The N-Terminal Carbamate is Key to High Cellular and Antiviral Potency for Boceprevir-Based SARS-CoV-2 Main Protease Inhibitors

Boceprevir is an HCV NSP3 inhibitor that has been explored as a repurposed drug for COVID-19. It inhibits the SARS-CoV-2 main protease (MPro) and contains an α-ketoamide warhead, a P1 β-cyclobutylalanyl moiety, a P2 dimethylcyclopropylproline, a P3 tert-butylglycine, and a P4 N-terminal tert-butylcarbamide. By introducing modifications at all four positions, we synthesized 20 boceprevir-based MPro inhibitors including PF-07321332 and characterized their MPro inhibition potency in test tubes (in vitro) and human host cells (in cellulo). Crystal structures of MPro bound with 10 inhibitors and antiviral potency of 4 inhibitors were characterized as well. Replacing the P1 site with a β-(S-2-oxopyrrolidin-3-yl)-alanyl (opal) residue and the war-head with an aldehyde leads to high in vitro potency. The original moieties at P2, P3 and the P4 N-terminal cap positions in boceprevir are better than other tested chemical moieties for high in vitro potency. In crystal structures, all inhibitors form a covalent adduct with the MPro active site cysteine. The P1 opal residue, P2 dime-thylcyclopropylproline and P4 N-terminal tert-butylcarbamide make strong hydrophobic interactions with MPro, explaining high in vitro potency of inhibitors that contain these moieties. A unique observation was made with an inhibitor that contains a P4 N-terminal isovaleramide. In its MPro complex structure, the P4 N-terminal isovaleramide is tucked deep in a small pocket of MPro that originally recognizes a P4 alanine side chain in a substrate. Although all inhibitors show high in vitro potency, they have drastically different in cellulo potency in inhibiting ectopically expressed MPro in human 293T cells. All inhibitors including PF-07321332 with a P4 N-terminal carbamide or amide have low in cellulo potency. This trend is reversed when the P4 N-terminal cap is changed to a carbamate. The installation of a P3 O-tert-butyl-threonine improves in cellulo potency. Three molecules that contain a P4 N-terminal carbamate were advanced to antiviral tests on three SARS-CoV-2 variants. They all have high potency with EC50 values around 1 μM. A control compound with a nitrile warhead and a P4 N-terminal amide has undetectable antiviral potency. Based on all observations, we conclude that a P4 N-terminal carbamate in a boceprevir derivative is key for high antiviral potency against SARS-CoV-2.

A New β-Carboline Alkaloid From the Aerial Part of Hedyotis capitellata

A new β-carboline alkaloid, 10-hydroxy-capitelline (1) together with three known anthraquinones, hedanthroside B (2), hedanthroside C (3), and rubiadin (4) were isolated from the aerial part methanol extract of Hedyotis capitellata. Their structures were established by spectroscopic data (one-dimensional, two-dimensional nuclear magnetic resonance (1D, 2D-NMR) and high-resolution-electrospray ionization-mass spectrometry, HR-ESI-MS) and comparison with those reported in the literature. The anti-inflammatory activity of the isolated compounds is evaluated by their inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. At a concentration of 20 µM, compounds 1 to 4 showed weak inhibitory effects on NO production with inhibitory values ranging from 1.2% to 23.9% compared to a value of 74.5% for the positive control compound, NG-monomethyl-L-arginine (L-NMMA).

Computational Screening of Natural Compounds for Identification of Potential Anti-Cancer Agents Targeting MCM7 Protein

Minichromosome maintenance complex component 7 (MCM7) is involved in replicative licensing and the synthesis of DNA, and its overexpression is a fascinating biomarker for various cancer types. There is currently no effective agent that can prevent the development of cancer caused by the MCM7 protein. However, on the molecular level, inhibiting MCM7 lowers cancer-related cellular growth. With this purpose, this study screened 452 biogenic compounds extracted from the UEFS Natural Products dataset against MCM protein by using the in silico art of technique. The hit compounds UEFS99, UEFS137, and UEFS428 showed good binding with the MCM7 protein with binding energy values of −9.95, −8.92, and −8.71 kcal/mol, which was comparatively higher than that of the control compound ciprofloxacin (−6.50). The hit (UEFS99) with the minimum binding energy was picked for molecular dynamics (MD) simulation investigation, and it demonstrated stability at 30 ns. Computational prediction of physicochemical property evaluation revealed that these hits are non-toxic and have good drug-likeness features. It is suggested that hit compounds UEFS99, UEFS137, and UEFS428 pave the way for further bench work validation in novel inhibitor development against MCM7 to fight the cancers.

