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Quinoxalines, a class of N-heterocyclic compounds, are important biological agents, and a significant amount of research activity has been directed towards this class. They have several prominent pharmacological effects like antifungal, antibacterial, antiviral, and antimicrobial. Quinoxaline derivatives have diverse therapeutic uses and have become the crucial component in drugs used to treat cancerous cells, AIDS, plant viruses, schizophrenia, certifying them a great future in medicinal chemistry. Due to the current pandemic situation caused by SARS-COVID 19, it has become essential to synthesize drugs to combat deadly pathogens (bacteria, fungi, viruses) for now and near future. Since quinoxalines is an essential moiety to treat infectious diseases, numerous synthetic routes have been developed by researchers, with a prime focus on green chemistry and cost-effective methods. This review paper highlights the various synthetic routes to prepare quinoxaline and its derivatives, covering the literature for the last two decades. A total of 31 schemes have been explained using the green chemistry approach, cost-effective methods, and quinoxaline derivatives’ therapeutic uses.

The synergistic anticancer effect of docetaxel (DTX) and curcumin (CCM) has emerged as an attractive therapeutic candidate for lung cancer treatment. However, the lack of optimal bioavailability because of high toxicity, low stability, and poor solubility has limited their clinical success. Given this, an aerosolized nanoemulsion system for pulmonary delivery is recommended to mitigate these drawbacks. In this study, DTX- and CCM-loaded nanoemulsions were optimized using the D-optimal mixture experimental design (MED). The effect of nanoemulsion compositions towards two response variables, namely, particle size and aerosol size, was studied. The optimized formulations for both DTX- and CCM-loaded nanoemulsions were determined, and their physicochemical and aerodynamic properties were evaluated as well. The MED models achieved the optimum formulation for DTX- and CCM-loaded nanoemulsions containing a 6.0 wt% mixture of palm kernel oil ester (PKOE) and safflower seed oils (1:1), 2.5 wt% of lecithin, 2.0 wt% mixture of Tween 85 and Span 85 (9:1), and 2.5 wt% of glycerol in the aqueous phase. The actual values of the optimized formulations were in line with the predicted values obtained from the MED, and they exhibited desirable attributes of physicochemical and aerodynamic properties for inhalation therapy. Thus, the optimized formulations have potential use as a drug delivery system for a pulmonary application.

Metal-organic frameworks (MOFs) are porous materials made from coordination bonding of organic linkers and metal nodes. Nowadays, MOFs have already achieved a considerable growth in many fields including in bio-related applications. In this review, we focus on the alternative, green route of MOFs synthesis as well as their toxicological properties. We also highlighted the potential of MOFs as therapeutic agents and nano-MOFs (NMOFs) for biomedical sensing. Water as an alternative media for MOF synthesis showed excellent results in term of particle size, stability and selectivity. Toxicological assessments revealed Fe (III) and MIL-100 as the most promising metal and MOF for medical applications. It was also shown that MOFs are sensitive towards physiological and pathological criteria such as pH, fluorescence and O2. Although many attempts have been made in utilizing MOFs for bio applications, further improvements should be considered before MOFs can become effective therapeutics options.

Copper(II)-peptides are widely used as industrial catalysts such as in the aerobic oxidation of organic molecules, formation of new C–H bonds and in the azide–alkyne cycloaddition reaction. The length of peptides and the effect of adding copper metal into peptides were questioned in their field of applications. Five novel histidine-based tetrapeptides with the sequences HAAD (P1), HAFD (P2), HAVD (P3), AGHD (P4) and PGHD (P5) were synthesized using the solid phase peptide scheme and analysed with high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) with percentage purities as high as 99.5%. All the peptides were positively charged (+1) and the molecular weight calculated from m/z values of MS results coincided with the theoretical molecular weight of the peptides. Copper(II)-peptides derived from these peptides and copper(II) acetate monohydrate (CuP1–CuP5) in a 1 : 2 ratio was synthesised, purified and characterised by ultraviolet-visible spectroscopy (UV-Vis), ultraviolet-fluorescence spectroscopy (fluorescence) and fourier transform infrared spectroscopy (FTIR), circular dichroism spectroscopy (CD) and optical rotation polarimetry. It provided the necessary information on the secondary structure and the successful binding of copper(II) to the specific amino acids, hence leading to the putative geometry of copper(II)-peptides and the difference in the chirality of amino acids, peptides and copper(II)-peptides. The catalytic activities of the synthesised complexes were evaluated. CuP1 & CuP3 catalysed both the asymmetric aldol reactions with high enantioselectivity of p-nitrobenzaldehyde with cyclohexanone (% ee = 87.3 & 80.3, respectively) and of p-anisaldehyde with cyclohexanone (% ee = 95.5 & 90.9, respectively).

