Enzyme-catalysed synthesis of plant steryl laurate in non-aqueous media using salt hydrate pairs and its characterisation

Preparation of functional oils rich in phytosterol esters and diacylglycerols by enzymatic transesterification

Phytosterol esters (PEs) and diacylglycerols (DAGs) have various health benefits in humans. In this study, PEs and DAGs were synthesized by lipase-catalyzed transesterification between a natural oil and phytosterols. First, commercial lipases were screened for transesterification and were further verified using multiple-ligand molecular docking. AYS "Amano" (a lipase from Candida rugosa) was found to be the optimum lipase. Subsequently, the enzymatic transesterification conditions were optimized. The optimized conditions were determined to be a 1:2 M ratio of phytosterols to oil, 100 mmol/L phytosterols, and 9 % AYS "Amano", and 50 °C for 24 h in 20 mL n-hexane. Under these conditions, over 70 % of phytosterols were converted to PEs. In this study, an efficient enzymatic process was developed to produce value-added functional oils rich in PEs and DAGs, with PEs content ≥ 31.6 %, DAGs content ≥ 11.2 %, acid value ≤ 0.91 mg KOH/g, and peroxide value ≤ 2.38 mmol/kg.

Guggulsterone - a potent bioactive phytosteroid: synthesis, structural modification, and its improved bioactivities

Guggulsterone is a phytosteroid derived from the oleo-gum resin of the critically endangered plant Commiphora wightii. This molecule has attracted increasing attention due to its excellent biochemistry potential and the compound has consequently been evaluated in clinical trials. With a low concentration in natural resources but wide medicinal and therapeutic value, chemists have developed several synthetic routes for guggulsterone starting from various steroid precursors. Moreover, numerous studies have attempted to modify its structure to improve the biological properties. Nowadays, green and sustainable chemistry has also attracted more attention for advanced chemical processes and reactions in steroid chemistry. The present review aimed to summarize the literature and provide an update about the improvements in the chemical synthesis and structural modification of guggulsterone from the view of green chemistry. Moreover, this review encompasses the improved activities of structurally modified guggulsterone derivatives. We expect that the information provided here will be useful to researchers working in this field and on this molecule.

The preparation of phytosteryl succinyl sucrose esters and improvement of their water solubility and emulsifying properties

Phytosterols have gained much attention due to their outstanding cholesterol-reducing effect, while the insolubility in water limits their application. The aim of this study was to synthesize a novel hydrophilic phytosteryl derivatives-phytosteryl succinyl sucrose esters (PSSEs) and investigated their water solubility and emulsifying properties. PSSEs were synthesized by esterifying phytosterol hemisuccinates with sucrose through a mild chemical reaction. PSSEs were characterized by fourier transform infrared spectroscopy, mass spectroscopy, and nuclear magnetic resonance spectroscopy. The yield of PSSEs exceeded 84% in N,N-dimethylformamide for 36 h of reaction under the selected conditions: 100 mmol/L phytosteryl hemisuccinates, 150 mmol/L sucrose, 110 mmol/L 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochlide, 10 mmol/L 4-dimethylaminopyridine and 10 mmol/L p-toluenesulfonic acid. The water insolubility of phytosterols was overcome and the water solubility of PSSEs achieved 2.13 mg/mL. The emulsifying activity of PSSEs was 2.5 times that of phytosterols, reaching 0.95 mg/mL. PSSEs with better water solubility and emulsification properties could facilitate the widespread use of phytosterols in foods.

An efficient and robust continuous-flow bioreactor for the enzymatic preparation of phytosterol esters based on hollow lipase microarray

In this study, a continuous-flow bioreactor packed with well-organized lipase microarrays was developed for the sustainable synthesis of functional lipid-phytosterol esters (PEs). Hollow mesoporous silicon spheres with a suitable pore size were prepared for lipase immobilization, and the hydrophobic modification endowed the lipase with excellent catalytic activity and stability. The results showed that the condensely packed lipase microarrays offered large specific surface areas and guaranteed the thorough interaction between the lipase and substrates in the continuous-flow bioreactor. Meanwhile, the substrate could pass through the reactor at 1 mL/min with a high conversion of 93.6% due to the hollow structure of the packing spheres. Moreover, the reactors were able to produce 1564 g PEs/g catalyst in a continuous 30-day processing period, which set the highest records for PEs synthesis. This sustainable and highly-converting flow system provided a feasible path for scale-up production of PEs in the food processing area.

Lipases as Effective Green Biocatalysts for Phytosterol Esters’ Production: A Review

Lipases are versatile enzymes widely used in the pharmaceutical, cosmetic, and food industries. They are green biocatalysts with a high potential for industrial use compared to traditional chemical methods. In recent years, lipases have been used to synthesize a wide variety of molecules of industrial interest, and extraordinary results have been reported. In this sense, this review describes the important role of lipases in the synthesis of phytosterol esters, which have attracted the scientific community’s attention due to their beneficial effects on health. A systematic search for articles and patents published in the last 20 years with the terms “phytosterol AND esters AND lipase” was carried out using the Scopus, Web of Science, Scielo, and Google Scholar databases, and the results showed that Candida rugosa lipases are the most relevant biocatalysts for the production of phytosterol esters, being used in more than 50% of the studies. The optimal temperature and time for the enzymatic synthesis of phytosterol esters mainly ranged from 30 to 101 °C and from 1 to 72 h. The esterification yield was greater than 90% for most analyzed studies. Therefore, this manuscript presents the new technological approaches and the gaps that need to be filled by future studies so that the enzymatic synthesis of phytosterol esters is widely developed.

