Inhibition of α-glucosidase by trilobatin and its mechanism: kinetics, interaction mechanism and molecular docking

Comparative study on metabolite variations of two rose teas by plant metabolomics and revealing their skin-whitening candidates by spectrum-effect relationship analysis

INTRODUCTION

Rosa rugosa var. plena Rehd (CBR) and Rosa chinensis cv. "JinBian" (JBR) are two common species used in rose tea among different original species. CBR, the officially documented original plant of the rose species for food and medicinal purposes, is more costly than JBR. With increasing demand for different rose teas, it is meaningful to compare the chemical constituents for their quality control and reveal their skin-whitening components that will provide in-depth insights for the expansion of the rose tea industry.

OBJECTIVE

This study aims to reveal the chemical variances between CBR and JBR and determine their skin-whitening components.

METHODOLOGY

A strategy obtained by combining MS-based plant-metabolomics with spectrum-effect relationship analysis has been proposed for unveiling chemical differences between CBR and JBR and further exploring their potential skin-whitening components.

RESULTS

A total of 2030 metabolites were found that revealed considerable differences between CBR and JBR. The results of bioactivity assay demonstrated that JBR exhibited stronger tyrosinase inhibition activity than CBR. Six potential skin-whitening compounds (di-O-galloyl-HHDP-glucoside, tri-O-galloyl-HHDP-glucoside, spiraeoside, quinic acid, rugosin A, and 1,2,3,6-tetra-O-galloyl-glucose) were discovered as potential tyrosinase inhibitors, via spectrum-effect relationship analysis. This is the first time that di-O-galloyl-HHDP-glucoside, tri-O-galloyl-HHDP-glucoside, rugosin A, and 1,2,3,6-tetra-O-galloyl-glucose have been reported with tyrosinase inhibitory activity. Additionally, molecular docking analysis was used to reveal the inhibition mechanism of these compounds toward tyrosinase.

CONCLUSION

The finding of this study will be of great importance for the quality control of the two types of rose teas, and the revealed active ingredients will provide in-depth insights for the expansion of the rose tea industry.

Inhibition of α-glucosidase activity and intestinal glucose transport to assess the in vivo anti-hyperglycemic potential of dodecyl-acylated phlorizin and polydatin derivatives

A diet containing natural active compounds that can inhibit the hydrolytic activity of α-glucosidase on carbohydrates and intestinal glucose absorption is an effective means of controlling postprandial hyperglycemia. Phlorizin and polydatin as phenolic glycosides have a high affinity for the catalytic site of α-glucosidase, but exhibited unsatisfactory competitive inhibitory capacity, with an IC50 of 0.97 and >2 mM, respectively. However, dodecyl-acylated derivatives of phlorizin and polydatin exerted α-glucosidase inhibitory capacity, with an IC50 of 55.10 and 70.95 μM, respectively, which were greatly enhanced and much stronger than that of acarbose with an IC50 of 2.46 mM. The SPR assay suggested the high affinity of dodecyl phlorizin and dodecyl polydatin to α-glucosidase with equilibrium dissociation constant (KD) values of 12.0 and 7.9 μM, respectively. Both dodecyl phlorizin and dodecyl polydatin reduced the catalytic ability of α-glucosidase by reversible noncompetitive and uncompetitive mixed inhibition, which bind noncovalently to the allosteric site 2 through hydrogen bonds and hydrophobic interactions, thereby inducing the secondary structure unfolding and intrinsic fluorescence quenching of α-glucosidase. Confocal microscopy detection visually showed significant inhibitory effects on FITC-labeled glucose uptake in intestinal Caco-2 cells by phlorizin, polydatin, dodecyl phlorizin and dodecyl polydatin. In addition, based on the differentiated Caco-2 cell monolayer model, dodecyl phlorizin and dodecyl polydatin suppressed intestinal glucose transport more effectively than phlorizin and polydatin, suggesting that they were promising in vivo hypoglycemic active compounds.

