Enzymatic Synthesis of a Novel Kaempferol-3-O-β-d-glucopyranosyl-(1→4)-O-α-d-glucopyranoside Using Cyclodextrin Glucanotransferase and Its Inhibitory Effects on Aldose Reductase, Inflammation, and Oxidative Stress

Kaempferol attenuates hyperuricemia combined with gouty arthritis via urate transporters and NLRP3/NF-κB pathway modulation

Hyperuricemia (HUA), caused by purine disorders, can lead to gouty arthritis (GA). Kaempferol (KPF), a natural flavonoid, has anti-inflammatory properties, though its mechanism in treating HUA combined with GA remains unclear. This study used a mouse model of HUA combined with GA and in vitro models with HK-2 and THP-1 cells to explore KPF's effects. Cells were treated with KPF or inhibitors of ABCG2, ROS, NLRP3 inflammasome, and nuclear factor κB (NF-κB) pathway. Quantitative assays measured uric acid (UA), creatinine, oxidative stress biomarkers, and pro-inflammatory cytokines. Histopathological analyses showed KPF improved renal and joint inflammation caused by HUA and GA. KPF alleviated oxidative stress, reduced pro-inflammatory cytokines, and regulated UA levels through the modulation of urate transporters, NLRP3 inflammasome, and NF-κB pathway. KPF's actions, partly mediated by ROS reduction, suggest it is a promising candidate for treating HUA combined with GA.

Efficient glycosylation of polyphenols via dynamic complexation of cyclodextrin and synchronous coupling reaction with cyclodextrin glycosyltransferase in water

Glycosylation is an effective way to promote the total intake of polyphenols in humans by increasing the solubility of polyphenols. In this study, an efficient glycosylation system was built via the dynamic complexation of CD with polyphenols and synchronous coupling reaction with cyclodextrin glycosyltransferase (CGTase) in water. The glycosylation efficiencies of quercetin, naringenin, rutin, resveratrol and caffeic acid were 20.9, 3.6, 2.7, 3.4 and 1.5 times higher than the non-complexed system. To quantify conversion rate and determine the rate-limiting step, the mixed product was treated with amyloglucosidase to obtain α-glucosyl rutin, which was identified as rutin 4"-O-α-D-glucopyranoside with purity of 93.6 % and yield of 34.8 % from NMR, MS and HPLC analysis. The results of half-reaction kinetics showed that the catalytic efficiencies of ring-opening of γ-CD (k1) and glycosylation reaction of rutin (k2) were 621.92 and 9.43 mM-1·s-1. The rate-limiting step was clarified for the first time, showing that the ring-opening ability of CGTase to CD was much higher than its glycosylation ability to polyphenols. It is speculated that the rapid ring-opening reaction of CD affected its dynamic complexation, releasing many polyphenols which were not utilized by CGTase in time. Therefore, adjusting the ratio and concentration of CD resulted in an optimal glycosylation molar yield of 84.1 % for rutin, which was the highest yield reported so far in water. This study established a universal system and clarified the rate-limiting step in the enzymatic glycosylation, providing theoretical guidance for efficient production of polyphenol glycosylation.

Glycosylation of flavonoids by sucrose- and starch-utilizing glycoside hydrolases: A practical approach to enhance glycodiversification

Flavonoids are ubiquitous and diverse in plants and inseparable from the human diet. However, in terms of human health, their further research and application in functional food and pharmaceutical industries are hindered by their low water solubility. Therefore, flavonoid glycosylation has recently attracted research attention because it can modulate the physicochemical and biochemical properties of flavonoids. This review represents a comprehensive overview of the O-glycosylation of flavonoids catalyzed by sucrose- and starch-utilizing glycoside hydrolases (GHs). The characteristics of this feasible biosynthesis approach are systematically summarized, including catalytic mechanism, specificity, reaction conditions, and yields of the enzymatic reaction, as well as the physicochemical properties and bioactivities of the product flavonoid glycosides. The cheap glycosyl donor substrates and high yields undoubtedly make it a practical flavonoid modification approach to enhance glycodiversification.

