Microplastics in the commercially available branded milk in Bangladesh: An emerging threat for human health.

Microplastics (MPs) are polymer-based particles commonly found in diverse foods that pose serious human health impacts throughout the food chain. Assessment of MPs in different food products is a prime measure to combat MP-related food contamination. Therefore, this study first investigated the identification, characterization, and potential risks of MPs in the commercially available milk brands (19 dry powders and 06 liquid brands) in Bangladesh.

Appraisal of microplastic pollution and its related risks for urban indoor environment in Bangladesh using machine learning and diverse risk evolution indices.

The widespread presence of Microplastics (MPs) is increasing in the indoor environment due to increasing annual plastic usage, which is becoming a global threat to human health. Therefore, this is the first research in Bangladesh to identify, and characterize, MP pollution and its allied threats to human health in the indoor urban environment, where 80 household dust samples were collected from the whole study area. The presence of MPs in household dust of the urban indoor environment was 25.

Application of machine learning and multivariate approaches for assessing microplastic pollution and its associated risks in the urban outdoor environment of Bangladesh.

Microplastics (MPs) are an emerging global concern due to severe toxicological risks for ecosystems and public health. Therefore, this is the first study in Bangladesh to assess MP pollution and its associated risks for ecosystems and human health in the outdoor urban environment using machine learning and multivariate approaches. The occurrences of MPs in the urban road dust were 52.

Assessment of Heavy Metal Contamination and Health Risk Associated with Cultivated Vegetables along Dhaka-Mymensingh Highway, Bangladesh.

The purpose of this research work is to evaluate the degree of eight heavy metals (Fe, Mn, Cu, Zn, Cd, Pb, Cr, and Ni) contamination and health risks of three regularly consumed vegetables (papaya, bottle gourd, and esculent) near one of Bangladesh's busiest roadways, the Dhaka-Mymensingh highway. The heavy metal concentrations in 45 vegetable samples were analyzed using an atomic absorption spectrometer (AAS). These samples were collected from five different sampling sites based on various land use patterns adjacent to the highway.

Receptor model-based sources and risk assessment of metals in sediment of the coastal construction-oriented aquatic system in Bangladesh.

Metal pollution in sediment from construction areas raises ecological and health concerns, yet source-based sediment pollution in Bangladesh remains understudied. Our investigation focused on fifteen locations in the Kohelia River and the coastal regions near the Matarbari projects (Matarbari Power Plant, Matarbari Deep Seaport), assessing metal concentrations' sources and impacts on ecology and human well-being. Sediment quality indices indicated high Cd and Cr contamination, with sites near Matarbari projects being the most polluted.

Removal of hazardous textile dye from simulated wastewater by municipal organic solid waste charcoal using machine learning approaches: Kinetics, isotherm, and thermodynamics.

This study focuses on the probable use of municipal organic solid waste charcoal (MOSWC) as an adsorbent for Methyl orange (MO) adsorption. The prepared MOSWC is characterized by FE-SEM and FT-IR. Batch adsorption experiments were conducted with the influencing of different operational conditions namely time of contact (1-180 min), adsorbate concentration (60-140 mg/L), adsorbent dose (1-5 g/L), pH (3-11), and temperature (25-60 °C).

CpTiCl-Promoted Radical Cyclization to Six- and Seven-Membered Carbocycles: Synthesis of (±)-Isoclavukerin A.

A systematic study is undertaken to investigate the less explored radical cyclization in activated olefin-appended epoxides using CpTiCl. The radical generated by the Ti(III)-promoted reductive opening of the epoxy ring promptly underwent cyclization, giving access to differently 1,3-disubstituted six- and seven-membered carbocycles in good yields and diastereoselectivity. This protocol was successfully employed in the construction of 5,7- and 6,7-fused bicyclic frameworks entailing a de novo synthesis of (±)-isoclavukerin A belonging to tri--guaiane class of sesquiterpene natural products in eight simple steps from commercially available starting materials.

An attempt to construct an indole-fused azabicyclo[3.3.1]nonane framework radical cyclization.

The structural motif of an indole-fused azabicyclo[3.3.1]nonane is common in many biologically significant indole-based natural products.

Receptor model-based sources and risks appraisal of potentially toxic elements in the urban soils of Bangladesh.

Rapid urbanization and industrial development have prompted potentially toxic elements (PTEs) in urban soil in Bangladesh, which is a great concern for ecological and public health matters. The present study explored the receptor-based sources, probable human health and ecological risks of PTEs (As, Cd, Pb, Cr, Ni, and Cu) in the urban soil of the Jashore district, Bangladesh. The USEPA modified method 3050B and atomic absorption spectrophotometers were used to digest and evaluate the PTEs concentration in 71 soil samples collected from eleven different land use areas, respectively.

