The Inhibiting Effect of GB-2, (+)-Catechin, Theaflavin, and Theaflavin 3-Gallate on Interaction between ACE2 and SARS-CoV-2 EG.5.1 and HV.1 Variants.

The ongoing COVID-19 pandemic, caused by SARS-CoV-2, continues to pose significant global health challenges. The results demonstrated that GB-2 at 200 µg/mL effectively increased the population of 293T-ACE2 cells with low RBD binding for both SARS-CoV-2 Omicron EG.5.1 and HV.1 variants by dual-color flow cytometry, indicating its ability to inhibit virus attachment. Further investigation revealed that (+)-catechin at 25 and 50 µg/mL did not significantly alter the ACE2-RBD interaction for the EG.5.1 variant. In contrast, theaflavin showed inhibitory effects at both 25 and 50 µg/mL for EG.5.1, while only the higher concentration was effective for HV.1. Notably, theaflavin 3-gallate exhibited a potent inhibition of ACE2-RBD binding for both variants at both concentrations tested. Molecular docking studies provided insight into the binding mechanisms of theaflavin and theaflavin 3-gallate with the RBD of EG.5.1 and HV.1 variants. Both compounds showed favorable docking scores, with theaflavin 3-gallate demonstrating slightly lower scores (-8 kcal/mol) compared to theaflavin (-7 kcal/mol) for both variants. These results suggest stable interactions between the compounds and key residues in the RBD, potentially explaining their inhibitory effects on virus attachment. In conclusion, GB-2, theaflavin, and theaflavin 3-gallate demonstrate significant potential as inhibitors of the ACE2-RBD interaction in Omicron variants, highlighting their therapeutic promise against COVID-19. However, these findings are primarily based on computational and in vitro studies, necessitating further in vivo research and clinical trials to confirm their efficacy and safety in humans.

Robustaflavone as a novel scaffold for inhibitors of native and auto-proteolysed human neutrophil elastase.

Human neutrophil elastase (HNE) plays a key role in initiating inflammation in the cardiopulmonary and systemic contexts. Pathological auto-proteolysed two-chain (tc) HNE exhibits reduced binding affinity with inhibitors. Using AutoDock Vina v1.2.0, 66 flavonoid inhibitors, sivelestat and alvelestat were docked with single-chain (sc) HNE and tcHNE. Schrodinger PHASE v13.4.132 was used to generate a 3D-QSAR model. Molecular dynamics (MD) simulations were conducted with AMBER v18. The 3D-QSAR model for flavonoids with scHNE showed r2 = 0.95 and q2 = 0.91. High-activity compounds had hydrophobic A/A2 and C/C2 rings in the S1 subsite, with hydrogen bond donors at C5 and C7 positions of the A/A2 ring, and the C4' position of the B/B1 ring. All flavonoids except robustaflavone occupied the S1'-S2' subsites of tcHNE with decreased AutoDock binding affinities. During MD simulations, robustaflavone remained highly stable with both HNE forms. Principal Component Analysis suggested that robustaflavone binding induced structural stability in both HNE forms. Cluster analysis and free energy landscape plots showed that robustaflavone remained within the sc and tcHNE binding site throughout the 100 ns MD simulation. The robustaflavone scaffold likely inhibits both tcHNE and scHNE. It is potentially superior to sivelestat and alvelestat and can aid in developing therapeutics targeting both forms of HNE.

Theaflavins mitigate diabetic symptoms in GK rats by modulating the INSR/PI3K-Akt/GSK-3 pathway and intestinal microbiota.

