Asian Journal of Applied Chemistry Research

Emerging Applications of HILIC-MS/MS in Metabolomics and Drug Discovery

2026-07-04T11:49:47+00:00

Hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry (HILIC-MS/MS) is a complementary analytical approach for the separation and sensitive detection of polar, ionic and hydrophilic compounds that are often inadequately retained by conventional reversed-phase chromatography. The technique uses a polar stationary phase and a mobile phase with a high proportion of organic solvent, commonly acetonitrile, with a small aqueous buffer component. This arrangement supports the retention of analytes such as polar metabolites, carbohydrates, peptides, nucleotides, nucleosides, amino acids and selected pharmaceutical compounds. When HILIC is coupled with tandem mass spectrometry, particularly through electrospray ionisation, the high organic content of the mobile phase can support efficient desolvation and sensitive ion detection. Tandem mass spectrometry provides additional selectivity through precursor-ion selection, fragmentation and product-ion monitoring, enabling targeted and untargeted analysis in complex matrices. This review summarises the principles, instrumentation and major ionisation interfaces used in HILIC-MS/MS, including electrospray ionisation, atmospheric pressure chemical ionisation, fast atom bombardment and matrix-assisted laser desorption/ionisation. It also describes tandem mass analyser configurations, including quadrupole, ion-trap and Orbitrap systems, and outlines detector options such as electron multipliers, Faraday cups and array detectors. The manuscript further discusses applications in metabolomics, pharmaceutical analysis, clinical studies, proteomics and polar lipid profiling through selected case studies. Overall, HILIC-MS/MS is presented as a useful analytical platform for polar analyte retention, structural confirmation and quantitative measurement, while recognising that method optimisation, retention-time reproducibility and matrix effects remain important practical considerations for reliable analytical performance across diverse sample types and laboratory workflows in contemporary biomedical research.

Emerging Strategies in Pesticide Remediation: A Critical Review of Nanotechnology, Computational Chemistry, and Integrated Treatment Approaches

2026-07-06T09:19:45+00:00

Pesticide contamination remains a major environmental challenge because residues occur across soil, surface water, groundwater, and atmospheric compartments, while pesticide classes differ widely in persistence, mobility, toxicity, and treatability. This review critically evaluates conventional, advanced, and emerging remediation technologies to identify practical treatment pathways that can address diverse pesticide contamination under economic and environmental sustainability constraints. The review compares eleven technology classes, including activated carbon adsorption, clay minerals, biological treatment, advanced oxidation processes, metal-organic frameworks, covalent organic frameworks, MXene-based composites, magnetic nanocomposites, photocatalytic nanocomposites, constructed wetlands, and integrated treatment trains. Particular attention is given to nanotechnology and computational chemistry as innovation drivers, especially the use of density functional theory, molecular dynamics, machine learning, and process-scale modelling to guide material selection, predict interactions, and support treatment optimisation. The synthesis indicates that nanomaterials can provide high removal efficiency and selectivity, especially for trace-level and chemically diverse pesticides, but their wider application is constrained by uncertain environmental fate, scale-up costs, real-matrix performance losses, and regulatory delays. Biological and nature-based systems offer stronger sustainability profiles but may be slower and less suitable for some persistent contaminants. The review concludes that the most defensible pathway is the integration of computationally designed nanomaterials within adaptive treatment trains that combine performance, sustainability, field validation, and regulatory acceptability.

Phytochemicals as Antibiotic Adjuvants: Mechanistic Insights into Synergistic Activity against Multidrug-Resistant Pathogens

