Mulberry Component Kuwanon C Exerts Potent Therapeutic Efficacy In Vitro against COVID-19 by Blocking the SARS-CoV-2 Spike S1 RBD:ACE2 Receptor Interaction.

There has been an immense effort by global pharmaceutical companies to develop anti-COVID-19 drugs, including small molecule-based RNA replication inhibitors via drug repositioning and antibody-based spike protein blockers related to cell entry by SARS-CoV-2. However, several limitations to their clinical use have emerged in addition to a lack of progress in the development of small molecule-based cell entry inhibitors from natural products. In this study, we tested the effectiveness of kuwanon C (KC), which has mainly been researched using in silico docking simulation and can serve as an effective building block for developing anti-COVID-19 drugs, in blocking the spike S1 RBD:ACE2 receptor interaction. KC is a natural product derived from Morus alba L., commonly known as mulberry, which has known antiviral efficacy. Molecular interaction studies using competitive ELISA and the BLItz system revealed that KC targets both the spike S1 RBD and the ACE2 receptor, successfully disrupting their interaction, as supported by the in silico docking simulation. Furthermore, we established a mechanism of action by observing how KC prevents the infection of SARS-CoV-2 spike pseudotyped virus in ACE2/TPRSS2-overexpressing HEK293T cells. Finally, we demonstrated that KC inhibits clinical isolates of SARS-CoV-2 in Vero cells. Future combinations of small molecule-based cell entry inhibitors, such as KC, with the currently prescribed RNA replication inhibitors are anticipated to significantly enhance the efficacy of COVID-19 therapies.

Mulberrofuran G, a Mulberry Component, Prevents SARS-CoV-2 Infection by Blocking the Interaction between SARS-CoV-2 Spike Protein S1 Receptor-Binding Domain and Human Angiotensin-Converting Enzyme 2 Receptor.

Despite the recent development of RNA replication-targeted COVID-19 drugs by global pharmaceutical companies, their prescription in clinical practice is limited by certain factors, including drug interaction, reproductive toxicity, and drug resistance. COVID-19 drugs with multiple targets for the SARS-CoV-2 life cycle may lead to a successful reduction in drug resistance as well as enhanced therapeutic efficacy, and natural products are a potential source of molecules with therapeutic effects against COVID-19. In this study, we investigated the inhibitory efficacy of mulberrofuran G (MG), a component of Morus alba L., also known as mulberry, which has been used as food and traditional medicine, on the binding of the spike S1 receptor-binding domain (RBD) protein to the angiotensin-converting enzyme 2 (ACE2) receptor, which is the initial stage of the SARS-CoV-2 infection. In competitive enzyme-linked immunosorbent assays, MG effectively blocked the spike S1 RBD: ACE2 receptor molecular binding, and investigations using the BLItz system and in silico modeling revealed that MG has high affinity for both proteins. Finally, we confirmed that MG inhibits the entry of SARS-CoV-2 spike pseudotyped virus and a clinical isolate of SARS-CoV-2 into cells, suggesting that MG might be a promising therapeutic candidate for preventing SARS-CoV-2 binding to the cell surface during early infection.

Inhibitory effects and mechanisms of the anti-covid-19 traditional Chinese prescription, Keguan-1, on acute lung injury.

ETHNOPHARMACOLOGICAL RELEVANCE: Keguan-1, a new traditional Chinese medicine (TCM) prescription contained seven Chinese herbs, is developed to treat coronavirus disease 19 (COVID-19). The first internationally registered COVID-19 randomised clinical trial on integrated therapy demonstrated that Keguan-1 significantly reduced the incidence of ARDS and inhibited the severe progression of COVID-19. AIM OF THE STUDY: To investigate the protective mechanism of Keguan-1 on ARDS, a lipopolysaccharide (LPS)-induced acute lung injury (ALI) model was used to simulate the pathological state of ARDS in patients with COVID-19, focusing on its effect and mechanism on ALI. MATERIALS AND METHODS: Mice were challenged with LPS (2 mg/kg) by intratracheal instillation (i.t.) and were orally administered Keguan-1 (low dose, 1.25 g/kg; medium dose, 2.5 g/kg; high dose, 5 g/kg) after 2 h. Bronchoalveolar lavage fluid (BALF) and lung tissue were collected 6 h and 24 h after i.t. administration of LPS. The levels of inflammatory factors tumour necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1ß, keratinocyte-derived chemokine (KC or mCXCL1), macrophage inflammatory protein 2 (MIP2 or mCXCL2), angiotensin II (Ang II), and endothelial cell junction-associated proteins were analysed using ELISA or western blotting. RESULTS: Keguan-1 improved the survival rate, respiratory condition, and pathological lung injury; decreased the production of proinflammatory factors (TNF-α, IL-6, IL-1ß, KC, and MIP2) in BALF and the number of neutrophils in the lung tissues; and ameliorated inflammatory injury in the lung tissues of the mice with LPS-induced ALI. Keguan-1 also reduced the expression of Ang II and the adhesion molecule ICAM-1; increased tight junction proteins (JAM-1 and claudin-5) and VE-cadherin expression; and alleviated pulmonary vascular endothelial injury in LPS-induced ALI. CONCLUSION: These results demonstrate that Keguan-1 can improve LPS-induced ALI by reducing inflammation and pulmonary vascular endothelial injury, providing scientific support for the clinical treatment of patients with COVID-19. Moreover, it also provides a theoretical basis and technical support for the scientific use of TCMs in emerging infectious diseases.

