Hue University Journal of Science: Natural Science

QSPR-based calculation model for stability constants of new metal-thiosemicarbazone complexes with hybrid techniques

2023-11-06T06:52:41+00:00

In the present study, we calculated the logb₁₂ stability constant of twenty new ML₂ complexes between thiosemicarbazone and metal ions based on the modelling techniques of the quantitative structure and property relationship (QSPR). The QSPR models were developed by combining the genetic algorithm (GA) with multivariate linear regression techniques (QSPR_GA-MLR), support vector regression (QSPR_GA-SVR), and artificial neural network (QSPR_GA-ANN). The descriptive parameters were calculated from semi-empirical quantum computation with the new versions PM7 and PM7/sparkle. The resulting QSPR_GA-MLR models had three variables, and the QSPR_GA-SVR and QSPR_GA-ANN models were developed from the variables of the QSPR_GA-MLR model. The results show that the best QSPR_GA-SVR model had the following optimal parameters: C = 10.0; g = 0.333; e = 0.10 with 51 support vectors, and a QSPR_GA-ANNmodel with the network architecture I(3)-HL(10)-O(1) was successfully developed. Furthermore, the quality of QSPR models conformed to statistical values according to OECD principles and Tropsha’s criteria.

Non-hydrophilic components from roots of Vietnamese ginseng (Panax vietnamensis Ha & Grushv.)

2023-09-30T02:59:09+00:00

Vietnamese ginseng is a precious medicinal herb and contains various ginsenosides as the main components. We studied the less polar constituents of the title ginseng and isolated falcarinol (1) and 20S-protopanaxatriol (4) for the first time, along with two common phytosterols: β-sitosterol (2) and daucosterol (3). Their structures were elucidated with nuclear magnetic resonance (NMR) and mass spectrometry (MS) spectra and compared with the literature data. Falcarinol was obtained from the non-polar portion of the crude residue, with a high content. The occurrence of 20S-protopanaxatriol becomes evidence for similar biosynthesis of ginsenoside in Panax spp. The obtained results contributed partly to the phytochemical database of Vietnamese ginseng and the Panax genus.

Characterization of schweinfurthinol 9-O-β-D-pyranoglucoside as a potential anti-diabetic compound via in-silico studies

2023-09-30T03:18:21+00:00

Schweinfurthinol 9-O-β-D-pyranoglucoside (SP) was isolated from Euonymus laxiflorus Champ. (ELC) and found as novel α-glucosidase and α-amylase inhibitors in our previous works via experimental studies. This work aims to further characterize SP as a potential inhibitor of α-glucosidase and α-amylase and develop an anti-diabetic drug via in-silico studies. Molecular docking indicated that SP interacted with targeting enzymes α-glucosidase (Q6P7A9) and α-amylase (1SMD) with acceptable RMSD values (≤2.0 Å) and showed an efficient binding energy with DS values of –10.4 and –12.0 kcal/mol, respectively. The binding energy of SP is comparable with that of acarbose, an anti-diabetic compound, with DS values of –11.2 to –12.7 kcal/mol for enzymes Q6P7A9 and 1SMD, respectively. The analysis indicated that SP satisfied all the requirements of Lipinski’s Rules of Five while acarbose might conform to approximately 20% of Lipinski’s rules criteria. Furthermore, SP showed satisfied ADMET properties in the required permitted limit. The result of this work suggested that SP might be a potential candidate with good drug-likeness properties and a high possibility of being an anti-diabetic drug.

Electrochemical determination of clenbuterol with differential pulse voltammetry technique at carbon dots-based rice straw-modified electrode

2024-03-05T02:21:12+00:00

In the present study, the carbon dots (CD) were extracted from rice straw (RS) and denoted as RSCD. The obtained material was examined by using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption/desorption isotherms. The RSCD material was employed as an electrode modifier to improve the effectiveness of an electrochemical sensor for determining clenbuterol (CLB). RSCD showed fabulous oxidation towards clenbuterol. The modest detection limit could confirm an LOD value of 0.094 µM within a linear range between 0.1 and 1.8 µM under suitable conditions and the proposed technique –– the differential pulse voltammetry (DPV). The developed sensor exhibited several benefits: simplicity, low cost, effortless generation, fabulous selectivity, and good reproducibility.

