Potent Natural Inhibitor Research Articles

Indian red rice phenolic metabolites as potential natural inhibitors of SARS-CoV-2 main protease: A metabolomic and in silico study

COVID-19 is a viral respiratory infectious disease caused by the novel strain of SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2). SARS-CoV-2 main protease (M-pro) is associated with viral replication and transcription, thereby making it a potent target for combating COVID-19. Natural compounds from plants are being widely explored for viral inhibitors due to their safety aspect. Therefore, the present study aimed at predicting the antiviral property of red rice phenolic metabolites (RRPM) from three Indian rice varieties against SARS-CoV-2 M-pro through metabolomics and in silico studies. The Indian red rice cultivars, i.e., Veethi vadankan, Samba mosanam and Kuzhiadichan, were subjected to Q-TOF-LC-MS analysis and eighteen abundant polyphenols were selected using hierarchical cluster analysis. The abundant RRPM were virtually screened using Swiss ADME, a web-based tool. All the abundant polyphenols obeyed the Lipinski's rule except for hesperetin 3'-O-glucuronide, thereby exhibiting drug likeliness. Based on ADME analysis, fifteen of the RRPM showed good oral bioavailability, high GI absorption and acceptable overall bioavailability score. The 15 RRPM were further subjected to molecular docking analysis using Auto dock 1.5.6 against SARS-CoV-2M(pro). The analysis revealed 7, 4'-dihydroxy flavone and eriodictyol to have strong binding affinity (>10 kcal/mol) higher than nelfinavir (-8.53 kcal/mol). Eight other compounds also proved to be potential natural inhibitors of SARS-CoV-2 M-pro. The present study has revealed Kuzhiadichan as a good source of eight potent natural inhibitors of SARS-CoV-2 M-pro and as a potential functional food for COVID-19 management.

Potential phytochemical inhibitors of SARS-CoV-2 helicase Nsp13: a molecular docking and dynamic simulation study.

The SARS-CoV-2 helicase Nsp13 is a promising target for developing anti-COVID drugs. In the present study, we have identified potential natural product inhibitors of SARS-CoV-2 Nsp13 targeting the ATP-binding site using molecular docking and molecular dynamics (MD) simulations. MD simulation of the prepared crystal structure of SARS-CoV-2 Nsp13 was performed to generate an ensemble of structures of helicase Nsp13 capturing the conformational diversity of the ATP-binding site. A natural product library of more than 14,000 phytochemicals from Indian medicinal plants was used to perform virtual screening against the ensemble of Nsp13 structures. Subsequently, a two-stage filter, first based on protein–ligand docking binding energy value and second based on protein residues in the ligand-binding site and non-covalent interactions between the protein residues and the ligand in the best-docked pose, was used to identify 368 phytochemicals as potential inhibitors of SARS-CoV-2 helicase Nsp13. MD simulations of the top inhibitors complexed with protein were performed to confirm stable binding, and to compute MM-PBSA based binding energy. From among the 368 potential phytochemical inhibitors, the top identified potential inhibitors of SARS-CoV-2 helicase Nsp13 namely, Picrasidine M, (+)-Epiexcelsin, Isorhoeadine, Euphorbetin and Picrasidine N, can be taken up initially for experimental studies.Graphic abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s11030-021-10251-1.

A NIR fluorescent probe for Vanin-1 and its applications in imaging, kidney injury diagnosis, and the development of inhibitor

Vanin-1 is an amidohydrolase that catalyses the conversion of pantetheine into the amino-thiol cysteamine and pantothenic acid (coenzyme A precursor), which plays a vital role in multiple physiological and pathological processes. In this study, an enzyme-activated near-infrared (NIR) fluorescent probe (DDAV) has been constructed for sensitively detecting Vanin-1 activity in complicated biosamples on the basis of its catalytic characteristics. DDAV exhibited a high selectivity and sensitivity toward Vanin-1 and was successfully applied to the early diagnosis of kidney injury in cisplatin-induced kidney injury model. In addition, DDAV could serve as a visual tool for in situ imaging endogenous Vanin-1 in vivo. More importantly, Enterococcus faecalis 20247 which possessed high expression of Vanin-1 was screened out from intestinal bacteria using DDAV, provided useful guidance for the rational use of NSAIDs in clinic. Finally, oleuropein as a potent natural inhibitor for Vanin-1 was discovered from herbal medicines library using a high-throughput screening method using DDAV, which held great promise for clinical therapy of inflammatory bowel disease.

