The objective of this study was to optimize the extraction of oil from pre-dried roselle seeds using response surface methodology (RSM). We also determined the oxidative stability of oil extracted from oven and freeze-dried roselle seed in terms of iodine value (IV), free fatty acid (FFA) value, peroxide value (PV), P-anisidine and total oxidation values (TOTOX value). The RSM was designated based on the central composite design with the usage of three optimum parameters ranged from 8 to 16 g of sample weight, 250-350 mL of solvent volume, and 6-8 h of extraction time. The highest oil yielded from roselle seed using the optimization process was 22.11% with the parameters at sample weight of 14.4 g, solvent volume of 329.70 mL, and extraction time of 7.6 h. Besides, the oil extracted from the oven dried roselle seed had the values of 89.04, 2.11, 4.13, 3.76 and 12.03 for IV, FFA, PV, P-anisidine, and TOTOX values, respectively. While for the oil extracted from freeze-dried roselle seed showed IV of 90.31, FFA of 1.64, PV of 2.47, P-anisidine value of 3.48, and TOTOX value of 8.42. PV and TOTOX values showed significant differences whereas; IV, FFA, and P-anisidine values showed no significant differences between the oven and freeze-dried roselle seed oils.
In this work, an electrochemical method for detection of trace amount of aluminium (Al3+), a heavy metal ion, based on a bare gold electrode (AuE) was developed. Current responses of the AuE under various type of electrolytes, redox indicators, pH, scan rate and accumulation time were investigated using cyclic voltammetry (CV) method to obtain the optimum conditions for Al3+ detection. The sensing properties of the AuE towards the target ion with different concentrations were investigated using differential pulse voltammetry (DPV) method. From the CV results, the optimal conditions for the detection of Al3+ were Tris-HCl buffer (0.1 M, pH 2) supported by 5 mM Prussian blue with scan rate and accumulation time respectively of 100 mVs−1 and 15 s. Under the optimum conditions, the DPV method was detected with different concentrations of aluminium ion ranging from 0.2 to 1.0 ppm resulted in a good linear regression r² = 0.9806. This result suggests that the optimisation of the basic parameters in electrochemical detection using AuE is crucial before further modification of the Au-electrode to improve the sensitivity and selectivity especially for the low concentration of ion detection. The developed method has a great potential for rapid detection of heavy metal ion (Al3+) in drinking water samples.
Over the past decade, research involving immunometabolism, has been gaining much interest. The immune cell re-sponses of an individual may be influenced by metabolites released by the host or derived from the microbiota. How-ever, the immune response of an individual may vary depending on the health condition of an individual. During infection, the metabolic processes derived from the infectious diseases can effect the function of immune cells and thus determine the response or survival of the host during infection. Immunometabolism also has a role in tumor development although the mechanism of how tumor cells influence immune cell function is not well understood. Among the major meatbolic pathways that have been studied in immune cells include glycolysis, the tricarboxylic acid cycle, the pentose phosphate pathway, fatty acid oxidation, fatty acid synthesis and amino acid metabolism. Understanding the tight connection between metabolomics and immunity in health and disease will be crucial as this could lead to therapeutic interventions or in developing metabolomic biomarkers in immunology.
A systematic study on the FeCl3-induced oxidation of 1,2-diarylalkenes was carried out with the focus on the variation of product type as a function of aromatic substitution, as well as to compare the reactivity of stilbene cation radicals generated via Fe(III) oxidation with those generated by anodic oxidation. The aromatic substituents were found to fall into three main categories, namely those that give rise to tetralins and/or dehydrotetralins, those that give products possessing pallidol and ampelopsin F-type carbon skeletons, and last, those that give rise to trimeric products, indanes, and dehydrotetralins/tetralins. The latter are those stilbenes with a para-methoxy substituent in one ring and a para- or meta-EWG (CF3, NO2, Cl, F) in the other, and represent the most prominent departure when compared with the behavior of the same stilbenes under the conditions of anodic oxidation. Reaction pathways to rationalize the formation of the different products are presented.
The present work focuses on the development of cellulose nanofibrils (CNF) film that derived from sustainable biomass resources, which potentially to work as bio-based conductive membranes that assembled into supercapacitors. The chemically purified cellulose was isolated from different parts of coconut (coconut shell and its husk) and further subjected to 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation for CNF preparation. Physicochemical properties of prepared CNFs were studied in terms of chemical characteristics & crystallinity, surface functionalities, surface morphology, and thermal properties. Both coconut shell-derived CNF and coconut husk-derived CNF fulfilled with nanocellulose's characteristics with fibres width ranged of 70-120 nm and 150-330 nm, respectively. CNF films were further prepared by solvent casting method to measure the modulus elasticity, piezoelectric and dielectric properties of the films. Mechanical study indicated that coconut shell-derived CNF film showed a higher value of elastic modulus than the coconut husk-derived CNF film, which was 8.39 GPa and 5.36 GPa, respectively. The effectiveness of electrical aspects for CNF films are well correlated with the crystallinity and thermal properties, associated with it's composition of different coconut's part.