Dietary management and interventions are crucial in the clinical management of diabetes. Numerous active dietary components in black tea have demonstrated positive effects on blood glucose levels and metabolic functions. However, limited research has explored the potential of theaflavins (TF), polyphenols in black tea, for diabetes management. In this study, high-purity TF was administered to Goto-Kakizaki (GK) diabetic model rats for four weeks to investigate its impact on diabetic pathology and analyze the underlying mechanisms through liver transcriptomics, hepatocyte metabolomics, and gut microbiome analysis. The findings indicated that continuous administration of TF (100 mg/kg) significantly suppressed blood glucose levels, reduced insulin resistance, and decreased the expression of oxidative stress indicators and inflammatory factors in GK rats. Further analysis revealed that TF might alleviate insulin resistance by improving hepatic glycogen conversion and reducing hepatic lipid deposition through modulation of key pathways, such as peroxisome proliferator-activated receptors and PI3K/AKT/GSK-3 pathways within the liver, thereby ameliorating diabetic symptoms. Additionally, TF intake facilitated the restoration of the intestinal microbial community structure by reducing the abundance of harmful bacteria and increasing the abundance of beneficial bacteria. It also reduced endotoxin lipopolysaccharide production, thereby lowering the chances of insulin resistance development and enhancing its efficacy in regulating blood glucose levels. These findings offer a novel perspective on the potential of black tea and its active constituents to prevent and treat diabetes and other metabolic disorders, providing valuable references for identifying and applying active dietary components from tea.

Procyanidin B1 and p-coumaric acid from whole highland barley ameliorated HFD-induced impaired glucose tolerance via small intestinal barrier and hepatic glucose metabolism.

Highland barley is a natural source for the development of phenolic compounds that exhibit potential in preventing type 2 diabetes, which is important for the agricultural and industrial utilization of highland barley. However, very few studies have focused on their effect on small intestinal absorption and barrier dysfunction, as well as the direct target for the modulation of hepatic glucose metabolism. In this study, procyanidin B1 (PB) and p-coumaric acid (CA) isolated from highland barley supplementation in impaired glucose tolerance (IGT) mice significantly increased lactase-phlorizin hydrolase (LPH), sulfotransferase 1A1 (SULT1A1), UDP glucuronosyltransferase 1A (UGT1A) families and sodium-dependent glucose transporter 1 (SGLT1) expression in the small intestine of IGT mice, indicating beneficial effects on polyphenol deglycosylation and transportation. Supplementation with PB and CA also exhibited attenuation of small intestinal barrier dysfunction by improving the mucus layer and tight junctions, which was closely related to the transportation of phenolic compounds. In addition, PB and CA supplementation were explored directly to bind to the insulin receptor and activate the insulin receptor substrate-1 (IRS-1)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway, thereby modulating hepatic glucose metabolism and ameliorating hyperglycemic in IGT mice. These results offer crucial insights into the potential development of PB and CA as non-food nutraceuticals, as well as the extensive utilization of highland barley as an industrial crop.

Enzyme-esterified grape seed proanthocyanidin derivatives as novel lipid-lowering agents.

Grape seed proanthocyanidin (GSP), as a natural antioxidant, has great potential to be developed into a lipid-lowering agent, but its low lipophilicity and stability greatly limit its application. In this study, an enzymatic esterification strategy was developed to introduce fatty acid chains into GSP, resulting in the successful synthesis of a series of new GSP derivatives. The results showed that up to 85% conversion of GSP and 35% TAG inhibition rate of GSP derivatives were achieved. The structures of GSP derivatives were identified by UPLC-MS/MS, and seven derivatives were confirmed as catechin-3'-O-laurate, epicatechin-3'-O-laurate, epicatechin gallate-3″,5″-di-O-laurate, epicatechin gallate-3',3″,5″-tri-O-laurate, procyanidin B1-3',3″-di-O-laurate, procyanidin B2-3',3″-di-O-laurate and procyanidin C1-3',3″,3‴-tri-O-laurate by NMR. GSP derivatives exhibited higher inhibitory effects on lipid accumulation, intracellular TAG and TC than parent GSP. These results indicate that GSP derivatives have potential as lipid-lowering agents for utilization in the food industry.

Identification of procyanidins as α-glucosidase inhibitors, pancreatic lipase inhibitors, and antioxidants from the bark of Cinnamomum cassia by multi-bioactivity-labeled molecular networking.