Acetylation of the polysaccharide from Houttuynia cordata rhizome and their α-glucosidase inhibition mechanism

In this study, the polysaccharide (RHCP) extracted from Houttuynia cordata rhizome was acetylated through the acetic anhydride method. The physicochemical properties of RHCP and its acetylated derivatives (Ac-RHCP) were determined by infrared spectra, scanning electron microscopy, and Congo red test. Meanwhile, the α-glucosidase inhibition mechanism of RHCP and Ac-RHCP was analyzed by inhibition kinetics, and circular dichroism and fluorescence spectroscopy. Ac-RHCP resulted in a more porous surface structure and 1.83-fold higher solubility compared with RHCP. At a concentration of 6 mg/mL, the α-glucosidase inhibition rate of Ac-RHCP was 75.40%, while that of RHCP was 44.68%. RHCP and Ac-RHCP inhibited α-glucosidase in a mixed-type manner, reduced the endogenous fluorescence of α-glucosidase, affected the microenvironment of amino acid residues, and changed the conformation of α-glucosidase. The study indicates that Ac-RHCP exhibits a certain level of α-glucosidase inhibition, demonstrating its potential as a functional food for glycemic control.

Rapid and green quantification of phloridzin and trilobatin in Lithocarpus litseifolius (Hance) Chun (sweet tea) using an online pressurized liquid extraction high-performance liquid chromatography at equal absorption wavelength method

Sweet tea is a functional herbal tea with anti-inflammatory, anti-diabetic, and other effects, in which phloridzin and trilobatin are two functional compounds. However, the current methods for their quantification are time-consuming, costly, and environmentally unfriendly. In this paper, we propose a rapid method that integrates online pressurized liquid extraction and high-performance liquid chromatography featuring a superficially porous column for fast separation. Moreover, we employ an equal absorption wavelength method to eliminate using multiple standard solutions and relative calibration factors. Our verification process corroborated the technique's selectivity, accuracy, precision, linearity, and detection limitations. Separately, our methodology demonstrated excellent analytical efficiency, cost-effectiveness, and environmental friendliness. Practical application using six distinct batches of sweet tea samples yielded results in congruence with the external standard method. The analytical rate of this technique is up to over 18 times faster than traditional methods, and organic solvent consumption has been reduced to less than 1.5 mL. Therefore, this method provides a valuable way to achieve quality control and green analysis of sweet tea and other herbal teas.

Developing Lipase Inhibitor as a Novel Approach to Address the Rice Bran Rancidity Issue─A Critical Review

Rice bran is a valuable byproduct from the food processing industry, which contains abundant protein, essential unsaturated fatty acids, and numerous bioactive compounds. However, its susceptibility to rancidity greatly restricts its wide utilization. Many strategies have been proposed to delay the rancidity of rice bran, but most of them have their respective limitations. Here, we proposed that developing rice ban lipase peptide inhibitors represents an alternative and promising prescription for impeding the rancidity of rice bran, in contrast to the conventional stabilization approaches for rice bran. For this reason, the rancidity mechanisms of rice bran and the research progress of rice bran lipases were discussed. In addition, the feasibility of utilizing in silico screening and phage display, two state-of-the-art technologies, in the design of the related peptide inhibitors was also highlighted. This knowledge is expected to provide a theoretical basis for opening a new avenue for stabilizing rice bran.

In vitro inhibitory effect of five natural sweeteners on α-glucosidase and α-amylase

A promising and efficacious approach to manage diabetes is inhibiting α-glucosidase and α-amylase activity. Therefore, the inhibitory activities of five natural sweeteners (mogrosides (Mog), stevioside (Ste), glycyrrhizinic acid (GA), crude trilobatin (CT), and crude rubusoside (CR)) against α-glucosidase and α-amylase and their interactions were evaluated in vitro using enzyme kinetics, fluorescence spectroscopy, Fourier infrared spectroscopy, and molecular docking. The inhibitor sequence was CT > GA > Ste, as GA competitively inhibited α-glycosidase activity while CT and Ste exhibited mixed inhibitory effects. Compared to a positive control acarbose, the inhibitory activity of CT was higher. For α-amylase, the mixed inhibitors CT, CR, and Mog and the competitive inhibitor Ste effectively inhibited the enzyme, with the following order: CT > CR > Ste > Mog; nevertheless, the inhibitors were slightly inferior to acarbose. Three-dimensional fluorescence spectra depicted that GA, CT, and CR bound to the hydrophobic cavity of α-glucosidase or α-amylase and changed the polarity of the hydrophobic amino acid-based microenvironment and structure of the polypeptide chain backbone. Infrared spectroscopy revealed that GA, CT, and CR could disrupt the secondary structure of α-glucosidase or α-amylase, which decreased enzyme activity. GA, trilobatin and rubusoside bound to amino acid residues through hydrogen bonds and hydrophobic interactions, changing the conformation of enzyme molecules to decrease the enzymatic activity. Thus, CT, CR and GA exhibit promising inhibitory effects against α-glucosidase and α-amylase.