We present an electrochemical long period fiber grating (LPFG) sensor for electroactive species with an optically transparent electrode. The sensor was fabricated by coating indium tin oxide onto the surface of LPFG using a polygonal barrel-sputtering method. LPFG was produced by an electric arc-induced technique. The sensing is based on change in the detection of electron density on the electrode surface during potential application and its reduction by electrochemical redox of analytes. Four typical electroactive species of methylene blue, hexaammineruthenium(III), ferrocyanide, and ferrocenedimethanol were used to investigate the sensor performance. The concentrations of analytes were determined by the modulation of the potential as the change in transmittance around the resonance band of LPFG. The sensitivity of the sensor, particularly to methylene blue, was high, and the sensor responded to a wide concentration range of 0.001 mM to 1 mM.
Alzheimer's disease (AD) is a fatal neurodegenerative disease that requires immediate attention. Oxidative stress that leads to the generation of reactive oxygen species is a contributing factor to the disease progression by promoting synthesis and deposition of amyloid-β, the main hallmark protein in AD. It has been previously demonstrated that nanoyttria possesses antioxidant properties and can alleviate cellular oxidative injury in various toxicity and disease models. This review proposed that nanoyttria could be used for the treatment of AD. In this paper, the evidence on the antioxidant potential of nanoyttria is presented and its prospects on AD therapy are discussed.
Pharmaceutical delivery systems are developed to improve the physicochemical properties of therapeutic compounds. Emulsions are one of these drug delivering systems formulated using water, oils and lipids as main ingredients. Extensive data are usually generated on the physical and chemical characteristics of these oil-in-water and lipid emulsions. However, the oxidative tendency of emulsions is often overlooked. Oxidation impacts the overall quality and safety of these pharmaceutical emulsions. Additionally, introducing oxidatively unstable emulsions into biological systems further promotes oxidation in situ. Products of these reactions then continue to pose serious harm to cells and fuel other physiological oxidation reactions. Consequently, the increase of oxidation products leads to oxidative damage to biological systems. Thus, emulsions with lower lipid peroxidation are more stable and will reduce the negative effects of oxidation in situ. Preventive measures during the formulation of emulsions are important. Many naturally occurring and cost effective substances possess low oxidation tendencies and confer oxidative protection when used in emulsions. Additionally, certain preparatory methods should be employed to reduce or better control lipid peroxidation. Finally, emulsions must be evaluated for their oxidation susceptibility using the various techniques available. Careful attention to the preparation of emulsions and assessment of their oxidative stability will help produce safer emulsions without compromising efficacy.
This study investigates the potential of using small amounts of ionic liquids (IL) to enhance ultrasound-assisted extraction of lipids content from green microalgae. Three imidazolium-based ILs (butyl, octyl and dodecyl), each of them with two anions (bromide and acetate) were tested as additives. Viscosity and surface tension of the ILs aqueous mixtures were analyzed to determine the influence of ILs' anions and alkyl chain length, whereas KI dosimetry experiments were used as an indicator of radicals formation. A key finding suggests that the small addition of ILs improves the ultrasonication either by enhancing the viscosity and reducing the water surface tension, leading to a more powerful acoustic cavitation process or by increasing HO° production likely to oxidize the microalgae cells membranes, and consequently disrupting them on a more efficient manner. KI dosimetry also revealed that long ILs alkyl chain is detrimental. This experimental observation is confirmed thus strengthened as the yield of extracted lipids from green microalgae has shown an incremental trend when the IL concentration also increased. These hypotheses are currently under investigation to spot detailed impact of ILs on cavitation process.
