Structural, optimization of and mechanistic insights into a new thiosemicarbazone derivative as a highly sensitive and selective chemosensor for Hg2+ recognition using DFT, COSMO-RS, RSM, and molecular dynamics simulation approaches

A new thiosemicarbazone derivative, N-(2-hydroxyphenyl)-2-[1-(pyridin-4-yl)ethylidene]hydrazinecarbothioamide (HPEH), has been synthesized, characterized, and further developed as a highly selective and sensitive colorimetric chemosensor for Hg2+ recognition in environmental water samples. Structural conformers of HPEH were successfully identified using a combination of the potential energy surface (PES) and time-dependent density functional theory (TD-DFT) methods. The synthesized HPEH was successfully characterized further and analyzed based on its harmonic vibrational frequencies, NMR spectra, and electronic transitions using the DFT approach. Sigma profiles were generated using the COSMO-RS approach to identify a compatible medium for HPEH to act as a chemosensor. The conditions for the highly sensitive and selective detection of Hg2+ by HPEH were successfully optimized using the statistical response surface methodology approach. The optimum sensing of HPEH occurred in an 8:2 v/v DMSO/pH 7.8 solution at a 20:60 μM HPEH/Hg2+ concentration and after a reaction time of 18 minutes, with statistically significant independent variables (p < 0.05) for all parameters. The lowest Hg2+ concentration detected by HPEH under the optimum conditions was 3.56 µM, which is lower than that for other previously reported Hg2+ chemosensors. Using the optimized results, the interaction between HPEH and Hg2+ in the chemosensor system was successfully modeled, and the model was subsequently used with the TD-DFT, non-covalent interaction-reduced density gradient (NCI-RDG), and molecular dynamics approaches to gain mechanistic insights into the interaction. The results showed that the newly synthesized HPEH, in addition to being cost-effective, could serve as a suitable alternative and comparable chemosensor for Hg2+ recognition in water samples, with the advantages of being efficient, portable, and eco-friendly, and offering rapid analysis without the need of specialized training

Protease extraction from Horse mango (Mangifera foetida lour) kernels

Horse mango is one of the tropical fruits that belongs from a family Anacardiaceae (mango). However, its latex is notorious for human skin due to blistering effect, suggesting the presence of strong proteolytic activity. In general, the extraction of enzymes from plants is comparatively difficult due to the presence of indigenous polyphenoloxidases and high concentration of polyphenolic compounds which promote enzymatic browning resulting in the inactivation of the enzymes and therefore compared to animals and micro-organisms, higher plants have not received much attention for enzyme histochemistry. During recent year, several new methods have been developed and many of the existing ones have been improved. These methods have been applied to the plant enzyme to understanding the properties of the enzyme. Therefore, this book is written for the scientists who are primary interested in histochemical detection of protease in plants especially horse mango (Mangifera foetida Lour). Procedure to extract, identify and assay activity in the horse mango are also given. The procedures include recommended methods and all of them have been checked by the author themselves and published in the Bioscience, Biotechnology and Biochemistry and Malaysia Journal of Chemistry

2-acetylpyrazine thiosemicarbazone as multifunctional food spoilage inhibitor: insights from Tyrosinase Kinetic, microbial activity and computational approaches

Nowadays, the demand of high-quality food has increased among the consumers. However, their appearance and color are the critical factors during food purchasing. Therefore, maintaining of their shelf life has become a challenge to food industries. Chemical and biological oxidation have been identified as the main factors that affect the food quality. In this study, 2-acetylpyrazine thiosemicarbazone (2APT) has been synthesized, and characterized using spectroscopy methods. Based on the IC50 obtained, it shows that 2APT was significantly inhibited tyrosinase activity (chemical spoilage) at 8 μM concentration. Kinetic study shows that 2APT was a mixed-type inhibitor with Km and Vmax value were 8.20 mM and 0.013 μM/min, respectively. 2APT also inhibits E. coli, B. cereus, and C. albican at concentrations of 1.4 ± 0.1 cm, 1.6 ± 0.1 cm, and 1.2 ± 0.1 cm, respectively. In the light of these study, we performed in silico study involving Reduced Density Gradient (RDG), Molecular Electrostatic Potential (MEP) and molecular docking simulation technique. RDG used to find the weak non-covalent interaction (Van der Wall interaction) and strong repulsion (steric effect) of the 2APT. MEP and molecular docking were done to identify and investigate the key structural features of 2APT that are important for their activity and the interaction that contribute to tyrosinase inhibition, respectively

Modifications of Poly(lactic Acid) with Blends and Plasticization for Tenacity and Toughness Improvement