This study examined the suppressive effects of 16 selected plant-based foods on α-glucosidase and pancreatic lipase and their antioxidant properties. Among these, the bark of Cinnamomum cassia (Cinnamon, WLN-FM 15) showed the highest inhibitory activity against α-glucosidase and the highest antioxidant activity. Additionally, WLN-FM 15 showed promising results in the other tests. To further identify the bioactive constituents of WLN-FM 15, a multi-bioactivity-labeled molecular networking approach was used through a combination of GNPS-based molecular networking, DPPH-HPLC, and affinity-based ultrafiltration-HPLC. A total of nine procyanidins were identified as antioxidants and inhibitors of α-glucosidase and pancreatic lipase in WLN-FM 15. Subsequently, procyanidins A1, A2, B1, and C1 were isolated, and their efficacy was confirmed through functional assays. In summary, WLN-FM 15 has the potential to serve as a functional food ingredient with the procyanidins as its bioactive constituents. These results also suggest that the multi-bioactivity-labeled molecular networking approach is reliable for identifying bioactive constituents in plant-based foods.

Procyanidin B2-3'-O-Gallate Derived from Grape Seed Polymeric Procyanidins via the Galloyl-Attached Nucleophilic Degradation as a Potential Hepatoprotective Agent.

An effective method was developed for preparing galloylated procyanidins (GPCs) using galloyl-attached nucleophilic degradation. Under degradation conditions optimized through Box-Behnken design and single-factor experiments, two dimeric and three tetrameric GPCs were produced, with the yield of procyanidin B2-3'-O-gallate (B2-3'-G) reaching up to 232 mg/g (PPCs). The structure of B2-3'-G was identified by UV, FTIR, NMR, CD, MS, and phloroglucinolysis. Furthermore, the protective effect of B2-3'-G against alcohol-induced liver injury (ALI) was investigated. Compared with the parent compounds, B2-3'-G exhibited a stronger capacity for inhibiting ALI, attributed to its polymerization degree and galloyl group. Subsequent experiments revealed that the pretreatment of BRL-3A cells with B2-3'-G prior to ethanol improved ALI through activation of the Nrf2-HO-1/NQO1 pathway and initiation of enzymatic antioxidant systems. These findings suggest that GPC B2-3'-G is a potential hepatoprotective agent, which provides a new perspective for functional development of GPCs.

Ginkgetin attenuates bone loss in OVX mice by inhibiting the NF-κB/IκBα signaling pathway.

Background: Osteoporosis is a disease associated with bone resorption, characterized primarily by the excessive activation of osteoclasts. Ginkgetin is a compound purified from natural ginkgo leaves which has various biological properties, including anti-inflammation, antioxidant, and anti-tumor effects. This study investigated the bone-protective effects of ginkgetin in ovariectomized (OVX) mice and explored their potential signaling pathway in inhibiting osteoclastogenesis in a mouse model of osteoporosis. Methods: Biochemical assays were performed to assess the levels of Ca, ALP, and P in the blood. Micro CT scanning was used to evaluate the impact of ginkgetin on bone loss in mice. RT-PCR was employed to detect the expression of osteoclast-related genes (ctsk, c-fos, trap) in their femoral tissue. Hematoxylin and eosin (H&E) staining was utilized to assess the histopathological changes in femoral tissue due to ginkgetin. The TRAP staining was used to evaluate the impact of ginkgetin osteoclast generation in vivo. Western blot analysis was conducted to investigate the effect of ginkgetin on the expression of p-NF-κB p65 and IκBα proteins in mice. Results: Our findings indicate that ginkgetin may increase the serum levels of ALP and P, while decreasing the serum level of Ca in OVX mice. H&E staining and micro CT scanning results suggest that ginkgetin can inhibit bone loss in OVX mice. The TRAP staining results showed ginkgetin suppresses the generation of osteoclasts in OVX mice. RT-PCR results demonstrate that ginkgetin downregulate the expression of osteoclast-related genes (ctsk, c-fos, trap) in the femoral tissue of mice, and this effect is dose-dependent. Western blot analysis results reveal that ginkgetin can inhibit the expression of p-NF-κB p65 and IκBα proteins in mice. Conclusion: Ginkgetin can impact osteoclast formation and activation in OVX mice by inhibiting the NF-κB/IκBα signaling pathway, thereby attenuating bone loss in mice.