Isolation and Antibacterial Properties of Phenyl Acrylic Acid Derivatives from Balanophora elongata Blume

Balanophora elongata (Balanophoraceae) is a tropical parasitic flowering plant 9 cm in height. Four known phenyl acrylic acid derivatives, methyl caffeate (1), caffeic acid (2), 1,6-di-O-caffeoyl-β-D-glucopyranose (3), and coniferin (4), were isolated from this plant. Structural elucidation of the isolated compounds was determined by IR, LC-ESI-MS, 1D and 2D NMR. Extracts and isolated compounds were tested toward some standard human pathogenic bacteria using the agar disk diffusion method. Their inhibition zones were compared to that of chloramphenicol as positive control. Compound 1 showed inhibition toward Streptococcus mutans, while compound 3 and 4 inhibited Staphylococcus aureus.

New Nitric Oxide Inhibitory Spirostane Glycosides from Polygonatum kingianum Collett & Hemsl

Two new spirostane glycosides, (25 R)-12 β-hydroxyspirost-5-en-3 β-yl O- β-D-glucopyranosyl-(1→4)- β-D-galactopyranoside (1) and (25 S)-spirost-5-en-7-one-3 β-yl O- β-D-glucopyranosyl-(1→2)- β-D-glucopyranosyl-(1→4)- β-D-galactopyranoside (2), and a known spirostane glycoside, funkioside C (3), were isolated from the roots of Polygonatum kingianum Collett & Hemsl. (Asparagaceae). Their structures were determined by extensive analysis of mass spectrometry high resolution electron spray ionization mass spectrum and nuclear magnetic resonance spectral data, as well as by comparison of the spectral data with those reported in the literature. Compound 2 showed inhibitory effects on nitric oxide production in the lipopolysaccharide stimulated RAW 264.7 cells with an IC50 value of 8.78 ± 0.05 µM compared to a value of 7.12 ± 0.08 µM for the positive control compound, NG-monomethyl-L-arginine.

Antibacterial activity of secondary metabolites isolated from Ficus aurata (Miq.) fruits

This research aimed to isolate chemical constituents from ethyl acetate and n-hexane fractions of Ficus aurata (Miq.) fruits and investigated their antibacterial activities. Chemical constituents were separated by using vacuum column chromatography, gravity column chromatography, and thin layer chromatography. The structures of the isolated compounds 3,4-dihydroxybenzoic acid (1) and β-sitosterol (2) were elucidated using various spectroscopic methods, including UV, IR, and NMR (1H-NMR, 13C-NMR, and DEPT). While, antibacterial activity was done by assay using Resazurin Microtiter Assay method. These 2 compounds reported as new constituents from F. aurata fruit. In addition, analysis of the bioassay showed that compound 1 had a notable antibacterial activity against gram negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATTC 27853), and gram-positive bacteria (Staphylococcus aureusATCC 23235) with the Minimum Inhibitory Concentration (MIC) value of 0.1563 µg/mL, and it indicated the same MIC as cefadroxil (positive control). Compound 2 has weak antibacterial activity compared to cefadroxil (positive control). The results found that Ficus aurata (Miq.) fruits metabolites have antibacterial activity and show potency as antibacterial agent. Different kinds of bacteria and assay could be needed to investigate and support its antibacterial activity in the future.

Aramatosides C and D, 2 Previously Undescribed Triterpene Glycosides Isolated From the Roots of Aralia armata

The 2 new oleanane-type triterpene glycosides, 23-hydroxyoleanolic acid-[28- O- β-D-glucopyranosyl]-3- O-{ β-D-glucopyranosyl-(1→2)-[ β-D-glucopyranosyl-(1→3)]- β-D-galactopyranoside}, (1) and oleanolic acid-[28- O- β-D-glucopyranosyl]-3- O-{ β-D-glucopyranosyl-(1→2)-[ β-D-glucopyranosyl-(1→3)]- β-D-galactopyranoside} (2) were isolated from the roots of Aralia armata. Their chemical structures were elucidated by using a combination of high resolution electrospray ionization mass spectrometry (HR-ESI-MS), 1 dimensional (1D), and 2 dimensional (2D) nuclear magnetic resonance spectral data, as well as by comparison with the previous literature. Compounds 1 and 2 displayed weak cytotoxic activity toward KB and HepG2 cell lines with IC50 values of 25.1 ± 1.2 and 23.7 ± 0.9 µM (for 1) and 29.5 ± 1.3 and 23.9 ± 0.7 µM (for 2), respectively, compared to that of the positive control compound, ellipticine (IC50: 1.3 ± 0.1 and 1.6 ± 0.1 µM, respectively) in in vitro assay.