Inhibitory mechanism of chrysin and diosmetin to α-glucosidase: insights from kinetics, multispectroscopy and molecular docking investigations

Inhibition of α-glucosidase activity is a promising method to prevent postprandial hyperglycemia. The inhibitory effect and interaction of chrysin and diosmetin on α-glucosidase were studied in this study. The results of inhibition kinetics showed that chrysin and diosmetin reversibly inhibited α-glucosidase activity with IC50 value of 26.445 ± 1.406 μmol L-1 and 18.380 ± 1.264 μmol L-1, respectively. Further research revealed that chrysin exhibited a mixed-type inhibitory pattern against α-glucosidase, while diosmetin was noncompetitive inhibitory with Ki value of (2.6 ± 0.04) ×10-4 mol L-1. Fluorescence spectroscopy showed that both chrysin and diosmetin could quench the intrinsic fluorescence of α-glucosidase, the maximum emission wavelength of tyrosine (Tyr) and tryptophan (Trp) were not moved by chrysin, but red shifted by diosmetin. UV-Vis, fourier transform infrared spectroscopy (FT-IR) and circular dichroism (CD) measurements showed that the secondary structure and microenvironment of α-glucosidase were changed by chrysin and diosmetin. Further analysis of molecular docking showed that chrysin and diosmetin could bind with α-glucosidase and might cause the decrease of α-glucosidase activity. The results of molecular dynamics (MD) simulation showed that the stability of chrysin (or diosmetin)-α-glucosidase complex system was changed during binding process. In conclusion, chrysin and diosmetin are good α-glucosidase inhibitors.Communicated by Ramaswamy H. Sarma.

Inhibition of α-glucosidase activity by curcumin loaded on ZnO@rGO nanocarrier for potential treatment of diabetes mellitus

Curcumin (Cur) is an acidic polyphenol with some effects on α-glucosidase (α-Glu), but Cur has disadvantages such as being a weak target, lacking passing the blood-brain barrier and having low bioavailability. To enhance the curative effect of Cur, the hybrid composed of ZnO nanoparticles decorated on rGO was used to load Cur (ZnO@rGO-Cur). The use of the multispectral method and enzyme inhibition kinetics analysis certify the inhibitory effect and interaction mechanism of ZnO@rGO-Cur with α-Glu. The static quenching of α-Glu with both Cur and ZnO@rGO-Cur is primarily driven by hydrogen bond and van der Waals interactions. The conformation-changing ability by binding to the neighbouring phenolic hydroxyl group of Cur increased their ability to alter the secondary structure of α-Glu, resulting in the inhibition of enzyme activity. The inhibition constant (Ki, Cur  > Kis,ZnO@rGO-Cur ) showed that the inhibition effect of ZnO@rGO-Cur on α-Glu was larger than that of Cur. The CCK-8 experiments proved that ZnO@rGO nanocomposites have good biocompatibility. These results suggest that the therapeutic potential of ZnO@rGO-Cur composite is an emerging nanocarrier platform for drug delivery systems for the potential treatment of diabetes mellitus.

Chemical profile of phenolic extracts from rapeseed meal and inhibitory effects on α-glucosidase: UPLC-MS/MS analysis, multispectral approaches, molecular simulation and ADMET analysis