Ginkgetin Pretreatment Reduces Inflammatory Response in DCD Donor Liver via JAK2/STAT3 Signaling Pathway.

BACKGROUND Ginkgetin inhibits growth of tumor cells, reducing blood lipids, and improving atherosclerosis, but the protective effect of ginkgetin in donation after cardiac death (DCD) livers is still unknown. The aim of this study was to determine whether pretreatment of DCD donor livers with ginkgetin can reduce inflammatory response through the JAK2/STAT3 signaling pathway. MATERIAL AND METHODS Twenty male Sprague-Dawley rats (200-250 g) were randomly divided into 4 groups: Sham, DCD, Ginkgetin (0.6 mg/kg) pretreatment 1 h before surgery, and Ginkgetin (0.6 mg/kg) plus broussonin E (0.3 mg/kg) (JAK2/STAT3 signaling agonist) pretreatment 1 h before surgery. Rat livers were subjected to 30 min warm ischemia and 24 h cold storage to simulate the preservation process of DCD donor livers, followed by normothermic machine perfusion for 1 h to simulate liver reperfusion in vivo. Liver tissues and perfusate samples were collected for further studies. RESULTS Ginkgetin pretreatment significantly decreased the values of ALT and AST (P<0.05), and improved histological alterations according to improved Suzuki's Score (P<0.05). Ginkgetin also inhibited the protein expression levels of p-JAK2/JAK2 and p-STAT3/STAT3 (P<0.05). Furthermore, ginkgetin pretreatment inhibited levels of interleukin-1ß, interleukin-6 and tumor necrosis factor a (P<0.05) to suppress inflammatory response. In addition, broussonin E reversed the improvement of ginkgetin on DCD donor livers. CONCLUSIONS Ginkgetin can inhibit the inflammatory response through the JAK2/STAT3 signaling pathway to improve the quality of DCD donor livers.

Ginkgetin improved experimental colitis by inhibiting intestinal epithelial cell apoptosis through EGFR/PI3K/AKT signaling.

Excessive apoptosis of intestinal epithelial cells leads to intestinal barrier dysfunction, which is not only one of the pathological features of inflammatory bowel disease (IBD) but also a therapeutic target. A natural plant extract, Ginkgetin (GK), has been reported to have anti-apoptotic activity, but its role in IBD is unknown. This study aimed to explore whether GK has anti-colitis effects and related mechanisms. An experimental colitis model induced by dextran sulfate sodium (DSS) was established, and GK was found to relieve colitis in DSS-induced mice as evidenced by improvements in weight loss, colon shortening, Disease Activity Index (DAI), macroscopic and tissue scores, and proinflammatory mediators. In addition, in DSS mice and TNF-α-induced colonic organoids, GK protected the intestinal barrier and inhibited intestinal epithelial cell apoptosis, by improving permeability and inhibiting the number of apoptotic cells and the expression of key apoptotic regulators (cleaved caspase 3, Bax and Bcl-2). The underlying mechanism of GK's protective effect was explored by bioinformatics, rescue experiments and molecular docking, and it was found that GK might directly target and activate EGFR, thereby interfering with PI3K/AKT signaling to inhibit apoptosis of intestinal epithelial cells in vivo and in vitro. In conclusion, GK inhibited intestinal epithelial apoptosis in mice with experimental colitis, at least in part, by activating EGFR and interfering with PI3K/AKT activation, explaining the underlying mechanism for ameliorating colitis, which may provide new options for the treatment of IBD.

Procyanidin C1 inhibits bleomycin-induced pulmonary fibrosis in mice by selective clearance of senescent myofibroblasts.

