In Vitro Effect of Taraxacum officinale Leaf Aqueous Extract on the Interaction between ACE2 Cell Surface Receptor and SARS-CoV-2 Spike Protein D614 and Four Mutants

Inhibition of SARS-CoV-2-Induced NLRP3 Inflammasome-Mediated Lung Cell Inflammation by Triphala-Loaded Nanoparticle Targeting Spike Glycoprotein S1

The COVID-19 pandemic, caused by SARS-CoV-2, poses a significant global health threat. The spike glycoprotein S1 of the SARS-CoV-2 virus is known to induce the production of pro-inflammatory mediators, contributing to hyperinflammation in COVID-19 patients. Triphala, an ancient Ayurvedic remedy composed of dried fruits from three plant species-Emblica officinalis (Family Euphorbiaceae), Terminalia bellerica (Family Combretaceae), and Terminalia chebula (Family Combretaceae)-shows promise in addressing inflammation. However, the limited water solubility of its ethanolic extract impedes its bioavailability. In this study, we aimed to develop nanoparticles loaded with Triphala extract, termed "nanotriphala", as a drug delivery system. Additionally, we investigated the in vitro anti-inflammatory properties of nanotriphala and its major compounds, namely gallic acid, chebulagic acid, and chebulinic acid, in lung epithelial cells (A549) induced by CoV2-SP. The nanotriphala formulation was prepared using the solvent displacement method. The encapsulation efficiency of Triphala in nanotriphala was determined to be 87.96 ± 2.60% based on total phenolic content. In terms of in vitro release, nanotriphala exhibited a biphasic release profile with zero-order kinetics over 0-8 h. A549 cells were treated with nanotriphala or its active compounds and then induced with 100 ng/mL of spike S1 subunit (CoV2-SP). The results demonstrate that chebulagic acid and chebulinic acid are the active compounds in nanotriphala, which significantly reduced cytokine release (IL-6, IL-1β, and IL-18) and suppressed the expression of inflammatory genes (IL-6, IL-1β, IL-18, and NLRP3) (p < 0.05). Mechanistically, nanotriphala and its active compounds notably attenuated the expression of inflammasome machinery proteins (NLRP3, ASC, and Caspase-1) (p < 0.05). In conclusion, the nanoparticle formulation of Triphala enhances its stability and exhibits anti-inflammatory properties against CoV2-SP-induction. This was achieved by suppressing inflammatory mediators and the NLRP3 inflammasome machinery. Thus, nanotriphala holds promise as a supportive preventive anti-inflammatory therapy for COVID-19-related chronic inflammation.

Dandelion root extracts and taraxasterol inhibit LPS‑induced colorectal cancer cell viability by blocking TLR4‑NFκB‑driven ACE2 and TMPRSS2 pathways

Colorectal cancer is the fourth leading cause of cancer-related death worldwide. Notably, abnormalities in intestinal bacteria may contribute to the initiation or progression of colorectal cancer. Lipopolysaccharide (LPS), a bacterial endotoxin, is elevated in patients with colorectal cancer. The present study investigated the protective effects of dandelion root extracts and taraxasterol (TS; a major pharmacologically active compound in dandelion root extracts) on LPS-induced colorectal cancer cell viability, as well as the underlying mechanisms. Cell viability was assessed by MTT assay, and protein and gene expression levels were determined by western blotting and quantitative PCR. It was revealed that LPS at a low dose (0.5 µg/ml) significantly promoted the viability of human colorectal cancer cells but did not affect normal colon epithelial cells. The addition of dandelion root extracts (0.1-1 mg/ml) or TS (0.05-1 µg/ml) was able to reverse the LPS-induced increase in colorectal cancer cell viability and colony formation. Mechanistically, dandelion root extracts or TS may inhibit the LPS-promoted toll-like receptor 4 (TLR4)/NFκB-p65 pathway and transcription levels of pro-inflammatory genes (TNFα, IL4 and IL6). Compared with normal colon epithelial cells, human colorectal cancer cells had higher expression levels of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), which could be further enhanced by LPS treatment but this was reversed by co-incubation with dandelion root extracts or TS. In addition, suppression of the TLR4/NFκB-p65 pathway with CLI095 significantly reversed the stimulatory effect of LPS on the expression levels of ACE2 and TMPRSS2, whereas TNFα (10 ng/ml) markedly induced the expression levels of ACE2 and TMPRSS2. In conclusion, the present study suggested that dandelion root extracts and TS could be used as prevention strategies for reversing bacteria-driven colorectal cancer cell viability.