One-Pot Tandem Aldol-Cycloetherification Protocol in the Enantioselective Synthesis of Davanoids.

Total synthesis of and diastereomers of prenylated davanoids like davanone, nordavanone, and davana acid ethyl ester was achieved in an enantioselective strategy. Various other davanoids could also be synthesized using standard procedures from the Weinreb amides derived from davana acids. Enantioselectivity in our synthesis was achieved employing a Crimmins' non-Evans syn aldol reaction that fixed the stereochemistry of the C3-hydroxyl group, while the C2-methyl group was epimerized in a late stage of the synthesis.

Human health risk ​and receptor model-oriented sources of heavy metal pollution in commonly consume vegetable and fish species of high Ganges river floodplain agro-ecological area, Bangladesh.

This study was intended to assess heavy metal contents and sources in commonly consumed vegetables and fish collected from the Jashore district of Bangladesh and to evaluate the probable human health risks via the ingesting of those vegetables and fish species. A total of 130 vegetable and fish samples were analyzed for As, Mn, Cu, Cr, Ni, and Pb concentration by an atomic absorption spectrophotometer. Metals and metalloids like As, Pb, and Cr in vegetable species were greater than the maximum allowable concentration (MAC), while Pb and cu in fish species exceeded the MAC.

Arsenic, iron, and manganese in groundwater and its associated human health risk assessment in the rural area of Jashore, Bangladesh.

This study investigated groundwater pollution and potential human health risks from arsenic, iron, and manganese in the rural area of Jashore, Bangladesh. Study results show that the mean value of groundwater pH is 7.25 ± 0.

CpTiCl-Mediated Reductive Cyclization: Total Synthesis of Pestalotiolactone A, Myrotheciumone A, and Scabrol A.

The first stereoselective total syntheses of fungal secondary metabolites monoterpenoid (+)-pestalotiolactone A, meroterpenoid (-)-myrotheciumone A, and iridoid lactone (+)-scabrol A have been accomplished in an expedient unified approach starting from d-(+)-malic acid employing an epoxide opening-radical cyclization protocol initiated by CpTi(III)Cl as a key step to assemble the core bicyclic lactone moieties of these molecules with complete diastereoselective control. Finally, the deoxygenation and methylation delivered the target natural products.

Environment-Sensitive Fluorescence of 7-Nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)-Labeled Ligands for Serotonin Receptors.

Serotonin is a neurotransmitter that plays a crucial role in the regulation of several behavioral and cognitive functions by binding to a number of different serotonin receptors present on the cell surface. We report here the synthesis and characterization of several novel fluorescent analogs of serotonin in which the fluorescent NBD (7-nitrobenz-2-oxa-1,3-diazol-4-yl) group is covalently attached to serotonin. The fluorescent ligands compete with the serotonin receptor specific radiolabeled agonist for binding to the receptor.

Total Synthesis of Panaginsene.

The total synthesis of panaginsene has been accomplished in 11 linear steps starting from methyl 3,3-dimethyl-5-oxocyclopent-1-ene-1-carboxylate. The key steps are a Sharpless asymmetric epoxidation and Ti(III)-mediated reductive epoxide opening-radical cyclization to construct the chiral quaternary carbon stereocenter followed by a very challenging HWE olefination reaction on an 1,3-keto aldehyde and a late stage McMurry olefination using low valent titanium to construct the highly constrained angular tetrasubstituted olefin in a five-membered ring.

Application of CpTiCl-Promoted Radical-Induced Cyclization: An Expeditious Access to []-Annelated Indoles.

An efficient and novel route for assembling pyrrolo/piperido[1,2-]indoles is portrayed involving a radical-mediated reductive epoxide opening reaction of -tethered epoxy-indoles that trigger facile intramolecular cyclization followed by an oxidative quenching step. Capitalizing on the operational simplicity of the method involving just two steps and use of an efficient C-C bond-forming reaction, this radical-based protocol enables the modular assembly of an important class of -fused indole derivatives with versatile functional and structural diversity.

Development of Minimal Diguanosinyl Motif toward RNA G-Quadruplex-Like Structures in Solution.

Among the non-canonical structures of B-DNA, the G-quadruplex is of particular interest because of its well-defined conformation, high stability, and versatility. Herein we report our studies on the development of an amide-linked minimal diguanosinyl motif that forms a G-quadruplex-like structure in solution in the presence of potassium cations; various linear guanosine amino acid dimers were synthesized with linkers of different chain lengths to investigate the optimum flexibility required to form such structures.