Pulmonary fibrosis is a formidable challenge in chronic and age-related lung diseases. Myofibroblasts secrete large amounts of extracellular matrix and induce pro-repair responses during normal wound healing. Successful tissue repair results in termination of myofibroblast activity via apoptosis; however, some myofibroblasts exhibit a senescent phenotype and escape apoptosis, causing over-repair that is characterized by pathological fibrotic scarring. Therefore, the removal of senescent myofibroblasts using senolytics is an important method for the treatment of pulmonary fibrosis. Procyanidin C1 (PCC1) has recently been discovered as a senolytic compound with very low toxicity and few side effects. This study aimed to determine whether PCC1 could improve lung fibrosis by promoting apoptosis in senescent myofibroblasts and to investigate the mechanisms involved. The results showed that PCC1 attenuates bleomycin (BLM)-induced pulmonary fibrosis in mice. In addition, we found that PCC1 inhibited extracellular matrix deposition and promoted the apoptosis of senescent myofibroblasts by increasing PUMA expression and activating the BAX signaling pathway. Our findings represent a new method of pulmonary fibrosis management and emphasize the potential of PCC1 as a senotherapeutic agent for the treatment of pulmonary fibrosis, providing hope for patients with pulmonary fibrosis worldwide. Our results advance our understanding of age-related diseases and highlight the importance of addressing cellular senescence in treatment.

Structure-dependent capacity of procyanidin dimers to inhibit inflammation-induced barrier dysfunction in a cell model of intestinal epithelium.

Diet is of major importance in modulating intestinal inflammation, as the gastrointestinal tract is directly exposed to high concentrations of dietary components. Procyanidins are flavan-3-ol oligomers abundant in fruits and vegetables. Although with limited or no intestinal absorption, they can have GI health benefits which can promote overall health. We previously observed that epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) dimers inhibit in vitro colorectal cancer cell proliferation and invasiveness. Inflammation-mediated intestinal barrier permeabilization can result in a chronic inflammatory condition and promote colorectal cancer onset/progression. Thus, this study investigated the structure-dependent capacity of ECG, EGCG and (-)-epicatechin (EC) dimers to inhibit tumor necrosis factor alpha (TNFα)-induced inflammation, oxidative stress, and loss of barrier integrity in Caco-2 cells differentiated into an intestinal epithelial cell monolayer. Cells were incubated with TNFα (10 ng/ml), in the absence/presence of ECG, EGCG and EC dimers. The three dimers inhibited TNFα-mediated Caco-2 cell monolayer permeabilization, modulating events involved in the loss of barrier function and inflammation, i.e. decreased tight junction protein levels; increased matrix metalloproteinases expression and activity; increased NADPH oxidase expression and oxidant production; activation of the NF-κB and ERK1/2 pathways and downstream events leading to tight junction opening. For some of these mechanisms, the galloylated ECG and EGCG dimers had stronger protective potency than the non-galloylated EC dimer. These differences could be due to differential membrane interactions as pointed out by molecular dynamics simulation of procyanidin dimers-cell membrane interactions and/or by differential interactions with NOX1. Results show that dimeric procyanidins, although poorly absorbed, can promote health by alleviating intestinal inflammation, oxidative stress and barrier permeabilization.

Exploring the cytotoxic potential of biflavones of Araucaria cunninghamii: Precise identification combined by LC-HRMS-metabolomics and database mining, targeted isolation, network pharmacology, in vitro cytotoxicity, and docking studies.