Advances on Antiviral Activity of Morus spp. Plant Extracts: Human Coronavirus and Virus-Related Respiratory Tract Infections in the Spotlight.

(1) Background: Viral respiratory infections cause life-threatening diseases in millions of people worldwide every year. Human coronavirus and several picornaviruses are responsible for worldwide epidemic outbreaks, thus representing a heavy burden to their hosts. In the absence of specific treatments for human viral infections, natural products offer an alternative in terms of innovative drug therapies. (2) Methods: We analyzed the antiviral properties of the leaves and stem bark of the mulberry tree (Morus spp.). We compared the antiviral activity of Morus spp. on enveloped and nonenveloped viral pathogens, such as human coronavirus (HCoV 229E) and different members of the Picornaviridae family-human poliovirus 1, human parechovirus 1 and 3, and human echovirus 11. The antiviral activity of 12 water and water-alcohol plant extracts of the leaves and stem bark of three different species of mulberry-Morus alba var. alba, Morus alba var. rosa, and Morus rubra-were evaluated. We also evaluated the antiviral activities of kuwanon G against HCoV-229E. (3) Results: Our results showed that several extracts reduced the viral titer and cytopathogenic effects (CPE). Leaves' water-alcohol extracts exhibited maximum antiviral activity on human coronavirus, while stem bark and leaves' water and water-alcohol extracts were the most effective on picornaviruses. (4) Conclusions: The analysis of the antiviral activities of Morus spp. offer promising applications in antiviral strategies.

The Positive Modulation Effect of a 6-Week Consumption of an Anthocyanin-Rich Mulberry Milk on Working Memory, Cholinergic, and Monoaminergic Functions in Healthy Working-Age Adults.

Due to the increase of stress-related memory impairment accompanying with the COVID-19 pandemic and financial crisis, the prevention of cognitive decline induced by stress has gained much attention. Based on the evidence that an anthocyanin-rich mulberry milk demonstrated the cognitive enhancing effect, we hypothesized that it should be able to enhance memory in working-age volunteers who are exposed to working stress. This study is an open-label, two-arm randomized study. Both men and women volunteers at age between 18 and 60 years old were randomly assigned to consume the tested product either 1 or 2 servings daily for 6 weeks. All subjects were assessed for cortisol, acetylcholinesterase (AChE), monoamine oxidase (MAO), monoamine oxidase type A (MAO-A), and monoamine oxidase type B (MAO-B) in saliva, and their working memory was determined both at baseline and at a 6-week period. The results showed that the working memory of subjects in both groups was enhanced at the end of the study period together with the reduction of saliva cortisol. The suppression of AChE, MAO, and MAO-A was also observed in subjects who consumed the tested product 2 servings daily. Therefore, we suggest the memory enhancing effect of an anthocyanin-rich mulberry milk. The possible mechanism may occur primarily via the suppression of cortisol. In addition, the high dose of mulberry milk also suppresses AChE, MAO, and MAO-A.

A combined network pharmacology and molecular biology approach to investigate the active ingredients and potential mechanisms of mulberry (Morus alba L.) leaf on obesity.