Titanocene(III)-Mediated 5-exo-trig Radical Cyclization: En Route to Spirooxindole-Based Tetrahydrofuran and Bicyclic Lactone.

The isatin core system is of immense importance due to the highly reactive prochiral C-3 position, which paves an easy way to construct large arrays of spirooxindole heterocyclic motifs. Herein, we depict an isatin-derived and 3,3'-disubstituted oxindole-appended epoxy-acrylate undergoing CpTi(III)Cl-mediated reductive oxirane-ring opening with concomitant intramolecular 5-exo-trig radical cyclization leading to tetrahydrofuran-based oxa-spirooxindole systems. The fused spirooxindole structural feature is embedded in many natural products and tends to exhibit a wide spectrum of biological activities.

Studies on sugar puckering and glycosidic stabilities of 3'-amino-5'-carboxymethyl-3',5'-dideoxy nucleoside mimics.

The synthesis of nucleoside amino acid monomers and dimers has been carried out to evaluate and characterize the impact of the neutral amide backbone on key attributes like puckering of the sugar rings and glycosidic bond strengths of these analogs. The conformational analysis suggests that amide-linked nucleotides have a high predilection towards N-type conformers. The glycosidic bond strength was found to be slightly weaker compared to ribonucleosides under acidic conditions at high temperatures.

Application of CpTiCl-Promoted Radical Cyclization: A Unified Strategy for the Syntheses of Iridoid Monoterpenes.

An expedient approach toward the unified total syntheses of (+)-iridomyrmecin, (-)-isoiridomyrmecin, (+)-7- epi-boschnialactone, (+)-teucriumlactone, and (-)-dolichodial in chirally pure forms starting from readily available (+)-β-citronellene is delineated combining step economy and simplicity. Highlights include a Ti(III)-mediated reductive epoxide opening-cyclization for the construction of the core cyclopenta[ c]pyran skeleton of the iridoid lactones with complete diastereoselectivity for the newly created bridgehead stereogenic centers. Subsequent transformations facilitate a short access to (+)-teucriumlactone and (-)-dolichodial and formal access to potentially other iridoids.

Conformation Analysis of GalNAc-Appended Sugar Amino Acid Foldamers as Glycopeptide Mimics.

Sugar amino acid (SAA)-based foldamers with well-defined secondary structures were appended with N-acetylgalactosamine (GalNAc) sugars to access sequence-defined, multidentate glycoconjugates with full control over number, spacing and position. Conformation analysis of these glycopeptides by extensive NMR spectroscopic studies revealed that the appended GalNAc units had a profound influence on the native conformational behaviour of the SAA foldamers. Whereas the 2,5-cis glycoconjugate showed a helical structure in water, comprising of two consecutive 16-membered hydrogen bonds, its 2,5-trans congener displayed an unprecedented 16/10-mixed turn structure not seen before in any glycopeptide foldamer.

Diversity-Oriented Approach to N-Heterocyclic Compounds from α-Phenyl-β-enamino Ester via a Mitsunobu-Michael Reaction Sequence.

Herein we delineate a novel route for the diastereoselective construction of diversely substituted N-heterocyclic ring systems as valuable scaffolds for natural products and pharmaceuticals, starting from an easily accessible prochiral α-phenyl-β-enamino ester. The reaction sequence relies on the unexplored reactivity of α-phenyl-β-enamino ester as a nucleophilic partner in the Mitsunobu reaction to forge the N-tethered alkene-alcohol/thiol/amine intermediate, which was subjected to an intramolecular hetero-Michael addition reaction under mild conditions to furnish the respective N-heterocyclic compounds embedded with an exocyclic chiral center in high yields and excellent diastereoselectivities. The methodology is amenable for a broad range of substrates based on a metal-free approach.

Synthesis, SAR and biological studies of sugar amino acid-based almiramide analogues: N-methylation leads the way.

Leishmaniasis, caused by the protozoan parasites of the genus Leishmania, is one of the most neglected diseases endemic in many continents posing enormous global health threats and therefore the discovery of new antileishmanial compounds is of utmost urgency. The antileishmanial activities of a library of sugar amino acid-based linear lipopeptide analogues were examined with the aim to identify potential drug candidates to treat visceral leishmaniasis. It was found that among the synthesized analogues, most of the permethylated compounds exhibited more activity in in vitro studies against intra-macrophagic amastigotes than the non-methylated analogues.