Xanthohumol and echinocystic acid induces PSTVd tolerance in tomato

Tomato is a popular vegetable worldwide; its production is highly threatened by infection with the potato spindle tuber viroid (PSTVd). We obtained the full-length genome sequence of previously conserved PSTVd and inoculated it on four genotypes of semi-cultivated tomatoes selected from a local tomato germplasm resource. SC-5, which is a PSTVd-resistant genotype, and SC-96, which is a PSTVd-sensitive genotype, were identified by detecting the fruit yield, plant growth, biomass accumulation, physiological indices, and PSTVd genome titer after PSTVd inoculation. A non-target metabolomics study was conducted on PSTVd-infected and control SC-5 to identify potential anti-PSTVd metabolites. The platform of liquid chromatography-mass spectrometry detected 158 or 123 differential regulated metabolites in modes of positive ion or negative ion. Principal component analysis revealed a clear separation of the global metabolite profile between PSTVd-infected leaves and control regardless of the detection mode. The potential anti-PSTVd compounds, xanthohumol, oxalicine B, indole-3-carbinol, and rosmarinic acid were significantly upregulated in positive ion mode, whereas echinocystic acid, chlorogenic acid, and 5-acetylsalicylic acid were upregulated in negative ion mode. Xanthohumol and echinocystic acid were detected as the most upregulated metabolites and were exogenously applied on PSTVd-diseased SC-96 seedlings. Both xanthohumol and echinocystic acid had instant and long-term inhibition effect on PSTVd titer. The highest reduction of disease symptom was induced by 2.6 mg/L of xanthohumol and 2.0 mg/L of echinocystic acid after 10 days of leaf spraying, respectively. A superior effect was seen on echinocystic acid than on xanthohumol. Our study provides a statistical basis for breeding anti-viroid tomato genotypes and creating plant-originating chemical preparations to prevent viroid disease.

Research Progress on Anti-Inflammatory Effects and Related Mechanisms of Astragalin

Chronic inflammation is a significant contributor to the development of cancer, cardiovascular disease, diabetes, obesity, autoimmune disease, inflammatory bowel disease, and other illnesses. In the academic field, there is a constant demand for effective methods to alleviate inflammation. Astragalin (AST), a type of flavonoid glycoside that is the primary component in several widely used traditional Chinese anti-inflammatory medications in clinical practice, has garnered attention from numerous experts and scholars. This article focuses on the anti-inflammatory effects of AST and conducts research on relevant literature from 2003 to 2023. The findings indicate that AST demonstrates promising anti-inflammatory potential in various models of inflammatory diseases. Specifically, AST is believed to possess inhibitory effects on inflammation-related factors and protein levels in various in vitro cell models, such as macrophages, microglia, and epithelial cells. In vivo studies have shown that AST effectively alleviates neuroinflammation and brain damage while also exhibiting potential for treating moderate diseases such as depression and stroke; it also demonstrates significant anti-inflammatory effects on both large and small intestinal epithelial cells. Animal experiments have further demonstrated that AST exerts therapeutic effects on colitis mice. Molecular biology studies have revealed that AST regulates complex signaling networks, including NF-κB, MAPK, JAK/STAT pathways, etc. In conclusion, this review will provide insights and references for the development of AST as an anti-inflammatory agent as well as for related drug development.

Production of highly water-soluble genistein α-diglucoside using an engineered O-α-glycoligase with enhanced transglycosylation activity and altered substrate specificity

Genistein is one of isoflavones, showing various biological functions for human health. MalA-D416A, termed O-α-glycoligase, is an acid/base catalytic residue-deficient mutant of a α-glucosidase from Sulfolobus solfataricus, synthesizing genistein 7-O-α-glucoside using α-glucosyl fluoride as the donor substrate. Through mutagenesis toward MalA-D416A, an O-α-glycoligase variant with two mutations (D416R and Q450S) was identified as a biocatalyst with a 58.8-fold enhanced catalytic efficiency for genistein compared to the parent enzyme. The use of a 2:1 ratio of α-glucosyl fluoride and genistein at pH 9 facilitated the synthesis of genistein 7,4'-O-α-diglucoside by MalA-D416R/Q450S. The α-diglucoside exhibited 2,459-fold improved water solubility compared to genistein itself as well as facile deglycosylation by the intestinal α-glucosidase from rat, suggesting the potential of the α-diglucoside for improved bioavailability in human intestine. Through molecular docking analyses the modulation of the active site conformation by these mutations was expected for proper binding of both genistein and the monoglucoside.