Deep eutectic solvents (DES) were utilised as pretreatment media on oil palm trunk (OPT) fibre in order to change the morphology of the highly crystalline cellulose prior to enzymatic hydrolysis. Among all the DESs tested, ethylammonium chloride: ethylene glycol (EAC:EG) was found to be the most efficient solvent for the pretreatment of OPT fibre. The pretreatment of OPT by EAC:EG had removed 42% lignin and 83% hemicellulose with the ability to dissolve the OPT biomass (58%) after heating at 100 °C for 48 h. FTIR analysis was used in determining the chemical characteristic changes where OPT treated in EAC:EG had more disruption of hydroxyl bond and indication of delignification compared to OPT treated with other DESs. Enzymatic hydrolysis was carried out on OPT treated in EAC:EG and the highest glucose production (74%) was achieved at 50 °C after 24 h with 15 mg/mL substrate concentration, 50 FPU/g of Celluclast 1.5 L and 100 CBU/ml of Novozyme 188.

Pre-treatment is a crucial step in biomass processing prior to the hydrolysis or fermentation to bioethanol. Herein, the potential of deep eutectic solvent (DES) in the pretreatment of oil palm biomass were described. The mechanism of swelling and dissolution of oil palm trunk (OPT) was studied under optical microscopy. The OPT fibres were stirred and heated at 100 °C in choline chloride:glycerol (ChCl:Gly), choline chloride:ethylene glycol (ChCl:EG), ethylammonium chloride:glycerol (EAC:Gly) and ethylammonium chloride:ethylene glycol (EAC:EG) with 1:2 molar ratio each. All DESs tested had showed homogenous swelling and disintegration of small fragments interaction mode with OPT. There were more small fragments observed in EAC-based DES compared to ChCl-based DES. This finding supports the result for the percentage of dissolution where OPT in EAC-based DES recorded higher dissolution with 55% and 50% in EAC:EG and EAC:Gly respectively whereas ChCl-based DES recorded only 33% and 29% in ChCl:EG and ChCl:Gly, respectively. In ChCl-based DESs the fragmentations were accompanied by large unswollen section of fibres. The formation of small fragments indicates that the fibres experienced a fast dissolution. Therefore, the EAC-based DESs proved to be a better swelling and dissolution media for oil palm biomass pretreatment compared to ChCl-based DES.

The properties of DNA in ionic liquids (ILs) have been well studied. However, it is not widely known about the quantitative analysis of ILs such as the binding profile, which could offer a detailed insight of their binding characteristic. In this study, the binding energy of alkylimidazolium-based ILs ([Cnbim]Br where n = 2, 4 and 6) to calf thymus DNA was determined using fluorescence spectroscopy. It was found that the binding constant increased while the values of binding Gibbs energy decreased linearly with increase of alkyl chain length of the ILs. Based on these data, the contribution of each methylene group in the tail of ILs in IL-DNA complex was determined. Moreover, low quenching constant was observed from the competitive displacement of intercalation of ethidium bromide to DNA, hence confirming that ILs are not intercalator. The length of alkyl chain contributed to the increase in the thermal stability of DNA as observed from UV–visible spectra while the CD results indicated that DNA retained its B-form without significant change in the conformation of its base pairs. The findings show that although the stability of DNA is mainly due to the electrostatic attraction between cationic head charge group of imidazolium cation and the DNA phosphate groups, the contribution from the length of alkyl chains also plays a significant role in IL-DNA complex.

A predictive model of a virgin coconut oil (VCO) nanoemulsion system for the topical delivery of copper peptide (an anti-aging compound) was developed using an artificial neural network (ANN) to investigate the factors that influence particle size. Four independent variables including the amount of VCO, Tween 80: Pluronic F68 (T80:PF68), xanthan gum and water were the inputs whereas particle size was taken as the response for the trained network. Genetic algorithms (GA) were used to model the data which were divided into training sets, testing sets and validation sets. The model obtained indicated the high quality performance of the neural network and its capability to identify the critical composition factors for the VCO nanoemulsion. The main factor controlling the particle size was found out to be xanthan gum (28.56%) followed by T80:PF68 (26.9%), VCO (22.8%) and water (21.74%). The formulation containing copper peptide was then successfully prepared using optimum conditions and particle sizes of 120.7 nm were obtained. The final formulation exhibited a zeta potential lower than -25 mV and showed good physical stability towards centrifugation test, freeze-thaw cycle test and storage at temperature 25°C and 45°C.

