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Optimisation of microwave-assisted extraction (MAE) of anthraquinone and flavonoids from Senna alata (L.) Roxb

Yeong YL, Pang SF, Putranto A, Gimbun J

Nat Prod Res, 2021 Feb 04.
PMID: 33538194 DOI: 10.1080/14786419.2021.1881096

This paper investigates the optimum processing conditions of microwave assisted extraction (MAE) of anthraquinone (aloe emodin, AE) and flavonoids (kaempferol 3-gentiobioside, K3G and kaempferol, KA) from Senna alata (L.) Roxb. The kinetic study indicates that MAE showed a greater extraction rate, compared to ultrasonic-assisted and maceration, due to the enhanced power which altered the leaf microstructures. The optimisation was undertaken using one-factor-at-a-time, two-level factorial design and central composite design were used to maximise the yield of the target compounds. The optimum yield of K3G (4.27 mg/g DW), KA (8.54 mg/g DW) and AE (0.86 mg/g DW) was obtained at 90.5% ethanol, microwave power of 18.6 W/mL with a desirability of 0.82. In addition, the yield of K3G and KA is correlated positively with the antioxidant activity.
An Overview of Chitosan Nanofibers and their Applications in the Drug Delivery Process

Al-Jbour ND, Beg MD, Gimbun J, Alam AKMM

Curr Drug Deliv, 2019;16(4):272-294.
PMID: 30674256 DOI: 10.2174/1567201816666190123121425

Chitosan is a polycationic natural polymer which is abundant in nature. Chitosan has gained much attention as natural polymer in the biomedical field. The up to date drug delivery as well as the nanotechnology in controlled release of drugs from chitosan nanofibers are focused in this review. Electrospinning is one of the most established and widely used techniques for preparing nanofibers. This method is versatile and efficient for the production of continuous nanofibers. The chitosan-based nanofibers are emerging materials in the arena of biomaterials. Recent studies revealed that various drugs such as antibiotics, chemotherapeutic agents, proteins and anti-inflammatory analgesic drugs were successfully loaded onto electrospun nanofibers. Chitosan nanofibers have several outstanding properties for different significant pharmaceutical applications such as wound dressing, tissue engineering, enzyme immobilization, and drug delivery systems. This review highlights different issues of chitosan nanofibers in drug delivery applications, starting from the preparation of chitosan nanofibers, followed by giving an idea about the biocompatibility and degradation of chitosan nanofibers, then describing how to load the drug into the nanofibers. Finally, the major applications of chitosan nanofibers in drug delivery systems.
Effect of Solution Properties and Operating Parameters on Needleless Electrospinning of Poly(Ethylene Oxide) Nanofibers Loaded with Bovine Serum Albumin

Ramakrishnan R, Gimbun J, Ramakrishnan P, Ranganathan B, Reddy SMM, Shanmugam G

Curr Drug Deliv, 2019;16(10):913-922.
PMID: 31663478 DOI: 10.2174/1567201816666191029122445

BACKGROUND: This paper presents the effect of solution properties and operating parameters of polyethylene oxide (PEO) based nanofiber using a wire electrode-based needleless electrospinning.
METHODS: The feed solution was prepared using a PEO dissolved in water or a water-ethanol mixture. The PEO solution is blended with Bovine Serum Albumin protein (BSA) as a model drug to study the effect of the electrospinning process on the stability of the loaded protein. The polymer solution properties such as viscosity, surface tension, and conductivity were controlled by adjusting the solvent and salt content. The morphology and fiber size distribution of the nanofiber was analyzed using scanning electron microscopy.
RESULTS: The results show that the issue of a beaded nanofiber can be eliminated either by increasing the solution viscosity or by the addition of salt and ethanol to the PEO-water system. The addition of salt and solvent produced a high frequency of smaller fiber diameter ranging from 100 to 150 nm. The encapsulation of BSA in PEO nanofiber was characterized by three different spectroscopy techniques (i.e. circular dichroism, Fourier transform infrared, and fluorescence) and the results showed the BSA is well encapsulated in the PEO matrix with no changes in the protein structure.
CONCLUSION: This work may serve as a useful guide for a drug delivery industry to process a nanofiber at a large and continuous scale with a blend of drugs in nanofiber using a wire electrode electrospinning.
Biodiesel synthesized from waste cooking oil in a continuous microwave assisted reactor reduced PM and NOx emissions

Mohd Ali MA, Gimbun J, Lau KL, Cheng CK, Vo DN, Lam SS, et al.

Environ Res, 2020 06;185:109452.
PMID: 32259725 DOI: 10.1016/j.envres.2020.109452

A synergistic effect of the activated limestone-based catalyst (LBC) and microwave irradiation on the transesterification of waste cooking oil (WCO) was screened using a two-level factorial design and response surface methodology. The catalyst was prepared using a wet-impregnation method and was characterised for its surface element, surface morphology, surface area and porosity. The reaction was performed in a purpose-built continuous microwave assisted reactor (CMAR), while the conversion and yield of biodiesel were measured using a gas chromatography. The results showed that the catalyst loading, methanol to oil molar ratio and the reaction time significantly affect the WCO conversion. The optimum conversion of oil to biodiesel up to 96.65% was achieved at catalyst loading of 5.47 wt%, methanol to oil molar ratio of 12.21:1 and the reaction time of 55.26 min. The application of CMAR in this work reduced the transesterification time by about 77% compared to the reaction time needed for a conventional reactor. The biodiesel produced in this work met the specification of American Society for Testing and Materials (ASTM D6751). Engine test results shows the biodiesel has a lower NOx and particulate matters emissions compared to petrodiesel.