Plant-derived compounds as potential leads for new drug development targeting COVID-19

COVID-19, which was first identified in 2019 in Wuhan, China, is a respiratory illness caused by a virus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although some patients infected with COVID-19 can remain asymptomatic, most experience a range of symptoms that can be mild to severe. Common symptoms include fever, cough, shortness of breath, fatigue, loss of taste or smell and muscle aches. In severe cases, complications can arise including pneumonia, acute respiratory distress syndrome, organ failure and even death, particularly in older adults or individuals with underlying health conditions. Treatments for COVID-19 include remdesivir, which has been authorised for emergency use in some countries, and dexamethasone, a corticosteroid used to reduce inflammation in severe cases. Biological drugs including monoclonal antibodies, such as casirivimab and imdevimab, have also been authorised for emergency use in certain situations. While these treatments have improved the outcome for many patients, there is still an urgent need for new treatments. Medicinal plants have long served as a valuable source of new drug leads and may serve as a valuable resource in the development of COVID-19 treatments due to their broad-spectrum antiviral activity. To date, various medicinal plant extracts have been studied for their cellular and molecular interactions, with some demonstrating anti-SARS-CoV-2 activity in vitro. This review explores the evaluation and potential therapeutic applications of these plants against SARS-CoV-2. This review summarises the latest evidence on the activity of different plant extracts and their isolated bioactive compounds against SARS-CoV-2, with a focus on the application of plant-derived compounds in animal models and in human studies.

Treating COVID-19 with Medicinal Plants: Is It Even Conceivable? A Comprehensive Review

In 2020, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) challenged the world with a global outbreak that led to millions of deaths worldwide. Coronavirus disease 2019 (COVID-19) is the symptomatic manifestation of this virus, which can range from flu-like symptoms to utter clinical complications and even death. Since there was no clear medicine that could tackle this infection or lower its complications with minimal adverse effects on the patients' health, the world health organization (WHO) developed awareness programs to lower the infection rate and limit the fast spread of this virus. Although vaccines have been developed as preventative tools, people still prefer going back to traditional herbal medicine, which provides remarkable health benefits that can either prevent the viral infection or limit the progression of severe symptoms through different mechanistic pathways with relatively insignificant side effects. This comprehensive review provides scientific evidence elucidating the effect of 10 different plants against SARS-CoV-2, paving the way for further studies to reconsider plant-based extracts, rich in bioactive compounds, into more advanced clinical assessments in order to identify their impact on patients suffering from COVID-19.

Taraxacum: A Review of Ethnopharmacology, Phytochemistry and Pharmacological Activity

Taraxacum refers to the genus Taraxacum, which has a long history of use as a medicinal plant and is widely distributed around the world. There are over 2500 species in the genus Taraxacum recorded as medicinal plants in China, Central Asia, Europe, and the Americas. It has traditionally been used for detoxification, diuresis, liver protection, the treatment of various inflammations, antimicrobial properties, and so on. We used the most typically reported Taraxacum officinale as an example and assembled its chemical makeup, including sesquiterpene, triterpene, steroids, flavone, sugar and its derivatives, phenolic acids, fatty acids, and other compounds, which are also the material basis for its pharmacological effects. Pharmacological investigations have revealed that Taraxacum crude extracts and chemical compounds contain antimicrobial infection, anti-inflammatory, antitumor, anti-oxidative, liver protective, and blood sugar and blood lipid management properties. These findings adequately confirm the previously described traditional uses and aid in explaining its therapeutic applications.

Strategies for the Management of Spike Protein-Related Pathology

In the wake of the COVID-19 crisis, a need has arisen to prevent and treat two related conditions, COVID-19 vaccine injury and long COVID-19, both of which can trace at least part of their aetiology to the spike protein, which can cause harm through several mechanisms. One significant mechanism of harm is vascular, and it is mediated by the spike protein, a common element of the COVID-19 illness, and it is related to receiving a COVID-19 vaccine. Given the significant number of people experiencing these two related conditions, it is imperative to develop treatment protocols, as well as to consider the diversity of people experiencing long COVID-19 and vaccine injury. This review summarizes the known treatment options for long COVID-19 and vaccine injury, their mechanisms, and their evidentiary basis.