The co-existence of heavy metals and organic compounds including Cr(VI) and p-cresol (pC) in water environment becoming a challenge in the treatment processes. Herein, the synchronous photocatalytic reduction of Cr(VI) and oxidation of pC by silver oxide decorated on fibrous silica zirconia (AgO/FSZr) was reported. In this study, the catalysts were successfully developed using microemulsion and electrochemical techniques with various AgO loading (1, 5 and 10 wt%) and presented as 1, 5 and 10-AgO/FSZr. Catalytic activity was tested towards simultaneous photoredox of hexavalent chromium and p-cresol (Cr(VI)/pC) and was ranked as followed: 5-AgO/FSZr (96/78%) > 10-AgO/FSZr (87/61%) > 1-AgO/FSZr (47/24%) > FSZr (34/20%). The highest photocatalytic activity of 5-AgO/FSZr was established due to the strong interaction between FSZr and AgO and the lowest band gap energy, which resulted in less electron-hole recombination and further enhanced the photoredox activity. Cr(VI) ions act as a bridge between the positive charge of catalyst and cationic pC in pH 1 solution which can improve the photocatalytic reduction and oxidation of Cr(VI) and pC, respectively. The scavenger experiments further confirmed that the photogenerated electrons (e-) act as the main species for Cr(VI) to be reduced to Cr(III) while holes (h+) and hydroxyl radicals are domain for photooxidation of pC. The 5-AgO/FSZr was stable after 5 cycles of reaction, suggesting its potential for removal of Cr(VI) and pC simultaneously in the chemical industries.
Glycerol electro-oxidation offers a green route to produce the high value added chemicals. Here in, we report the glycerol electro-oxidation over a series of multi walled carbon nano tubes supported monometallic (Pt/CNT and Pd/CNT) and bimetallic (Pt-Pd/CNT) catalysts in alkaline medium. The cyclic voltammetry, linear sweep voltammetry and chronoamperometry measurements were used to evaluate the activity and stability of the catalysts. The Pt-Pd/CNT electrocatalyst exhibited the highest activity in terms of higher current density (129.25 A/m²) and electrochemical surface area (382 m²/g). The glycerol electro-oxidation products formed at a potential of 0.013 V were analyzed systematically by high performance liquid chromatography. Overall, six compounds were found including mesoxalic acid, 1,3-dihydroxyacetone, glyceraldehyde, glyceric acid, tartronic acid and oxalic acid. A highest mesoxalic acid selectivity of 86.42% was obtained for Pt-Pd/CNT catalyst while a maximum tartronic acid selectivity of 50.17% and 46.02% was achieved for Pd/CNT and Pt/CNT respectively. It was found that the introduction of Pd into Pt/CNT lattice facilitated the formation of C3 products in terms of maximum selectivity achieved (86.42%) while the monometallic catalysts (Pd/CNT and Pt/CNT) showed a poor performance in comparison to their counterpart.
Recently, microbial-based iron reduction has been considered as a viable alternative to typical chemical-based treatments. The iron reduction is an important process in kaolin refining, where iron-bearing impurities in kaolin clay affects the whiteness, refractory properties, and its commercial value. In recent years, Gram-negative bacteria has been in the center stage of iron reduction research, whereas little is known about the potential use of Gram-positive bacteria to refine kaolin clay. In this study, we investigated the ferric reducing capabilities of five microbes by manipulating the microbial growth conditions. Out of the five, we discovered that Bacillus cereus and Staphylococcus aureus outperformed the other microbes under nitrogen-rich media. Through the biochemical changes and the microbial behavior, we mapped the hypothetical pathway leading to the iron reduction cellular properties, and found that the iron reduction properties of these Gram-positive bacteria rely heavily on the media composition. The media composition results in increased basification of the media that is a prerequisite for the cellular reduction of ferric ions. Further, these changes impact the formation of biofilm, suggesting that the cellular interaction for the iron(III)oxide reduction is not solely reliant on the formation of biofilms. This article reveals the potential development of Gram-positive microbes in facilitating the microbial-based removal of metal contaminants from clays or ores. Further studies to elucidate the corresponding pathways would be crucial for the further development of the field.
Synthetic antioxidants are added to food in the powdered form to preserve it. However these compounds posed serious health concern since they have been associated with causing cancer. Thus using fresh herbs with antioxidant activities would be good alternative. The objectives of this study were to evaluate and compare the total phenolic contents and antioxidant activities of both powdered and fresh forms of turmeric leaf, pandan leaf and torch ginger flower. Total phenolic content (TPC) was assayed based on the redox reaction between Folin-Ciocalteu with phenolics in the sample extracts. Antioxidant activity (AA) was assayed using the ß-carotene linoleate model system and the percentage of antioxidant activity was calculated from the values of degradation rate. Scavenging activity (SA) was assayed using the DPPH radical scavenging model system whereby EC50 value was determined from the plotted graph of scavenging activity against the concentration of sample extracts. Analyses revealed that powdered forms of turmeric leaf, pandan leaf and torch ginger flower had higher TPC (2013.09 ± 5.13, 1784.25 ± 7.59 and 1937.42 ± 6.61 mg GAE/100g, respectively) than their respective fresh forms (348.75 ± 1.26, 356.42 ± 1.32 and 211.59 ± 6.29 mg GAE/100g, respectively). Similarly, powdered forms of turmeric leaf, pandan leaf and torch ginger flower possessed better AA (64.31 ± 0.99, 65.09 ± 0.74 and 11.80 ± 0.40 %, respectively) than their respective fresh forms (24.93 ± 0.71, 16.91 ± 0.70 and 1.45 ± 0.10 %, respectively). Powdered forms of turmeric leaf, pandan leaf and torch ginger flower were also better radical scavenger as compared to their respective fresh forms. In conclusion, all samples in their powdered forms have high total phenolic contents, antioxidant and scavenging activities than their respective fresh forms.