Dicentrine and Dicentrinone Isolated from Stephania tetrandrae Radix Suppress HepG2 Proliferation through Inhibiting PDI Activity

Inhibition of protein disulfide isomerase (PDI) has been attempted as a promising anti-cancer strategy. However, there is still no currently available PDI inhibitors approved for clinical use. Here, we isolated seven high yield alkaloids from Stephaniae tetrandrae Radix (STR), a medical herb frequently prescribed in anti-tumor condition, and identified two potent natural PDI inhibitors, dicentrine and dicentrinone. Among the seven alkaloids isolated, dicentrinone (1), dicentrine (2), tetrandrine (4), and fangchinoline (5) could significantly reduce cell viability in a dosage dependent manner detected by MTT assay in human hepatoma cells. To examine whether the candidate compounds are potent PDI inhibitors, we performed insulin turbidity assay and found dicentrine and dicentrinone, but not tetrandrine and fangchinoline, could effectively inhibit PDI activity, with IC50 of 56.70 μM and 43.95 μM respectively. Meanwhile, dicentrine and dicentrinone failed to further reduce the cell number index when co-treated with siRNA of PDI, suggesting the compounds behave as PDI inhibitors. Furthermore, dicentrinone and dicentrine have been successfully docked to the active pocket of PDI (PDB #3UEM) by molecular docking, suggesting the existence of physical interaction between compounds and PDI. Our results suggested that dicentrine and dicentrinone may be developed into safe PDI inhibitors.

SARS-CoV-2 and its Predicted Potential Natural Inhibitors: A Review and Perspective

: SARS-CoV-2, a novel coronavirus, has caused the pneumonia outbreak in the entire world and every day, the number of cases is increasing in an exponential manner. Unfortunately, there is no clinically approved drug or vaccine specific for SARS-CoV-2 to date, and analysis of the current rate of spread of infection suggests that there is no time to wait for the approval of drugs and vaccine production. The sequence and phylogenetic analysis of SARS-CoV-2 has shown that it is very much similar to SARS/SARS-like coronaviruses and belongs to the betacoronavirus genera and bats are likely to be the native host of the SARS-CoV-2. Interestingly, the SARS-CoV-2 S protein and SARS-CoV S protein shared an almost identical 3-D structure in the RBD domain and the SARS-CoV-2 S protein was found to have a significant binding affinity to human ACE2. Further, RdRp and 3CLpro protease of SARSCoV- 2 share over 95% of sequence similarity with those of SARS-CoV. Recently, various molecular docking studies have been carried out to search for natural compounds that can target S protein, RdRp, 3CLpro, and nsp proteins of SARS-CoV-2. This review is an attempt to give a comprehensive idea of the different natural products that can be used to target SARS-CoV-2. However, further research is necessary to investigate the potential uses of these predicted SARS-CoV-2 inhibitors in combating the COVID-19 pandemic.