2026-07-08T12:50:35+00:00

The global spread of multidrug-resistant bacterial pathogens has narrowed treatment options for common infections and threatens to reverse decades of progress in clinical medicine. Combination strategies that pair conventional antibiotics with non-antibiotic potentiators, commonly termed adjuvants, offer a pragmatic route to extend the useful life of existing drugs while new antimicrobial classes remain scarce. Plant-derived secondary metabolites, or phytochemicals, have attracted sustained attention as candidate adjuvants because many act through mechanisms distinct from, and complementary to, the primary targets of antibiotics. This review synthesises evidence on flavonoids, alkaloids, terpenoids and polyphenolic compounds that restore or enhance antibiotic activity against multidrug-resistant bacteria. The mechanistic basis of these interactions is examined across four broad categories: membrane and cell wall perturbation, efflux pump inhibition, enzymatic and gene-expression modulation, and quorum sensing or biofilm interference. Evidence from checkerboard and fractional inhibitory concentration index assays is critically appraised alongside emerging delivery strategies that address the poor aqueous solubility and limited bioavailability of many phytochemicals. Combinations involving methicillin-resistant Staphylococcus aureus, multidrug-resistant Pseudomonas aeruginosa and drug-resistant Mycobacterium tuberculosis are considered in depth, given their prominence on international priority pathogen lists. The review closes by identifying gaps in pharmacokinetic characterisation, standardisation of synergy testing, and clinical translation that must be addressed before phytochemical adjuvants can move from bench to bedside.

Persistent Organic Pollutants: Chemistry, Environmental Fate, and Toxicological Impact

2026-07-09T10:51:18+00:00

Persistent organic pollutants remain one of the most consequential classes of anthropogenic chemicals identified in modern environmental science. Their defining characteristics, chemical stability, resistance to biotic and abiotic degradation, high lipophilicity, and capacity for long-range transport, allow them to accumulate in soils, waters, sediments and living tissues far from the point at which they were released. This review synthesises current understanding of the chemistry underpinning environmental persistence, the mechanisms governing global transport and fate, and the toxicological consequences observed in wildlife and human populations. The molecular architecture of legacy pollutants such as polychlorinated biphenyls, dichlorodiphenyltrichloroethane, dioxins and furans is examined alongside emerging classes including per- and polyfluoroalkyl substances, polybrominated diphenyl ethers and chlorinated paraffins. Attention is given to the physicochemical descriptors that predict environmental behaviour, the phenomenon of global fractionation that concentrates certain compounds in polar and mountain regions, and the trophic processes of bioaccumulation and biomagnification that elevate exposure in apex predators and human consumers. Toxicological evidence spanning endocrine disruption, immunotoxicity, reproductive and developmental harm, and carcinogenicity is critically appraised, with particular focus on receptor-mediated mechanisms such as aryl hydrocarbon receptor activation. The governance architecture established under the Stockholm Convention is evaluated, including persistent implementation gaps in low- and middle-income regions and the accelerating identification of emerging contaminants requiring regulatory attention. The review closes by identifying priority research directions, drawing overall conclusions, and outlining the methodological limitations inherent to a narrative synthesis of this breadth.

A Review on the Removal of Cu²⁺ and Ni²⁺ Ions from Water Using Biodegradable Organic Materials

2026-07-10T13:12:30+00:00

Water contamination by copper (Cu²⁺) and nickel (Ni²⁺) ions remains an important environmental and public health concern because these metals persist in aquatic systems, accumulate in living organisms and may cause toxic effects at elevated concentrations. Conventional removal methods, including chemical precipitation, membrane filtration, ion exchange and electrochemical treatment, are useful but may be restricted by cost, energy demand, sludge generation and limited selectivity under some treatment conditions. This review examines biodegradable and naturally sourced organic materials for the removal of Cu²⁺ and Ni²⁺ from aqueous media, with emphasis on agricultural waste-derived adsorbents, biopolymer-based materials, bio-derived nanocomposites and vegetable-oil-based green extractants. The discussion considers material classification, adsorption and extraction mechanisms, kinetic and thermodynamic behaviour, and operational factors such as pH, contact time, adsorbent dosage, initial metal concentration and temperature. Reported studies indicate that many modified agricultural residues, chitosan- and cellulose-based materials, nanocomposites and fatty-acid-rich oils can achieve high removal efficiencies under laboratory conditions. However, comparison across studies remains difficult because experimental designs, wastewater matrices and regeneration assessments vary considerably. The review identifies key research gaps, including limited evidence from real industrial wastewater, insufficient reuse data, selectivity challenges in multi-metal systems and uncertainty about spent adsorbent management. Future work should prioritise scalable, selective and environmentally responsible treatment systems.

