Activated effect of lignin on α-amylase

Emerging trends in cellulose and lignin-based nanomaterials for water treatment

Several industrial and agricultural practices contribute significantly to water contamination. These activities release several amount of pollutants, including pesticides, heavy metals, and organic compounds, into water sources, posing health risks and causing environmental damage. Industries such as mining, textiles, and pharmaceuticals discharge harmful toxins, further polluting water. Processes like ball-milling, adsorption, filtration, and flocculation are commonly used for wastewater treatment. Recent advancements have focused on the study of green nanomaterials (NMs), particularly cellulose-based and lignin-based NMs, due to their various properties, biodegradability, and low toxicity. This review covers the fabrication methods, modification techniques, and applications of cellulose-based and lignin-based NMs, such as cellulose nanofibers, nanocrystals, lignin-based aerogels, and hydrogels for wastewater treatment. The unique properties of lignin and cellulose, including their high surface area, functionalization, and biocompatibility, make them suitable for water purification. The paper also discusses a SWOT analysis, which will be useful for future researchers, highlighting both opportunities and challenges in this area. This paper aims to provide valuable insights into ongoing research and development in cellulose and lignin-based nanomaterials for next-generation water treatment solutions.

Inhibition of pancreatic lipase and cholesterol by hawthorn extract: A study of binding mechanisms and inhibitor screening

Inhibiting the activity of pancreatic lipase and reducing intestinal cholesterol absorption are potential strategies to combat obesity. This study investigated the mechanisms by which hawthorn (Crataegus pinnatifida) extract affects pancreatic lipase (PL) and disrupts cholesterol micelle formation. Enriched with bioactive compounds, hawthorn extract (HE) inhibited PL activity through reversible mixed inhibition, with a half-maximal inhibitory concentration (IC50) of 2.92 mg/mL. Infrared spectroscopy, circular dichroism and fluorescence quenching experiments demonstrated that HE binding to PL induces conformational changes in both tertiary and secondary structures. This interaction facilitated the transformation of β-turns to random coils and quenched the fluorescence of the protein through a static quenching mechanism. HPLC, immobilized enzymes and molecular docking studies collectively revealed that rutin, chlorogenic acid, and isoquercitrin in HE exhibited strong binding affinity with PL, serving as key components in inhibiting PL activity. Furthermore, HE increased the particle size of cholesterol micelles while decreasing their solubility, which makes it more difficult for lipases to function in the intestine. Overall, our study suggests that HE may serve as an effective pancreatic lipase inhibitor, presenting potential applications in the development of functional foods for obesity reduction and lipid-lowering.

Activated effect of chondroitin sulfate on α-glucosidase: An in vitro and in silico approach

Chondroitin sulfate (CS), a glycosaminoglycan (GAG), plays a pivotal role in various physiological functions and is extensively utilized in medical and clinical applications. This study aimed to explore the enhancing effects and underlying mechanisms of three commonly encountered sulfated glycosaminoglycans CS-A, CS-C and CS-D on α-glucosidase activity. In vitro enzyme kinetic studies demonstrated that all three types of CS promoted α-glucosidase activity, with CS-D exhibiting the most pronounced effect, reaching 124.7 %. Fluorescence and circular dichroism (CD) spectroscopy, along with molecular docking experiments, revealed that CSs spontaneously interacted with the enzyme's active site, forming hydrogen bonds with Arg600 and His674. Additionally, hydrophobic interactions with Trp376 and Trp481 further strengthened these hydrogen bonds. These interactions increased the flexibility of the α-glucosidase polypeptide backbone, leading to greater solvent exposure of Trp residues and alterations in the enzyme's secondary structure composition. Furthermore, trajectory analysis from kinetic simulations indicated that activation of the α-glucosidase active site induced an inward folding and contraction of the region, thereby enlarging the internal cavity and enhancing its hydrophobic nature. This structural reconfiguration not only provided additional space for substrate hydrolysis but also minimized interference from water molecules, collectively contributing to an overall enhancement of α-glucosidase hydrolytic activity. In conclusion, this study identifies CS as an α-glucosidase activator and elucidates its interaction mechanisms through both in vitro and in silico approaches, highlighting its potential applications in the food industry.