The leaves of Araucaria cunninghamii are known to be nonedible and toxic. Previous studies have identified biflavones in various Araucaria species. This study aimed to investigate the in vitro cytotoxicity of the isolated compounds from Araucaria cunninghamii after metabolomics and network pharmacological analysis. Methanol extract of Araucaria cunninghamii leaves was subjected to bioassay-guided fractionation. The active fraction was analyzed using LC-HRMS, through strategic database mining, by comparing the data to the Dictionary of Natural Products to identify 12 biflavones, along with abietic acid, beta-sitosterol, and phthalate. Eight compounds were screened for network pharmacology study, where in silico ADME analysis, prediction of gene targets, compound-gene-pathway network and hierarchical network analysis, protein-protein interaction, KEGG pathway, and Gene Ontology analyses were done, that showed PI3KR1, EGFR, GSK3B, and ABCB1 as the common targets for all the compounds that may act in the gastric cancer pathway. Simultaneously, four biflavones were isolated via chromatography and identified through NMR as dimeric apigenin with varying methoxy substitutions. Cytotoxicity study against the AGS cell line for gastric cancer showed that AC1 biflavone (IC50 90.58 µM) exhibits the highest cytotoxicity and monomeric apigenin (IC50 174.5 µM) the lowest. Besides, the biflavones were docked to the previously identified targets to analyze their binding affinities, and all the ligands were found to bind with energy ≤-7 Kcal/mol.

Comparisons of procyanidins with different low polymerization degrees on prevention of lipid metabolism in high-fat diet/streptozotocin-induced diabetic mice.

Procyanidins, which are oligomerized flavan-3-ols with a polyphenolic structure, are bioactive substances that exhibit various biological effects. However, the relationship between the degree of polymerization (DP) of procyanidins and their bioactivities remains largely unknown. In this study, the preventive effects of procyanidins with different DP (EC, PB2 and PC1) on glucose improvement and liver lipid deposition were investigated using a high-fat diet/streptozotocin-induced diabetes mouse model. The results demonstrated that all the procyanidins with different DP effectively reduced fasting blood glucose and glucose/insulin tolerance, decreased the lipid profile (total cholesterol, triglyceride, and low-density lipoprotein cholesterol content) in serum and liver tissue as well as the liver oil red staining, indicating the improvement of glucose metabolism, insulin sensitivity and hepatic lipid deposition in diabetic mice. Furthermore, the procyanidins down-regulated expression of glucose regulated 78-kDa protein (GRP78) and C/EBP homologous protein (CHOP), indicating a regulation role of endoplasmic reticulum (ER) stress. The inhibition of ER stress by tauroursodeoxycholic acid (TUDCA) treatment abolished the effects of procyanidins with different DP in PA-induced HepG2 cells, confirming that procyanidins alleviate liver hyperlipidemia through the modulation of ER stress. Molecular docking results showed that EC and PB2 could better bind GRP78 and CHOP. Collectively, our study reveals that the structure of procyanidins, particularly DP, is not directly correlated with the improvement of blood glucose and lipid deposition, while highlighting the important role of ER stress in the bioactivities of procyanidins.

Amentoflavone reverses epithelial-mesenchymal transition in hepatocellular carcinoma cells by targeting p53 signalling pathway axis.

Epithelial-mesenchymal transition (EMT) and its reversal process are important potential mechanisms in the development of HCC. Selaginella doederleinii Hieron is widely used in Traditional Chinese Medicine for the treatment of various tumours and Amentoflavone is its main active ingredient. This study investigates the mechanism of action of Amentoflavone on EMT in hepatocellular carcinoma from the perspective of bioinformatics and network pharmacology. Bioinformatics was used to screen Amentoflavone-regulated EMT genes that are closely related to the prognosis of HCC, and a molecular prediction model was established to assess the prognosis of HCC. The network pharmacology was used to predict the pathway axis regulated by Amentoflavone. Molecular docking of Amentoflavone with corresponding targets was performed. Detection and evaluation of the effects of Amentoflavone on cell proliferation, migration, invasion and apoptosis by CCK-8 kit, wound healing assay, Transwell assay and annexin V-FITC/propidium iodide staining. Eventually three core genes were screened, inculding NR1I2, CDK1 and CHEK1. A total of 590 GO enrichment entries were obtained, and five enrichment results were obtained by KEGG pathway analysis. Genes were mainly enriched in the p53 signalling pathway. The outcomes derived from both the wound healing assay and Transwell assay demonstrated significant inhibition of migration and invasion in HCC cells upon exposure to different concentrations of Amentoflavone. The results of Annexin V-FITC/PI staining assay showed that different concentrations of Amentoflavone induces apoptosis in HCC cells. This study revealed that the mechanism of Amentoflavone reverses EMT in hepatocellular carcinoma, possibly by inhibiting the expression of core genes and blocking the p53 signalling pathway axis to inhibit the migration and invasion of HCC cells.