Recent Advances in Flavonoid Extraction Technology and its Nitrite-Scavenging Activity

2026-06-25T12:12:06+00:00

This review examines recent advances in flavonoid extraction technologies and their relevance to nitrite scavenging in pickled vegetable systems. Nitrite accumulation during vegetable fermentation is associated with raw-material nitrate content and microbial nitrate reduction, and it may pose health risks through acute toxicity and potential nitrosamine formation. The manuscript summarises current nitrite detection and control strategies, with emphasis on plant-derived flavonoids as natural scavenging agents. Three mechanisms are considered: direct electron-transfer-based nitrite scavenging, inhibition of nitrosation reactions, and regulation of nitric oxide metabolism. Extraction technology is identified as a key factor influencing flavonoid yield, structural retention, and nitrite-scavenging performance. Conventional methods, including reflux extraction, water extraction, and ethanol maceration, are discussed alongside advanced approaches such as semi-bionic extraction, ultrasound-assisted aqueous two-phase extraction, ultrasound-assisted extraction, microwave-assisted extraction, and supercritical fluid extraction. Green extraction using deep eutectic solvents and natural deep eutectic solvents is further reviewed because of its potential to improve extraction efficiency and preserve bioactivity. Evidence from pickled food and in vitro systems suggests that flavonoid extracts can reduce nitrite levels, although efficacy depends on plant source, extraction method, pH, temperature, reaction time, and dosage. The review highlights the need to connect extraction optimisation with practical food-system validation and to assess flavonoid stability in complex fermentation matrices.

Structural Characterization, Computational Investigation and Electrochemical Properties of 1-(2′-Hydroxy-3-methoxybenzylidene)-5-(1′-pyridylethylidene)-carbonohydrazide

2026-06-12T12:04:20+00:00

Asymmetric carbonohydrazide-derived Schiff bases have attracted increasing attention owing to their versatile coordination behaviour, tunable electronic properties, and potential applications in catalysis and bioactive metal-complex design. In this work, 1-(2'-hydroxy-3-methoxybenzylidene) -5-(1'-pyridylethylidene) -carbonohydrazide (H₃L²), an asymmetric Schiff base obtained by the condensation of carbohydrazide with o-vanillin and 2-acetylpyridine, was synthesised and comprehensively characterised. The crystal structure, determined by X-ray diffraction analysis, reveals a triclinic system (P-1) stabilised by a network of intra- and intermolecular hydrogen bonds. DFT calculations performed using the 6-31+G(d,p) basis set accurately reproduce the experimental geometric parameters and confirm the conjugated planarity of the molecule. Mulliken population analysis highlights the nucleophilic sites (O, N) as well as the polarisation of hydrogen bonds. The investigation of the frontier molecular orbitals HOMO and LUMO reveals an energy gap of 3.93 eV and a pronounced electrophilic character (ω = 25.55 eV). Global reactivity descriptors, particularly chemical hardness (η = 0.95 eV) and the high dipole moment (13.14 D), indicate moderate reactivity and strong electronic polarization favoring intermolecular interactions. FTIR spectroscopic characterisation is in good agreement with the calculated vibrational frequencies. Electrochemical studies performed by cyclic voltammetry reveal quasi-reversible electron transfer processes involving oxygen and nitrogen atoms, accompanied by remarkable stability in solution. Altogether, these structural, electronic, and electrochemical properties confer particular interest to this ligand as a promising candidate for the synthesis of metal complexes with potential biological or catalytic applications.

Production of Mosquito Repellent Cream with Extract from Lemon Grass (Cymbopogon citratus), Clove (Syzygium aromaticum) and Neem (Azadirachta indica)

