Due to the increased and excessive consumption of fossil fuels, sustainable alternative energy sources are badly needed to replace fossil fuels. The conversion of biomass into energy and value-added chemicals is one of the most promising potential pathways to solve this problem. Millions of tons of lignin, one of the major components of biomass, are produced annually as a byproduct of various industries, where it is treated as a low-value material. However, since it has an aromatic polymer nature, lignin is a proven source for different value-added products. Studies suggest that the selective cleavage of a specific bond of the complex lignin structure is one of the major challenges of converting lignin to a targeted product. In this study, eight different lignin depolymerization methods, both traditional and green, are reviewed. Acid and base catalytic depolymerization methods are straightforward, but due to their low selectivity and comparatively severe reaction conditions, they are expensive and not eco-friendly. Pyrolysis-based depolymerization comes with similar problems but has a higher conversion. In contrast, greener approaches, such as oxidative, microwave-assisted, super/sub-critical fluids (SCF), ionic liquid (IL), and deep eutectic solvent (DES)-based depolymerization techniques, have shown higher efficiency in terms of converting the lignin into phenolic compounds even under milder reaction conditions. SCF, IL, and DES-based approaches will likely become more popular in the future for their greener nature. Overall, depolymerization of lignin with greener technologies could make this process more economically viable and sustainable.

The catalytic depolymerization of alkali lignin into phenolic monomers was studied using subcritical water. In this study, subcritical water was used as the greener solvent with heterogeneous catalysts. The goal of this study was to screen for the best catalyst for the depolymerization, to optimize the reaction conditions, and to increase the yield of the phenolic monomers. The depolymerization reactions were performed at 200 and 240 °C for 5, 10, and 15 min, using subcritical water as the solvent with different catalysts. The treatment of the lignin sample with Ni-Graphene catalyst in subcritical water at 240 °C for 10 min resulted in the highest total yield of phenolic monomers, which was 41.16 ± 0.27 mg/g of alkali lignin. The catalysts also resulted the highest yield for each of the phenolic monomers guaiacol (G), vanillin (G), and homovanillic acid (G) compared to other catalysts studied. The optimized method proved to be an excellent approach to depolymerize alkali lignin.

Lonchocarpus cyanescens Benth is a native African plant commonly known as "African Indigo" or "Indigo Vine" because locals extract dyestuff from its leaves that gives it a brilliant indigo-like hue. Several scientists have reported this plant to contain indigo dye; however, there has been no evidence to justify their claim. Therefore, the primary dye component(s) responsible for the indigo-like hue has been scientifically unexplored. In this study, we utilized UV-Vis and HPLC-DAD-ESI-HRMS (OrbitrapTM) techniques to identify the main chemical compound(s) responsible for the color of the dyestuff. To our surprise, the presence of indigo dye was not detected in the isolated dye extract; we discovered that crystal violet dye and crystal violet-like molecules are present in the extract, which can be responsible for the blue color observed. In addition to its natural dye-producing capability, this plant is used by local traditional healers to heal ailments including ulcers, arthritis, intestinal disorders, etc. Many scientists have proved that the effect of this plant extract on many of these disease states was justified; however, the molecular identities of the compounds responsible for the plant's medicinal value have been unexplored. Therefore, we also analyzed the leaf extract of L. cyanescens and identified several chemical compounds having structural similarities to active drug compounds. The details of our findings will be the focus of our research work.

Screen technology for “smart” devices continues to advance as researches seek to enhance display performance by reducing energy consumption and improving color characteristics. To that end, researchers are turning to organic light-emitting diodes (OLEDs) as the display materials due to higher energy saving and richer color compared to liquid crystal displays (LCDs). However, one major setback of the OLED technology is that the devices are very sensitive to the impurities present in the OLED materials, impacting device lifetime, stability, and overall performance. The isolation of large quantities of the main OLED components from the synthetic impurities is challenging using the traditional purification process (i.e., train sublimation), which has poor reproducibility, and high capital and operating cost. Supercritical fluid chromatography (SFC) could lend itself as an alternative technique for the profiling of impurities and their purification. In this study, we investigated the use of SFC to analyze a mixture of amorphous monomeric molecular glasses with charge-transporting property typical of OLED materials. The separation behavior of four different chromatographic columns containing the stationary phases 1-aminoanthracene (1-AA), naphthyl, 2-ethylpyridine, and C-18 were examined to perform the SFC separations. The effect of using three different co-solvents (i.e., isopropyl alcohol, acetonitrile, and tetrahydrofuran) to the CO2 mobile phase on the separation selectivity and resolution was also investigated. For the probe mixture used, the naphthyl column in combination with the addition of acetonitrile as co-solvent provided the best separation in terms of resolution. The SFC method was farther optimized for co-solvent composition, temperature, pressure, and flow rate. The SFC analysis showed high resolution and short analysis time compared to HPLC, and also provided for the separation of small components that have been attributed to impurities in the sample.