Food-Derived Bioactive Peptides with Antioxidative Capacity, Xanthine Oxidase and Tyrosinase Inhibitory Activity

Bioactive peptides (BPs) released by proteases from different food protein sources are often served as antioxidants in food applications. This study aims to investigate 11 BPs derived from fish and egg white as potential natural antioxidants by antioxidant activity assays. The kinetic activity of the BPs against xanthine oxidase (XOD) and tyrosinase was also analyzed. The antioxidative capacity of the BPs indicated that VWWW (VW4, mackerel meat), followed by IRW (IW3, egg white) and VKAGFAWTANQQLS (VS14, tuna backbone protein), possessed the highest antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and reducing power (RP) assays. Both the free-radical scavenging score predicted from the AnOxPePred algorithm and the DPPH, ABTS and RP results indicated that VW4 was the best antioxidant. Furthermore, the XOD and tyrosinase inhibition by three selected peptides exhibited competitive patterns of effective inhibition. The half maximal inhibitory concentrations (IC50) of the peptides for XOD inhibition were 5.310, 3.935, and 1.804 mM for VW4, IW3, and VS14, respectively, and they could serve as competitive natural XOD inhibitors. The IC50 of the peptides for tyrosinase inhibition were 1.254, 2.895, and 0.595 mM for VW4, IW3, and VS14, respectively. Overall, VW4, IW3, and VS14 are potential antioxidants and natural XOD inhibitors for preventing milk-fat oxidation, and anti-browning sources for inhibiting food-derived tyrosinase oxidation.

A deep insight into the suppression mechanism of Sedum alfredii root exudates on Pseudomonas aeruginosa based on quorum sensing

Quorum sensing (QS) plays an important role in the intensive communication between plants and microbes in the rhizosphere during the phytoremediation. This study explored the influence of the root exudates of hyperaccumulator Sedum alfredii on Pseudomonas aeruginosa based on QS. The effects of the components of root exudates, genes expression and transcription regulation of QS system (especially the las system) in Pseudomonas aeruginosa wild-type strain (WT) and rhl system mutant strain (ΔrhlI) were systematically analyzed and discussed. The WT and ΔrhlI exposed to gradient root exudates (0×, 1×, 2×, 5× and 10×) showed a concentration-corrective inhibition on protease production, with the inhibition rates of 51.4–74.5% and 31.2–50.0%, respectively. Among the components of the root exudates of Sedum alfredii, only thymol had an inhibition effects to the root exudates on the activity of protease and elastase. The inhibition rates of 50 μmol/L thymol on protease and elastase in WT were 44.7% and 24.3%, respectively, which was consistent with the variation in ΔrhlI. The gene expression of lasB declined 36.0% under the 1× root exudate treatment and 73.0% under the 50 μmol/L thymol treatment. Meanwhile, there was no significant impact on N-3-oxo-dodecanoyl-L-homoserine lactone signal production and the gene expression of lasI and lasR. Therefore, thymol from Sedum alfredii root exudates could inhibit the formation of protease and elastase in Pseudomonas aeruginosa by suppressing the expression of lasB, without any significant influence on the main las system as a potential natural QS inhibitor.

Identification of potential natural inhibitors of the receptor-binding domain of the SARS-CoV-2 spike protein using a computational docking approach.

Background: The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the only zoonotic-origin CoV to reach the pandemic stage, to which neither an effective vaccine nor a specific therapy is available. The spike glycoprotein harbors the receptor-binding domain (RBD) that mediates the virus's entry to host cells. This study aimed to identify novel inhibitors that target the spike protein's RBD domain through computational screening of chemical and natural compounds. Method: The spike protein was modeled from the recently reported electron microscopy protein structure (PDB ID: 6VSB) and the previously described SARS-CoV protein structure (PDB ID: 6ACD and 6ACJ). Virtual lab bench CLC Drug Discovery was used to computationally screen for potential inhibitory effects of currently prescribed drugs (n = 22), natural antiviral drugs (n = 100), and natural compounds (n = 35032). Quantitative Structure-Activity Relationship (QSAR) studies were also performed to determine the leading binders known for their antiviral activity. Results: Among the drugs currently used to treat SARS-CoV2, hydroxychloroquine and favipiravir were identified as the best binders with an average of four H-bonds, with a binding affinity of − 36.66 kcal/mol and a minimum interaction energy of − 6.63 kcal/mol. In an evaluation of antiviral compounds, fosamprenavir and abacavir showed effective binding of five H-bonds, with an average binding affinity of − 18.75 kcal.mol− 1 and minimum interaction energy of − 3.57 kcal/mol. Furthermore, screening of 100 natural antiviral compounds predicted potential binding modes of glycyrrhizin, nepritin, punicalagin, epigallocatechin gallate, and theaflavin (average binding affinity of − 49.88 kcal/mol and minimum interaction energy of − 4.35 kcal/mol). Additionally, the study reports a list of 25 natural compounds that showed effective binding with an improved average binding affinity of − 51.46 kcal/mol. Conclusions: Using computational screening, we identified potential SARS-CoV-2 S glycoprotein inhibitors that bind to the RBD region. Using structure-based design and combination-based drug therapy, the identified molecules could be used to generate anti-SARS-CoV-2 drug candidates.