This review focuses on the modification of the inherent brittleness of biodegradable poly(lactic acid) (PLA) to increase its toughness, as well as recent advances in this field. The most often utilized toughening methods are melt blending, plasticization, and rubber toughening. The process of selecting a toughening scheme is still difficult, although it directly affects the blend's mechanical properties. There has been a lot of development, but there is still a long way to go before we get easily processable, totally bio-based, 100% biodegradable PLA. The blends of PLA with other polymers, such as plasticizers or rubber, are often incompatible with one another, which causes the blend's individual components to behave in a manner consistent with phase separation. Polymer blending has been shown to be particularly effective in attaining high-impact strength. This review addresses the recent progress in improving the toughened PLA to gain properties necessary for the material's future engineering applications. As 3D and 4D printing becomes more accessible, PLA characteristics may be modified and treated utilizing more sophisticated production techniques

DFT/TD-DFT study on development and optimization of 1- anilino-3- phenyliminourea as a colorimetric chemosensor for Hg2+ recognition in aqueous medium

Mercury is a toxic metal that can be found everywhere - it is used in many products of our daily life and mercury contamination usually cannot be detected by any of the five human senses. Continuous exposure to mercury has severe implications neurologically, gastrointestinally and with respect to renal organ systems. This study was conducted to develop a portable and easy-to-use chemosensor with 1- anilino- 3-phenyliminourea (AP) for detecting Hg2+ ions in aqueous system. The sensitivity of AP in acting as a chemosensor was optimized based on solvent/co-solvent ratio and pH. The result showed that AP has a highly sensitivity against Hg2+ in DMSO/citrate buffer (8/2, v/v, pH = 4.0). The LOD of AP against Hg2+ ions was calculated at 69.02 mM. The stoichiometric ratio of AP-Hg2+ was 1:1 as determined by the Job’s plot analysis. COSMO-RS results show that DMSO and AP formed stronger hydrogen bonds due to the peaks of both appearing at greater positive and negative sigma profile values in the H-bond acceptor and H-bond donor regions, respectively. Molecular electrostatic potential, Fukui function and electronic transition were successfully performed using the DFT method to characterize and support the experimental data in predicting the interaction that occurs between AP and Hg2+ ions. The calculated HOMO-LUMO energy gaps of AP and Ap-Hg2+ were 3.72 eV and 1.95 eV, respectively. The result aligned with the UV-vis analysis where a redshift occurred after formation of the complex. Using naked eye observation, the developed test strip using the AP chemosensor also demonstrated a colour change in recognizing Hg2+ ions in aqueous media

Chemosensor development of Cu2+ recognition using 1,5-diphenylthiocarbazone: optimization, COSMO-RS and DFT studies

The sensitive and selective chemosensor for copper(II) ions (Cu2+) was successfully optimized using the 1,5-diphenylthiocarbazone (DPT) compound. The result showed that dimethyl sulfoxide (DMSO) in a 9:1 (DMSO:water) ratio at a pH of 3 was the optimum medium for DPT to act as chemosensor of Cu2+ recognition. The DPT chemosensor did not encounter any interference from other metal ions, including Fe3+, Ag+, Cr3+, Pb2+, Mg2+, Cd2+, Zn2+, K+, Ni2+ and Co2+. The presence of Cu2+ led to an absorption peak at 658 nm, where the color changed from cantaloupe to gray-green color indicating the interaction by the formation of the DPT-Cu complex in 2:1 stoichiometry. The theoretical σ-profile calculation using conductor-like screening model for real solvents (COSMO- RS) showed the compatibility of DPT with the DMSO solvent through hydrogen bonding. In the density functional theory (DFT) calculations, the formation energy of DPT and DPT-Cu were −1113.79645660 and −2435.71832681 a.u., respectively. Under optimal conditions, a detection limit of 6.08 μM for the DPT chemosensor for Cu2+ recognition can compete with the flame atomic absorption spectroscopy (FAAS) value of 6.21 μM. Finally, DPT was able to provide less expensive, more portable and convenient chemosensor for Cu2+ recognition in environmental water samples

Artocarpus altilis extracts as a foodborne pathogen and oxidation inhibitors: RSM, COSMO RS, and molecular docking approaches