2026-06-15T09:40:52+00:00

The increasing health and environmental concerns associated with synthetic mosquito repellents have necessitated the development of safer, plant-based alternatives. This study produced and evaluated mosquito repellent creams formulated from lemon grass (Cymbopogon citratus), clove (Syzygium aromaticum), and neem (Azadirachta indica) extracts, including their combinations. Fixed oils were extracted using n-hexane and incorporated into seven oil-in-water cream formulations. Physicochemical properties, chemical composition (GC-MS), antimicrobial activity (agar well diffusion against Salmonella sp., Escherichia coli, Candida albicans, and Aspergillus sp.) were determined. Repellency efficacy (modified Arm-in-Cage method) was evaluated using anopheles mosquito (Anopheles gambiae). The experiments were performed in triplicates. Statistical analysis of the results was done by one –way analysis of variance (ANOVA) and post hoc test. GC-MS revealed that lemon grass extraction with n-hexane altered its composition, yielding mainly 9-Octadecenoic acid (42.52%) instead of volatile citral, reducing its repellency. Significant difference was observed in the density, refractive index and viscosities of the extracted oils. There was significant difference in the oxidative properties of the extracted oils except in thiobarbituric acid (TBA) levels. ANOVA revealed distinct concentration – dependent behaviors for Salmonella sp., Candida albicans, and Aspergillus sp., whereas E. coli showed no statistically significant sensitivity to concentration variance. The extracted oils provided better antioxidant, antimicrobial and mosquito repellent efficiency while standing alone. Formulations combining the extracts yielded antagonistic rather than synergistic effects in most cases.

Biological Activities and Isolation of Bioactive Compounds from Zanthoxylum thouvenotii H. Perr. (Rutaceae) Bark

2026-06-23T11:38:12+00:00

Background: Zanthoxylum thouvenotii H. Perr. (Rutaceae) is used in Malagasy traditional medicine for toothache, malaria and metabolic disorders, but information on the biological activities and chemical constituents of its bark remains limited. Aim: This study evaluated the anti-hyperglycaemic, antimicrobial, antioxidant and anti-inflammatory activities of bark extracts and isolated bioactive constituents. Methods: Air-dried bark was extracted with ethanol/water and cyclohexane to obtain EE1, CE and EE2. Phytochemical screening was performed on EE1. Acute oral toxicity, antimicrobial activity by disc diffusion, hypoglycaemic activity in glucose-induced transient and high-fat diet-induced chronic hyperglycaemia, antioxidant activity by DPPH bioautography and anti-inflammatory activity using carrageenan-induced paw oedema were assessed. The active cyclohexane extract was fractionated by silica gel column chromatography, and isolated compounds were identified using NMR data. Results: EE1 contained steroids, alkaloids and triterpenoids, showed no mortality or clinical signs of acute toxicity up to 5 g/kg, and produced inhibition zones below 7 mm against the tested microorganisms. In the transient hyperglycaemia model, EE1 reduced blood glucose to 7.0 ± 0.8 mmol/L at 200 mg/kg after glucose administration, but did not restore glycaemia in obese mice. CE and EE2 were positive in the DPPH assay and inhibited carrageenan-induced oedema by 66.63% and 45.12%, respectively, at 250 mg/kg after 2 h. Fractionation of CE yielded lupeol and a mixture of β-sitosterol and stigmasterol. Lupeol inhibited paw oedema by 83.76% at 25 mg/kg. Conclusion: The findings indicate that Z. thouvenotii bark contains compounds associated with antioxidant and anti-inflammatory activity, with lupeol contributing to the observed anti-inflammatory effect.

Mining Activities and the Risks Associated with Fish Consumption

2026-06-23T13:00:48+00:00

Freshwater fish may accumulate heavy metals from contaminated aquatic environments, thereby creating potential health concerns for populations that depend on fish as a dietary protein source. This study assessed selected heavy metals and associated health risks in edible fish samples from Jibia Dam, Jibia Local Government Area, Katsina State, Nigeria, an area affected by illegal mining activities. Eight samples each of Clarias gariepinus, Ameiurus nebulosus and Tilapia zilli were obtained from commercial anglers and analysed for Fe, Pb, Cd, Cu, Mn, Zn and Ni using spectrophotometric procedures after ashing and acid digestion. The daily intake of metals, target hazard quotient (THQ), health risk index (HRI), incremental lifetime cancer risk (ILCR) and cumulative incremental lifetime cancer risk (ΣILCR) were calculated for children and adults using the stated exposure assumptions. The results showed that mean Pb concentrations in Ameiurus nebulosus and Tilapia zilli exceeded the maximum allowable concentration, whereas the Pb concentration in Clarias gariepinus and the concentrations of the other assessed metals in all three species were within the stated safety limits. The THQ values for individual metals were below 1 in both children and adults, suggesting no appreciable non-carcinogenic risk from single-metal exposure under the adopted assumptions. However, the HRI values for Ameiurus nebulosus and Tilapia zilli exceeded 1 in children, indicating potential concern from combined metal exposure in this group. The ILCR values for Ni, and the corresponding ΣILCR values, exceeded the acceptable cancer risk range in both children and adults. These findings indicate that fish consumption from Jibia Dam may present health concerns, particularly in relation to Pb exposure and Ni-related carcinogenic risk, and support the need for periodic monitoring of fish from the area.