Theaflavin-3,3'-digallate effectively attenuates biofilm formation by Enterococcus faecalis via the targeting of specific quorum sensing pathways.

Enterococcus faecalis, an opportunistic pathogen responsible for nosocomial infections, exhibits increased pathogenicity via biofilm formation. Theaflavin-3,3'-digallate (TF3), a theaflavin extracted from black tea, exhibits potent antibacterial effects. In the present study, we investigated the inhibitory effect of TF3 on E. faecalis. Our results indicated that TF3 significantly inhibited E. faecalis ATCC 29212 biofilm formation. This observation was further confirmed via crystal violet staining, confocal laser scanning microscopy, and field emission-scanning electron microscopy. To disclose the underlying mechanisms, RNA-seq was applied. TF3 treatment significantly altered the transcriptomic profile of E. faecalis, as evidenced by identification of 248 differentially expressed genes (DEGs). Through functional annotation of these DEGs, several quorum-sensing pathways were found to be suppressed in TF3-treated cultures. Further, gene expression verification via real-time PCR confirmed the downregulation of gelE, sprE, and secY by TF3. These findings highlighted the ability of TF3 to impede E. faecalis biofilm formation, suggesting a novel preventive strategy against E. faecalis infections.

Discovery of procyanidin condensed tannins of (-)-epicatechin from Kratom, Mitragyna speciosa, as virucidal agents against SARS-CoV-2.

Kratom, Mitragyna speciosa, is one of the most popular herbs in the West and Southeast Asia. A number of previous works have focused on bioactive alkaloids in this plant; however, non-alkaloids have never been investigated for their biological activities. Antiviral and virucidal assays of a methanol leaf extract of Kratom, M. speciosa, revealed that a crude extract displayed virucidal activity against the SARS-CoV-2. Activity-guided isolation of a methanol leaf extract of Kratom led to the identification of B-type procyanidin condensed tannins of (-)-epicatechin as virucidal compounds against SARS-CoV-2. The fraction containing condensed tannins exhibited virucidal activity with an EC50 value of 8.38 µg/mL and a selectivity index (SI) value >23.86. LC-MS/MS analysis and MALDI-TOF MS identified the structure of the virucidal compounds in Kratom as B-type procyanidin condensed tannins, while gel permeation chromatograph (GPC) revealed weight average molecular weight of 238,946 Da for high molecular-weight condensed tannins. In addition to alkaloids, (-)-epicatechin was found as a major component in the leaves of M. speciosa, but it did not have virucidal activity. Macromolecules of (-)-epicatechin, i.e., procyanidin condensed tannins, showed potent virucidal activity against SARS-CoV-2, suggesting that the high molecular weights of these polyphenols are important for virucidal activity.

Inhibition mechanism of theaflavins on matrix metalloproteinase-2: inhibition kinetics, multispectral analysis, molecular docking and molecular dynamics simulation.

