Deep Eutectic Solvents for Efficient and Selective Extraction of α-Glucosidase Inhibitors from Waste Seeds of Refined Betel Nuts.

During the production process of refined betel nuts in China, a large amount of processing by-product, betel nut waste seeds, is generated. Betel nut waste seeds are rich in bioactive elements, but they have not been effectively utilized yet. In this study, an ultrasonic-assisted deep eutectic solvent method (DES) was used to selectively extract α-glucosidase inhibitors from waste seeds. Compared with traditional extraction solvents such as water and ethanol, the extraction efficiency of specific DESs is higher, and the content of alkaloids in the extracts is lower. However, it should be noted that some pure DESs exhibit inhibitory activity towards α-glucosidase. DESs, based on choline chloride/urea, were selected due to the high extraction efficiency of α-glucosidase inhibitors and their low alkaloid content as well as low inhibitory activity. The optimal extraction conditions were determined using single-factor experiments as follows: 30% (v/v) water content, a choline chloride/urea ratio of 5:3, a solid-liquid ratio of 1:10, extraction temperature of 40 °C, and a duration of 30 min. Through recovery experiments, it was found that the DES can be reused four times under these conditions, maintaining an inhibition rate comparable to alcohol extraction methods. The IC50 value of the extract was measured at 0.0066 mg/mL, superior to acarbose. In summary, this research has successfully developed an efficient and selective method for extracting α-glucosidase inhibitors from betel nut waste seeds, thereby presenting a promising avenue for future applications.

Biological Effects and Biomedical Applications of Areca Nut and Its Extract.

The dried, mature fruit of the palm tree species Areca catechu L. is known as the areca nut (AN) or betel nut. It is widely cultivated in the tropical regions. In many nations, AN is utilized for traditional herbal treatments or social activities. AN has historically been used to address various health issues, such as diarrhea, arthritis, dyspepsia, malaria, and so on. In this review, we have conducted a comprehensive summary of the biological effects and biomedical applications of AN and its extracts. Initially, we provided an overview of the constituents in AN extract. Subsequently, we summarized the biological effects of AN and its extracts on the digestive system, nervous system, and circulatory system. And we elucidated the contributions of AN and its extracts in antidepressant, anti-inflammatory, antioxidant, and antibacterial applications. Finally, we have discussed the challenges and future perspectives regarding the utilization of AN and its extracts as emerging pharmaceuticals or valuable adjuncts within the pharmaceutical field.

Virgin Camellia Seed Oil Improves Glycolipid Metabolism in the Kidney of High Fat-Fed Rats through AMPK-SREBP Pathway.

Camellia seed oil (CO) is used as edible oil in southern China because of its excellent fatty acid composition and abundant bioactive compounds. Chronic kidney disease (CKD) is one of the most common chronic degenerative diseases in China, and active compounds in vegetable oil, like virgin olive oil, have been demonstrated to be efficacious in the management of CKD. In this study, virgin CO was refined using a standard process. The refining had minimal impact on the fatty acid composition, but significantly reduced the presence of bioactive compounds like polyphenols in CO. Sprague-Dawley (SD) rats fed with high fat diet (Group G) were treated with either virgin (Group Z) or refined CO (Group R). The oral administration of CO alleviated lipid accumulation and decreased body and kidney weight gain. Furthermore, treatment with virgin CO increased the renal ATP content. The renal expression levels of AMPK and key enzymes involved in fatty acid oxidation (CPT-1 and ACOX1) and glycolysis (HK, PFK, PK and GAPDH) were up-regulated in Group Z, thereby enhancing the ATP production. Virgin CO treatment downregulated the expression level of SREBP2 and its downstream target genes, such as ACC, FAS, and HMGCR, which reduced lipid synthesis. These findings indicate that virgin CO improves glycolipid metabolism and restores energy homeostasis in the kidneys of rats fed with a high-fat diet by modulating the AMPK-SREBP-signaling pathway, suggesting the potential of active compounds in virgin CO for managing the renal failure associated with glycolipid dysmetabolism.

Peroxisomal ß-oxidation stimulates cholesterol biosynthesis in the liver in diabetic mice.