Astragalin ameliorates renal injury in diabetic mice by modulating mitochondrial quality control via AMPK-dependent PGC1α pathway

Diabetic kidney disease (DKD) is a common microvascular complication of diabetes mellitus, and oxidative stress and mitochondrial dysfunction play an important role in this process. It has been shown that aldose reductase (ALR2) catalyzes NADPH-dependent reduction of glucose to sorbitol, resulting in oxidative stress and mitochondrial dysfunction in diabetic patients. Astragalin (AG), a flavonoid extracted from Thesium chinense Turcz., shows an inhibitory activity on ALR2. In this study, we investigated the therapeutic effects of AG against renal injury in streptozocin (STZ)-induced diabetic mouse model. Diabetic mice were orally administered AG (5, 10 mg·kg-1·d-1) for 4 weeks. We showed that AG treatment greatly improved the proteinuria and ameliorated renal pathological damage without affecting the elevated blood glucose in diabetic mice. Furthermore, AG treatment significantly suppressed highly activated ALR2, and reduced oxidative stress in the kidney of diabetic mice and in high glucose and lipids-stimulated HK2 cells in vitro. We demonstrated that AG treatment modulated mitochondrial quality control and ameliorated apoptosis, boosting mitochondrial biogenesis, maintaining mitochondrial dynamic homeostasis, and improving energy metabolism disorder in vivo and in vitro. In high glucose and lipids-stimulated HK2 cells, we found that AG (20 μM) restored the phosphorylation level of AMPK, and upregulated the expression and transcriptional activity of PGC1α, whereas treatment with H2O2, blockade of AMPK with Compound C or knockdown of AMPKα with siRNA abolished the protective effect of AG on mitochondrial function, suggesting that antioxidant effects and activation of AMPK-dependent PGC1α pathway might be the molecular mechanisms underlying the protective effects of AG on mitochondrial quality control. We conclude that AG could be a promising drug candidate for the treatment of diabetic renal injury through activating AMPK.

Enzymatic Synthesis of α-Glucosyl-Baicalin through Transglucosylation via Cyclodextrin Glucanotransferase in Water

Baicalin is a biologically active flavone glucuronide with poor water solubility that can be enhanced via glucosylation. In this study, the transglucosylation of baicalin was successfully achieved with CGTases from Thermoanaerobacter sp. and Bacillus macerans using α-cyclodextrin as a glucosyl donor. The synthesis of baicalin glucosides was optimized with CGTase from Thermoanaerobacter sp. Enzymatically modified baicalin derivatives were α-glucosylated with 1 to 17 glucose moieties. The two main glucosides were identified as Baicalein-7-O-α-D-Glucuronidyl-(1→4')-O-α-D-Glucopyranoside (BG₁) and Baicalein-7-O-α-D-Glucuronidyl-(1→4')-O-α-D-Maltoside (BG₂), thereby confirming recent findings reporting that glucuronyl groups are acceptors of this CGTase. Optimized conditions allowed for the attainment of yields above 85% (with a total glucoside content higher than 30 mM). BG₁ and BG₂ were purified via centrifugal partition chromatography after an enrichment through deglucosylation with amyloglucosidase. Transglucosylation increased the water solubility of BG₁ by a factor of 188 in comparison to that of baicalin (molar concentrations), while the same value for BG₂ was increased by a factor of 320. Finally, BG₁ and BG₂ were evaluated using antioxidant and anti-glycation assays. Both glucosides presented antioxidant and anti-glycation properties in the same order of magnitude as that of baicalin, thereby indicating their potential biological activity.

Resveratrol and cyclodextrins, an easy alliance: Applications in nanomedicine, green chemistry and biotechnology