Consumption of mushroom has increased remarkably because of their desirable aroma, taste and high nutritional content. This study was undertaken to measure and compare the antioxidant activity, total phenolic content (TPC) and total flavonoid content (TFC) of Agaricus bisporous (white button mushroom) and Agaricus brasiliensis (Brazilian mushroom) in aqueous and 60% ethanol extract. Results showed that button mushroom (21.47 ± 0.48 mg GAE/g of dry weight) had significant higher TPC in aqueous whereas Brazilian mushroom (12.50 ± 0.22 mg GAE/g of dry weight) had significant higher TPC in 60% ethanol (p< 0.05). In terms of TFC, Brazilian mushroom had higher content than button mushroom in both types of solvents. For FRAP assay, Brazilian mushroom had significantly higher total antioxidant activity than the button mushroom in 60% ethanol (p < 0.05) but opposite trend with aqueous. For DPPH radical scavenging activity, Brazilian mushroom (60% ethanol) had the lowest EC50 value, followed by button mushroom (60% ethanol), Brazilian mushroom (aqueous) and button mushroom (aqueous). Pearson correlation test (p < 0.05) showed strong positive correlation between TPC and FRAP assay in both extracts (r = 0.969 for 60% ethanol extract; r = 0.973 for aqueous extract). For TFC, there was a strong positive, correlation with FRAP assay (r = 0.985) in aqueous extract. In conclusion, high antioxidant activity in ethanol extract of mushrooms due to presence of phenolic content can potentially be used as a source of natural antioxidants.
In this study, two types of plants materials were used namely Garcinia atrovirdis and Cynometra
cauliflora to determine the proximate composition, mineral content and antioxidant activities. Total phenolic content (TPC) and ferric reducing antioxidant power (FRAP) assay had been used to determine antioxidant activity in both samples. The moisture, ash, fiber, fat, protein and carbohydrate content in both samples were determined by using Association of Official Analytical Chemists (AOAC) methods. Mineral content in the sample was determined using Atomic absorption spectrophotpmetry (AAS). The results showed higher TPC and FRAP values in Cynometra cauliflora compared to Garcinia atrovirdis. Methanol extractions gave higher TPC and FRAP values compared to water extraction. The results obtained indicated that both samples have the potential to be as a source of natural antioxidants. Further study should be conducted to explore the benefits of underutilized fruits not only in antioxidant activity but other usages as well.
The effect of the addition of different concentrations of chitosan (0–2.0% w/w) on the gelling properties of surimi gels made from African catfish (Clarias gariepinus) was tested. Lipid oxidation, total volatile basic nitrogen (TVB-N), and aerobic plate count (APC) changes during 20 days of storage at 4oC also were evaluated. Surimi gels with 1.5% (w/w) chitosan added exhibited the highest improvement in gel strength (58.92%), whiteness (13.18%), and water holding capacity (36.8%). Incorporation of 2.0% (w/w) chitosan in gels resulted in the lowest TVB-N value (36.63 mg N/100 g) at the end of the 20 days storage period. Both the peroxide values and the 2-thiobarbituric acid values increased more slowly in the chitosan-treated gels than in the control gel during the storage period. Chitosan at concentrations of 1.75% and 2.0% (w/w) conferred the best antioxidant effect on catfish surimi gels and resulted in a significant reduction in APC. Based on the microbiological acceptability limit (106 cfu/g), the shelf life
of surimi gels with 1.75% and 2.0% (w/w) chitosan was extended to 12 days in refrigerated storage at 4oC, whereas the other samples lasted only 8 days. Hence, the addition of 1.5–2.0% (w/w) chitosan is a promising approach for the preparation of catfish surimi gels, as it improves texture, prevents lipid oxidation, and inhibits microbial growth.
