Complicated and strict protocols are followed to tune the size of gold nanoparticles (GNPs) in chemical synthesis methods. In this study, we address the polarity of solvents as a tool for tailoring the size of GNPs in the chemical reduction method. The effects of varying polarity index of the reaction medium on synthesizing gold nanoparticles by chemical reduction method have been investigated. Ethanol as a polar solvent, ethanol-water mixture as reaction medium, L-ascorbic acid as reducing agent, and polyvinylpyrrolidone as stabilizer were used to synthesize GNPs. The polarity index of the reaction medium was adjusted by changing the volume ratio of ethanol to water. UV-Vis, dynamic light scattering (DLS), and transmission electron microscopy (TEM) characterizations reveal that the growth of nanoparticles was gradually increased (~22 to 219 nm hydrodynamic diameter) with decreasing value of polarity index of the reaction medium (~8.2 to 5.2). Furthermore, the high polarity index of the reaction medium produced smaller and spherical nanoparticles, whereas lower polarity index of reaction medium results in bigger size of GNPs with different shapes. These results imply that the mechanistic of the growth, assembly, and aggregation phenomena of ligand or stabilizer-capped GNPs strongly rely on the polarity of solvent molecules. Using the proposed methodology, wide size range of GNPs with different morphology sizes can be synthesized by simply modulating the volume percentage of organic solvent in the reaction medium.

Different classes of solvents provide different polarity values, which influence the solubility of pharmaceutical solids. In this article, the solubility of mefenamic acid in different classes of organic solvents, including polar protic, dipolar aprotic, and apolar aprotics at a range of temperatures from (298 to 323) K are reported. It has been found that mefenamic acid shows high solubility in dipolar aprotic solvents (N,N-dimethylacetamide, N,N-dimethylformamide, ethyl acetate, and propanone), moderate solubility in polar protic solvents (ethanol and propan-2-ol), and poor solubility in apolar aprotic solvents (hexane, heptane, and cyclohexane) and water.

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Abstract:The main objective of this work is to develop film and study the thermal characteristics of polysaccharides films at various concentration of carrageenan in the mixture by calculating activation energy of polysaccharides films. There were four (4) film samples of two polysaccharides combination; arabic gum (AG) and carrageenan (C) with different formulations; sample A, sample B, sample C and sample D prepared. Sample A film is the control sample that contained only arabic gum and distilled water (DI) with 40% weight arabic gum per volume DI water (w/v%). Meanwhile for sample B and C were prepared with concentration 40 w/v% of Arabic gum and two differents of carrageenan concentrations; 1 w/v% and 10 w/v% respectively. Polyethylene glycol 400 (PEG 400) as a plasticiser was added into sample D film. The sample films were thermally characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) under nitrogen atmosphere. The major thermal transitions as well as, activation energies of the major decomposition stages were determined. Sample A and B films exhibited the highest (112.43 kJ/mol) and the lowest (102.89 kJ/mol) activation energy of thermal decomposition, respectively. The activation energies were lower at larger amounts of sulfate groups from carrageenan on the degradation reactions. The DSC trend for all samples shows two (2) major intense peaks recorded in the DSC thermograms; an endothermic transition at temperature around 100 °C and followed by an exothermic transition at temperature around 300 °C. The endothermic transition is due to the heat absorption for dehydration of water, H 2 O and the decomposition of samples process. Meanwhile, the exothermic transition is caused by the formation of H 2 O, CO and CH 4 in polysaccharide film from dehydration, depolymerisation and decomposition at the high-temperature stages.

At present, plant-based hard capsule such as hydroxypropyl methylcellulose (HPMC) has a high demand in drug delivery application but the production process is expensive with limited reactant supply. κ-carrageenan has been used as a gelling agent in HPMC hard capsule production. This study aims to develop gum Arabic (GA)-κ-carrageenan biocomposite, a potential material to produce hard capsule. The GA-κ-carrageenan biocomposite films were prepared at different κcarrageenan weight ratios of 33% (GC33), 50% (GC50) and 67% (GC67) at constant concentration of polyethylene glycol and alginate. The control films of GA film and κ-carrageenan film were compared. The film and hard capsule formed from GC67 shows the highest tensile strength and capsule loop of 36.21 MPa and 34.11 N, respectively at 1058 mPa.s solution viscosity at 300 rpm shear rate. The hard capsule disintegrated at 7.30 min. The addition of GA is compatible to make the hard capsule surface smoother. Thus, this biocomposite has the potential to be developed for future hard capsule.

Patchouli is a plant which is native in Malaysia. It is an economic crop, planted for its essential oil. Patchouli oil has a characteristic woody scent and is used commercially as an ingredient in fragrance and cosmetic products. The average yearly consumption around the globe is around one metric ton. A marker compound responsible for the patchouli oil scent is patchoulol (C15H26O). It is the major compound in patchouli oil representing around 40–50% of the essential oil composition. The aim of this study is to simulate the patchouli oil extraction process using patchoulol as a modeled molecule in different solvents, namely acetone, ethanol, and hexane. The simulation aim is to recognize molecular interaction between patchoulol molecules with solvent molecules through hydrogen bonding and also the repulsion forces between them due to the abundance of hydrogen atoms in the patchoulol molecule. The simulation is equilibrated under moles, volume, and energy followed by moles, pressure, and temperature ensembles via molecular dynamics simulation using the Material Studio software package. The interaction in the system is analyzed through the radial distribution function to describe the structure of patchoulol in solvent solution. The rdf trend found that the interaction between patchoulol solutes is through the oxygen atom (O1P) and hydrogen (H1P) atom from the hydroxyl functional group of the patchoulol molecule. In the acetone–patchoulol and hexane–patchoulol systems, the patchoulol solutes tend to self-agglomerate indicated by first neighboring molecules in the range of 4.25 Å and 5.75 Å, respectively, while the first neighboring molecules of patchoulol solutes in the binary ethanol–patchoulol system is located at 7.75 Å. This might suggest that the patchoulol is much more soluble in ethanol then in acetone and hexane. The pattern observed in the simulations is in agreement with extraction yield results obtained from the extraction experiment.