Diselenide crosslinks for enhanced and simplified oxidative protein folding

The in vitro oxidative folding of proteins has been studied for over sixty years, providing critical insight into protein folding mechanisms. Hirudin, the most potent natural inhibitor of thrombin, is a 65-residue protein with three disulfide bonds, and is viewed as a folding model for a wide range of disulfide-rich proteins. Hirudin’s folding pathway is notorious for its highly heterogeneous intermediates and scrambled isomers, limiting its folding rate and yield in vitro. Aiming to overcome these limitations, we undertake systematic investigation of diselenide bridges at native and non-native positions and investigate their effect on hirudin’s folding, structure and activity. Our studies demonstrate that, regardless of the specific positions of these substitutions, the diselenide crosslinks enhanced the folding rate and yield of the corresponding hirudin analogues, while reducing the complexity and heterogeneity of the process. Moreover, crystal structure analysis confirms that the diselenide substitutions maintained the overall three-dimensional structure of the protein and left its function virtually unchanged. The choice of hirudin as a study model has implications beyond its specific folding mechanism, demonstrating the high potential of diselenide substitutions in the design, preparation and characterization of disulfide-rich proteins.

Repurposing of Some Natural Product Isolates as SARS-COV-2 Main Protease Inhibitors via In Vitro Cell Free and Cell-Based Antiviral Assessments and Molecular Modeling Approaches.

The emergence of the SARS-CoV-2 pandemic has prompted scientists to search for an efficient antiviral medicine to overcome the rapid spread and the marked increase in the number of patients worldwide. In this regard natural products could be a potential source of substances active against coronavirus infections. A systematic computer-aided virtual screening approach was carried out using commercially available natural products found on the Zinc Database in addition to an in-house compound library to identify potential natural product inhibitors of SARS-CoV-2 main protease (MPRO). The top eighteen hits from the screening were selected for in vitro evaluation on the viral protease (SARS-CoV-2 MPRO). Five compounds (naringenin, 2,3′,4,5′,6-pentahydroxybenzophenone, apigenin-7-O-glucoside, sennoside B, and acetoside) displayed high activity against the viral protein. Acteoside showed similar activity to the positive control GC376. The most potent compounds were tested in vitro on SARS-CoV-2 Egyptian strain where only naringenin showed moderate anti-SARS-CoV-2 activity at non-cytotoxic micromolar concentrations in vitro with a significant selectivity index (CC50/IC50 = 178.748/28.347 = 6.3). Moreover; a common feature pharmacophore model was generated to explain the requirements for enzyme inhibition by this diverse group of active ligands. These results pave a path for future repurposing and development of natural products to aid in the battle against COVID-19.

Assessment of inhibitory properties of flavonoid-rich fig (Ficus carica L.) peel extracts against tyrosinase, α-glucosidase, urease and cholinesterases enzymes, and relationship with antioxidant activity

