Catalytic Methods for the Production of Sugar Esters

Nowadays, Sugar esters (SEs) have become the focus of researchers due to their biocompatibility and extensive industrial applications as surfactants. This trend provides new methods and opportunities for the development of green synthetic chemistry. Taking the above into consideration, a critical review presented in this work emphasized the efficiency of catalyzing the synthesis of SEs with minimal hazardous by-products. These catalytic media have been employed with various impacts involving chemical, biological, and other catalytic materials. Chemical methods have been reported to show limitations in terms of preparation and bio-compatibility. To solve these shortcomings, therefore, other technologies have been adopted; ionic liquids (eutectic solvents), chemo-enzymatic systems and chemo-enzymatic systems on a catalytic surface. The use of chemo-enzymatic systems on catalytic surfaces has proved to be suitable in solving biocompatibility and stability problems and correspondingly increasing the yield of esters formed. Therefore, finding an improved catalytic surface, and the sustainable optimal reaction conditions for enzymes will be vital to improving sugar ester conversion. This study highlights the different catalytic advances employed in the esterification of SEs.

In Search of Effective Anticancer Agents—Novel Sugar Esters Based on Polyhydroxyalkanoate Monomers

Cancer is one of the deadliest illness globally. Searching for new solutions in cancer treatments is essential because commonly used mixed, targeted and personalized therapies are sometimes not sufficient or are too expensive for common patients. Sugar fatty acid esters (SFAEs) are already well-known as promising candidates for an alternative medical tool. The manuscript brings the reader closer to methods of obtaining various SFAEs using combined biological, chemical and enzymatic methods. It presents how modification of SFAE’s hydrophobic chains can influence their cytotoxicity against human skin melanoma and prostate cancer cell lines. The compound’s cytotoxicity was determined by an MTT assay, which followed an assessment of SFAEs’ potential metastatic properties in concentrations below IC50 values. Despite relatively high IC50 values (63.3–1737.6 μM) of the newly synthesized SFAE, they can compete with other sugar esters already described in the literature. The chosen bioactives caused low polymerization of microtubules and the depolymerization of actin filaments in nontoxic levels, which suggest an apoptotic rather than metastatic process. Altogether, cancer cells showed no propensity for metastasis after treating them with SFAE. They confirmed that lactose-based compounds seem the most promising surfactants among tested sugar esters. This manuscript creates a benchmark for creation of novel anticancer agents based on 3-hydroxylated fatty acids of bacterial origin.

In Silico Biological Profile Prediction of Some Selectively Synthesized Acyl Rhamnopyranosides

Over the past several decades significant biological activities including brains protective and antimicrobial activities have made sugar esters (SEs) as a topic of great interest. In this context, unimolar 3-chlorobenzoylation of methyl α-L-rhamnopyranoside (4) using dibutyltin oxide method regioselectively furnished only the 3-O-substitution product 5 in excellent yield. The reaction proceeded via the formation of a cyclic 2,3-O-dibutylstannylene intermediate where equatorial hydroxyl group is activated by the tin atom leading to the formation of product 5 only. To get biologically important rhamnopyranoside esters chlorobenzoate 5 was further converted into three newer 2,4-di-O-acyl products 6-9 with other acylating agents using direct acylation method. Prediction of activity spectra for substances (PASS) indicated that these rhamnopyranoside esters have many promising biological profiles including CYP2H substrate, membrane permeability inhibitor and better antifungal activities. Additionally, ADMET and drug likeness properties of SEs 5-8 were predicted and discussed.

CompassR-guided recombination unlocks design principles to stabilize a lipase in ILs with minimal experimental efforts

Biocatalysis in ionic liquids (ILs) has gained enormous attention in producing biodiesel, sugar esters, and pharmaceuticals. However, hydrophilic ILs interaction with enzymes often results in reduced activity or even inactivation....

Thioglycoligase derived from fungal GH3 β-xylosidase is a multi-glycoligase with broad acceptor tolerance

The synthesis of customized glycoconjugates constitutes a major goal for biocatalysis. To this end, engineered glycosidases have received great attention and, among them, thioglycoligases have proved useful to connect carbohydrates to non-sugar acceptors. However, hitherto the scope of these biocatalysts was considered limited to strong nucleophilic acceptors. Based on the particularities of the GH3 glycosidase family active site, we hypothesized that converting a suitable member into a thioglycoligase could boost the acceptor range. Herein we show the engineering of an acidophilic fungal β-xylosidase into a thioglycoligase with broad acceptor promiscuity. The mutant enzyme displays the ability to form O-, N-, S- and Se- glycosides together with sugar esters and phosphoesters with conversion yields from moderate to high. Analyses also indicate that the pKa of the target compound was the main factor to determine its suitability as glycosylation acceptor. These results expand on the glycoconjugate portfolio attainable through biocatalysis.

Quercetin Loaded Monolaurate Sugar Esters-Based Niosomes: Sustained Release and Mutual Antioxidant—Hepatoprotective Interplay

Flavonoids possess different interesting biological properties, including antibacterial, antiviral, anti-inflammatory and antioxidant activities. However, unfortunately, these molecules present different bottlenecks, such as low aqueous solubility, photo and oxidative degradability, high first-pass effect, poor intestinal absorption and, hence, low systemic bioavailability. A variety of delivery systems have been developed to circumvent these drawbacks, and among them, in this work niosomes have been selected to encapsulate the hepatoprotective natural flavonoid quercetin. The aim of this study was to prepare nanosized quercetin-loaded niosomes, formulated with different monolaurate sugar esters (i.e., sorbitan C12; glucose C12; trehalose C12; sucrose C12) that act as non-ionic surfactants and with cholesterol as stabilizer (1:1 and 2:1 ratio). Niosomes were characterized under the physicochemical, thermal and morphological points of view. Moreover, after the analyses of the in vitro biocompatibility and the drug-release profile, the hepatoprotective activity of the selected niosomes was evaluated in vivo, using the carbon tetrachloride (CCl4)-induced hepatotoxicity in rats. Furthermore, the levels of glutathione and glutathione peroxidase (GSH and GPX) were measured. Based on results, the best formulation selected was glucose laurate/cholesterol at molar ratio of 1:1, presenting spherical shape and a particle size (PS) of 161 ± 4.6 nm, with a drug encapsulation efficiency (EE%) as high as 83.6 ± 3.7% and sustained quercetin release. These niosomes showed higher hepatoprotective effect compared to free quercetin in vivo, measuring serum biomarker enzymes (i.e., alanine and aspartate transaminases (ALT and AST)) and serum biochemical parameters (i.e., alkaline phosphatase (ALP) and total proteins), while following the histopathological investigation. This study confirms the ability of quercetin loaded niosomes to reverse CCl4 intoxication and to carry out an antioxidant effect.