Although diabetes normally causes an elevation of cholesterol biosynthesis and induces hypercholesterolemia in animals and human, the mechanism linking diabetes to the dysregulation of cholesterol biosynthesis in the liver is not fully understood. As liver peroxisomal ß-oxidation is induced in the diabetic state and peroxisomal oxidation of fatty acids generates free acetate, we hypothesized that peroxisomal ß-oxidation might play a role in liver cholesterol biosynthesis in diabetes. Here, we used erucic acid, a specific substrate for peroxisomal ß-oxidation, and 10,12-tricosadiynoic acid, a specific inhibitor for peroxisomal ß-oxidation, to specifically induce and suppress peroxisomal ß-oxidation. Our results suggested that induction of peroxisomal ß-oxidation increased liver cholesterol biosynthesis in streptozotocin-induced diabetic mice. We found that excessive oxidation of fatty acids by peroxisomes generated considerable free acetate in the liver, which was used as a precursor for cholesterol biosynthesis. In addition, we show that specific inhibition of peroxisomal ß-oxidation decreased cholesterol biosynthesis by reducing acetate formation in the liver in diabetic mice, demonstrating a crosstalk between peroxisomal ß-oxidation and cholesterol biosynthesis. Based on these results, we propose that induction of peroxisomal ß-oxidation serves as a mechanism for a fatty acid-induced upregulation in cholesterol biosynthesis and also plays a role in diabetes-induced hypercholesterolemia.

Fasting induces hepatic lipid accumulation by stimulating peroxisomal dicarboxylic acid oxidation.

Fasting induces lipid accumulation in the liver, while the mechanisms by which fasting dysregulates liver fatty acid oxidation are not clear. Fatty acid ω-oxidation is induced in the fasting state, and administration of dicarboxylic acids to fasting animals decreases plasma ketone bodies. We hypothesized that endogenous dicarboxylic acids might play a role in controlling mitochondrial ß-oxidation in fasting animals. A peroxisome proliferator-activated receptor-alpha agonist and an inhibitor for peroxisomal ß-oxidation were administered to the fasting rats to investigate the role of dicarboxylic acids in liver fatty acid oxidation and lipid homeostasis. We observed that excessive ß-oxidation of endogenous dicarboxylic acids by peroxisomes generated considerable levels of succinate in the liver. Excessive succinate oxidation subsequently increased the mitochondrial NADH/NAD+ ratio and led to an accumulation of 3-OH-CoA and 2-enoyl-CoA intermediates in the liver. This further induced feedback suppression of mitochondrial ß-oxidation and promoted hepatic lipid deposition and steatosis. Specific inhibition of peroxisomal ß-oxidation attenuated fasting-induced lipid deposition in the liver by reducing succinate production and enhancing mitochondrial fatty acid oxidation. We conclude that suppression of mitochondrial ß-oxidation by oxidation of dicarboxylic acids serves as a mechanism for fasting-induced hepatic lipid accumulation and identifies cross talk between peroxisomal and mitochondrial fatty acid oxidation.

Peroxisomal oxidation of erucic acid suppresses mitochondrial fatty acid oxidation by stimulating malonyl-CoA formation in the rat liver.

Feeding of rapeseed (canola) oil with a high erucic acid concentration is known to cause hepatic steatosis in animals. Mitochondrial fatty acid oxidation plays a central role in liver lipid homeostasis, so it is possible that hepatic metabolism of erucic acid might decrease mitochondrial fatty acid oxidation. However, the precise mechanistic relationship between erucic acid levels and mitochondrial fatty acid oxidation is unclear. Using male Sprague-Dawley rats, along with biochemical and molecular biology approaches, we report here that peroxisomal ß-oxidation of erucic acid stimulates malonyl-CoA formation in the liver and thereby suppresses mitochondrial fatty acid oxidation. Excessive hepatic uptake and peroxisomal ß-oxidation of erucic acid resulted in appreciable peroxisomal release of free acetate, which was then used in the synthesis of cytosolic acetyl-CoA. Peroxisomal metabolism of erucic acid also remarkably increased the cytosolic NADH/NAD+ ratio, suppressed sirtuin 1 (SIRT1) activity, and thereby activated acetyl-CoA carboxylase, which stimulated malonyl-CoA biosynthesis from acetyl-CoA. Chronic feeding of a diet including high-erucic-acid rapeseed oil diminished mitochondrial fatty acid oxidation and caused hepatic steatosis and insulin resistance in the rats. Of note, administration of a specific peroxisomal ß-oxidation inhibitor attenuated these effects. Our findings establish a cross-talk between peroxisomal and mitochondrial fatty acid oxidation. They suggest that peroxisomal oxidation of long-chain fatty acids suppresses mitochondrial fatty acid oxidation by stimulating malonyl-CoA formation, which might play a role in fatty acid-induced hepatic steatosis and related metabolic disorders.

Magnetic combined cross-linked enzyme aggregates (Combi-CLEAs) for cofactor regeneration in the synthesis of chiral alcohol.