Rapeseed meal (RSM) is the by-product of rapeseed processing that enriches phenolic compounds. However, the comprehensive characterization of its phenolic substances in terms of composition and potential activities remains incomplete, leading to limited utilization in the food industry. In this study, the phenolic profile from RSM (referred to as RMP) was identified, and their inhibitory effects on α-glucosidase were investigated. UPLC-MS/MS analysis showed that a total of 466 phenolic compounds were detected in RMP. The primary components were sinapic acid (SA), caffeic acid (CA), salicylic acid (SAA), and astragalin (AS). Multispectral approaches demonstrated significant inhibitory capacity of RMP against α-glucosidase with a half inhibition value (IC50) of 0.32 mg/mL, with a stronger inhibition compared to CA/SAA/AS (IC50: 4.0, 5.9, and 0.9 mg/mL) in addition to the previously reported SA, suggesting a synergistic effect. Both RMP and CA/SAA/AS altered the secondary structure of α-glucosidase to quench its intrinsic fluorescence. Molecular simulation results revealed that hydrogen bonds and van der Waals forces primarily contributed to the interaction between CA/SAA/AS and α-glucosidase, as well as verified the stability of the binding process over the entire simulation duration. The ADMET analysis showed that CYP2D6 was not inhibited by CA/SAA/AS, which had no AMES toxicity, hepatotoxicity, and skin sensitization. This finding suggests the potential of RMP against α-glucosidase for the treatment of diabetes.

Antihyperglycemic effects of Lysiphyllum strychnifolium leaf extract in vitro and in vivo

CONTEXT

Lysiphyllum strychnifolium (Craib) A. Schmitz (LS) (Fabaceae) has traditionally been used to treat diabetes mellitus.

OBJECTIVE

This study demonstrates the antidiabetic and antioxidant effects of aqueous extract of LS leaves in vivo and in vitro.

MATERIALS AND METHODS

The effects of aqueous LS leaf extract on glucose uptake, sodium-dependent glucose cotransporter 1 (SGLT1) and glucose transporter 2 (GLUT2) mRNA expression in Caco-2 cells, α-glucosidase, and lipid peroxidation were evaluated in vitro. The antidiabetic effects were evaluated using an oral glucose tolerance test (OGTT) and a 28-day consecutive administration to streptozotocin (STZ)-nicotinamide (NA)-induced type 2 diabetic mice.

RESULTS

The extract significantly inhibited glucose uptake (IC₅₀: 236.2 ± 36.05 µg/mL) and downregulated SGLT1 and GLUT2 mRNA expression by approximately 90% in Caco-2 cells. Furthermore, it non-competitively inhibited α-glucosidase in a concentration-dependent manner with the IC₅₀ and K_i of 6.52 ± 0.42 and 1.32 µg/mL, respectively. The extract at 1000 mg/kg significantly reduced fasting blood glucose levels in both the OGTT and 28-day consecutive administration models as compared with untreated STZ-NA-induced diabetic mice (p < 0.05). Significant improvements of serum insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and GLUT4 levels were observed. Furthermore, the extract markedly decreased oxidative stress markers by 37-53% reduction of superoxide dismutase 1 (SOD1) in muscle and malondialdehyde (MDA) in muscle and pancreas, which correlated with the reduction of MDA production in vitro (IC₅₀: 24.80 ± 7.24 µg/mL).

CONCLUSION

The LS extract has potent antihyperglycemic activity to be used as alternative medicine to treat diabetes mellitus.

Insight into the Inhibitory Mechanisms of Hesperidin on α-Glucosidase through Kinetics, Fluorescence Quenching, and Molecular Docking Studies

The α-glucosidase inhibitor is of interest to researchers due to its association with type-II diabetes treatment by suppressing postprandial hyperglycemia. Hesperidin is a major flavonoid in orange fruit with diverse biological properties. This paper evaluates the effects of hesperidin on α-glucosidase through inhibitory kinetics, fluorescence quenching, and molecular docking methods for the first time. The inhibition kinetic analysis shows that hesperidin reversibly inhibited the α-glucosidase activity with an IC50 value of 18.52 μM and the inhibition was performed in an uncompetitive type. The fluorescence quenching studies indicate that the intrinsic fluorescence of α-glucosidase was quenched via a static quenching process and only one binding site was present between the hesperidin and α-glucosidase. The interaction between them was spontaneous and mainly driven by hydrogen bonds, as well as hydrophobic forces. Furthermore, the molecular docking results suggest that hesperidin might bond to the entrance or outlet part of the active site of α-glucosidase through a network of five hydrogen bonds formed between hesperidin and the four amino acid residues (Trp709, Arg422, Asn424, and Arg467) of α-glucosidase and the hydrophobic effects. These results provide new insight into the inhibitory mechanisms of hesperidin on α-glucosidase, supporting the potential application of a hesperidin-rich orange product as a hypoglycemic functional food.