IntroductionKey-enzyme inhibition is a recent approach for the treatment of some health disorders, including diabetes, skin hyperpigmentation, Alzheimer's disease, and some microbial infections. Looking for potential natural multi-target inhibitors, flavonoid-rich extracts from the peel of Ficus carica fruits were simultaneously tested against five enzymes and various methods were used to evaluate their antioxidant activity. MethodsExtracts from peels from F. carica cultivars (Bakor Noir, Bouankik, Azenjer, and Tazegaght) were prepared using methanol acidified by 5% citric acid. Inhibitory activities of extracts at 10 mg/mL were measured in vitro against α-glucosidase, tyrosinase, urease, acetylcholinesterase, and butyrylcholinesterase. Also, the antioxidant activity was evaluated using free radical scavenging, iron and copper chelating, and reducing assays. ResultsExtracts were efficient in inhibiting tyrosinase and α-glucosidase (IC50 values from 0.09 to 0.45, and 1.18 to 3.38 mg/mL, respectively). However, a weak inhibition was observed against urease and cholinesterases. Among the antioxidant activities studied, extracts were more efficient for copper chelation and radical scavenging (IC50 values from 0.05 to 0.13, and 0.30 to 1.33 mg/mL, respectively). Phytochemical analysis revealed the extraction of large quantities of flavonoids (up to 50.4 mg/g of peels), mainly flavonols (up to 81% of total flavonoids). Given the specific extract composition, including two fractions (flavonoids and citric acid), a strong synergy was observed for enzyme inhibition and metal chelation. ConclusionFlavonoid-rich extracts from F. carica could be considered as multifunctional bioactive ingredients to be used in anti-hyperglycemic and skin-whitening pharmaceutical formulations.

Identification of molecular fingerprints of natural products for the inhibition of breast cancer resistance protein (BCRP)

BackgroundExtensive research over the past several decades, explored that the natural compounds contain different plant secondary metabolites and have the potential to inhibit breast cancer resistance protein (BCRP). PurposeTo identify crucial molecular fingerprints of some natural products for the inhibition of breast cancer resistance protein and also to screen out some potent natural BCRP inhibitors. Study designMultiple modelling strategies were applied with three main mottos: (a) Generation of robust classification models to identify the linear and non-linear relationships among the natural compounds and the inhibition of BCRP, (b) Identification of important structural fingerprints that modulate BCRP inhibition and screening of natural database to find the probable hit molecules, (c) Comprehensive ligand-receptor interactions analysis of those against the putative breast cancer resistant protein through molecular docking analysis. MethodsMonte Carlo optimization and SPCI analysis was used to identify important structural fingerprints. QSARCo. and swissADME analysis were used for screening and prediction of hits. Finally, docking analysis was performed for interaction study. ResultsIn this study, some important structural fingerprints of BCRP inhibitors were identified. Additionally, eleven natural anti-cancer compounds were predicted to be active against the BCRP and also satisfy the different drug-likeliness properties. Among them, apigenin was found to have better binding affinities against the putative target as obtained from molecular docking analysis. ConclusionThis study is an attempt to understand about the molecular fingerprints of natural compounds for the inhibition of BCRP and also to dig out some novel natural inhibitors against BCRP.

Discovery of higenamine as a potent, selective and cellular active natural LSD1 inhibitor for MLL-rearranged leukemia therapy

Natural products are a rich source of lead compounds and have shown promise for epigenetic drug discovery. In this work, we discovered higenamine from our natural product library as a potent, selective and cellular active natural LSD1 inhibitor. Higenamine shows acceptable potency against LSD1 and high selectivity towards LSD1 over MAOA/B. Higenamine significantly increases expression of LSD1 substrates H3K4me1 and H3K4me2 in MLL-rearranged leukemia cells MV4-11 and MOLM-13, but nearly had no effect on LSD1 and H3K4Me3. Meanwhile, higenamine dose-dependently suppresses the levels of HOXA9 and MEIS1 that are overexpressed in leukemia cell lines. Notably, higenamine induces cell differentiation of MV4-11 and MOLM-13 cells accompanying by increased expression of CD11b, CD14 and CD86. Higenamine promotes cell apoptosis, inhibits colony formation, but does not inhibit proliferation of leukemia cells significantly. In addition, the expression levels of p53 are dramatically changed by higenamine in an LSD1-dependent manner in MV4-11 cells. Taken together, higenamine could be employed as a starting point for the development of more selective and potent LSD1 inhibitors. Our work firstly reveals the non-classical epigenetic regulation mechanism of higenamine in cancers, and also demonstrates the efficacy of higenamine for MLL-rearranged leukemia therapy.