Most drugs or the natural substances reputed to display some biological activity are hydrophobic molecules that demonstrate low bioavailability regardless of their mode of absorption. Resveratrol and its derivatives belong to the chemical group of stilbenes; while stilbenes are known to possess very interesting properties, these are limited by their poor aqueous solubility as well as low bioavailability in animals and humans. Among the substances capable of forming nanomolecular inclusion complexes which can be used for drug delivery, cyclodextrins show spectacular physicochemical and biomedical implications in stilbene chemistry for their possible application in nanomedicine. By virtue of their properties, cyclodextrins have also demonstrated their possible use in green chemistry for the synthesis of stilbene glucosylated derivatives with potential applications in dermatology and cosmetics. Compared to chemical synthesis and genetically modified microorganisms, plant cell or tissue systems provide excellent models for obtaining stilbenes in few g/L quantities, making feasible the production of these compounds at a large scale. However, the biosynthesis of stilbenes is only possible in the presence of the so-called elicitor compounds, the most commonly used of which are cyclodextrins. We also report here on the induction of resveratrol production by cyclodextrins or combinatory elicitation with methyljasmonate in plant cell systems as well as the mechanisms by which they are able to trigger a stilbene response. The present article therefore discusses the role of cyclodextrins in stilbene chemistry both at the physico-chemical level as well as the biomedical and biotechnological levels, emphasizing the notion of "easy alliance" between these compounds and stilbenes.

Natural Compounds as Source of Aldose Reductase (AR) Inhibitors for the Treatment of Diabetic Complications: A Mini Review

BACKGROUND

Aldol reductase (AR) is the polyol pathway's main enzyme that portrays a crucial part in developing 'complications of diabetes' involving cataract, retinopathy, nephropathy, and neuropathy. These diabetic abnormalities are triggered tremendously via aggregation of sorbitol formation (catalyzed by AR) in the polyol pathway. Consequently, it represents an admirable therapeutic target and vast research was done for the discovery of novel molecules as potential AR inhibitors for diabetic complications.

OBJECTIVE

This review article has been planned to discuss an outline of diabetic complications, AR and its role in diabetic complications, natural compounds reported as AR inhibitors, and benefits of natural/plant derived AR inhibitors for the management of diabetic abnormalities.

RESULTS

The goal of AR inhibition remedy is to stabilize the increased flux of blood glucose and sorbitol via the 'polyol pathway' in the affected tissues. A variety of synthetic inhibitors of AR have been established such as tolrestat and sorbinil, but both of these face limitations including low permeability and health problems. Pharmaceutical industries and other scientists were also undertaking work to develop newer, active, and 'safe' AR inhibitors from natural sources. Therefore, several naturally found molecules were documented to possess a potent inhibitory action on AR activity.

CONCLUSION

Natural inhibitors of AR appeared as harmless pharmacological agents for controlling diabetic complications. The detailed literature throughout this article shows the significance of herbal extracts and phytochemicals as prospective useful AR inhibitors in treating diabetic complications.

Kaempferol alleviates calcium oxalate crystal-induced renal injury and crystal deposition via regulation of the AR/NOX2 signaling pathway

BACKGROUND

Calcium oxalate (CaOx) crystal deposition and crystal-induced renal tubular epithelial cell injury have been found to fundamentally contribute to the formation of CaOx nephrolithiasis.

PURPOSE

In the current work, we aim to study the role and mechanism of kaempferol in CaOx crystal kidney deposition and crystal-induced renal injury.

STUDY DESIGN

Mice models and HK-2 cells were used to investigate the effect of kaempferol in CaOx crystal-induced renal injury and crystal deposition in the kidney and its underlying mechanism by a series of experiments.

METHODS

CaOx crystal deposition in mice renal tubulars and tubular damage were evaluated. And crystal adhesion to HK-2 cells, as well as cellular injury were identified. Furthermore, the effect of kaempferol on the expression of androgen receptor (AR) in renal tubular epithelial cells was assessed. The interaction between AR and nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2), and the intrinsic molecular mechanism of how AR regulated NOX2 in HK-2 cells were dissected. Additionally, several different assays were applied to analyze the expression levels of various related genes in this study.

RESULTS

It was revealed that kaempferol reduced CaOx crystal deposition in renal tubulars and crystal adhesion to HK-2 cells. Meanwhile, the results of in vivo and in vitro experiments corroborated that crystal-associated cellular injury, oxidative stress, inflammation and over-expression of OPN and CD44 in the kidney were ameliorated by kaempferol. Moreover, kaempferol functioned on inhibiting the expression of AR in renal tubular epithelial cells, and AR was able to up-regulate the expression of NOX2 at the transcriptional level by directly binding to the promoter of NOX2. Kaempferol decreased crystal deposition and crystal-induced renal oxidative and inflammatory injury by the down-regulation of AR/NOX2 signaling pathway.