The enhancement mechanisms of chondroitin sulfate on α-amylase activity: Exploring the interaction using in vitro and in silico studies

Glycosaminoglycans (GAG) are bioactive polysaccharide rich in -SO3- and -COO- groups, also known as acidic mucopolysaccharides. In this study, the feasibility of three structurally distinct forms of chondroitin sulfate (CS-A, CS-C, and CS-D) from the GAG family was explored as a potential strategy to enhance industrial α-amylase activity. All three CSs were found to increase α-amylase activity to varying degrees, with CS-D showing the most significant increase, exceeding 78 %. Furthermore, fluorescence quenching experiments indicated that the interaction between CS and α-amylase is primarily driven by hydrophobic interactions. In silico, molecular docking revealed that the sulfate groups of all three CSs form hydrogen bonds with α-amylase, with CS-D exhibiting the lowest binding energy due to its two sulfate groups. Kinetic simulations further suggested that binding to CS increases the flexibility of key active site residues (Asp197, Glu233, and Asp300), modifies the secondary structure, and enlarges the substrate-binding pocket, thereby promoting α-amylase's hydrolytic activity. Thus, this work revealed CS as an α-amylase activator and further elucidated its interaction mechanism using in vitro and in silico studies, which may be beneficial to apply CS in pharmaceutical or food industry.

The enhancement mechanisms of mucin and lactoferrin on α-amylase activity in saliva: Exploring the interactions using QCM-D and molecular docking

α-Amylase activity differs between individuals and is influenced by dietary behavior and salivary constituents, but limited information is available on the relationship between α-amylase activity and saliva components. This study investigated the impact of salivary proteins on α-amylase activity, their various correlations, the effect of mucin (MUC5B and MUC7) and lactoferrin on the enzymatic kinetics of α-amylase, and the mechanisms of these interactions using the quartz crystal microbalance with dissipation (QCM-D) technique and molecular docking. The results showed that α-amylase activity was significantly correlated with the concentrations of MUC5B (R2 = 0.42, p < 0.05), MUC7 (R2 = 0.35, p < 0.05), and lactoferrin (R2 = 0.35, p < 0.05). An in vitro study demonstrated that α-amylase activity could be significantly increased by mucins and lactoferrin by decreasing the Michaelis constant (Km) of α-amylase. Moreover, the results from the QCM-D and molecule docking suggested that mucin and lactoferrin could interact with α-amylase to form stable α-amylase-mucin and α-amylase-lactoferrin complexes through hydrophobic interactions, electrostatic interactions, Van der Waals forces, and hydrogen bonds. In conclusion, these findings indicated that the salivary α-amylase activity depended not only on the α-amylase content, but also could be enhanced by the interactions of mucin/lactoferrin with α-amylase.

Identification of the effective α-amylase inhibitors from Dalbergia odorifera: Virtual screening, spectroscopy, molecular docking, and molecular dynamic simulation

Inhibiting the activity of α-amylase has been considered as one efficient way to prevent and treat type 2 diabetes recently. Dalbergia odorifera, a kind of Leguminosae plant, has a positive therapeutic effect on type 2 diabetes, possibly contributing by some constituents that can inhibit the activity of α-amylase. In this study, we found that eriodictyol was one potential constituent through virtual screening. The interaction mode between eriodictyol and α-amylase was elucidated by molecular docking, multi-spectroscopic analysis, and molecular dynamic simulation. The results revealed that eriodictyol quenched the intrinsic fluorescence of α-amylase, and the quenching mode was static quenching. Eriodictyol could spontaneously interact with α-amylase, mostly stabilized and influenced by the hydrophobic interaction, while the binding sites (n) was 1.13 ± 0.07 and binding constant (K_b) was (1.43 ± 0.14) × 10⁵ at 310 K, respectively. In addition, FT-IR and CD had been applied to identify that eriodictyol can trigger the conformational change of α-amylase. Taken together, the results provided some experimental data for developing new α-amylase inhibitors from Dalbergia odorifera, which may further prevent and treat diabetes and diabetes complications.