Evaluation of Physicochemical, Phytochemical and Chemical Composition of Methanolic Crude Oil Extracts from Ripe and Unripe Citrus sinensis Epicarp

2026-06-30T10:15:18+00:00

Sweet orange peels are commonly discarded as waste materials, although recent scientific research on the peel of Citrus sinensis has shown that it has considerable potential for conversion into useful community products, including antimicrobial agents, antioxidants, biochar, biogas and materials for water purification. This study aimed to compare methanolic crude oil extracts from ripe and unripe Citrus sinensis epicarp by analysing their physicochemical properties, phytoconstituents and fatty acid composition. All analyses were conducted using standard laboratory procedures. The oil yield from ripe Citrus sinensis epicarp extract was significantly higher (26.54%) than that from unripe Citrus sinensis epicarp extract (17.11%). Physicochemical analysis showed that ripe epicarp oil had higher saponification value (97.79 mg KOH/100 g), peroxide value (56.29 mg KOH/100 g) and free fatty acid value (21.82 mg KOH/100 g) than the unripe epicarp extract (87.74, 37.71 and 20.87 mg KOH/100 g, respectively). Both extracts contained bioactive constituents, including alkaloids, terpenoids, saponins, tannins and flavonoids, with ripe epicarp oil showing the highest flavonoid value (4.19%) compared with unripe epicarp oil (1.5%). GC-MS profiling indicated that the ripe epicarp extract was richer in unsaturated fatty acid derivatives, whereas the unripe extract contained more saturated fatty acid derivatives. Overall, the findings suggest that methanolic crude oil extracts from ripe and unripe Citrus sinensis epicarp may have nutritional, immunological and pharmaceutical relevance, supporting their potential use in functional food, nutraceutical and industrial applications.

Assessment of Heavy Metal Pollution Indices and Human Health Risks in Playground Soils from Filin Police Station, Batagarawa Local Government Area, Katsina State, Nigeria

2026-07-13T06:16:22+00:00

Heavy metal contamination in recreational soils may present environmental and public health concerns, particularly in areas exposed to traffic, commercial activities, and other anthropogenic inputs. This study assessed the concentrations, pollution status, ecological risk, and human health risks associated with selected heavy metals in playground soil collected from Filin Police Station, Batagarawa Local Government Area, Katsina State, Nigeria. Topsoil samples were collected from three locations at a depth of 0–10 cm using a systematic sampling approach. Heavy metal concentrations were determined using atomic absorption spectrophotometry after sample preparation and acid digestion. The results were used to estimate the geo-accumulation index, enrichment factor, contamination factor, pollution load index, potential ecological risk index, target hazard quotient, hazard index, and incremental lifetime cancer risk. Iron (1.42 ± 0.0201 mg/kg), manganese (1.34 ± 0.0045 mg/kg), and chromium (1.27 ± 0.0125 mg/kg) had the highest measured concentrations, while cadmium (0.09 ± 0.0010 mg/kg) and copper (0.04 ± 0.0048 mg/kg) occurred at the lowest levels. The geo-accumulation index, contamination factor, pollution load index, and potential ecological risk index generally indicated low contamination and low ecological risk. However, enrichment factor values suggested possible anthropogenic influence for chromium, lead, and zinc. Health risk estimates indicated that dermal exposure was the main contributor to non-carcinogenic risk in both children and adults. Chromium, nickel, and cadmium indicated potential carcinogenic concern for children, while lead, chromium, and nickel indicated potential carcinogenic concern for adults.