Five different histidine and aspartic acid based tetrapeptides were designed using LOMETS and PyMol. They were chemically synthesized following the solid phase Fmoc-peptide synthesis protocols and were analysed using the reverse-phase High Performance Liquid Chromatography (HPLC) C18 analytical column for the purity. The peptides were further analysed by Liquid Chromatography Mass Spectrometry (LCMS) to see if the desired peptides were synthesized systematically. Copper(II) acetate monohydrate was bound to the peptides and the best molar ratio for the binding of these metal salts to peptides was 2:1. These observations were monitored through several spectroscopic techniques. The first physical observations for the successful synthesis of metallopeptides were the colour change, the melting/decomposition points and the solubility of these metallopeptides. Due to the visible colour change of the peptides to metallopeptides, UV-Visible spectroscopy and UV-Fluorescence spectroscopy were used as a qualitative analysis tests and the results were in agreement with other researchers’ data from similar researches.

The lipase catalysed synthesis of xylose caproate ester was performed by condensation of xylose, an aldopentose and caproic acid in organic solvents. A dual-solvent system containing DMSO and acetone (1:10 v/v) was used to determine the optimal conditions for the reaction. Different reaction parameters (solvent system, reaction time, substrate molar ratio and the amount of enzyme loaded) were studied. The highest conversion rate (64%) was obtained within 24 h with the optimal conditions of 16% (w/v) Novozym 435 and a molar ratio of xylose to caproic acid of 1:4.

Condensed tannins (CTs) form insoluble complexes with proteins and are able to protect them from degradation, which could lead to rumen bypass proteins. Depending on their degrees of polymerization (DP) and molecular weights, CT fractions vary in their capability to bind proteins. In this study, purified condensed tannins (CTs) from a Leucaena leucocephala hybrid were fractionated into five different molecular weight fractions. The structures of the CT fractions were investigated using 13C-NMR. The DP of the CT fractions were determined using a modified vanillin assay and their molecular weights were determined using Q-TOF LC-MS. The protein-binding affinities of the respective CT fractions were determined using a protein precipitation assay. The DP of the five CT fractions (fractions F1–F5) measured by the vanillin assay in acetic acid ranged from 4.86 to 1.56. The 13C-NMR results showed that the CT fractions possessed monomer unit structural heterogeneity. The number-average molecular weights (Mn) of the different fractions were 1265.8, 1028.6, 652.2, 562.2, and 469.6 for fractions F1, F2, F3, F4, and F5, respectively. The b values representing the CT quantities needed to bind half of the maximum precipitable bovine serum albumin increased with decreasing molecular weight—from fraction F1 to fraction F5 with values of 0.216, 0.295, 0.359, 0.425, and 0.460, respectively. This indicated that higher molecular weight fractions of CTs from L. leucocephala have higher protein-binding affinities than those with lower molecular weights.

The study of formation of nanoemulsions by low energy emulsification method was carried out in water/surfactant/oil system. Palm kernel oil ester (PKOE) was used as the oil phase while Pluronic F-127 was chosen as the surfactant. A ternary phase diagram was constructed for the water/Pluronic F-127/PKOE system by changing the composition concentration at constant temperature. The pre-emulsions were prepared based on the constructed phase diagram via a low energy emulsification and these were characterised with respect to centrifugation force and particle size. Since the particle size formed was large, they were then subjected to high energy emulsification to reduce the particle to nano-size. Formulations with particle size from 93-127 nm were successfully formed. Kinetic stability was assessed by measuring particle size as a function of time and storage condition. Droplet size of the formulations did not show any significant changes with 135 nm after three months. The morphology study was carried out on two formulations using low energy and high energy emulsification. Formulation using high energy emulsification showed an image with smaller and well distributed droplets compared to low energy emulsification.

Herein, an efficient epoxidation of 1-nonene is described. In a simple epoxidation system, commercially available Novozym 435, an immobilized Candida antarctica lipase B, and hydrogen peroxide (H2O2) were utilized to facilitate the in situ oxidation of phenylacetic acid to the corresponding peroxy acid which then reacted with 1-nonene to give 1-nonene oxide with high yield and selectivity. The aliphatic terminal alkene was epoxidised efficiently in chloroform to give an excellent yield (97%–99%) under the optimum reaction conditions, including temperature (35 °C), initial H2O2 concentration (30%), H2O2 amount (4.4 mmol), H2O2 addition rate (one step), acid amount (8.8 mmol), and stirring speed (250 rpm). Interestingly, the enzyme was stable under the single-step addition of H2O2 with a catalytic activity of 190.0 Ug−1. The entire epoxidation process was carried out within 12 h using a conventional water bath shaker.