Exploring in vitro effect of silver nanoparticles and Holothuria parva extracts on kinetic and stability of α- amylase

Diabetes is a chronic metabolic disorder characterized by elevated blood glucose levels. Major limitations of synthetic drugs, including high cost, efficacy, and adverse side effects, have prompted researchers to seek more effective and low-cost alternative therapies with fewer adverse effects. Marine life forms are considered the most important sources of biologically active natural products due to their secondary metabolites. In this research, sea cucumber Holothuria parva was collected from coastal areas of Bandar Lengeh, Hormozgan, Iran, and was then subjected to extraction. The results showed that compounds extracted from Holothuria parva had a stimulatory effect on enzyme activity, and in the presence of these compounds, the V_max value of the enzyme was increased about two times, while the K_m value was reduced. The phosphate buffer form of extracts had the greatest impact on enzyme activity. Upon an increase in the concentration of silver nanoparticles (AgNPs), the α-amylase activity was inhibited in parallel. Silver nanoparticles exhibited the highest enzyme inhibition with an IC₅₀ of 0.86 mg/mL. Silver nanoparticles showed anti-α-amylase activity and had the ability to decrease intestinal glucose uptake in diabetic individuals when prescribed as a novel supplementary medicine. This article is protected by copyright. All rights reserved.

Lignin Synthesis, Affected by Sucrose in Lotus (Nelumbo nucifera) Seedlings, Was Involved in Regulation of Root Formation in the Arabidopsis thanliana

Adventitious roots (ARs) have an unmatched status in plant growth and metabolism due to the degeneration of primary roots in lotuses. In the present study, we sought to assess the effect of sucrose on ARs formation and observed that lignin synthesis was involved in ARs development. We found that the lignification degree of the ARs primordium was weaker in plants treated with 20 g/L sucrose than in 50 g/L sucrose treatment and control plants. The contents of lignin were lower in plants treated with 20 g/L sucrose and higher in plants treated with 50 g/L sucrose. The precursors of monomer lignin, including p-coumaric acid, caffeate, sinapinal aldehyde, and ferulic acid, were lower in the GL50 library than in the GL20 library. Further analysis revealed that the gene expression of these four metabolites had no novel difference in the GL50/GL20 libraries. However, a laccase17 gene (NnLAC17), involved in polymer lignin synthesis, had a higher expression in the GL50 library than in the GL20 library. Therefore, NnLAC17 was cloned and the overexpression of NnLAC17 was found to directly result in a decrease in the root number in transgenic Arabidopsis plants. These findings suggest that lignin synthesis is probably involved in ARs formation in lotus seedlings.

The mechanism of delaying starch digestion by luteolin

In this study, the mechanisms of the delay of starch digestion by luteolin were revealed by studying the luteolin-PPA (porcine pancreatic α-amylase) interaction and luteolin-starch interaction. The luteolin-PPA interaction was investigated by inhibitory kinetics analysis, fluorescence quenching, circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy and molecular docking. The results of the inhibitory kinetics revealed that luteolin was a mixed-type inhibitor of PPA and that the inhibitory action was reversible. Fluorescence spectroscopy (including fluorescence quenching and thermodynamics) and molecular docking analyses indicated that hydrogen bonds and hydrophobic forces were the main forces between PPA and luteolin. CD and FT-IR spectroscopy analyses showed that the interaction between luteolin and PPA changed the secondary structure of PPA and induced a decline in its activity. In addition, the luteolin-starch interaction was also studied using UV-visible absorption and X-ray diffraction analyses. These indicated that luteolin could bind with PPA, and that hydrogen bonds and van der Waals forces may be present. Overall, luteolin delayed starch digestion not only by binding with PPA but also by binding with starch. Thus, luteolin has the potential to prevent and control diabetes by being added into starch-based food to delay starch digestion.

