Sonochemical enzyme-catalyzed regioselective acylation of flavonoid glycosides

Enhanced Enzymatic Synthesis of Puerarin Palmitate with Different Acyl Donors for Lipid Solubility Improvement

Puerarin is a flavonoid known as a natural antioxidant found in the root of Pueraria robata. Its antioxidant, anticancer, and anti-inflammatory effects have attracted attention as a potential functional ingredient in various bioindustries. However, puerarin has limited bioavailability owing to its low lipid solubility and stability. Acylation is proposed as a synthesis method to overcome this limitation. In this study, lipase-catalyzed acylation of puerarin and various acyl donors was performed, and the enzymatic synthetic condition was optimized. Under the condition (20 g/L of Novozym 435, palmitic anhydride, 1:15, 40 °C, tetrahydrofuran (THF)), the synthesis of puerarin ester achieved a significantly high conversion (98.97%) within a short time (3 h). The molecule of the synthesized puerarin palmitate was identified by various analyses such as liquid chromatography-mass spectrometry (LC-MS), Fourier-transform infrared spectroscopy (FT-IR), and carbon-13 nuclear magnetic resonance (13C NMR). The lipid solubility and the radical scavenging activity were also evaluated. Puerarin palmitate showed a slight decrease in antioxidant activity, but lipid solubility was significantly improved, improving bioavailability. The high conversion achieved for puerarin esters in this study will provide the foundation for industrial applications.

Chemo- and regio-selective enzymatic lipophilisation of rutin, and physicochemical and antioxidant properties of rutin ester derivatives

Enzymes are one of the most powerful tools in organic Green Chemistry and enzymatic reactions offer numerous advantages like regio- and enantio-selectivity along with their eco-friendly and sustainable nature. More specifically, lipases can catalyse both ester hydrolysis and formation depending on the nature of the substrate and water content. Herein, the focus is on the development of an enzymatically catalysed lipophilisation of natural compounds using lipases of microbial origin and the investigation of the optimal reaction conditions, aiming ultimately to ameliorate the compounds' properties. The flavonoid disaccharide rutin (quercetin-3-O-rutinoside) was the model compound on which the acylation protocol was built, allowing an efficient procedure to be established, while simultaneously offering the possibility of developing rapid, clear and robust methodologies, using state-of-the-art techniques, for analysis and purification of the synthesized compounds. An optimal 72 h reaction at 55 °C, using Candida antarctica lipase B immobilized on acrylic resin, combined with silicon dioxide as dehydrating agent, followed by product purification, achieved conversion ratios up to 50%. Full characterization and evaluation of the physicochemical and antioxidant properties of the esterified compounds was obtained. The lipophilicity of the rutin esters produced increased with increasing alkyl chain length, yet antioxidant properties were unaffected in comparison with the parent compound. A preparatively useful acylation protocol was established, allowing full investigation into the properties of the acylated compounds. It is also applicable for use on mixtures of compounds as most natural products are found in nature in mixtures and such a development greatly enhances the potential of this method for future commercial applications.

Fatty acid acylated flavonol glycosides from the seeds of Nephelium lappaceum and their nitric oxide suppression activity

Five undescribed fatty acid esters of flavonol glycosides, nephelosides A-E, along with eight known compounds, were isolated from the seeds of Nephelium lappaceum L. The structures were elucidated by extensive analysis of spectroscopic data in combination with GC-MS analysis. Potency of compounds toward nitric oxide suppression was assessed by monitoring the inhibition of lipopolysaccharide-stimulated nitric oxide production in J744.A1 macrophage cells. Nepheloside D, kaempferol and kaempferol 7-O-α-L-rhamnopyranoside showed significant activity with IC₅₀ values of 26.5, 11.6 and 12.0 μM, respectively.

Highly Efficient Regioselective Acylation of Dihydromyricetin Catalyzed by Lipase in Nonaqueous Solvents

This study aimed to explore the enzymatic acylation of dihydromyricetin (DHM) to synthesized DHM derivatives with a different substituted carbon chain to improve its liposolubility. In the presence of Lipozyme TL IM, DHM was butyrylated in a 96.28% conversion in methyl tert-butyl ether under the optimized conditions (molar ratio of DHM to vinyl butyrate, 1:20; lipase dosage, 0.4 U/mg DHM; temperature, 50 °C; stirrer speed, 200 rpm; reaction time, 72 h). Liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy revealed that two acylation products were formed; these were 7-O-acyl-DHM and 3-O-acyl-DHM. In addition, the liposolubility of the DHM derivatives increased with the increase in the substituted carbon chain length; their antioxidant activities were higher than that of DHM in the lecithin peroxidation system, and C8-DHM had a better effect. Therefore, enzymatic acylation broadens the application of DHM in a lipid system in the food field.

Mechanoenzymology in the Kinetic Resolution of β-Blockers: Propranolol as a Case Study

Recent advances in biotechnology, protein engineering, and enzymatic immobilization have made it possible to carry out biocatalytic transformations through alternative non-conventional activation strategies. In particular, mechanoenzymology (i.e., the use of the mechanical force produced by milling or grinding to activate a biotransformation) has become a new area in so-called "green chemistry", reshaping key fundaments of biocatalysis and leading to the exploration of enzymatic transformations under more sustainable conditions. Significantly, numerous chiral active pharmaceutical ingredients have been synthesized via mechanoenzymatic methods, boosting the use of biocatalysis in the synthesis of chiral drugs. In this regard and aiming to widen the scope of the young field of mechanoenzymology, a dual kinetic resolution of propranolol precursors was explored. The biocatalytic methodology mediated by Candida antarctica Lipase B (CALB) and activated by mechanical force allowed the isolation of both enantiomeric precursors of propranolol with high enantiomeric excess (up to 99% ee), complete conversion (c = 50%), and excellent enantiodifferentiation (E > 300). Moreover, the enantiomerically pure products were used to synthesize both enantiomers of the β-blocker propranolol with high enantiopurity.

