Comparative Anti-Inflammatory Effects of Salix Cortex Extracts and Acetylsalicylic Acid in SARS-CoV-2 Peptide and LPS-Activated Human In Vitro Systems

Green Synthesis and Characterization of Silver Nanoparticles Using Anchusa Officinalis: Antimicrobial and Cytotoxic Potential

Objective

Anchusa officinalis L. (A. officinalis) is a herbaceous traditional medicinal plant used in the treatment of some diseases. The presence of its medicinal properties suggested that A. officinalis (AO) leaf extract could be used as a coating agent for the environmentally friendly production of silver nanoparticles (AgNPs).

Methods

The synthesized biogenic silver nanoparticles (AO-AgNPs) were characterized using different techniques. The antimicrobial activity of AgNPs against common bacterial pathogenic strains was determined by the minimum inhibitory concentration (MIC) method. The presence of phytochemicals was determined by LSMS/MS. The MTT assay was used to investigate AO-AgNPs' cytotoxic activity in malignant (LnCap, Caco2, MDA-MB2, A549) and healthy (HEK-293) cell lines.

Results

LC-MS/MS analysis detected the presence of rich phytochemicals that may be responsible for reduction reactions. Biogenic AO-AgNPs exhibited effective inhibition of the growth of pathogenic microorganisms at low concentrations. The most effective antimicrobial activity was measured as 0.5 µg/mL MIC against S. aureus, E. coli, and C. albicans. Moreover, AO-AgNPs showed significant inhibition on the growth of cancerous cell lines, especially at a concentration of 25 μg/mL. On the contrary, it was determined that the inhibition rate decreased in the growth of healthy cell lines due to the increase in concentration. The lowest EC50 values were determined as 15.15 µg/mL in A549 cells.

Conclusion

The obtained results showed that AO could be an important source for the synthesis of AgNPs. Especially their ability to inhibit the growth of antibiotic-resistant pathogenic bacteria at low concentrations compared to common antibiotics indicates that AO-AgNPs can be used as biomedical agents in various areas. Moreover, their suppressive effect on cancerous cell lines showed that they have the potential to be used as an anticancer agent, but due to their proliferative effect on healthy cell lines, care should be taken in determining the appropriate dose.

Potential skin anti-aging effects of main phenolic compounds, tremulacin and tremuloidin from Salix chaenomeloides leaves on TNF-α-stimulated human dermal fibroblasts

The genus Salix spp. has long been recognized as a healing herb for its use in treating fever, inflammation, and pain relief, as well as a food source for its nutritional value. In this study, we aimed to explore the potential bioactive natural products in the leaves of Salix chaenomeloides, commonly known as Korean pussy willow, for their protective effects against skin damage, including aging. Utilizing LC/MS-guided chemical analysis of the ethanol extract of S. chaenomeloides leaves, with a focus on major compounds, we successfully isolated two main phenolic compounds, tremulacin (1) and tremuloidin (2). Subsequently, we investigated the protective effects of tremulacin (1) and tremuloidin (2) in TNF-α-stimulated human dermal fibroblasts (HDFs). The results revealed that both tremulacin (1) and tremuloidin (2) inhibited TNF-α-stimulation-induced ROS, suppressed matrix metalloproteinase-1 (MMP-1) expression, and enhanced collagen secretion. This implies that both tremulacin (1) and tremuloidin (2) hold promise as preventive agents against photoaging-induced skin aging. Furthermore, we assessed the activity of mitogen-activated protein kinases (MAPKs), cyclooxygenase-2 (COX-2), and heme oxygenase 1 (HO-1) to elucidate the mechanism of photoaging inhibition by tremuloidin (2), which exhibited superior efficacy. We found that tremuloidin (2) inhibited ERK and p38 phosphorylation and notably suppressed COX-2 expression while significantly upregulating HO-1 expression. These findings suggest potent anti-inflammatory and antioxidant properties of tremuloidin (2), positioning it as a potential candidate for combating photoaging-induced skin aging.