Effect of quercetin on the in vitro Tartary buckwheat starch digestibility

Tartary buckwheat is one of the few pseudocereals with abundant flavonoids and starch. However, there are different views on the digestibility of Tartary buckwheat starch (TBS) because of its particle size and structure. In this study, fluorescence spectrum methods and enzymatic kinetics were used to investigate the interaction between TBS /two glycosidase (α-amylase and α-glucosidase) and quercetin to explore its digestive properties and provide a perspective regarding the application of TBS in functional starch products. The results showed that the interaction between TBS and quercetin was probably weak hydrophobic force and hydrogen bonding. The inhibitory effect of quercetin on α-amylase was better than that on α-glucosidase. The half inhibitory concentrations (IC₅₀) of quercetin to α-amylase and α- glucosidase was (270 ± 3.31) and (544 ± 9.01) μg/mL, respectively. The intrinsic fluorescence of two enzymes was statically quenched by forming a complex with quercetin. Quercetin also increased the microenvironment hydrophilicity of tryptophan residues in glycosidase. In vitro digestion experiment demonstrated that quercetin and TBS co-gelatinized together was more effective to inhibit TBS hydrolysis than quercetin itself alone. In the first-order kinetic and LOS model, quercetin-starch gel structure and quercetin inhibitory activity against enzymes had synergistic effects of the TBS digestion.

Inhibitory effect of lignin from Canna edulis Ker residues on trypsin: kinetics and molecular docking studies

BACKGROUND

Lignin extracted from Canna edulis Ker residues shows a strong inhibitory effect on α-glucosidase and a promoting effect on α-amylase. Protease activity inhibition may play a key role in disease processes, such as metastasis, tumor invasion and bacterial colonization. Hence, in the present study, the inhibitory mechanism of lignin on trypsin was examined, including the interaction type, thermodynamic parameters, structure, reaction site and molecular docking.

RESULTS

The isolated lignin presented an inhibitory effect on trypsin activity with an IC₅₀ value of 1.35 μmol L^-1 . This inhibition was a mixed linear type with a constant K_i of 3.92 μmol L^-1 . The lignin could bind with the key amino acid residue Ser195 on the active site of the trypsin molecule to inhibit its activity, and the phenolic hydroxyl group and -OH on the β-O-4 structure of the lignin molecule were the major groups bound with trypsin.

CONCLUSION

These results illustrate the inhibitory effects of Canna edulis residue lignin on protease, which helps with respect to understanding the possible application of lignin in the food industry in functional foods. © 2020 Society of Chemical Industry.

Thermally processed lignin reduces the apparent hydrolysis rate of pancreatic α-amylase in starchy foods

Lignin, despite being the second most abundant constituent of plant cell walls, is thought to be chemically inert during gastrointestinal digestion and therefore attracts little attention for its role in the human diet. This study explores the heat modifications of lignin to derive species capable of slowing starch digestion in vitro. We applied various advanced biochemical (e.g. enzymic digestion, solubility) and physio-chemical (e.g. scanning electron microscopy, Fourier-Transform-Infrared Spectroscopy, ¹³C-NMR) analyses to characterize the structure-function of lignin induced by heat treatment. It was found that lignin thermally processed above 300 °C reduced the apparent hydrolysis rate of pancreatic α-amylase, which is ascribed mainly to the insoluble lignin with a modified particle surface morphology. Further kinetic experiments showed that lignin species derived by thermal processing slowed in vitro digestion rates of potato starch and pasta. These findings highlight the potential for utilizing thermally processed lignin in slowing digestion of starchy foods.

Analysis of kinetic parameters and mechanisms of nanocrystalline cellulose inhibition of α-amylase and α-glucosidase in simulated digestion of starch

This study evaluated the in vitro inhibitory influence of particle size of nanocrystalline cellulose (NCC) fractions against α-amylase and α-glucosidase using cooked potato starch-protein food model system. The kinetics of the resulting inhibitions in the presence of NCC of the two tested enzymes were examined and characterised. Both the size and dose of NCC significantly (p < 0.05) inhibited α-amylase and α-glucosidase by modulating the rate of hydrolysis of starch in the food model system lower than that of the control (no added fibre). At equal concentrations of each NCC fraction, the smallest particle size (≤125 nm) exhibited the highest potency as an inhibitor (median inhibitory concentration (IC₅₀) = 2.98 mg mL^-1 and 4.57 mg mL^-1 for α-amylase and α-glucosidase, respectively). Increasing concentrations of each NCC fraction caused an apparent significant decrease in V_max values (p < 0.05) with insignificant change in the K_m values for both the tested enzymes. Furthermore, binding assays demonstrated that NCC particles may bind to the two tested enzymes in a non-specific manner. Analysis of the kinetics of the enzymes suggested that the mechanism of inhibition showed that the two tested enzymes mainly exhibited non-competitive mode of inhibition. The observed inhibition of the two tested enzymes suggests that reducing the cellulose size ≤125 nm may enhance its inhibition potency and potentially attenuate starch hydrolysis when added to diet.