Magnetic Fe3O4 nanoparticles were prepared and embedded into the Combi-CLEAs to produce the magnetic Combi-CLEAs in this work. The process for magnetic Combi-CLEAs preparation was optimized, and its properties were investigated. The optimum temperature, thermal stability and optimum pH of magnetic Combi-CLEAs were similar to those of Combi-CLEAs. The catalytic performance of magnetic Combi-CLEAs was tested with the biosynthesis of (S)-ethyl 4-chloro-3-hydroxybutyrate ((S)-CHBE). Magnetic Combi-CLEAs could tolerate higher substrate concentration in the biphasic system. The catalytic efficiency and long-term operational stability of magnetic Combi-CLEAs were obviously superior to those of Combi-CLEAs in both aqueous and biphasic systems. Embedding of magnetic Fe3O4 nanoparticles endowing rigidity contributed to these improvements. Furthermore, the preparation of magnetic Combi-CLEAs was easy, and its recovery during multiple batches of reactions could be fulfilled by magnetic field. Aforementioned advantages make the magnetic Combi-CLEAs hold obvious potential for industrial application.

Tyrosine Residues 232 and 401 Play a Critical Role in the Binding of the Cofactor FAD of Acyl-coA Oxidase.

Acyl-coA oxidase (ACO) is an important flavoenzyme responsible for the first step of peroxisomal fatty acid ß-oxidation. In this study, the roles of Tyr232 and Tyr401 in flavin adenine dinucleotide (FAD) binding and enzyme catalysis of ACO were explored using site-directed mutagenesis. For mutant proteins, different levels of activity loss were observed. Wavelength scanning of Y232 and Y401 mutant proteins indicated that there is no FAD binding in Y401S and Y401G mutant ACO. Structure analysis indicated that the phenolic hydroxyl and benzene ring of the side chain could stabilize FAD binding through hydrogen bonds network and hydrophobic pocket formation. These results indicated that these two tyrosine residues play a critical role in the FAD binding of ACO.

Integrating a light-driven coenzyme regeneration system by expression of an alcohol dehydrogenase in phototrophic bacteria for synthesis of chiral alcohol.

Herein, we reported that Rhodobacter sphaeroides (R. sphaeroides) can be engineered by heterologous expression of an alcohol dehydrogenase (adh) from Leifsonia sp. to build a light-driven cofactor regeneration system for synthesis of chiral alcohol. The model substrate, 3'-chloroacetophenone, can be reduced by the engineered R. sphaeroides to (R)-1-(3-chlorophenyl) ethanol with an enantiomeric excess (e.e.) value of more than 99% in an n-hexane/aqueous biphasic media. This system, which is fully controlled by light, exhibited potential power to be an alternative cofactor regeneration platform for cheap synthesis of various chiral alcohols via the cloning other oxidoreductases with diverse characteristics.

Identification of the Catalytic Residue of Rat Acyl-CoA Dehydrogenase 9 by Site-Directed Mutagenesis.

Acyl-CoA dehydrogenase 9 (ACAD 9) is the ninth member of ACADs involved in mitochondrial fatty acid oxidation and possibly complex I assembly. Sequence alignment suggested that Glu389 of rat ACAD 9 was highly conserved and located near the active center and might act as an important base for the dehydrogenation reaction. The role of Glu389 in the catalytic reaction was investigated by site-directed mutagenesis. Both wild-type and mutant ACAD 9 proteins were purified and their catalytic characterization was studied. When Glu389 was replaced by other residues, the enzyme activity could be lost to a large extent. Those results suggested that Glu389 could function as the catalytic base that abstracted the α-proton of the acyl-CoA substrate in a proposed catalytic mechanism.

Specific Inhibition of Acyl-CoA Oxidase-1 by an Acetylenic Acid Improves Hepatic Lipid and Reactive Oxygen Species (ROS) Metabolism in Rats Fed a High Fat Diet.

A chronic high fat diet results in hepatic mitochondrial dysfunction and induction of peroxisomal fatty acid oxidation (FAO); whether specific inhibition of peroxisomal FAO benefits mitochondrial FAO and reactive oxygen species (ROS) metabolism remains unclear. In this study a specific inhibitor for the rate-limiting enzyme involved in peroxisomal FAO, acyl-CoA oxidase-1 (ACOX1) was developed and used for the investigation of peroxisomal FAO inhibition upon mitochondrial FAO and ROS metabolism. Specific inhibition of ACOX1 by 10,12-tricosadiynoic acid increased hepatic mitochondrial FAO via activation of the SIRT1-AMPK (adenosine 5'-monophosphate-activated protein kinase) pathway and proliferator activator receptor α and reduced hydrogen peroxide accumulation in high fat diet-fed rats, which significantly decreased hepatic lipid and ROS contents, reduced body weight gain, and decreased serum triglyceride and insulin levels. Inhibition of ACOX1 is a novel and effective approach for the treatment of high fat diet- or obesity-induced metabolic diseases by improving mitochondrial lipid and ROS metabolism.

Efficient cascade synthesis of ampicillin from penicillin G potassium salt using wild and mutant penicillin G acylase from Alcaligenes faecalis.