BACKGROUND: As one of traditional Chinese medicine, mulberry leaf is abundant in diverse active ingredients and widely used for the treatment of metabolic disease and its complications. However, there are a few of reports on its application in the prevention and treatment of obesity. And the molecular mechanism on the anti-obesity of mulberry leaf are unknown till now. PURPOSE: The present study aimed to evaluate the potential ingredients and targets of mulberry leaf and uncover the anti-obesity mechanisms by using the network pharmacology tactics and verify its effect by biological experiments. STUDY DESIGN: Active ingredients and key targets of mulberry leaf, genes related to obesity were screened through public database. Based on the results of network pharmacology, the flavonoids-enriched fraction of mulberry leaf (MLF) was extracted and composition of this fraction was identified. After that, HepG2 cells model of lipid accumulation was established for verifying the effect of MLF and related mechanisms. RESULTS: A total of 37 active ingredients in mulberry leaf, 192 predicted biological targets and 8813 obesity-related targets were determined, of which 180 overlapping targets might have obvious curative effects on obesity. The networks showed that mulberry leaf might play a role through key targets, such as AKT, MAPK and IL-6, and regulated PI3K-Akt signaling pathway. Based on HPLC-ESI-QQQ-MS analysis, 13 constituents of MLF were identified, including 9 flavonoids. Furthermore, HepG2 cells model of lipid accumulation was established. The results indicated that MLF treatment could down-regulate the secretion of inflammatory cytokines, as well as clearly inhibited lipid droplets formation and alleviated TC, TG, HDL-C and LDL-C levels. Positive effect was observed on hypolipidemic efficacy due to the regulation of PI3K/Akt/Bcl-xl pathway, as indicated by the amelioration of PI3K, Akt and Bcl-xl gene and protein expression. CONCLUSION: This study firstly systematically disclose the multi-ingredients, multi-targets mechanisms of mulberry leaf on obesity by using network pharmacology approach, and validate in HepG2 cells that the protective effect of MLF against obesity involved both inflammation response and lipid metabolism involving PI3K/Akt/Bcl-xl signaling pathway. It provides indications for further mechanistic research of mulberry leaf and also for the development as a potential candidate for the therapy for obese patients.

Pharmacoinformatics-based identification of transmembrane protease serine-2 inhibitors from Morus Alba as SARS-CoV-2 cell entry inhibitors.

Transmembrane protease serine-2 (TMPRSS2) is a cell-surface protein expressed by epithelial cells of specific tissues including those in the aerodigestive tract. It helps the entry of novel coronavirus (n-CoV) or Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in the host cell. Successful inhibition of the TMPRSS2 can be one of the crucial strategies to stop the SARS-CoV-2 infection. In the present study, a set of bioactive molecules from Morus alba Linn. were screened against the TMPRSS2 through two widely used molecular docking engines such as Autodock vina and Glide. Molecules having a higher binding affinity toward the TMPRSS2 compared to Camostat and Ambroxol were considered for in-silico pharmacokinetic analyses. Based on acceptable pharmacokinetic parameters and drug-likeness, finally, five molecules were found to be important for the TMPRSS2 inhibition. A number of bonding interactions in terms of hydrogen bond and hydrophobic interactions were observed between the proposed molecules and ligand-interacting amino acids of the TMPRSS2. The dynamic behavior and stability of best-docked complex between TRMPRSS2 and proposed molecules were assessed through molecular dynamics (MD) simulation. Several parameters from MD simulation have suggested the stability between the protein and ligands. Binding free energy of each molecule calculated through MM-GBSA approach from the MD simulation trajectory suggested strong affection toward the TMPRSS2. Hence, proposed molecules might be crucial chemical components for the TMPRSS2 inhibition.

Improvement of stilbene production by mulberry Morus alba root culture via precursor feeding and co-elicitation.

Large amounts of Morus alba L. (MA) roots are needed as the source of active stilbenes in the industrial production of traditional medicines and cosmeceuticals. A recent investigation demonstrated resveratrol and its derivatives to be promising anti-COVID-19 agents. However, conventional cultivation of MA does not meet the demand for its stilbenes, and root quality usually varies between crops. This study established the in vitro non-GMO root culture of MA and optimized the root density, precursor feeding, and elicitors for stilbene productivity. A root culture with optimal inoculum density (3 g/flask of 30 mL medium) accumulated mulberroside A, oxyresveratrol, and resveratrol at 18.7 ± 1.00 mg/g, 136 ± 5.05 µg/g, and 41.6 ± 5.84 µg/g dry weight (DW), respectively. The feeding of L-tyrosine shortened the time required to reach the stilbene productive stage. Root cultures co-treated with 200 µM methyl jasmonate and 2 mg/mL yeast extract accumulated the highest contents of mulberroside A (30.3 ± 2.68 mg/g DW), oxyresveratrol (68.6 ± 3.53 µg/g DW), and resveratrol (10.2 ± 0.53 µg/g DW). In summary, root culture is a promising and sustainable source of stilbenes for the development of health products and agents for further investigation as potential anti-COVID-19 agents.