use in cosmetic and pharmaceutical formulation since they present high antioxidant activity towards different radicals, combined with the high sun protection factor.

Applications of computational chemistry to the study of the antiradical activity of carotenoids: A review.

A summary of the various quantum chemical analyses that have been employed to evaluate the free radical scavenger capacity of carotenoid molecules are tabulated in this review and the most important observations are discussed. These molecules are able to interact with reactive oxygen species through singlet oxygen scavenging, electron transfer, hydrogen atom abstraction and radical adduct formation. Most studies employ density functional theory to compare the antiradical capacity of different carotenoids with the ones that are most explored theoretically, such as lycopene and ß-carotene. A significant number of these applications have been directed towards understanding the electron transfer mechanism, and a useful tool called the FEDAM (full-electron donor-acceptor map) was developed to better evaluate this mechanism. Important aspects that may affect the radical scavenging capacity of carotenoids, such as synergistic effects and solubility, are sometimes overlooked, and a greater number of such compounds should be explored.

Ethnopharmacological study and topical anti-inflammatory activity of crude extract from Poikilacanthus glandulosus (Nees) Ariza leaves.

ETHNOPHARMACOLOGICAL RELEVANCE: Ethnopharmacological studies are important tools as records and documentation of the empirical uses of medicinal plants in traditional communities with the purpose of generating useful knowledge to lead to the development of new medicines, biodiversity conservation and enhancement of knowledge and local culture. Poikilacanthus glandulosus is widely used by the population of City of Santiago, in Brazil, nevertheless, it does not have any validation regarding its use and its medicinal effects. AIM: The objective of this study was to perform one ethnopharmacological survey about P. glandulosus in the City of Santiago and determine the anti-inflammatory activity in order to prove its uses in popular medicine. METHODS: Personal and ethnopharmacological data were collected through a prepared questionnaire. The phytochemical analysis was performed observing the individual methodology for each reaction and by HPLC-UV. The antiedematogenic and anti-inflammatory (cell infiltration and histological procedure) activities of the P. glandulosus (0.01-1000µg/ear) were evaluated in the ear edema model induced by topical application of croton oil. RESULTS: P. glandulosus is known in City of Santiago as "Gaiana" and its macerated leaves and branches are prepared with alcohol or sugarcane liquor especially for insect bites, cicatrization and inflammation. HPLC analysis revealed the presence of maslinic acid (2.024±0.10mg/g), uvaol (0.124±0.02mg/g) and sitosterol (0.502±0.05mg/g). The topical application of crude extract of P. glandulosus reduced in a dose-dependent manner the croton oil-induced ear edema and myeloperoxidase activity (neutrophils infiltration marker) with maximum inhibition of 87±2% and 64±12%, respectively at 1000µg/ear. Dexamethasone (100µg/ear), used as a positive control, inhibited croton oil-induced ear edema in 89±3% and decreased myeloperoxidase activity in 50±3%. Both P. glandulosus as dexamethasone reduced cell infiltration when evaluated by histological procedure CONCLUSION: This work allowed us to understand the specie P. glandulosus through ethnopharmacological study and it showed that the crude extract presented antiedematogenic and anti-inflammatory actions, proving their traditional use as anti-inflammatory.

Supercritical CO2 extraction, chemical characterisation and antioxidant potential of Brassica oleracea var capitata against HO·, O2(·-) and ROO·.

In this work were extracted bioactive compounds from Brassica oleracea var capitata using supercritical CO2 and evaluated the antioxidant potential of the extracts. Five extractions were accomplished to investigate the influence of pressure (10-25 MPa) and temperature (20-60 °C) in the extraction yield, chemical composition and antioxidant potential towards peroxyl, superoxide and hydroxyl radicals. The highest extraction yield was obtained at 60 °C and 25 MPa, which was 0.47 wt% (run 2). In the characterisation of the extracts obtained was possible the identification of sulforaphane and iberin nitrile that present known biological properties. The extracts of all runs presented antioxidant activities towards the three radicals, but the highest activities for all radicals were using the extracts obtained in the run 2. The use of supercritical CO2 extraction to obtain bioactive compounds of B. oleracea var capitata showed to be a promising alternative to conventional extraction methods, since allowed the extraction of compounds with scientific and industrial interest.

Antifungal activity of extracts from Piper aduncum leaves prepared by different solvents and extraction techniques against dermatophytes Trichophyton rubrum and Trichophyton interdigitale.

The effects of different solvents and extraction techniques upon the phytochemical profile and anti-Trichophyton activity of extracts from Piper aduncum leaves were evaluated. Extract done by maceration method with ethanol has higher content of sesquiterpenes and antifungal activity. This extract may be useful as an alternative treatment for dermatophytosis.