A novel electrochemical sensor based on gold nanobipyramids and poly-L-cysteine for the sensitive determination of trilobatin

Trilobatin is a flavonoid that has wide application prospects due to its various pharmacological effects, such as anti-inflammation and anti-oxidation. In this work, a novel electrochemical sensor based on gold nanobipyramids (AuNBs) and L-cysteine (L-cys) was constructed for the sensitive and selective determination of trilobatin. The AuNBs, which were prepared by a seed-mediated growth method, had large specific surface areas and excellent electrical conductivity. A layer of L-cys film, which provided more active sites through the amino and hydroxyl groups, was modified on the surface of the AuNBs by electropolymerization. Significantly, the Au-S bond between the L-cys film and AuNBs could improve the stability of the sensor and it exhibited satisfactory electrocatalytic oxidation activity for trilobatin. Under optimized conditions, the sensor based on poly-L-cys/AuNBs/GCE was used to determine trilobatin by differential pulse voltammetry (DPV). Two wide linear ranges between the current peak and the concentration of trilobatin were obtained in the range from 5 to 100 μM and 100 to 1000 μM, and the low detection limit (LOD) was up to 2.55 μM (S/N = 3). The sensor demonstrated desirable reproducibility, stability, and selectivity and was applied to detect real trilobatin samples extracted from Lithocarpus polystachyus Rehd.'s leaves, showing recoveries of 98.36%-104.96%, with satisfactory results.

Studies on the inhibition of α-glucosidase by biflavonoids and their interaction mechanisms

Biflavonoids are a kind of polyphenol compounds with numerous biological functions. However, the potential inhibitory activities of biflavonoids on α-glucosidase are yet unknown. Here, the inhibitory effects of two biflavonoids (amentoflavone and hinokiflavone) on α-glucosidase and their interaction mechanisms were explored using multispectral approaches and molecular docking. The results showed that the inhibitory activities of biflavonoids were much better compared with monoflavonoid (apigenin) and acarbose, and the order of inhibition ability was hinokiflavone > amentoflavone > apigenin > acarbose. These flavonoids were noncompetitive inhibitors of α-glucosidase and showed synergistic inhibition effects with acarbose. Additionally, they could statically quench the intrinsic fluorescence of α-glucosidase, and form the non-covalent complexes with enzyme primarily through hydrogen bonds and van der Waals forces. The binding of flavonoids changed the conformational structure of α-glucosidase, therefore impairing the enzyme activity. The findings suggested that biflavonoids could be considered as potential hypoglycemic functional foods in diabetes therapy.

Pectolinarigenin shows lipid-lowering effects by inhibiting fatty acid biosynthesis in vitro and in vivo

Pectolinarigenin is the main flavonoid compound and presents in Linaria vulgaris and Cirsium chanroenicum. In this study, RNA sequencing (RNA-seq) was applied to dissect the effect of pectolinarigenin on the transcriptome changes in the high lipid Huh-7 cells induced by oleic acid. RNA-seq results revealed that 15 pathways enriched by downregulated genes are associated with cell metabolism including cholesterol metabolism, glycerophospholipid metabolism, steroid biosynthesis, steroid hormone biosynthesis, fatty acid biosynthesis, etc. Moreover, 13 key genes related to lipid metabolism were selected. Among them, PPARG coactivator 1 beta (PPARGC1B) and carnitine palmitoyltransferase 1A (CPT1A) were found to be upregulated, solute carrier family 27 member 1(SLC27A1), acetyl-CoA carboxylase alpha (ACACA), fatty-acid synthase (FASN), 3-Hydroxy-3-Methylglutaryl-CoA Reductase (HMGCR), etc. were found to be downregulated. Glycolysis/gluconeogenesis, steroid hormone biosynthesis, and fatty acid biosynthesis were all significantly downregulated, according to gene set variation analysis and gene set enrichment analysis. Besides, protein levels of FASN, ACACA, and SLC27A1 were all decreased, whereas PPARγ and CPT1A were increased. Docking models showed that PPARγ may be a target for pectolinarigenin. Furthermore, pectolinarigenin reduced serum TG and hepatic TG, and improved insulin sensitivity in vivo. Our findings suggest that pectolinarigenin may target PPARγ and prevent fatty acid biosynthesis.

