Myrtucommulones and Related Acylphloroglucinols from Myrtaceae as a Promising Source of Multitarget SARS-CoV-2 Cycle Inhibitors.

The LABEXTRACT plant extract bank, featuring diverse members of the Myrtaceae family from Brazilian hot spot regions, provides a promising avenue for bioprospection. Given the pivotal roles of the Spike protein and 3CLpro and PLpro proteases in SARS-CoV-2 infection, this study delves into the correlations between the Myrtaceae species from the Atlantic Forest and these targets, as well as an antiviral activity through both in vitro and in silico analyses. The results uncovered notable inhibitory effects, with Eugenia prasina and E. mosenii standing out, while E. mosenii proved to be multitarget, presenting inhibition values above 72% in the three targets analyzed. All extracts inhibited viral replication in Calu-3 cells (EC50 was lower than 8.3 µg·mL-1). Chemometric analyses, through LC-MS/MS, encompassing prediction models and molecular networking, identified potential active compounds, such as myrtucommulones, described in the literature for their antiviral activity. Docking analyses showed that one undescribed myrtucommulone (m/z 841 [M - H]-) had a higher fitness score when interacting with the targets of this study, including ACE2, Spike, PLpro and 3CLpro of SARS-CoV-2. Also, the study concludes that Myrtaceae extracts, particularly from E. mosenii and E. prasina, exhibit promising inhibitory effects against crucial stages in SARS-CoV-2 infection. Compounds like myrtucommulones emerge as potential anti-SARS-CoV-2 agents, warranting further exploration.

Bactericidal and anti-inflammatory effects of Moquilea tomentosa Benth. flavonoid-rich leaf extract.

BACKGROUND: Natural products are an important source of bioproducts with pharmacological properties. Here we investigate the components of leaves from M. tomentosa Benth. (Fritsch) (Chrysobalanaceae) and its effects on bacterial cell growth, biofilm production and macrophage activity. METHODS: The effect of the different leaf extracts against bacterial cell growth was performed using the microdilution method. The most active extract was analyzed by mass spectrometry, and its effect on bacterial biofilm production was evaluated on polystyrene plates. The extract effect on macrophage activity was tested in the RAW264.7 cell line, which was stimulated with different concentrations of the extract in the presence or absence of LPS. RESULTS: We show that the ethyl acetate (EtOAc) extract was the most effective against bacterial cell growth. EtOAc extract DI-ESI (-)MSn analysis showed the presence of a glycosylated flavonoid tentatively assigned as myricetin 3-O-xylosyl-rhamnoside (MW 596). Also, the EtOAc extract increased biofilm formation by S. aureus and inhibited cytokine and NO production induced by LPS in RAW macrophages. CONCLUSION: M. tomentosa flavonoid-enriched EtOAc extract presented a bactericidal and anti-inflammatory pharmacological potential.

Anti-SARS-CoV-2 Activity of Ampelozizyphus amazonicus (Saracura-Mirá): Focus on the Modulation of the Spike-ACE2 Interaction by Chemically Characterized Bark Extracts by LC-DAD-APCI-MS/MS.

Traditional medicine shows several treatment protocols for COVID-19 based on natural products, revealing its potential as a possible source of anti-SARS-CoV-2 agents. Ampelozizyphus amazonicus is popularly used in the Brazilian Amazon as a fortifier and tonic, and recently, it has been reported to relieve COVID-19 symptoms. This work aimed to investigate the antiviral potential of A. amazonicus, focusing on the inhibition of spike and ACE2 receptor interaction, a key step in successful infection. Although saponins are the major compounds of this plant and often reported as its active principles, a polyphenol-rich extract was the best inhibitor of the spike and ACE2 interaction. Chemical characterization of A. amazonicus bark extracts by LC-DAD-APCI-MS/MS before and after clean-up steps for polyphenol removal showed that the latter play an essential role in maintaining this activity. The effects of the extracts on viral replication were also assessed, and all samples (aqueous and ethanol extracts) demonstrated in vitro activity, inhibiting viral titers in the supernatant of Calu-3 cells after 24 hpi. By acting both in the SARS-CoV-2 cell entry process and its replication, A. amazonicus bark extracts stand out as a multitarget agent, highlighting the species as a promising candidate in the development of anti-SARS-CoV-2 drugs.

In silico screening of phenylethanoid glycosides, a class of pharmacologically active compounds as natural inhibitors of SARS-CoV-2 proteases.