CONCLUSION

Taken together, our study findings suggest that kaempferol has a suppressive effect on renal AR expression, which can attenuate CaOx crystal deposition and crystal-induced kidney injury through repressing oxidative stress and inflammation in the kidney by modulating the AR/NOX2 signaling pathway. It demonstrates that kaempferol may have preventive and therapeutic potential for CaOx nephrolithiasis.

One-Pot Bi-Enzymatic Cascade Synthesis of Novel Ganoderma Triterpenoid Saponins

Ganoderma lucidum is a medicinal fungus whose numerous triterpenoids are its main bioactive constituents. Although hundreds of Ganoderma triterpenoids have been identified, Ganoderma triterpenoid glycosides, also named triterpenoid saponins, have been rarely found. Ganoderic acid A (GAA), a major Ganoderma triterpenoid, was synthetically cascaded to form GAA-15-O-β-glucopyranoside (GAA-15-G) by glycosyltransferase (BtGT_16345) from Bacillus thuringiensis GA A07 and subsequently biotransformed into a series of GAA glucosides by cyclodextrin glucanotransferase (Toruzyme® 3.0 L) from Thermoanaerobacter sp. The optimal reaction conditions for the second-step biotransformation of GAA-15-G were found to be 20% of maltose; pH 5; 60 °C. A series of GAA glucosides (GAA-G2, GAA-G3, and GAA-G4) could be purified with preparative high-performance liquid chromatography (HPLC) and identified by mass and nucleic magnetic resonance (NMR) spectral analysis. The major product, GAA-15-O-[α-glucopyranosyl-(1→4)-β-glucopyranoside] (GAA-G2), showed over 4554-fold higher aqueous solubility than GAA. The present study demonstrated that multiple Ganoderma triterpenoid saponins could be produced by sequential actions of BtGT_16345 and Toruzyme®, and the synthetic strategy that we proposed might be applied to many other Ganoderma triterpenoids to produce numerous novel Ganoderma triterpenoid saponins in the future.

Comprehensive study on transglycosylation of CGTase from various sources

Transglycosylation is the in-vivo or in-vitro process of transferring glycosyl groups from a donor to an acceptor, which is usually performed by enzymatic reactions because of their simplicity, low steric hindrance, high region-specificity, low production cost, and mild processing conditions. One of the enzymes commonly used in the transglycosylation reaction is cyclodextrin glucanotransferase (CGTase). The transglycosylated products, catalyzed by CGTase, are widely used in food additives, supplements, and personal care and cosmetic products. This is due to improvements in the solubility, stability, bioactivity and length of the synthesized products. This paper's focus is on the importance of enzymes used in the transglycosylation reaction, their characteristics and mechanism of action, sources and production yield, and donor and acceptor specificities. Moreover, the influence of intrinsic and extrinsic factors on the enzymatic reaction, catalysis of glycosidic linkages, and advantages of CGTase transglycosylation reactions are discussed in detail.

High-Yield Synthesis of Transglycosylated Mogrosides Improves the Flavor Profile of Monk Fruit Extract Sweeteners

Luo Han Guo fruit extract (Siraitia grosvenorii), mainly composed of mogroside V (50%), could be considered a suitable alternative to free sugars; however, its commercial applications are limited by its unpleasant off-notes. In the present work, a central composite design method was employed to optimize the transglycosylation of a mogroside extract using cyclodextrin glucosyltransferases (CGTases) from three different bacteriological sources (Paenibacillus macerans, Geobacillus sp., and Thermoanaerobacter sp.) considering various experimental parameters such as maltodextrin and mogroside concentration, temperature, time of reaction, enzymatic activity, and pH. Product structures were determined by liquid chromatography coupled to a diode-array detector (LC-DAD), liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS), and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Sensory analysis of glucosylated mogrosides showed an improvement in flavor attributes relevant to licorice flavor and aftereffect. Consequently, an optimum methodology was developed to produce new modified mogrosides more suitable when formulating food products as free sugar substitutes.