Inhibition of glycosidase by ursolic acid: in vitro, in vivo and in silico study

BACKGROUND

Controlling the blood glucose level is an effective method to reduce type 2 diabetes and prevent diabetes-related complications. Ursolic acid is a plant extract that can reduce postprandial hyperglycemia effectively. This study aimed to explore the inhibitory effect and interaction mechanism of ursolic acid against α-amylase and α-glucosidase.

RESULTS

In this study, the effect of ursolic acid on glycosidase was studied in vitro, in vivo, and in silico. The half-maximal inhibitory concentration (IC50 ) of ursolic acid on α-amylase and α-glucosidase was 0.482 ± 0.12 mg mL-1 and 0.213 ± 0.042 mg mL-1 , respectively. The results of enzymatic kinetics showed that ursolic acid inhibited α-amylase and α-glucosidase activity in a non-competitive manner. The fluorescence spectrum showed that the combination of ursolic acid and glycosidase caused the intrinsic fluorescence quenching of glycosidase. The observation of starch granules revealed that the activity of α-amylase was inhibited and the hydrolysis of starch granules was prevented in the presence of ursolic acid. Molecular docking results showed that ursolic acid bound to the inactive site of α-amylase and α-glucosidase through the formation of ursolic acid-glucosidase complex. Ursolic acid interacted with α-amylase and α-glucosidase mainly through hydrogen bonding. The postprandial hypoglycemic effect of ursolic acid in C57BL/6J mice showed that the high concentration of ursolic acid could quickly reduce postprandial blood glucose level.

CONCLUSION

Ursolic acid can be considered as a natural ingredient in functional foods to control postprandial blood glucose levels and prevent diabetes by delaying the digestion of starch in foods. © 2019 Society of Chemical Industry.

Lignin - An underutilized, renewable and valuable material for food industry

Lignin is the second most abundant biorenewable polymers only next to cellulose and is ubiquitous in various plant foods. In food industry, lignin often presented as a major component of by-products from plant foods. In the last decade, the food and nutritional interests of lignin attracted more and more attentions and great progresses have been accomplished. In the present review, the structure, physicochemical properties, dietary occurrence and preparation methods of lignin from food resources were summarized. Then, the versatile activities of food lignin were introduced under the subtitles of antioxidant, antimicrobial, antiviral, antidiabetic and other activities. Finally, the potential applications of food lignin were proposed as a food bioactive ingredient, an improver of food package films and a novel material in fabricating drug delivery vehicles and contaminant passivators. Hopefully, this review could bring new insights in exploiting lignin from nutrition- and food-directed views.

Inhibition of α-amylase by flavonoids: Structure activity relationship (SAR)

Flavonoids are recognized to regulate animals' food digestion processes trough interaction with digestive enzymes. The binding capacity of hesperetin (HES), luteolin (LUT), quercetin (QUE), catechin (CAT) and rutin (RUT) with pancreatic α-amylase were evaluated, using UV-Vis spectroscopy, fluorescence and molecular docking. Using p-nitrophenyl-α-d-maltopentoside (pNPG5) as substrate analog, LUT showed the best inhibitory capacity, even better than that of the positive control, acarbose (ACA). A mixed-type inhibition was observed for HES, LUT and QUE, a competitive-type for ACA, while no inhibition was observed with CAT and RUT. In agreement with kinetic results, α-amylase presented a higher affinity for LUT, when analyzed by fluorescence quenching. The binding of flavonoids to amylase followed a static mechanism, where the binding of one flavonoid per enzyme molecule was observed. Docking analysis showed that flavonoids bound near to enzyme active site, while ACA bound in another site behind the catalytic triad. Extrinsic fluorescence analysis, together with docking analysis pointed out that hydrophobic interactions regulated the flavonoid-α-amylase interactions. The present study provides evidence to understand the relationship of flavonoids structure with their inhibition mechanism.