Chemical Composition of Honeysuckle (Lonicerae japonicae) Extracts and Their Potential in Inhibiting the SARS-CoV-2 Spike Protein and ACE2 Binding, Suppressing ACE2, and Scavenging Radicals

Honeysuckle (Lonicerae japonicae) has been used in functional tea products. The chemical compositions of the water and ethanol extracts of honeysuckle were examined in the present study, along with their potential in inhibiting SARS-CoV-2 spike protein binding to ACE2, suppressing ACE2 activity, and scavenging reactive free radicals. Thirty-six compounds were tentatively identified from the honeysuckle extracts using HPLC-MS/MS, with ten reported for the first time in honeysuckle. Both honeysuckle extracts inhibited the binding of SARS-CoV-2 spike protein to ACE2, as well as ACE2 activity. The ethanol extract exhibited a 100% inhibition on binding of the SARS-CoV-2 spike protein to ACE2 at 100 mg botanical equivalent/mL, whereas the water extract had a 65% binding inhibition at the same concentration. Furthermore, the water extract exhibited 90% ACE2 activity inhibition, which was stronger than that of the ethanol extract (62% inhibition) at the same botanical weight concentration. In addition, higher total phenolic contents and greater scavenging activities against hydroxyl (HO•), DPPH•, and ABTS•+ radicals were observed in the water extract than the ethanol extract counterpart on a dry botanical weight concentration basis. These findings suggest honeysuckle has the potential to reduce the risk of SARS-CoV-2 infection and the development of severe COVID-19 symptoms.

Plant Extracts and SARS-CoV-2: Research and Applications

The recent pandemic of COVID-19 caused by the SARS-CoV-2 virus has brought upon the world an unprecedented challenge. During its acute dissemination, a rush for vaccines started, making the scientific community come together and contribute to the development of efficient therapeutic agents and vaccines. Natural products have been used as sources of individual molecules and extracts capable of inhibiting/neutralizing several microorganisms, including viruses. Natural extracts have shown effective results against the coronavirus family, when first tested in the outbreak of SARS-CoV-1, back in 2002. In this review, the relationship between natural extracts and SARS-CoV is discussed, while also providing insight into misinformation regarding the use of plants as possible therapeutic agents. Studies with plant extracts on coronaviruses are presented, as well as the main inhibition assays and trends for the future regarding the yet unknown long-lasting effects post-infection with SARS-CoV-2.

Chemical Compositions of Clove (Syzygium aromaticum (L.) Merr. & L.) Extracts and Their Potentials in Suppressing SARS-CoV-2 Spike Protein-ACE2 Binding, Inhibiting ACE2, and Scavenging Free Radicals

COVID-19 is initiated by binding the SARS-CoV-2 spike protein to angiotensin-converting enzyme 2 (ACE2) on host cells. Food factors capable of suppressing the binding between the SARS-CoV-2 spike protein and ACE2 or reducing the ACE2 availability through ACE2 inhibitions may potentially reduce the risk of SARS-CoV-2 infection and COVID-19. In this study, the chemical compositions of clove water and ethanol extracts were investigated, along with their potentials in suppressing SARS-CoV-2 spike protein-ACE2 binding, reducing ACE2 availability, and scavenging free radicals. Thirty-four compounds were tentatively identified in the clove water and ethanol extracts, with six reported in clove for the first time. Clove water and ethanol extracts dose-dependently suppressed SARS-CoV-2 spike protein binding to ACE2 and inhibited ACE2 activity. The water extract had stronger inhibitory effects than the ethanol extract on a dry weight basis. The clove water extract also had more potent free radical scavenging activities against DPPH^• and ABTS^•+ (536.9 and 3525.06 μmol TE/g, respectively) than the ethanol extract (58.44 and 2298.01 μmol TE/g, respectively). In contrast, the ethanol extract had greater total phenolic content (TPC) and relative HO^• scavenging capacity (HOSC) values (180.03 mg GAE/g and 2181.08 μmol TE/g, respectively) than the water extract (120.12 mg GAE/g and 1483.02 μmol TE/g, respectively). The present study demonstrated the potential of clove in reducing the risk of SARS-CoV-2 infection and COVID-19 development.