Computational Screening of Natural Compounds for the Discovery of Potential Aromatase Inhibitors: A Promising Therapy for Estrogen-Dependent Breast Cancer

Aromatase plays a significant role in the progression of estrogen receptor-positive (ER-positive) breast cancer. The adverse side effects of currently used aromatase inhibitors (AIs) necessitate the development of new AIs that are more active, selective, and less toxic. This study used a computational approach to screen 503 natural compounds ZINC database against the aromatase active site. The best scoring hits ZINC69482055, ZINC69482510, and ZINC406719 exhibited strong binding with aromatase, with binding energy values of -8.45, -10.35, and -8.75 kcal/mol, respectively, which is comparatively higher than that of the control compound Anastrozole (-6.43 kcal/mol). Docking analysis showed that the selected hits interacted with the crucial residues of the aromatase active site. This study suggested that these compounds could be used as possible AIs in the cure of breast cancer. Hands-on bench work validation is needed to optimize these compounds as AIs.

Synergistic activities of binary accelerators in presence of magnesium oxide as a cure activator in the vulcanization of natural rubber

We describe the synergistic activities of binary vulcanizing accelerators in presence of magnesium oxide as cure activator in the vulcanization of natural rubber. Thiuram type tetramethyl thiuram disulfide (TMTD) and thiocarbamate type zinc dimethyl dithiocarbamate (ZDMC) accelerators in combination with dibenzothiazyl disulfide (MBTS) were investigated for the vulcanization of rubber. The cure, mechanical, and thermal properties of rubber vulcanizates were studied with magnesium oxide-based cure activator. Notable synergism in the delta torque, cross-link density, and mechanical properties was found when using binary accelerators with magnesium oxide. The zinc-containing thiocarbamate accelerator, ZDMC, showed better synergistic activity in presence of magnesium oxide than the non-zinc-based thiuram accelerator, TMTD. To find out the possibility of making a zinc-oxide-free natural rubber compound, a control compound was prepared with 5 phr of zinc oxide as a cure activator with the best evaluated binary accelerators system with magnesium oxide (3:6 millimolar ratio of ZDMC to MBTS). We also compared the curing and mechanical properties of carbon black-reinforced rubber with zinc oxide and magnesium oxide separately with this binary accelerators system. The results indicated that a completely zinc-oxide-free natural rubber compound was possible with comparable values in the mechanical properties, thermal properties and a higher rate of vulcanization.

Panabipinoside A and panabipinoside B, two new oleanane triterpenoid saponins from the roots of Panax bipinnatifidus with nitric oxide inhibitory activity

Panax bipinnatifidus belongs to the ginseng genus and it is used in traditional Vietnamese and Chinese medicine. Phytochemical studies of the roots of this plant led to the isolation of two new oleanane triterpenoid saponins, panabipinoside A and panabipinoside B, and three known compounds, ginsennoside Ro, 3- O- β-D-glucopyranosyl-(1→3)- β-glucuronopyranosyl oleanolic acid, and spinasaponin A 28- O-glucoside. Their structures are established by extensive spectroscopic analysis (IR, high-resolution electrospray ionization mass spectrometry, and nuclear magnetic resonance) and by comparison of the spectral data with those reported in the literature. The anti-inflammatory activity of the isolated compounds is evaluated by their inhibition of nitric oxide production in lipopolysaccharide stimulated RAW 264.7 cells. Compounds 2–5 showed inhibitory effects on nitric oxide production with IC50 values of 0.62 ± 0.09, 0.21 ± 0.04, 0.30 ± 0.03, and 0.45 ± 0.05 µg/mL, respectively, compared to value of 8.08 ± 0.09 µg/mL for the positive control compound, NG-monomethyl-L-arginine.