To avoid isolation and purification of the intermediate 6-aminopenicillanic acid (6-APA), a two-enzyme two-step cascade synthesis of ampicillin from penicillin G was established. In purely aqueous medium, penicillin G hydrolysis and ampicillin synthesis were catalyzed by immobilized wild-type and mutagenized penicillin G acylases from Alcaligenes faecalis (Af PGA), respectively (Fig. 1). The ßF24 G mutant Af PGA (the 24th Phenylalanine of the ß-subunit was replaced by Glycine) was employed for its superior performance in enzymatic synthesis of ampicillin. By optimizing the reaction conditions, including enzyme loading, temperature, initial pH and D-PGME/6-APA ratio, the conversion of the second step of ampicillin synthesis reached approximately 90% in 240 min and less than 1.7 mole D-PGME were required to produce 1 mole ampicillin. Overall, in a 285 min continuous two-step procedure, an ampicillin yield of 87% was achieved, demonstrating the possibility of improving the cascade synthesis of ampicillin by mutagenized PGA, providing an economically efficient and environmentally benign procedure for semi-synthetic penicillins antibiotics synthesis.

Efficient enzymatic synthesis of ampicillin by mutant Alcaligenes faecalis penicillin G acylase.

Semi-synthetic ß-lactam antibiotics (SSBAs) are one of the most important antibiotic families in the world market. Their enzymatic synthesis can be catalyzed by penicillin G acylases (PGAs). In this study, to improve enzymatic synthesis of ampicillin, site-saturating mutagenesis was performed on three conserved amino acid residues: ßF24, αR146, and αF147 of thermo-stable penicillin G acylase from Alcaligenes faecalis (Af PGA). Four mutants ßF24G, ßF24A, ßF24S, and ßF24P were recovered by screening the mutant bank. Kinetic analysis of them showed up to 800-fold increased kcat/Km value for activated acyl donor D-phenylglycine methyl ester (D-PGME). When ßF24G was used for ampicillin synthesis under kinetic control at industrially relevant conditions, 95% of nucleophile 6-aminopenicillanic acid (6-APA) was converted to ampicillin in aqueous medium at room temperature while 12% process time is needed to reach maximum product accumulation at 25% enzyme concentration compared with the wild-type Af PGA. Consequently, process productivity of enzymatic synthesis of ampicillin catalyzed by Af PGA was improved by more than 130 times, which indicated an enzyme viable for efficient SSBAs synthesis.

High-level soluble and functional expression of Trigonopsis variabilis D-amino acid oxidase in Escherichia coli.

D-Amino acid oxidase is an important biocatalyst used in a variety of fields, and its economically justified level recombinant expression in Escherichia coli has not been established. To accomplish this, after a single Phe54Tyr substitution, fusion proteins of D-amino acid oxidase from Trigonopsis variabilis (TvDAO) with 6 × His-tags were constructed and expressed in E. coli. The effects of his-tags fusing position were revealed. Significant increase in holoenzyme percent and protein solubility made N-terminus tagged TvDAO (termed NHDAO) a suitable choice for TvDAO production. However, reduced cell growth and protein production rates were also observed for the NHDAO bearing strains. To optimize the performance of NHDAO production, changes of culture medium were tested. Finally, a production of 140 U/mL or 3.48 g active enzyme per liter which accounted for 41.4 % of the total protein, and a specific activity of 16.68 U/mg for the crude extract, were achieved in a 3.7 L fermenter in 28.5 h. This indicated a possibility for functional and economical TvDAO expression in E. coli to meet the industrial need.

High-level expression of glutaryl-7-aminocephalosporanic acid acylase from Pseudomonas diminuta NK703 in Escherichia coli by combined optimization strategies.

In this work, a glutaryl-7-aminocephalosporanic acid acylase (GLA) coding gene was cloned from Pseudomonas diminuta NK703 which was screened from oilfield. The concerted effects of the expression system, inducing condition and culture medium on the expression of NK703 GLA in E. coli were firstly investigated. The best combination was the recombinant E. coli strain of pET-28a+GLA/BL21(DE3) with 2.0% (w/v) lactose inducing in YT medium at 25°C. Then, by optimizing the components of culture medium, a synthetic medium with dextrin and a feeding medium with glycerol as the carbon sources were developed to further enhance the GLA yield and improve the GLA solubility. In the end, the NK703 GLA activity increased about 50-fold, reached 14,470 ± 465 U/L, and the GLA productivity and the proportion of soluble GLA to the total soluble protein attained 206.0 ± 9.033 UL(-1)h(-1) and 60.13%, respectively. Scaling up the GLA production in 3.7 L fermenter under the optimized conditions identified in shake flask, the GLA activity also reached 12,406±521U/L, which was the highest report at fermenter level.