Inhibitory Effects of Cortex Dictamni Aqueous Extract on Dipeptidyl Peptidase I and Chymase Activities and the Screening of Active Ingredients in Cortex Dictamni Based on Molecular Docking Technique

Dipeptidyl peptidase I (DPPI) and chymase, the granulo-proteases produced and released by mast cells, are important targets of anti-inflammatory drug research and development. Cortex Dictamni is a definite nature drug with anti-inflammatory activity, but the mechanism is unclear and effects of Cortex Dictamni on DPPI and chymase are unknown. This study focuses on effects of Cortex Dictamni aqueous extract (CDAE) on DPPI and chymase activities using cell model, bio-molecular interactions and the Molecular docking study by Discovery Studio (DS) analysis. The results showed that CDAE could significantly inhibit DPPI and chymase activities in vitro and in living rat spleen lymphocytes. Molecular docking simulation demonstrated that Troxerutin, the one of the active compounds of Cortex Dictamni, formed a hydrogen bond with amino acid ILE429 and a strong hydrophobic interaction with TYR64 CYS234 PRO279 ALA382 of DPPI. These interactions allow Troxerutin to form a stable complex with the DPPI, implicating that Troxerutin might be a potential natural inhibitor of DPPI. Dictamnoside M, another active compound of Cortex Dictamni formed hydrogen bonds and hydrophobic interactions within the binding pocket of chymase domain and form a stable complex with the chymase. Dictamnoside M maybe a potential natural inhibitor of chymase. This study suggested a new nature inhibitor Cortex Dictamni and its active components with the anti-inflammatory effects.

Membrane dynamics simulation and virtual screening reveals potential dual natural inhibitors of endothelin receptors for targeting glaucomatous condition

Glaucoma is the second leading cause of blindness in the world and is characterized by the loss of retinal ganglion cells (RGC) over a period of time, leading to complete blindness. Recently, endothelin has been identified as an important factor that influences intraocular pressure IOP, OBF, and direct RGC damage. Targeting the endothelin receptor signaling pathway in glaucoma is considered to be highly beneficial, as it can effectively modulate IOP, OBF, and RGC damage, the key factors which are essential to modulate the disease progression holistically. Currently, synthetic drugs like Bosentan, BQ-123, and prostaglandin analogues are available as endothelin receptor antagonists, which are extensively used in the treatment of cardiovascular and other conditions like systemic hypertension. However, the usage of these drugs in glaucoma is limited due to toxicity and poor bioavailability in the ocular milieu. Thus, there is a need for potential natural compounds as endothelin receptor antagonists that acts as dual inhibitors by targeting both ETA and ETB and are highly efficient with the least toxicity. Hence, this study is intended to prioritize endothelin receptor antagonists by structural bioinformatics approaches involving molecular modeling, molecular dynamics, and molecular docking studies. Subsequently, High throughput virtual screening (HTVS) vs. Natural compound databases targeting the optimal binding sites of both ETA and ETB. Following this, the common hits were subjected to binding free energy calculations (MMGBSA) and ADMETox analysis. Finally, the most potential hits were analyzed for MD based binding stability analysis and binding free energy. Similarly, the known synthetic inhibitors were also docked to the receptors and the results were analyzed. From this study, it was inferred that among the natural compounds dataset (8929 compounds), only 4 common compounds were identified as hits. Among these, only one compound ST075640 surpassed all the prioritization criteria including MMGBSA, ADMETox prediction, dual inhibitory potential (ETA & ETB), and also in structural comparative analysis with bosentan it showed similar efficiency. Thus, the validated hit shall prove to be effective in modulating endothelin mediated IOP, OBF, and RGC damage in glaucomatous condition.