Enzymatic preparation of phytosterol esters with fatty acids from high-oleic sunflower seed oil using response surface methodology

Phytosterol esters are functional compounds that can effectively reduce plasma cholesterol concentration, and have wide applications in the food industry. In this study, a simple and efficient enzymatic method was successfully applied to synthesize phytosterol oleic acid esters with fatty acids from high-oleic sunflower seed oil. Among the tested lipases, Candida rugosa lipase (CRL) exhibited higher catalytic activity in the esterification of phytosterols with fatty acids (oleic acid 84%) from high-oleic sunflower seed oil. Box-Behnken design and response surface methodology were used to investigate the influence of reaction factors on the conversion of phytosterols. The maximum conversion of phytosterols (96.8%) and yield of phytosterol esters (92%) could be obtained under optimal conditions: reaction temperature 50 °C, a molar ratio of phytosterols to fatty acids at 1 : 2.3, enzyme loading of 5.8%, isooctane volume of 2 mL and reaction time of 2 h. It was noteworthy that this enzymatic esterification method indeed expended a much shorter reaction time (2 h) than that observed in previous reports. In general, the enzymatic preparation of phytosterol oleic acid esters with fatty acids from high-oleic sunflower seed oil will be a simple and rapid method for producing unsaturated fatty acid esters of phytosterol with both higher oil solubility and oxidative stability, which is beneficial as functional food ingredients.

Solvent-free synthesis of phytosterol linoleic acid esters at low temperature

Phytosterol unsaturated fatty acid esters show much higher oil solubility than free phytosterol. Thus, development of a green and low-cost method for the preparation of phytosterol fatty acid esters is highly desirable in the food industry. Herein, we have developed a simple chemical method toward efficient preparation of phytosterol linoleic acid esters at very mild temperature (60 °C) using 4-dodecylbenzenesulfonic acid (DBSA) as the catalyst. In this work, low-temperature esterification of phytosterols (soybean sterol) with linoleic acid could produce the corresponding phytosterol esters above 95% conversion under solvent-free conditions. In addition, this simple method could be applied to produce phytosterol esters through esterification of phytosterol with an unsaturated fatty acid mixture resulting from the hydrolysis of various vegetable oils. Importantly, no extra organic solvents and no extra water-removal operations or equipment were required in this chemical esterification method. The mechanism investigation suggested that the DBSA-catalyzed low-temperature esterification would form micro-emulsions of water-in-oil (W/O), which could achieve automatic separation of water from the hydrophobic system to avoid reverse reaction hydrolysis and rapidly promote the equilibrium reaction towards phytosterol esters.

Herein, we have developed a simple chemical method toward efficient preparation of phytosterol linoleic acid esters through esterification at very mild temperature (60 °C) using 4-dodecylbenzenesulfonic acid (DBSA) as the catalyst.

A review on chemical and physical modifications of phytosterols and their influence on bioavailability and safety

Phytosterols have been shown to lower cholesterol levels and to have antioxidant, anti-inflammatory and other biological activities. However, the high melting point and poor solubility limit their bioavailability and practical application. It is advantageous to modify phytosterols chemically and physically. This article reviews and discusses the chemical and physical modifications of phytosterols, as well as their effects on the bioavailability and possible toxicity in vivo. The current research on chemical modifications is mainly focused on esterification to increase the oil solubility and water solubility. For physical modifications (mainly microencapsulation), there are biopolymer-based, surfactant-based and lipid-based nanocarriers. Both chemical and physical modifications of phytosterols can effectively increase the absorption and bioavailability. The safety of modified phytosterols is also an important issue. Phytosterol esters are generally considered to be safe. However, phytosterol oxides, which may be produced during the synthesis of phytosterol esters, have shown toxicity in animal models. The toxicity of nanocarriers also needs further studies.

Sustainable and Green Synthesis of Stanol Esters from Oil Wastes

The recombinant lipase ofOphiostoma piceae (OPEr) is characterized by its prominent sterol esterase activity. The protein was immobilized on magnetic nanoparticles, giving four enzyme variants that have been tested in solvent-free transesterification of methyl oleate and sitostanol. The yields of stanol esters reached 85%, and the catalysts can be reused. Stanol esters were also obtained in a two-step cascade reaction; a mixture of fatty acid methyl esters was enzymatically synthesized from cooking oil wastes and then used for stanol transesterification. An 85% conversion was achieved in 2 h from the second cycle onward, maintaining the activity over 5 cycles. The biocatalysts can be safely used since they don't release toxic compounds for HeLa and A549 cell lines. These procedures comply with the principles of green chemistry and contribute to the sustainable production of these nutraceuticals from secondary raw materials, like the lipid fraction from industrial or agricultural residues.

Highly efficient synthesis of phytosterol linolenate in the presence of Bronsted acidic ionic liquid

Phytosterols are effective in reducing plasma cholesterol. However, phytosterols in a free form have some disadvantages because they have a high melting point and a poor oil solubility, thereby limiting their practical application in foods. The present study was to establish a green and highly efficient method to synthesize phytosterol linolenate for the first time by employing Bronsted acidic ionic liquid (IL) as a catalyst in order to improve its oil solubility. The product was separated, analyzed and subsequently characterized using thin layer chromatography, fourier transform infrared spectroscopy and mass spectroscopy. The conversion of phytosterols could reach above 96% in a very short time (30 min) under the following optimum conditions: 3% 1-butylsulfonate-3-methylimidazolium trifluoromethanesulfonate ([BSO₃HMim]OTf) as a catalyst, 110 °C and 1:1.75 M ratio of phytosterols to ethyl linolenate. The present method demonstrated that [BSO₃HMim]OTf would be a potential catalyst for phytosterol ester synthesis. Most importantly was that the oil solubility of phytosterol linolenate was much greater than its corresponding free phytosterols.