Lipid oxidation and microbial contamination are the major factors contributing to food deterioration. Food additives like antioxidants and antibacterials can prevent food spoilage by delaying oxidation and preventing the growth of bacteria. Artocarpus altilis leaves exhibited biological properties that suggested its use as a new source of natural antioxidant and antimicrobial. Supercritical fuid extraction (SFE) was used to optimize the extraction of bioactive compounds from the leaves using response surface methodology (yield and antioxidant activity). The optimum SFE conditions were 50.5°C temperature, 3784psi pressure and 52min extraction time. Verifcation test results (Tukey’s test) showed that no signifcant diference between the expected and experimental DPPH activity and yield value (99%) were found. Gas-chromatography –mass spectrometry (GC-MS) analysis revealed three major bioactive compounds existed in A. altilis extract. The extract demonstrated antioxidant and antibacterial properties with 2,3-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, ferric reducing ability of plasma (FRAP), hydroxyl radical scavenging activity, tyrosinase mushrrom inhibition of 41.5%, 8.15±1.31 (µg of ascorbic acid equivalents), 32%, 37% and inhibition zone diameter of 0.766±0.06cm (B. cereus) and 1.27±0.12cm (E. coli). Conductor like screening model for real solvents (COSMO RS) was performed to explain the extraction mechanism of the major bioactive compounds during SFE. Molecular electrostatic potential (MEP) shows the probability site of nucleophilic and electrophilic attack during bacterial inhibition. Based on molecular docking study, non-covalent interactions are the main interaction occurring between the major bioactive compounds and bacteria (antibacterial inhibition)

COSMO-RS and DFT studies on development and optimization of quercetin as a chemosensor for Fe3þ recognition in aqueous medium

Quercetin is known as a bioflavonoid compound that has been successfully optimized to be a chemo- sensor probe for Fe3þ recognition. The sensitivity of quercetin towards Fe3þ increased in DMSO:deionized water with a 9:1 ratio at pH 4. There was also no significant interference from other metal ions, such as Kþ, Cr3þ, Agþ, Cd2þ, Mg2þ, Pb2þ, Co2þ, Ni2þ, Zn2þ and Cu2þ in the selectivity optimization. The detection limit of the probe was 20.5 mM. The stoichiometry of 1:1 quercetin:Fe3þ was calculated using the Job plot method. The sigma profile was calculated using COSMO-RS, which showed that quercetin formed stronger hydrogen bonds with the DMSO solvent. Density functional theory (DFT) calculations, such as molecular electrostatic potential (MEP) and the Fukui function, were performed to visualize and clarify the region of interaction between quercetin and Fe3þ. The TD-DFT method was successfully used to investigate the electronic properties of quercetin and quercetineFe3þ and it showed good agreement between experimental and theoretical results

Statistical study on the interaction factors of polypropylene-graft-maleic anhydride (PP-g-MA) with graphene nanoplatelet (GNP) at various Poly(Lactic Acid)/Polypropylene (PLA/PP) blends ratio

This paper reports the effects of polypropylene-graft-maleic anhydride (PP-gMA) and graphene nanoplatelet (GNP on tensile stress of various PLA/PP weight ratio. The PLA/PP blends prepared with the ratio 70/30, 80/20, and 90/10 with the addition of PP-g-MA (1 to 5 phr) and GNP (1 to 3 phr) by using an injection molding machine. The tensile stress (MPa) was analyzed based on 11 runs of full factorial design. The results showed that the tensile stress of PLA/PP blends gradually increased after the addition of PP-g-MA and GNP. There is a relationship between PP-g-MA and GNP which causes a positive impact on the mechanical properties of PLA/PP blends. The optimum tensile stress of 50.06 MPa achieved at the ratio of 90/10 blends with 5 phr of PP-g-MA and 3 phr of GN

Preliminary study in discovering 2-propen-1-one, 1-(2,4-dihydroxyphenyl)-3-(4-methoxyphenyl)- from syzygium aqueum leaves as a tyrosinase inhibitor in food product: experimental and theoretical approach

In this study, response surface methodology (RSM) in combination with central composite rotatable design (CCRD) were performed to optimize the extraction parameters for total phenolic content (TPC) on Syzygium aqueum (S. aqueum) leaves. The effect of operational conditions on the extraction of S. aqueum leaves using carbon dioxide (CO2) on TPC was investigated. The conditions used in the supercritical extraction with CO2 included temperatures of (40-70 °C), pressures (2200-4500 psi) and extraction time (40-100 min). The highest TPC (3.5893 mg GAE/mg) was obtained at optimum conditions of 55 °C, 3350 psi and 70 min. The major compound in the optimized crude extract was2-propen-1-one,1-(2,4Dihydroxyphenyl)-3-(4-methoxyphenyl)- (82.65 %) which was identified by GC-MS. COSMO-RS was introduced to study the σ-profile between CO2 and 2-propen-1-one,1-(2,4-Dihydroxyphenyl)-3-(4methoxyphenyl)-. Principal component analysis (PCA) was performed to classify major compound which exhibit similar chemical properties with selected control. 2-propen-1-one,1-(2,4-Dihydroxyphenyl)-3-(4methoxyphenyl)- has similar chemical properties with kaempferol as tyrosinase inhibitor. Molecular electrostatic potential (MEP) and molecular docking were plotted to investigate a recognition manner of 2-propen-1-one,1-(2,4-Dihydroxyphenyl)-3-(4-methoxyphenyl)-upon tyrosinase receptor