Antitumor potential of the protein phosphatase inhibitor, cantharidin, and selected derivatives

Cantharidin is a potent natural protein phosphatase monoterpene anhydride inhibitor secreted by several species of blister beetle, with its demethylated anhydride analogue, (S)-palasonin, occurring as a constituent of the higher plant Butea frondosa. Cantharidin shows both potent protein phosphatase inhibitory and cancer cell cytotoxic activities, but possible preclinical development of this anhydride has been limited thus far by its toxicity. Thus, several synthetic derivatives of cantharidin have been prepared, of which some compounds exhibit improved antitumor potential and may have use as lead compounds. In the present review, the potential antitumor activity, structure-activity relationships, and development of cantharidin-based anticancer drug conjugates are summarized, with protein phosphatase-related and other types of mechanisms of action discussed. Protein phosphatases play a key role in the tumor microenvironment, and thus described herein is also the potential for developing new tumor microenvironment-targeted cancer chemotherapeutic agents, based on cantharidin and its naturally occurring analogues and synthetic derivatives.

Potential natural inhibitors of xanthine oxidase and HMG-CoA reductase in cholesterol regulation: in silico analysis

BackgroundHypercholesterolemia has posed a serious threat of heart diseases and stroke worldwide. Xanthine oxidase (XO), the rate-limiting enzyme in uric acid biosynthesis, is regarded as the root of reactive oxygen species (ROS) that generate atherosclerosis and cholesterol crystals. β-Hydroxy β-methylglutaryl-coenzyme A reductase (HMGR) is a rate-limiting enzyme in cholesterol biosynthesis. Although some commercially available enzyme inhibiting drugs have effectively reduced cholesterol levels, most of them have failed to meet potential drug candidates’ requirements. Here, we have carried out an in-silico analysis of secondary metabolites that have already shown good inhibitory activity against XO and HMGR in a wet lab setup.MethodsOut of 118 secondary metabolites reviewed, sixteen molecules inhibiting XO and HMGR were selected based on the IC50 values reported in in vitro assays. Further, receptor-based virtual screening was carried out against secondary metabolites using GOLD Protein-Ligand Docking Software, combined with subsequent post-docking, to study the binding affinities of ligands to the enzymes. In-silico ADMET analysis was carried out to explore their pharmacokinetic properties, followed by toxicity prediction through ProTox-II.ResultsThe molecular docking of amentoflavone (GOLD score 70.54, ∆G calc. = − 10.4 Kcal/mol) and ganomycin I (GOLD score 59.61, ∆G calc. = − 6.8 Kcal/mol) displayed that the drug has effectively bound at the competitive site of XO and HMGR, respectively. Besides, 6-paradol and selgin could be potential drug candidates inhibiting XO. Likewise, n-octadecanyl-O-α-D-glucopyranosyl (6′ → 1″)-O-α-D-glucopyranoside could be potential drug candidates to maintain serum cholesterol. In-silico ADMET analysis has shown that these sixteen metabolites were optimal within the categorical range compared to commercially available XO and HMGR inhibitors, respectively. Toxicity analysis through ProTox-II revealed that 6-gingerol, ganoleucoin K, and ganoleucoin Z are toxic for human use.ConclusionThis computational analysis supports earlier experimental evidence towards the inhibition of XO and HMGR by natural products. Further study is necessary to explore the clinical efficacy of these secondary molecules, which might be alternatives for the treatment of hypercholesterolemia.

Anti-Melanogenesis Activity of 6-O-Isobutyrylbritannilactone from Inula britannica on B16F10 Melanocytes and In Vivo Zebrafish Models.

