Current advances in phytosterol free forms and esters: Classification, biosynthesis, chemistry, and detection

Phytosterols are plant sterols that are important secondary plant metabolites with significant pharmacological properties. Their presence in the plant kingdom concerns many unrelated botanical families such as oleageneous plants and cereals. The structures of phytosterols evoke those of cholesterol. These molecules are composed of a sterane ring, also known as perhydrocyclopentanophenanthrene, along with a methyl or ethyl group at C-24 in their side chains, a hydroxyl group at C-3 on ring A, and one or two double bonds in the B ring. Phytosterols display different oxidation degrees at the sterane ring and at the side chain as well as varying numbers of carbons with complex stereochemistries. Fats and water solubilities of phytosterols have been achieved by physical, chemical and enzymatic esterifications to favor their bioavailability and to improve the sensory quality of food, and the efficiency of pharmaceutic and cosmetic products. This review aims to provide comprehensive information starting from the definition and structural classification of phytosterols, and exposes an update of their biogenic relationships. Next, the synthesis of phytosterol esters and their applications as well as their effective roles as hormone precursors are discussed. Finally, a concise exploration of the latest advancements in phytosterol / oxyphytosterols analysis techniques is provided, with a particular focus on modern hyphenated techniques.

Cyrene: A Green Solvent for the Synthesis of Bioactive Molecules and Functional Biomaterials

In the panorama of sustainable chemistry, the use of green solvents is increasingly emerging for the optimization of more eco-friendly processes which look to a future of biocompatibility and recycling. The green solvent Cyrene, obtained from biomass via a two-step synthesis, is increasingly being introduced as the solvent of choice for the development of green synthetic transformations and for the production of biomaterials, thanks to its interesting biocompatibility, non-toxic and non-mutagenic properties. Our review offers an overview of the most important organic reactions that have been investigated to date in Cyrene as a medium, in particular focusing on those that could potentially lead to the formation of relevant chemical bonds in bioactive molecules. On the other hand, a description of the employment of Cyrene in the production of biomaterials has also been taken into consideration, providing a point-by-point overview of the use of Cyrene to date in the aforementioned fields.

Application of bio-based solvents for biocatalysed synthesis of amides with Pseudomonas stutzeri lipase (PSL)

Bio-based solvents were investigated for the biocatalysed amidation reactions of various ester-amine combinations by Pseudomonas stutzeri lipase (PSL). Reactions were undertaken in a range of green and potentially bio-based solvents including terpinolene, p-cymene, limonene, 2-methyl THF, ɣ-valerolactone, propylene carbonate, dimethyl isosorbide, glycerol triacetate and water. Solvent screenings demonstrated the importance and potential of using non-polar bio-based solvents for favouring aminolysis over hydrolysis; whilst substrate screenings highlighted the unfavourable impact of reactants bearing bulky para- or 4-substituents. Renewable terpene-based solvents (terpinolene, p-cymene, D-limonene) were demonstrated to be suitable bio-based media for PSL amidation reactions. Such solvents could provide a greener and more sustainable alternative to traditional petrochemical derived non-polar solvents. Importantly, once the enzyme (either PSL or CALB) binds with a bulky para-substituted substrate, only small reagents are able to access the active site. This therefore limits the possibility for aminolysis to take place, thereby promoting the hydrolysis. This mechanism of binding supports the widely accepted ‘Ping Pong – Bi Bi’ mechanism used to describe enzyme kinetics. The work highlights the need to further investigate enzyme activity in relation to para- or 4-substituted substrates. A priority in PSL chemistry remains a methodology to tackle the competing hydrolysis reaction.

Green Technologies for the Production of Modified Lipids

In recent years, the use of green solvents in enzyme catalysis of lipophilic compounds is achieving increasing interest from different perspectives. Conducting reactions under supercritical fluids, ionic liquids, deep eutectic solvents, and other green solvents affords opportunities to overcome problems associated with the lack of solubility of lipids in conventional solvents and the poor miscibility of substrates. Research on the biocatalytic production of modified lipids in the framework of green chemistry is conducted to improve the efficiency of obtaining the desired products as well as the selectivity, stability, and activity of the enzymatic systems. This overview describes the fundamentals and characteristics of several types of green solvents, the main variables involved in enzymatic processes, and examples and applications in the field of lipid modification.

Cyrene™ is a green alternative to DMSO as a solvent for antibacterial drug discovery against ESKAPE pathogens

Dimethyl sulfoxide (DMSO) is currently employed across the biomedical field, from cryopreservation to in vitro assays, despite the fact that it has been shown to have an assortment of biologically relevant effects. The amphiphilic nature of DMSO along with its relatively low toxicity at dilute concentrations make it a challenging solvent to replace. A possible alternative is Cyrene™ (dihydrolevoglucosenone), an aprotic dipolar solvent that is derived from waste biomass. In addition to being a green solvent, Cyrene™ has comparable solvation properties and is reported to have low toxicity. Herein the abilities of the two solvents to solubilize drug compounds and to act as non-participatory vehicles in drug discovery for antibacterials are compared. It was demonstrate that the results of standardised antimicrobial susceptibility testing do not differ between drugs prepared from either Cyrene™ or DMSO stock. Moreover, in contrast to DMSO, Cyrene™ does not offer protection from ROS mediated killing of bacteria and may therefore be an improvement over DMSO as a vehicle in antimicrobial drug discovery.

Bio-available Solvent Cyrene: Synthesis, Derivatization, and Applications

The development of green solvents is one of the key tenets of Green Chemistry as solvents account for the majority of waste stemming from the production of the chemicals on which we have all come to rely. An important class of solvents is the dipolar aprotics, which include N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP). In addition to being derived from non-renewable resources, these solvents are also under increased regulatory pressures that will limit their industrial applications. This Concept concerns the bio-available solvent Cyrene (dihydrolevoglucosenone) as a potential replacement for toxic dipolar aprotic solvents. An emphasis is placed on examining the strengths and weaknesses of Cyrene as a solvent and is accomplished by looking at the synthesis, derivatization, and application in synthetic protocols of Cyrene. With respect to the Twelve Principles of Green Chemistry, this Concept describes a bio-available solvent that should have a disruptive effect on the use of traditional industrial dipolar aprotic solvents.