Application of Molecular Simulation Methods in Food Science: Status and Prospects

Molecular simulation methods, such as molecular docking, molecular dynamic (MD) simulation, and quantum chemical (QC) calculation, have become popular as characterization and/or virtual screening tools because they can visually display interaction details that in vitro experiments can not capture and quickly screen bioactive compounds from large databases with millions of molecules. Currently, interdisciplinary research has expanded molecular simulation technology from computer aided drug design (CADD) to food science. More food scientists are supporting their hypotheses/results with this technology. To understand better the use of molecular simulation methods, it is necessary to systematically summarize the latest applications and usage trends of molecular simulation methods in the research field of food science. However, this type of review article is rare. To bridge this gap, we have comprehensively summarized the principle, combination usage, and application of molecular simulation methods in food science. We also analyzed the limitations and future trends and offered valuable strategies with the latest technologies to help food scientists use molecular simulation methods.

Effects of 6-Shogaol on Glucose Uptake and Intestinal Barrier Integrity in Caco-2 Cells

As the main bioactive component in dried ginger, 6-shogaol has potential hypoglycemic activity, but its mechanism is still unclear. The process of carbohydrate digestion and glucose absorption is closely related to the enzymatic activity of epithelial brush cells, expression of glucose transporters, and permeability of intestinal epithelial cells. Therefore, this study explored the hypoglycemic mechanism of 6-shogaol from the perspective of glucose uptake, absorption transport, and protection of intestinal barrier function. Based on molecular docking, the binding energy of 6-shogaol and α-glucosidase is -6.24 kcal/mol, showing a high binding affinity. Moreover, a-glucosidase enzymatic activity was reduced (-78.96%) when the 6-shogaol concentration was 500 µg/mL. After 6-shogaol intervention, the glucose uptake was reduced; the relative expression of glucose transporters GLUT2 and SGLT1 were down regulated; and tight junction proteins ZO-1, Occludin and Claudin were up regulated in differentiated Caco-2 cells. This study confirmed that 6-shogaol effectively inhibits the activity of α-glucosidase and has beneficial effects on glucose uptake, protection of intestinal barrier function, and promotion of intestinal material absorption.

Optimization of Extraction Process of Polysaccharides MAP-2 from Opuntia Milpa Alta by Response Surface Methodology and Evaluation of Its Potential as α-Glucosidase Inhibitor

The α-glucosidase inhibitors play an important role in blood glucose control in patients with type 2 diabetes. At present, the development of new α-glucosidase inhibitors is an urgent clinical need. Our previous studies have found that the polysaccharide MAP-2 in the cactus Opuntia Milpa Alta has significantly better activity than acarbose (one of the most widely used first-line α-glucosidase inhibitors in clinical practice), but its optimal extraction process parameters and inhibition kinetic characteristics are not clear, and whether it has the potential to become a new α-glucosidase inhibitors is also unclear. In this study, based on previous research, we used the combination of single factor experiments and the response surface method (RSM) to identify the optimal extraction conditions for MAP-2 as follows: solid-liquid ratio 1:4, extraction temperature 90 °C, extraction time 1 h. Under these conditions, the extraction yield of MAP-2 was 3.47 ± 0.062%. When the concentration of MAP-2 was 16 mg/mL, the inhibition rate of α-glucosidase was 91.13 ± 0.62%. In addition, the results of inhibition kinetics showed that the inhibition rate of MAP-2 on α-glucosidase was the highest at pH 7.4 for 30 min, and showed a good dose-effect relationship, which was a reversible competitive inhibition. Meanwhile, we also compared the activities of MAP-2 and acarbose on the side effects of acarbose related enzymes. Compared with acarbose, MAP-2 not only had a better activation effect on lactase, but also inhibited the activity of hyaluronidase, and the activation and inhibition rate were positively correlated with the concentration. However, under the same conditions, the effect of acarbose on hyaluronidase was opposite to that of MAP-2. At low concentration, acarbose had a certain activation effect on lactase, but gradually attained an inhibitory effect with the increase in concentration. In contrast, MAP-2 not only activates lactase activity, improves diarrhea, abdominal distension, and abdominal pain, but also inhibits hyaluronidase activity, to solve the side effects of allergic reactions, suggesting that MAP-2 has the potential to become a novel and effective inhibitor of α-glucosidase with fewer side effects.