Enzymatic Synthesis of Puerarin Glucosides Using Cyclodextrin Glucanotransferase with Enhanced Antiosteoporosis Activity

Puerarin (PU) is the most abundant isoflavone from the root of Pueraria lobata and exhibits a broad range of pharmacological activities. However, poor water solubility and low bioavailability limit its use. Enzymatic transglycosylation is emerging as a new strategy to improve the pharmacodynamic and pharmacokinetic properties of natural products for drug development. In this study, three PU glucosides (PU-G, PU-2G, and PU-3G) were synthesized by using a cyclodextrin glucanotransferase from Bacillus licheniformis with PU as the acceptor and α-cyclodextrin as the sugar donor. The transglycosylation products were isolated and structurally identified by mass spectrometry and nuclear magnetic resonance. The water solubilities of PU-G, PU-2G, and PU-3G were 15.6, 100.9, and 179.1 times higher than that of PU, respectively. Moreover, the antiosteoporosis activities of these glucosides were tested, and PU-G was found to show much more potent antiosteoporosis activity as compared to the original PU.

Characterization of novel α-galactosidase in glycohydrolase family 97 from Bacteroides thetaiotaomicron and its immobilization for industrial application

Bacteroides thetaiotaomicron (B. thetaiotaomicron), which resides in the human intestinal tract, has a number of carbohydrate enzymes, including glycoside hydrolase (GH) family 97. Only a few GH 97 enzymes have been characterized to date. In this study, a novel α-galactosidase (Bt_3294) was cloned from B. thetaiotaomicron, expressed in Escherichia coli, and purified using affinity chromatography. This novel enzyme showed optimal activity at 60 °C and pH 7.0. Enzyme activity was reduced by 94.4% and 95.7% in the presence of 5 mM Ca²⁺ and Fe²⁺, respectively. It is interesting that Bt_3294 specifically hydrolyzed shorter α-galactosyl oligosaccharides, such as melibiose and raffinose. The D-values of Bt_3294 at 40 °C and 50 °C were about 107 and 6 min, respectively. After immobilization of Bt_3294, the D-values at 40 °C and 50 °C were about 37.6 and 29.7 times higher than those of the free enzyme, respectively. As a practical application, the immobilized Bt_3294 was used to hydrolyze raffinose family oligosaccharides (RFOs) in soy milk, decreasing the RFOs by 98.9%.

Optimization of Regioselective α-Glucosylation of Hesperetin Catalyzed by Cyclodextrin Glucanotransferase

The regioselective α-glucosylation of hesperetin was achieved by a transglycosylation reaction catalyzed by cyclodextrin glucanotransferase (CGTase) from Thermoanaerobacter sp. using soluble starch as glucosyl donor. By combining mass spectrometry (ESI-TOF) and 2D-NMR analysis, the main monoglucosylated derivative was fully characterized (hesperetin 7-O-α-d-glucopyranoside). In order to increase the yield of monoglucoside, several reaction parameters were optimized: Nature and percentage of cosolvent, composition of the aqueous phase, glucosyl donor, temperature, and the concentrations of hesperetin and soluble starch. Under the optimal conditions, which included the presence of 30% of bis(2-methoxyethyl) ether as cosolvent, the maximum concentration of monoglucoside was approximately 2 mM, obtained after 24 h of reaction. To our knowledge, this is the first report of direct glucosylation of hesperetin employing free enzymes instead of whole cells.

Anti-glycation, Carbonyl Trapping and Anti-inflammatory Activities of Chrysin Derivatives

The aim of this study was searching anti-glycation, carbonyl trapping and anti-inflammatory activities of chrysin derivatives. The inhibitory effect of chrysin on advanced glycation end-products (AGEs) was investigated by trapping methylglyoxal (MGO), and MGO-conjugated adducts of chrysin were analyzed using LC-MS/MS. The mono- or di-MGO-conjugated adducts of chrysin were present at 63.86 and 29.69% upon 48 h of incubation at a chrysin:MGO ratio of 1:10. The MGO adducted positions on chrysin were at carbon 6 or 6 & 8 in the A ring by classic aldol condensation. To provide applicable knowledge for developing chrysin derivatives as AGE inhibitors, we synthesized several O-alkyl or ester derivatives of chrysin and compared their AGE formation inhibitory, anti-inflammatory, and water solubility characteristics. The results showed that 5,7-di-O-acetylchrysin possessed higher AGE inhibitory and water solubility qualities than original chrysin, and retained the anti-inflammation activity. These results suggested that 5,7-di-O-acetylchrysin could be a potent functional food ingredient as an AGE inhibitor and anti-inflammatory agent, and promotes the development of the use of chrysin in functional foods.