Lignin linked to slow biodegradability of urea-crosslinked starch in an anaerobic soil environment

For slowing fast solubility and increasing the period of urea’s release in soil, urea-crosslinked starch (UcS) was prepared and applied as a slow release fertilizer. The higher environmental biodegradability of UcS is a major drawback for slow release of urea yet it provides an important challenge for large scale production and application on anaerobic farm lands. Hence, in order to reduce biodegradability of UcS, impregnation of UcS with 5–20 wt% of lignin is proposed. Lignin impregnated UcS was buried for a maximum period of 28–64 days under a constructed anaerobic soil environment. Hill’s model predicted that mineralization of UcS by lignin would be reduced by 5.48%. Microbial growth on UcS was inhibited by lignin at the rate of 0.84 day−1. The α-amylase activity was retarded in response to UcS impregnation with lignin at the rate of 810.94 μg h−1 g−1 soil. Lignin also showed improvement in half-life of UcS up to 0.51 days. This work concluded that lignin impregnation was an efficient approach for improvement of UcS through increasing resistance against natural biodegraders.

Inhibitory kinetics and mechanism of flavonoids from lotus (Nelumbo nucifera Gaertn.) leaf against pancreatic α-amylase

In this study, lotus leaf flavonoids (LLF) were found to show a notable inhibition activity on α-amylase in a mixed-type manner with IC₅₀ value of (5.58 ± 0.10) mg/mL. The intrinsic fluorescence of α-amylase was quenched by the interaction with LLF through a static quenching mechanism, and LLF-α-amylase complex was spontaneously formed mainly driven by the hydrophobic interaction and hydrogen bonding. Multispectroscopic analyses (synchronous fluorescence, three-dimensional fluorescence, circular dichroism (CD) and fourier transform infrared spectra (FT-IR)) comprehensively demonstrated that the binding of LLF to α-amylase would change the conformation and microenvironment of α-amylase, resulting in inhibiting the enzyme activity. The present study indicated that LLF had potential to be as an ingredient in functional food for the prevention of type-2 diabetes.

Investigating inhibitory activity of novel synthetic sericin peptide on α-D-glucosidase: kinetics and interaction mechanism study using a docking simulation

BACKGROUND

We synthesised a novel sericin peptide (SP-GI) with α-d-glucosidase inhibitory activity, which has a sequence of SEDSSEVDIDLGN. The kinetics of its peptide-induced inhibition on α-d-glucosidase activity and its interaction mechanism merging with molecular docking were both investigated.

RESULTS

SP-GI exhibited significant inhibitory activity with an IC₅₀ of 2.9 ± 0.1 µmol L^-1 and this inhibition was reversible and non-competitive with a K_i value of 1.0 ± 0.1 µmol L^-1 . An interaction study with SP-GI revealed it bound to α-d-glucosidase at a single binding site, resulting in alterations in α-d-glucosidase secondary structure. This led to quenching of intrinsic α-d-glucosidase fluorescence by a static quenching mechanism. Molecular docking results showed that the SP-GI binding site on α-d-glucosidase differed from acarbose, with hydrogen bonding and van der Waals forces being the main binding drivers.

CONCLUSION

These findings suggest the potential use for SP-GI or other natural sericin peptides as dietary supplements for the treatment of type 2 diabetes. © 2017 Society of Chemical Industry.

In vitro Inhibition of Pancreatic Lipase by Polyphenols: A Kinetic, Fluorescence Spectroscopy and Molecular Docking Study

The inhibitory activity and binding characteristics of caffeic acid, p-coumaric acid, quercetin and capsaicin, four phenolic compounds found in hot pepper, against porcine pancreatic lipase activity were studied and compared to hot pepper extract. Quercetin was the strongest inhibitor (IC50=(6.1±2.4) µM), followed by p-coumaric acid ((170.2±20.6) µM) and caffeic acid ((401.5±32.1) µM), while capsaicin and a hot pepper extract had very low inhibitory activity. All polyphenolic compounds showed a mixed-type inhibition. Fluorescence spectroscopy studies showed that polyphenolic compounds had the ability to quench the intrinsic fluorescence of pancreatic lipase by a static mechanism. The sequence of Stern-Volmer constant was quercetin, followed by caffeic and p-coumaric acids. Molecular docking studies showed that caffeic acid, quercetin and p-coumaric acid bound near the active site, while capsaicin bound far away from the active site. Hydrogen bonds and π-stacking hydrophobic interactions are the main pancreatic lipase-polyphenolic compound interactions observed.

