Three different macroporous resins (XAD7HP, DAX-8, and XAD4) were evaluated for their adsorption and desorption properties in preparing flavonoid-enriched oil palm (Elaeis guineensis Jacq.) leaf extract. The influences of initial concentration, solution pH, contact time, and desorption solvent (ethanol) concentration were determined by static sorption/desorption methods. The optimal condition for adsorption of flavonoids was achieved when the solution of the extract was adjusted to pH 7, reaching equilibrium after 1440 min at 298 K. The adsorption process was well described by a pseudo-second-order kinetics model, while the adsorption isotherm data fitted well with a Freundlich model. The adsorption by each resin was via an exothermic and physical adsorption process. Based on the static experiment results, XAD7HP was found to be the most appropriate adsorbent, while 80% ethanol was the best solvent for desorbent. Further evaluation of its dynamic adsorption and desorption characteristics on a packed glass column showed that XAD7HP could enrich the OPL total flavonoid content by a 3.57-fold increment. Moreover, UHPLC–UV/PDA and UHPLC–MS/MS analysis revealed that apigenin and luteolin derivatives were selectively adsorbed by XAD7HP. Additionally, both the crude OPL extract and the flavonoid-enriched fraction have good DPPH and NO free radical scavenging activities. Multiple interactions between the flavonoids and cross-linked polymeric XAD7HP resin through van der Waals forces and hydrogen bonding described the sorption processes. Therefore, by utilizing this method, the flavonoid-enriched fraction from crude OPL extract could be used as a potential bioactive ingredient in nutraceutical and pharmaceutical applications at minimum cost with optimum efficiency.

Antibiotics are emerging water pollutants that have attracted significant attention from the scientific community. Antibiotics are generally released via hospital effluents, industrial production waste, animal manure, and irrigated agricultural land. Antibiotic residues can harm all living organisms, with the most detrimental consequence being the generation of antibiotic-resistant microorganisms, commonly known as “superbugs.” Antimicrobial resistance is a concern to the healthcare community as it complicates the treatment of infections. Thus, the development of effective and economical technologies to remove antibiotics from the environment is necessary. Adsorption is a promising technology owing to its effectiveness and high operational feasibility, and carbon-based adsorbents are primitive materials that are particularly suited for antibiotic adsorption. Herein, an overview of the current state of antibiotic pollution will be summarised, including the adverse effects of different antibiotics and challenges associated with antibiotic removal. The adsorption behaviours of tetracycline (TC), quinolone, penicillin, and macrolides on carbon-based adsorbents (i.e., activated carbon, carbon nanotubes, and graphene-based materials) are reviewed. The interactions between antibiotics and carbon-based adsorbents, adsorption mechanism, and adsorption behaviour under different conditions are emphasised. In addition, the limitations of adsorption technology are highlighted to direct future research.

Oil palm leaves (OPL) containing flavonoid C-glycosides are abundantly generated as oil palm byproducts. The performances of three macroporous resins with different physical and chemical properties for the enrichment of isoorientin, orientin, vitexin, and isovitexin from acid-hydrolyzed OPL (OPLAH) extract were screened. The XAD7HP resin exhibited the best sorption capacities for the targeted flavonoid C-glycosides and was thus selected for further evaluation. Static adsorption using the XAD7HP resin under optimal conditions (extract adjusted to pH 5, shaken at 298 K for 24 h) gave adsorption kinetics that fit well with a pseudo-second-order kinetic model. The adsorption of isoorientin and orientin was well described by Langmuir isotherms, while vitexin and isovitexin fit well with the Freundlich isotherms. Dynamic sorption trials using the column-packed XAD7HP resin produced 55–60-fold enrichment of isovitexin and between 11 and 25-fold enrichment of isoorientin, vitexin, and orientin using aqueous ethanol. The total flavonoid C-glycoside-enriched fractions (enriched OPLAH) with isoorientin (247.28–284.18 µg/mg), orientin (104.88–136.19 µg/mg), vitexin (1197.61–1726.11 µg/mg), and isovitexin (13.03–14.61 µg/mg) showed excellent antioxidant free radical scavenging activities compared with their crude extracts, with IC₅₀ values of 6.90–70.63 µg/mL and 44.58–200.00 µg/mL, respectively. Hence, this rapid and efficient procedure for the preliminary enrichment of flavonoid C-glycosides by using macroporous resin may have practical value in OPL biomass waste utilization programs to produce high value-added products, particularly in the nutraceuticals, cosmeceuticals, pharmaceuticals, and fine chemicals industries.