Impatiens malipoensis S. H. Huang, a new record for the flora of Vietnam

2024-02-28T07:47:55+00:00

Impatiens malipoensis S. H. Huang, a narrowly distributed species previously recorded only from Southern China, is newly found in the limestone mountains of Northeast Vietnam. Its morphological description, colour illustration, ecological and phenological characteristics, and taxonomic notes are provided in this paper.

Confirming correctness of procedure for determining soft parameters in Coulomb potential of noble atoms

2024-03-13T09:00:01+00:00

This paper verifies that the procedure described in [Computer Physics Communications, 276, 108372 (2022)] for determining the soft parameters in the Coulomb potential of noble atoms is accurate via the modification of the initial position value of x₀ and the parameter b range. In the case of nonsequential double ionization (NSDI), the results demonstrate that the value of x₀ is not contingent upon the range of computed parameter a. Furthermore, we examine the significance of parameter b in the NSDI process and conclude that the ideal value for the soft Coulomb parameter of b is that b ≤ 0.1 a.u.

Simplified model for predictive direct power control with fixed switching frequency for grid-tie inverters

2024-06-25T13:49:15+00:00

This study exhibits a simplified direct power control strategy based on the model predictive control for grid-tie inverters. To solve the problem of the variable switching frequency in the classical finite control set model predictive control (FCS-MPC), we combined the inverse predictive model and space vector modulation to calculate the desired inverter voltage. Furthermore, the computational burden is reduced thanks to the elimination of the optimization loop. A comparative study indicated that the proposed approach achieved better steady-state control performance concerning the low total harmonic distortion of the current model compared with the traditional FCS-MPC while guaranteeing a fast dynamic response. The effectiveness and feasibility of the proposed method were confirmed via simulations and experimental results.

Enhancing harvesting efficiency of Tetraselmis sp. biomass from aquaculture wastewater via electrocoagulation technology

2024-10-02T08:47:36+00:00

Harnessing nutrients in wastewater to cultivate microalgal biomass offers significant industrial and environmental benefits. However, the tiny size of marine microalgae Tetraselmis sp. makes traditional filtration methods ineffective, leading to high harvesting costs and energy consumption. This study deals with electrocoagulation and flocculation in recovering Tetraselmis sp. biomass from aquaculture wastewater, both individually and in combination, regarding their effectiveness. The results show that with an algal density of 1.16 ± 0.28 × 10⁶ cells/mL in shrimp farming wastewater (salinity 25.0 ± 1.8‰, pH 8.3), combining flocculation (2.5 mg chitosan/L, pH adjusted to 8.2) with electrochemical treatment (TiO₂ and RuO₂-IrO₂-TiO₂ electrodes, 12 V, 3.5 A) achieved a recovery efficiency of 92% after 21 min. This method also minimized cell damage, yielding biomass with 8.5% protein, 2.4% lipid, and 23.9% carbohydrate. However, when applied individually, electrochemical treatment attained a recovery efficiency of only 37%, and flocculation reached an efficiency of 22%. These findings highlight the significant potential of electrocoagulation for harvesting Tetraselmis sp. biomass from aquaculture wastewater.

A Determination of andrographolide from Andrographis paniculata growing in Thua Thien Hue with high performance liquid chromatography

2024-10-16T08:16:40+00:00

Andrographis paniculata (Acanthaceae) is a medicinal plant commonly used in Vietnam in the 1980s. The chemical composition of the plant includes a group of diterpene lactones with antimicrobial, cytotoxic, antidiabetic, and anti-inflammatory activities. In this group, andrographolide is a typical compound. This paper describes a method for quantifying andrographolide in A. paniculata grown in Thua Thien Hue by using high-performance liquid chromatography. Andrographolide was analyzed on an RP-C18 column with a methanol/acetonitrile/water (55/10/35, v/v/v) mobile phase, a detecting wavelength of 225 nm, a flow rate of 0.5 mL/min, and an injected sample volume of 10 μL. This method displays linearity for andrographolide in the range of 200–1,000 μg/mL, and the recovery of andrographolide is 99.63 ± 0.88 %. The contents of andrographolide in root, stem, and leaf of A. paniculata grown in Vietnam were determined for the first time, and the values are 0.03 ± 0.007%, 0.57 ± 0.021%, and 3.98 ± 0.034%, respectively.