Long-chain fatty acid acylated derivatives of isoflavone glycosides from the rhizomes of Iris domestica

Six undescribed long-chain fatty acid esters of isoflavone glycosides were obtained from the rhizomes of Iris domestica (L.). Their structures were elucidated by comprehensive spectroscopic data, alkaline hydrolysis, and acid hydrolysis. This is the first report of the long-chain (C₁₄-C₁₈) fatty acid derivatives of isoflavone glycosides from natural products. Belamcandnoate B and D exhibited moderate cytotoxic activities against HCT-116, HepG2, and BGC823 cell lines with IC₅₀ values of 1.69-6.86 μM. Belamcandnoate B and E exhibited 72.27 and 58.98% inhibitory activities, respectively, against Fe²⁺/cysteine-induced liver microsomal lipid peroxidation at a concentration of 10 μM.

Process intensification using immobilized enzymes for the development of white biotechnology

Process intensification of biocatalysed reactions using different techniques such as microwaves, ultrasound, hydrodynamic cavitation, ionic liquids, microreactors and flow chemistry in various industries is critically analysed and future directions provided.

Highly Efficient Regioselective Decanoylation of Hyperoside Using Nanobiocatalyst of Fe3O4@PDA-Thermomyces lanuginosus Lipase: Insights of Kinetics and Stability Evaluation

The immobilization of Thermomyces lanuginosus lipase on polydopamine-functionalized Fe₃O₄ magnetic nanoparticles (Fe₃O₄@PDA-TLL) as a nanobiocatalyst was successfully performed for the first time, and the Fe₃O₄@PDA-TLL was used for regioselective acylation of natural hyperoside with vinyl decanoate. The effects of several crucial factors, such as the reaction solvent, substrate molar ratio, temperature, and immobilized enzyme dosage, were investigated. Under optimum conditions, the reaction rate, 6″-regioselectivity, and maximum substrate conversion were as high as 12.6 mM/h, 100%, and 100%, respectively. An operational stability study demonstrated that the immobilized enzyme could maintain 90.1% of its initial maximum conversion even after reusing it five times. In addition, further investigations on the kinetic parameters, like V_max, K_m, V_max/K_m, and E_a, also revealed that the biocompatible Fe₃O₄@PDA could act as an alternative carrier for the immobilization of different enzymes.

Novozym 435: the “perfect” lipase immobilized biocatalyst?

Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes with its advantages and drawbacks.

An investigation of lipase catalysed sonochemical synthesis: A review

Ultrasonic irradiation has recently gained attention of researchers for its process intensification in numerous reactions. Earlier ultrasound was known for its application either to deactivate enzyme activity or to disrupt the cell. However, in recent years, practice of ultrasonic irradiation began to emerge as a tool for the activation of the enzymes under mild frequency conditions. The incorporation of ultrasound in any of enzymatic reactions not only increases yield but also accelerates the rate of reaction in the presence of mild conditions with better yield and less side-products. To attain maximum yield, it is crucial to understand the mechanism and effect of sonication on reaction especially for the lipase enzyme. Thus, the influence of ultrasound irradiation on reaction yield for different parameters including temperature, enzyme concentration, mole ratio of substrates, solvents ultrasonic frequency and power was reviewed and discussed. The physical effect of cavitation determined by bubble dynamics and rate of reaction through kinetic modelling also needs to be assessed for complete investigation and scale up of synthesis. Thus, prudish utilisation of ultrasound for enzymatic synthesis can serve better future for sustainable and green chemistry.

Docosahexaenoic acid-acylated phloridzin, a novel polyphenol fatty acid ester derivative, is cytotoxic to breast cancer cells

Docosahexaenoic acid-acylated phloridzin (PZ-DHA), a novel polyphenol fatty acid ester derivative, was synthesized through a regioselective acylation reaction with the aim of increasing the bioactivity of phloridzin (PZ) and docosahexaenoic acid (DHA). In this study, PZ-DHA's cytotoxic activity was explored using in vitro and in vivo models of mammary carcinoma. PZ-DHA was selectively cytotoxic for mammary carcinoma (MDA-MB-231, MDA-MB-468, 4T1, MCF-7 and T-47D) cells compared to non-malignant human mammary epithelial cells (HMEC and MCF-10A) and fibroblasts by MTS assay and Annexin-V-FLUOS/propidium iodide staining. Flow cytometric analysis of Oregon Green 488- and Ki-67-stained MDA-MB-231 cells showed antiproliferative activity of PZ-DHA at a subcytotoxic concentration. PZ-DHA also arrested MDA-MB-231 cell division at the G2/M phase and down-regulated expression of cyclin B1 and cyclin-dependent kinase 1 (CDK1). PZ-DHA-induced apoptosis in MDA-MB-231 cells was confirmed by caspase 3/7 activation in a luminescence assay and DNA fragmentation by TUNEL staining. Moreover, MDA-MB-231 xenograft growth in non-obese diabetic severe combined immunodeficient mice was suppressed by intra-tumoral administration of PZ-DHA. This study shows that PZ-DHA is selectively cytotoxic to breast cancer cells in vitro and in vivo, suggesting that further investigations of PZ-DHA are warranted as a potential treatment for breast cancer.