A potential natural melanogenesis inhibitor was discovered in the form of a sesquiterpene isolated from the flowers of Inula britannica, specifically 6-O-isobutyrylbritannilactone (IBL). We evaluated the antimelanogenesis effects of IBL on B16F10 melanocytes and zebrafish embryos. As a result, we found that 3-isobutyl-1-methylxanthine (IBMX)-induced melanin production was reduced in a dose-dependent manner in B16F10 cells by IBL. We also analyzed B16F10 cells that were and were not treated with IBMX, investigating the melanin concentration, tyrosinase activity, mRNA levels. We also studied the protein expressions of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related proteins (TRP1, and TRP2). Furthermore, we found that melanin synthesis and tyrosinase expression were also inhibited by IBL through the modulation of the following signaling pathways: ERK, phosphoinositide 3-kinase (PI3K)/AKT, and CREB. In addition, we studied antimelanogenic activity using zebrafish embryos and found that the embryos had significantly reduced pigmentation in the IBL-treated specimens compared to the untreated controls.

In Silico Identification of Potential Natural Product Inhibitors of Human Proteases Key to SARS-CoV-2 Infection.

Presently, there are no approved drugs or vaccines to treat COVID-19, which has spread to over 200 countries and at the time of writing was responsible for over 650,000 deaths worldwide. Recent studies have shown that two human proteases, TMPRSS2 and cathepsin L, play a key role in host cell entry of SARS-CoV-2. Importantly, inhibitors of these proteases were shown to block SARS-CoV-2 infection. Here, we perform virtual screening of 14,011 phytochemicals produced by Indian medicinal plants to identify natural product inhibitors of TMPRSS2 and cathepsin L. AutoDock Vina was used to perform molecular docking of phytochemicals against TMPRSS2 and cathepsin L. Potential phytochemical inhibitors were filtered by comparing their docked binding energies with those of known inhibitors of TMPRSS2 and cathepsin L. Further, the ligand binding site residues and non-covalent interactions between protein and ligand were used as an additional filter to identify phytochemical inhibitors that either bind to or form interactions with residues important for the specificity of the target proteases. This led to the identification of 96 inhibitors of TMPRSS2 and 9 inhibitors of cathepsin L among phytochemicals of Indian medicinal plants. Further, we have performed molecular dynamics (MD) simulations to analyze the stability of the protein-ligand complexes for the three top inhibitors of TMPRSS2 namely, qingdainone, edgeworoside C and adlumidine, and of cathepsin L namely, ararobinol, (+)-oxoturkiyenine and 3α,17α-cinchophylline. Interestingly, several herbal sources of identified phytochemical inhibitors have antiviral or anti-inflammatory use in traditional medicine. Further in vitro and in vivo testing is needed before clinical trials of the promising phytochemical inhibitors identified here.

Acute Epigallocatechin-3-Gallate Supplementation Alters Postprandial Lipids after a Fast-Food Meal in Healthy Young Women: A Randomized, Double-Blind, Placebo-Controlled Crossover Study.

A high-fat fast-food meal negatively impacts postprandial metabolism even in healthy young people. In experimental studies, epigallocatechin-3-gallate (EGCG), a bioactive compound present in green tea, has been described as a potent natural inhibitor of fatty acid synthase. Thus, we sought to evaluate the effects of acute EGCG supplementation on postprandial lipid profile, glucose, and insulin levels following a high-fat fast-food meal. Fourteen healthy young women 21 ± 1 years and body mass index 21.4 ± 0.41 kg/m2 were enrolled in a randomized, double-blind, placebo-controlled crossover study. Participants ingested capsules containing 800 mg EGCG or placebo immediately before a typical fast-food meal rich in saturated fatty acids. Blood samples were collected at baseline and then at 90 and 120 min after the meal. The EGCG treatment attenuated postprandial triglycerides (p = 0.029) and decreased high-density lipoprotein cholesterol (HDL-c) (p = 0.016) at 120 min. No treatment × time interaction was found for total cholesterol, low-density lipoprotein (LDL-c), and glucose or insulin levels. The incremental area under the curve (iAUC) for glucose was decreased by EGCG treatment (p < 0.05). No difference was observed in the iAUC for triglycerides and HDL-c. In healthy young women, acute EGCG supplementation attenuated postprandial triglycerides and glucose but negatively impacted HDL-c following a fast-food meal.