Structural Characterization of Lignin in Fruits and Stalks of Chinese Quince

Chinese quince (Chaenomeles sinensis) is used in food and pharmaceutical products, but it is seldom eaten as a raw fruit due to its astringent, woody flesh. The structural characterization of lignin fractions from Chinese quince was very important to investigate the structure-activity relationships of lignin. In this investigation, to characterize the structure of lignin in Chinese quince fruits, the milled wood lignin sample was isolated from the fruits (FMWL) and the chemical structure of FMWL was investigated by sugar analysis, FT-IR, GPC, pyrolysis-GC/MS analysis, UV spectra analysis, thermogravimetric analysis (TGA), and advanced NMR spectroscopic techniques. In addition, the lignin fraction from the stalk of Chinese quince (SMWL) was also prepared for comparison to obtained more information of lignin structure in the fruits. The results showed that the two lignin fractions isolated from fruit and stalk of Chinese quince exhibited different structural features. The two MWL samples were mainly composed of β-O-4 ether bonds, β-5 and β-β' carbon-carbon linkages in the lignin structural units. Compared to the SMWL, the FMWL fraction had the higher S/G ratio and more carbohydrates linkages. The predominant carbohydrates associated with FMWL and SMWL fractions were glucans-type hemicelluloses and xylan-type hemicelluloses, respectively. Understanding the structure of lignin could give insight into the properties of the lignin and enable the food processing industry to separate lignin more efficiently.

Lignin from bamboo shoot shells as an activator and novel immobilizing support for α-amylase

This study examined the feasibility of α-amylase activation and immobilization, using lignin from bamboo shoot shells (BSS). Our results demonstrated that BSS lignin is an excellent α-amylase activator and it elevated α-amylase activity more than two-fold at a concentration of 5mg/ml. For immobilization of α-amylase via adsorption, BSS lignin was incubated in an α-amylase solution (5mg/ml) for 20min, and the maximum specific activity, amount of loaded protein and activity recovery were 92.4U/mg, 19.0mg/g and 111%, respectively. In contrast to its free counterpart, immobilized α-amylase improved the catalytic efficiency and storage stability, under comparable working conditions (temperature and pH). Regarding its convenient usage, immobilized enzyme can be suspended in advance, but a suspension incubated at 60°C should be used within 30min. The residual activity after 14 re-uses remained at a reasonable level (53.2%). In conclusion, this study reveals a novel support for enzyme immobilization.

Isolation of α-Amylase Inhibitors from Kadsura longipedunculata Using a High-Speed Counter-Current Chromatography Target Guided by Centrifugal Ultrafiltration with LC-MS

In this study, a high-speed counter-current chromatography (HSCCC) separation method target guided by centrifugal ultrafiltration with high-performance liquid chromatography-mass spectrometry (CU-LC-MS) was proposed. This method was used to analyze α-amylase inhibitors from Kadsura longipedunculata extract. According to previous screening with CU-LC-MS, two screened potential α-amylase inhibitors was successfully isolated from Kadsura longipedunculata extract using HSCCC under the optimized experimental conditions. The isolated two target compounds (with purities of 92.3% and 94.6%) were, respectively, identified as quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) based on the MS, UV, and ¹H-NMR spectrometry data. To verify the inhibition of screened compounds, the inhibitory activities of quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) on α-amylase were tested, and it demonstrated that the experimental IC50 values of quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) were 28.8 and 12.5 μmol/L. These results proved that the hyphenated technique using CU-LC-MS and HSCCC was a rapid, competent, and reproductive method to screen and separate potential active compounds, like enzyme inhibitors from the extract of herbal medicines.

A novel method for classifying starch digestion by modelling the amylolysis of plant foods using first-order enzyme kinetic principles

LOS plots of first-order digestibility data enable the rapid identification of nutritionally-important starch fractions, and allow the final extent (C_∞) of starch amylolysis to be accurately predicted.