GWAS provides new insights into the genetic mechanisms of phytochemicals production and red skin colour in apple

Understanding the genetic architecture of apple phytochemicals, and their interplay with conventional selection traits, is critical for the development of new apple cultivars with enhanced health benefits. Apple accessions (n = 344) used for this genome-wide association study (GWAS) represented the wide diversity of metabolic profiles in the domesticated and wild Malus genepools. Fruit samples were phenotyped for 34 metabolites, including a stable vitamin C glycoside "ascorbic acid 2-β-glucoside" (AA-2βG), and the accessions were genotyped using the Apple 20 K SNP Array. Several fruit quality traits, including red skin over-colour (OCOL), were also assessed. Wild Malus accessions showed at least 2-fold higher average content of several metabolites (e.g. ascorbic acid, chlorogenic acid, phloridzin, and trilobatin) than Malus domestica accessions. Several new genomic regions and potential candidate genes underpinning the genetic diversity of apple phytochemicals were identified. The percentage of phenotypic variance explained by the best SNP ranged between 3% and 21% for the different metabolites. Novel association signals for OCOL in the syntenic regions on chromosomes 13 and 16 suggested that whole genome duplication has played a role in the evolution of apple red skin colour. Genetic correlations between phytochemicals and sensory traits were moderate. This study will assist in the selection of Malus accessions with specific phytochemical profiles to establish innovative genomics-based breeding strategies for the development of apple cultivars with enhanced nutritional value.

Effects of natural dihydrochalcones in sweet tea (Lithocarpus polystachyus) on diabetes: a systematical review and meta-analysis of animal studies

Sweet tea (Lithocarpus polystachyus Rehd.), a natural functional food highly rich in dihydrochalcones including trilobatin, phlorizin and phloretin, is reported to possess numerous biological activities especially for treating diabetes. Here, the aim of this systematical review and meta-analysis is to assess the effect of dihydrochalcones in sweet tea (DST) on diabetes and summarize their possible mechanisms. We searched in eight databases including Embase, PubMed, Cochrane, Web of Science, WanFang database, VIP database, China National Knowledge Infrastructure and China Biology Medicine from Jan 2000 to Nov 2021 and ultimately included 21 animal studies in this review. A total of 10 outcome measurements including blood lipid indexes, blood glucose, insulin resistance indicators and oxidative stress biomarkers were extracted for meta-analysis using RevMan 5.4 software. DST significantly decreased the levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), blood glucose (BG), homeostasis model assessment of insulin resistance (HOMA-IR) and malondialdehyde (MDA), and increased high-density lipoprotein cholesterol (HDL-c), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in diabetic animal models. In summary, DST could treat diabetes by regulation of blood glucose/lipid metabolism, oxidative/carbonyl stress, inflammatory response etc.

Regulation of β-Disaccharide Accumulation by β-Glucosidase Inhibitors to Enhance Cellulase Production in Trichoderma reesei

Trichoderma reesei is a high-yield producer of cellulase for applications in lignocellulosic biomass conversion, but its cellulase production requires induction. A mixture of glucose and β-disaccharide has been demonstrated to achieve high-level cellulase production. However, as inducers, β-disaccharides are prone to be hydrolyzed by β-glucosidase (BGL) during fermentation, therefore β-disaccharides need to be supplemented through feeding to overcome this problem. Here, miglitol, an α-glucosidase inhibitor, was investigated as a BGL inhibitor, and exhibited an IC50 value of 2.93 μg/mL. The cellulase titer was more than two-fold when miglitol was added to the fermentation medium of T. reesei. This method was similar to the prokaryotic expression system using unmetabolized isopropyl-β-D-thiogalactopyranoside (IPTG) as the inducer instead of lactose to continuously induce gene expression. However, cellulase activity was not enhanced with BGL inhibition when lactose or cellulose was used as an inducer, which demonstrated that the transglycosidase activity of BGL is important for the inducible activity of lactose and cellulose. This novel method demonstrates potential in stimulating cellulase production and provides a promising system for T. reesei protein expression.