Dental caries is a chronic and destructive disease and matrix metalloproteinase-2 (MMP-2) plays a major role in caries. The inhibitory mechanisms of theaflavins [theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3'-gallate (TF2B), and theaflavin-3,3'-digallate (TF3)] on MMP-2 were investigated using techniques such as enzyme inhibition kinetics, multi-spectral methods, molecular docking, and molecular dynamics simulations. The results showed that TF1, TF2A, TF2B, and TF3 all competitively and reversibly inhibited MMP-2 activity. Fluorescence spectra and molecular docking indicated that four theaflavins spontaneously bind to MMP-2 through noncovalent interactions, driven by hydrogen bonds and hydrophobic interactions, constituting a static quenching mechanism and resulting in an altered tryptophan residue environment around MMP-2. Molecular dynamic simulations demonstrated that four theaflavins can form stable, compact complexes with MMP-2. In addition, the order of theaflavins' ability to inhibit MMP-2 was found to be TF1 > TF2B > TF2A > TF3. Interestingly, the order of binding capacity between MMP-2 and TF1, TF2A, TF2B, and TF3 was consistent with the order of inhibitory capacity, and was opposite to the order of steric hindrance of theaflavins. This may be due to the narrow space of the active pocket of MMP-2, and the smaller the steric hindrance of theaflavins, the easier it is to enter the active pocket and bind to MMP-2. This study provided novel insights into theaflavins as functional components in the exploration of natural MMP-2 inhibitors.

Amentoflavone attenuates homocysteine-induced neuronal ferroptosis-mediated inflammatory response: Involvement of the SLC7A11/GPX4 axis activation.

Elevated homocysteine (Hcy) levels, referred to hyperhomocysteinemia, are associated with an increased risk of several neurological disorders. Ferroptosis and inflammation play a vital role in Hcy-induced neuronal dysfunction. Amentoflavone (AMF), an active natural biflavone compound, exhibits antioxidative, anti-inflammatory, and neuroprotective activities. This study aimed to explore the potential effects of AMF on Hcy-induced neuronal injury, with a particular focus on the underlying mechanisms involving ferroptosis and inflammation. We assessed neuronal damage in HT22 cells by measuring cell viability, lactate dehydrogenase (LDH) release, and proliferation rates. Additionally, we evaluated oxidative stress markers including the levels of reactive oxygen species (ROS), MitoSOX, mitochondrial membrane potential (MMP), malondialdehyde (MDA), and glutathione (GSH). Iron metabolism and ferroptosis-related gene expressions (Ptgs2, Tfr1, and Fth1) were quantified. TheSLC7A11/GPX4 axis was also detected. Our results showed that AMF treatment dramatically mitigated Hcy-induced neuronal injury by increasing cell viability, decreasing LDH release, and promoting cell proliferation. AMF treatment also reduced Hcy-induced oxidative stress and lipid peroxidation, as evidenced by reduced ROS, MitoSOX, MMP, and MDA levels, along with an increased GSH content in HT22 cells. In addition, AMF treatment reduced iron content and ferroptosis-related gene mRNA levels. However, Erastin, a ferroptosis inducer, blocked these neuroprotective effects of AMF. Ferroptosis inhibitor Ferrostatin-1 also attenuated Hcy-induced ferroptosis. Moreover, both AMF and Ferrostatin-1 effectively mitigated Hcy-induced inflammation, which was again antagonized by Erastin. Mechanistically, AMF treatment enhanced SLC7A11/GPX4 axis in Hcy-treated HT22 cells. In conclusion, these findings suggest that AMF possesses neuroprotection against Hcy-induced injury primarily by inhibiting ferroptosis-mediated inflammation, partly through the activation of SLC7A11/GPX4 axis.

A frontier exploration of ancient craftsmanship: Effects of various tea products in traditional Chinese cuisine "tea flavored beef".

Modern science often overlooks to reveal the scientific essence of traditional crafts to promote their inheritance and development. In this work, five different types of tea products were prepared using the same variety of tea leaves referring to traditional methods. The analysis of their components and activities indicated that the processing reduced total catechin contents (from 172.8 mg/g to 48.2 mg/g) and promoted the synthesis of theaflavins (from 17.9 mg/g to 43.4 mg/g), reducing antioxidant and antimicrobial abilities of the resulting tea products. On this basis, the tea products were applied to "tea flavored beef" to reveal long-term effects. Within 15 days of storage, tea treatment showed remarkable antimicrobial and antioxidant activities on the beef. Also, the declines of sensory scores and texture of the treated beef were significantly suppressed. Meanwhile, protein degradation in the beef was inhibited, limiting the contents of various biogenic amines within relatively low levels.