DNA aptamers inhibit SARS-CoV-2 spike-protein binding to hACE2 by an RBD- independent or dependent approach

Objective: Nobody knows when the COVID-19 pandemic will end or when and where the next coronavirus will outbreak. Therefore, it is still necessary to develop SARS-CoV-2 inhibitors for different variants or even the new coronavirus. Since SARS-CoV-2 uses its surface spike-protein to recognize hACE2, mediating its entry into cells, ligands that can specifically recognize the spike-protein have the potential to prevent infection. Methods: We have recently discovered DNA aptamers against the S2-domain of the WT spike-protein by exploiting the selection process called SELEX. After optimization, among all candidates, the aptamer S2A2C1 has the shortest sequence and the best binding affinity toward the S2-protein. More importantly, the S2A2C1 aptamer does not bind to the RBD of the spike-protein, but it efficiently blocks the spike-protein/hACE2 interaction, suggesting an RBD-independent inhibition approach. To further improve its performance, we conjugated the S2A2C1 aptamer with a reported anti-RBD aptamer, S1B6C3, using various linkers and constructed hetero-bivalent fusion aptamers. Binding affinities of mono and fusion aptamers against the spike-proteins were measured. The inhibition efficacies of mono and fusion aptamers to prevent the hACE2/spike-protein interaction were determined using ELISA. Results: Anti-spike-protein aptamers, including S2A2C1 and S1B6C3-A5-S2A2C1, maintained high binding affinity toward the WT, Delta, and Omicron spike-proteins and high inhibition efficacies to prevent them from binding to hACE2, rendering them well-suited as diagnostic and therapeutic molecular tools to target SARS-CoV-2 and its variants. Conclusions: Overall, we discovered the anti-S2 aptamer, S2A2C1, which inhibits the hACE2/spike-protein interaction via an RBD-independent approach. The anti-S2 and anti-RBD aptamers were conjugated to obtain the fusion aptamer, S1B6C3-A5-S2A2C1, which recognizes the spike-protein by an RBD-dependent approach. Our strategies, which discovered aptamer inhibitors targeting the highly conserved S2-protein, as well as the design of fusion aptamers, can be used to target new coronaviruses as they emerge.

A Newly Engineered A549 Cell Line Expressing ACE2 and TMPRSS2 Is Highly Permissive to SARS-CoV-2, Including the Delta and Omicron Variants

New variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to emerge, causing surges, breakthrough infections, and devastating losses—underscoring the importance of identifying SARS-CoV-2 antivirals. A simple, accessible human cell culture model permissive to SARS-CoV-2 variants is critical for identifying and assessing antivirals in a high-throughput manner. Although human alveolar A549 cells are a valuable model for studying respiratory virus infections, they lack two essential host factors for SARS-CoV-2 infection: angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2). SARS-CoV-2 uses the ACE2 receptor for viral entry and TMPRSS2 to prime the SARS-CoV-2 spike protein, both of which are negligibly expressed in A549 cells. Here, we report the generation of a suitable human cell line for SARS-CoV-2 studies by transducing human ACE2 and TMPRSS2 into A549 cells. We show that subclones highly expressing ACE2 and TMPRSS2 (“ACE2plus” and the subclone “ACE2plusC3”) are susceptible to infection with SARS-CoV-2, including the delta and omicron variants. These subclones express more ACE2 and TMPRSS2 transcripts than existing commercial A549 cells engineered to express ACE2 and TMPRSS2. Additionally, the antiviral drugs EIDD-1931, remdesivir, nirmatrelvir, and nelfinavir strongly inhibit SARS-CoV-2 variants in our infection model. Our data show that ACE2plusC3 cells are highly permissive to SARS-CoV-2 infection and can be used to identify anti-SARS-CoV-2 drugs.

Discovery of diminazene as a dual inhibitor of SARS-CoV-2 human host proteases TMPRSS2 and furin using cell-based assays

The proteases TMPRSS2 (transmembrane protease serine 2) and furin are known to play important roles in viral infectivity including systematic COVID-19 infection through priming of the spike protein of SARS-CoV-2 and related viruses. To discover small-molecules capable of inhibiting these host proteases, we established convenient and cost-effective cell-based assays employing Vero cells overexpressing TMPRSS2 and furin. A cell-based proteolytic assay for broad-spectrum protease inhibitors was also established using human prostate cancer cell line LNCaP. Evaluation of camostat, nafamostat, and gabexate in these cell-based assays confirmed their known TMPRSS2 inhibitory activities. Diminazene, a veterinary medicinal agent and a known furin inhibitor was found to inhibit both TMPRSS2 and furin with IC₅₀s of 1.35 and 13.2 μM, respectively. Establishment and the use of cell-based assays for evaluation TMPRSS2 and furin inhibitory activity and implications of dual activity of diminazene vs TMPRSS2 and furin are presented.