The plant extract serves not only as a good source of bioactive compounds but also as natural pigment that can be applied as colourants in food and pharmaceutical products. The aim of this study were to determine the anthocyanin content of Garcinia mangostana peel extract (GMPE), Clitoria ternatea extract (CTE) and Syzigium cumini extract (SCE) in relation to their antioxidant activity and their colour properties. The antioxidant activities related to the phenolic constituents including anthocyanin content were determined based on the EC50 of DPPH radical scavenging activity and Ferric Reducing Antioxidant Power (FRAP) assay. The colour properties of the plant extracts were measured based on their degradation index (DI), indices of polymeric colour (PC) and colour density (CD). GMPE showed higher FRAP value and lower EC50 value which were 79.37 mmoles/g and 0.11 mg/ml, respectively, as compared to SCE extract with FRAP value, 25.66 mmoles/g and EC50 value, 0.22 mg/ml. Total monomeric anthocyanin (tmAcy) exhibited a strong correlation between FRAP assay (r2 = 0.998) and DPPH assay (r2 = 0.859). GMPE showed high CD (1.63 AU), moderate PC (0.18 AU) but low in DI (1.19 AU) while SCE exhibited low in CD (0.55 AU) and PC (0.07 AU) but moderate DI (1.26 AU). CTE exhibited high in DI (5.39 AU) and PC (0.19 AU) but moderate in CD (0.55). Hence, it can be concluded that colour pigment obtained from GMPE exhibited high antioxidant activity and better colour properties as compared to SCE and the strong correlation between tmAcy and two antioxidant activity assays which are FRAP and DPPH indicated that monomeric anthocyanin plays a major role in antioxidant activity of these plant extracts.
Crude rubber seed oil is a potential source for biofuel production. However it contains undesirable impurities such as peroxides and high oxidative components that not only affect the oil stability, colour and shelf-life but promote insoluble gums formation with time that could cause deposition in the combustion engines. Therefore to overcome these problems the crude rubber seed oil is refined by undergoing degumming and bleaching process. The effect of bleaching earth dosage (15-40 wt %), phosphoric acid dosage (0.5-1.0 wt %) and reaction time (20-40 min) were studied over the reduction of the peroxide value in a refined crude rubber seed oil. The analysis of variance shows that bleaching earth dosage was the most influencing factor followed by reaction time and phosphoric acid dosage. A minimum peroxide value of 0.1 milliequivalents/gram was achieved under optimized conditions of 40 wt % of bleaching earth dosage, 1.0 wt % of phosphoric acid dosage and 20 min of reaction time using Response Surface Methodology design.
Heat treatment was introduced onto the aluminum coated low carbon steel to promote the formation of thin layer of oxide for enhancement of oxidation protection of steel. This process has transformed the existing intermetallic layer formed during hot dip aluminizing process. Experiment was conducted on the low carbon steel substrates with 10mm x 10mm x 2mm dimension. Hot dip aluminizing of low carbon steel was carried out at 750 ºC dipping temperature in a molten pure aluminum for 5 minutes. Aluminized samples were heat treated at 600 ºC, 700 ºC, 800 ºC, and 900 ºC for 1 hour. X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and EDAX were used in investigation. From the observation, it showed the intermetallic thickness increased with the increase in temperature. The result of EDAX analysis revealed the existence of oxide phase and the intermetallics. The XRD identified the intermetallics as Fe2Al5 and FeAl3.
Texture evolution of NiO formed during oxidation of polycrystalline single oriented (100) Ni-Cr was investigated. This foil was also termed rolling assisted biaxially textured substrate (RABiTS). X-ray diffractograms of oxidized Ni-Cr RABiTS foil showed the existence of mostly (200) NiO indicating (100)-type NiO formed exclusively on (100) singly oriented Ni-Cr grains. Epitaxial relationship between the two layers is observed. However the dual-in-plane texture was recorded.
The in-plane texture was assessed by conducting phi scan and plotting series of pole figures measured at (111) NiO peak. The mechanism of the oxides formation was proposed to take into account the formation of (100)-type NiO. Cross section morphology of the oxidised foils reveals two oxidation layers; fast growing external layer consisting of the (100)-type NiO and an internal layer consisted of mostly Cr2O3 and maybe NiCr2O4. The thickness of NiO was ~ 10Pm. Cr2O3 formed as needle-like oxides embedded in a matrix of Ni foil. Inward diffusion of oxygen is believed to have caused this to happen. The external NiO layer was consisted of duplex microstructure characterised by columnar layer growing vertical on the surface of the metal and a few micron thick of equiaxed NiO. Delamination of the outer NiO layer often occurred at the columnarequiaxed interface which could be cured by CeO2 deposition on the foil prior to the oxidation process. CeO2 was deposited by conversion immersion using Ce(NO3)3.6H2O solution. (200) NiO formed on this coated sample as well.