Since the advent of Covid-19, several natural products have been investigated regarding their in silico interactions with SARS-CoV-2 proteases - 3CLpro and PLpro, two of the most important pharmacological targets for antiviral development. Phenylethanoid glycosides (PG) are a class of natural products present in important medicinal plants and a drug containing this group of active ingredients has been successfully used in the treatment of Covid-19 in China. Thus, a dataset with 567 derivatives of this class was built from reviews published between 1994 and 2020, and their interaction against both SARS-CoV-2 proteases was investigated. The virtual screening was performed by filtering the PGs through the evaluation of scores based on the AutoDock Vina, GOLD/ChemPLP, and GOLD/GoldScore evaluation functions. The bRO5 pharmacokinetic parameters of the PGs ranked in the previous step were analyzed and their interaction with key amino acid residues of the 3CLpro and PLpro enzymes was evaluated. Ninety-eight compounds were identified by computational approaches against PLpro and 80 PGs against 3CLpro. Of these, four interacted with key catalytic residues of PLpro, which is an indicative of inhibitory activity, and three compounds interacted with catalytic key residues of 3CLpro. Of these, five PGs occur in plants of the Traditional Chinese Medicine (TCM), while two are components of plants/formulations currently used in the Covid-19 protocols in China. The data presented here show the potential of PGs as selective inhibitors of SARS-CoV-2 3CLpro and PLpro.

A SARS-CoV-2 Negative Antigen Rapid Diagnostic in RT-qPCR Positive Samples Correlates With a Low Likelihood of Infectious Viruses in the Nasopharynx.

Severe acute respiratory syndrome-related coronavirus (SARS-CoV-2) transmission occurs even among fully vaccinated individuals; thus, prompt identification of infected patients is central to control viral circulation. Antigen rapid diagnostic tests (Ag-RDTs) are highly specific, but sensitivity is variable. Discordant RT-qPCR vs. Ag-RDT results are reported, raising the question of whether negative Ag-RDT in positive RT-qPCR samples could imply the absence of infectious viruses. To study the relationship between negative Ag-RDT results with virological, molecular, and serological parameters, we selected a cross-sectional and a follow-up dataset and analyzed virus culture, subgenomic RNA quantification, and sequencing to determine infectious viruses and mutations. We demonstrated that RT-qPCR positive while SARS-CoV-2 Ag-RDT negative discordant results correlate with the absence of infectious virus in nasopharyngeal samples. A decrease in sgRNA detection together with an expected increase in detectable anti-S and anti-N IgGs was also verified in these samples. The data clearly demonstrate that a negative Ag-RDT sample is less likely to harbor infectious SARS-CoV-2 and, consequently, has a lower transmissible potential.

Amazonian Siparuna extracts as potential anti-influenza agents: Metabolic fingerprinting.

ETHNOPHARMACOLOGICAL RELEVANCE: Siparuna species are used in Brazilian Folk Medicine for the treatment and prophylaxis of colds, fever, headache, gastrointestinal disorders and rheumatic pain. AIM OF THE STUDY: This study aimed to investigate a possible anti-influenza activity of 25 extracts from leaves of Amazonian S. cristata, S. decipiens, S. glycycarpa, S. reginae and S. sarmentosa based on their folk medicinal uses as well as to investigate their metabolic fingerprinting. The chemical composition of the active extracts was further dereplicated. MATERIAL AND METHODS: The chemical composition of the crude EtOH extracts from five Siparuna species were investigated by ESI (±) LC-QTOF-MS2. Organic extracts were obtained by liquid-liquid partition with solvents of increasing polarity, generating 25 extracts which were subjected to a quick DI-ESI (±) IT-MS fingerprint analysis. These extracts were tested against influenza virus replication and cellular toxicity using MDCK cells and influenza A/Michigan/45/2015 (H1N1)pdm09 virus. The compounds in the active BuOH extracts from S. glycycarpa and S. sarmentosa were annotated by ESI (±) LC-QTOF-MS2. RESULTS: Analysis of the EtOH extracts revealed the presence of alkaloids and flavonoids, in the positive and negative ionization modes. Out of the 25 organic extracts screened for their antiviral activity, the BuOH extracts from S. glycycarpa and S. sarmentosa were the most active, inhibiting 96.0 ± 1.3% and 89.5 ± 0.8% of influenza virus replication 24 h post-infection. These inhibitory effects were maintained until 72hpi. Alkaloids, O- and C-flavonoid glycosides, dihydrochalcones and a procyanidin dimer were annotated in these extracts. CONCLUSIONS: The inhibitory effect against influenza A(H1N1)pdm09 virus replication shown by Amazonian Siparuna species corroborates the use of these plants in Brazilian Folk Medicine, showing their potential as anti-influenza agents. These promising results stimulate the continuation of this study with the aim of isolating the compound(s) responsible for this bioactivity, thus contributing to a better knowledge of those species and to the research of natural products with potential anti-influenza activity.