Riboflavin synthase is an important enzyme catalyzing the last step of riboflavin biosynthesis in microorganisms. Due to the absolute dependency of the microbes to this biosynthetic pathway coupled with its nonexistence in humans, riboflavin synthase (RiS) is considered as a prospective drug target. The riboflavin synthase for this study was derived from Leptospira kmetyi, a pathogenic bacterium locally isolated in Malaysia. Leptospirosis, an infectious disease caused by pathogenic Leptospira, is a serious growing public health issue. Treatment of leptospirosis with antibiotics over time resulted in the evolution of antibiotic resistance strains, thus requiring the development of newer but safe antimicrobial agents. In this study, a computational approach involving virtual screening followed by molecular dynamics (MD) simulation was implemented in order to identify possible inhibitors against riboflavin synthase. The model of Leptospira kmetyi riboflavin synthase predicted from E. coli riboflavin synthase (1I8D) was used as the drug target to screen for potential compounds from the ZINC database through virtual screening. The potential compound with the highest Glide score (−10.987 Kcal/mol) was identified to be ZINC21883831. Chemically it is 2-[(2-chloro-4-fluoro-phenyl)methylsulfanyl]-7-phenyl-3,5-dihydropyrrolo[2,3-e]pyrimidin-4-one. The top three docked complexes from the virtual screening and apo-structures were subjected to molecular dynamics simulation to predict the stabilities of the Leptospira kmetyi riboflavin synthase-ligand complexes. Stability parameters including RMSD, RMSF, SASA and Rg of the complexes were evaluated from 60 ns of the MD simulation trajectories. Insights from this study provide promising starting points for the rational designs of new effective and safe anti-leptospirosis drugs.

Background . Antimicrobial resistance is listed as one of the top ten global health issues driven by the misuse and overuse of antibiotics. Silver nanoparticles (AgNPs) have been used extensively in the past few decades as an antimicrobial agent to treat various skin infections due to their broad antibacterial spectrum. Despite their efficacy, high toxicity remains a major drawback. AgNPs can be conjugated with antimicrobial peptides (Bac8c), to form AgNP-Bac8c conjugates with enhanced antibacterial effect. Method . AgNPs were synthesised via the chemical reduction method. Various concentrations of Bac8c were used to mix with AgNPs to form AgNP-Bac8c conjugates. UV–vis spectra, size, and zeta potential measurements were performed on AgNPs and conjugates. FESEM/EDX was used to study morphology and actual size of AgNPs and the optimised conjugate (AgNP-Bac8c-8). Broth microdilution assay and MTT assay were performed to evaluate the antibacterial effects and cytotoxicities of AgNPs, Bac8c, and AgNP-Bac8c-8. Results . Synthesised AgNPs showed a λ _max at 418 nm in UV–vis spectrum, possessed an actual size of 37.8 ± 9.8 nm, and a zeta potential of −27.8 mV. AgNP-Bac8c-8 was found to be the optimised conjugate. AgNP-Bac8c-8 showed a size 51 ± 8.4 nm under FESEM and a zeta potential of +5 mV. AgNP-Bac8c-8 has demonstrated an enhanced antibacterial effect against both sensitive and resistant bacteria ( Staphylococcus aureus and Pseudomonas aeruginosa ) in contrast to AgNPs and Bac8c alone. AgNP-Bac8c-8 showed a lower cytotoxicity towards human skin cells as compared to Bac8c, but not AgNPs alone. Conclusion. AgNP-Bac8c conjugate has demonstrated an enhanced antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa , including resistant strains. A lower cytotoxicity was reported for AgNP-Bac8c compared to Bac8c, but not statistically significant, in terms of toxicity, compared to AgNPs. Stability, bioactivity, and cytotoxicity of the conjugate can be optimised further in future studies to provide a potent treatment option for skin infections.