Novel aldose reductase inhibitory and antioxidant chlorogenic acid derivatives obtained by heat treatment of chlorogenic acid and amino acids

A heating model system (HMS) of chlorogenic acid (CGA) and 20 amino acids was produced by heating at 120 °C for 4 h and evaluated for in vitro antioxidant and aldose reductase (AR). The CGA-glutamic acid (GT) HMS showed high in vitro antiradical activity indicated by ABTS⁺ (82.37%) and DPPH radical scavenging (83.21%) as well as AR (83.21%) inhibition. The structure of the new compound was established by NMR spectroscopy, as methyl-3-(((E)-3-(3,4-dihydroxyphenyl)acryloyl)oxy)-4,5-dihydroxycyclohexanecarboxylate (1) and 4-O-caffeoylquinic acid (2) from the CGA-GT HMS. The IC₅₀ values of compound 1 for ABTS⁺, DPPH and AR were 8.21, 56.97 and 3.68 μM, respectively. These activities were similar to or higher than those of known positive controls (5.49, 63.58 and 13.60 μM). We suggest that heat treatment generates novel CGA-GT HMS with increased antioxidant and AR inhibitory effects and contributes to the development of novel functional materials from CGA food products.

Enzymatic Synthesis of a Novel Pterostilbene α-Glucoside by the Combination of Cyclodextrin Glucanotransferase and Amyloglucosidase

The synthesis of a novel α-glucosylated derivative of pterostilbene was performed by a transglycosylation reaction using starch as glucosyl donor, catalyzed by cyclodextrin glucanotransferase (CGTase) from Thermoanaerobacter sp. The reaction was carried out in a buffer containing 20% (v/v) DMSO to enhance the solubility of pterostilbene. Due to the formation of several polyglucosylated products with CGTase, the yield of monoglucoside was increased by the treatment with a recombinant amyloglucosidase (STA1) from Saccharomyces cerevisiae (var. diastaticus). This enzyme was not able to hydrolyze the linkage between the glucose and pterostilbene. The monoglucoside was isolated and characterized by combining ESI-MS and 2D-NMR methods. Pterostilbene α-d-glucopyranoside is a novel compound. The α-glucosylation of pterostilbene enhanced its solubility in water to approximately 0.1 g/L. The α-glucosylation caused a slight loss of antioxidant activity towards ABTS˙⁺ radicals. Pterostilbene α-d-glucopyranoside was less toxic than pterostilbene for human SH-S5Y5 neurons, MRC5 fibroblasts and HT-29 colon cancer cells, and similar for RAW 264.7 macrophages.

Antioxidant activity and inhibitory effects of 2-hydroxy-3-methylcyclopent-2-enone isolated from ribose-histidine Maillard reaction products on aldose reductase and tyrosinase

This study aimed to better understand the functional properties of ribose and 20 amino acid Maillard reaction products (MRPs). The ABTS⁺ radical scavenging ability of the ribose-20 amino acid MRPs was evaluated. Among the MRPs, ribose-histidine MRPs (RH-MRPs) showed the highest inhibitory activities on the ABTS⁺ radical scavenging ability, aldose reductase (AR), and tyrosinase compared to other MRPs. Functional compounds with antioxidant and AR inhibitory activities have been recognized as an important strategy in the prevention and treatment of diabetic complications, and the search for tyrosinase inhibitors is important for the treatment of hyperpigmentation, development of skin-whitening agents, and use as preservatives in the food industry. On this basis, we sought to isolate and identify compounds with inhibitory activities against AR and tyrosinase. RH-MRPs were heated at 120 °C for 2 h and fractionated using four solvents: methylene chloride (MC), ethyl acetate, n-butanol, and water. The highest inhibitions were found in the MC fraction. The two compounds from this fraction were purified by silica gel column and preparative thin layer chromatography, and identified as 2-hydroxy-3-methylcyclopent-2-enone and furan-3-carboxylic acid. AR inhibition, tyrosinase inhibition, and ABTS⁺ scavenging (IC₅₀) of 2-hydroxy-3-methylcyclopent-2-enone were 4.47, 721.91 and 9.81 μg mL^-1, respectively. In this study, inhibitory effects of 2-hydroxy-3-methylcyclopent-2-enone isolated from RH-MRP were demonstrated on AR, tyrosinase, and its antioxidant activity for the first time. RH-MRP and its constituents can be developed as beneficial functional food sources and cosmetic materials and should be investigated further as potential functional food sources.