Boosting the anti-tumor activity of natural killer cells by caripe 8 - A Carapichea ipecacuanha isolated cyclotide

Cyclotides are head-to-tail cyclized peptides with a unique cystine-knot motif. Their structure provides exceptional resistance against enzymatic, chemical, or thermal degradation compared to other peptides. Peptide-based therapeutics promise high specificity, selectivity and lower immunogenicity, making them safer alternatives to small molecules or large biologicals. Cyclotides were researched due to their anti-cancer properties by inducing apoptosis in tumor cells in the past, but the impact of cyclotides on cytotoxic immune cells was poorly studied. Natural Killer (NK) cells are cytotoxic innate lymphoid cells and play an important role in the defense against infected, stressed and transformed cells. NK cells do not need prior sensitization and act in an antigen independent manner, holding promising potential in the field of immunotherapy. To investigate the effect of immunomodulatory cyclotides on NK cells, we evaluated several peptide-enriched plant extracts on NK cell mediated cytotoxicity. We observed that the extract samples derived from Carapichea ipecacuanha (Brot.) L. Andersson augments the killing potential of mouse NK cells against different tumor targets in vitro. Subsequent isolation of cyclotides from C. ipecacuanha extracts led to the identification of a primary candidate that enhances cytotoxicity of both mouse and human NK cells. The augmented killing is facilitated by the increased degranulation capacity of NK cells. In addition, we noted a direct toxic effect of caripe 8 on tumor cells, suggesting a dual therapeutic potential in cancer treatment. This study offers novel insights how natural peptides can influence NK cell cytotoxicity. These pre-clinical findings hold significant promise for advancing current immunotherapeutic approaches.

The in vitro intestinal cell model: different co-cultured cells create different applications

As a vitro absorption model, the Caco-2 cells originate from a human colon adenocarcinomas and can differentiate into a cell layer with enterocyte-like features. The Caco-2 cell model is popularly applied to explore drug transport mechanisms, to evaluate the permeability of drug and to predict the absorption of drugs or bioactive substances in the gut. However, there are limitations to the application of Caco-2 cell model due to lack of a mucus layer, the long culture period and the inability to accurately simulate the intestinal environment. The most frequent way to expand the Caco-2 cell model and address its limitations is by co-culturing it with other cells or substances. This article reviews the culture methods and applications of 3D and 2D co-culture cell models established around Caco-2 cells. It also concludes with a summary of model strengths and weaknesses.

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.

Chaenomelin, a New Phenolic Glycoside, and Anti-Helicobacter pylori Phenolic Compounds from the Leaves of Salix chaenomeloides

Salix chaenomeloides Kimura, commonly known as pussy willow, is a deciduous shrub and tree belonging to the Salicaceae family. The genus Salix spp. has been known as a healing herb for the treatment of fever, inflammation, and pain relief. The current study aimed to investigate the potential bioactive natural products from S. chaenomeloides leaves and evaluate their antibacterial activity against Helicobacter pylori. A phytochemical investigation of the ethanol (EtOH) extract of S. chaenomeloides leaves led to the isolation of 13 phenolic compounds (1-13) from the ethyl acetate (EtOAc) fraction, which showed antibacterial activity against H. pylori strain 51. The chemical structure of a new phenolic glycoside, chaenomelin (1), was established by a detailed analysis of 1D and 2D (1H-1H correlation spectroscopy (COSY), heteronuclear single-quantum coherence (HSQC), and heteronuclear multiple-bond correlation (HMBC)) nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectroscopy (HR-ESIMS), and chemical reactions. The other known compounds were identified as 5-O-trans-p-coumaroyl quinic acid methyl ester (2), tremulacin (3), citrusin C (4), benzyl 3-O-β-d-glucopyranosyl-7-hydroxybenzoate (5), tremuloidin (6), 1-[O-β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl]oxy-2-phenol (7), arbutin cinnamate (8), tremulacinol (9), catechol (10), 4-hydroxybenzaldehyde (11), kaempferol 3-rutinoside (12), and narcissin (13), based on the comparison of their NMR spectra with the reported data and liquid chromatography/mass spectrometry (LC/MS) analysis. The isolated compounds were evaluated for antibacterial activity against H. pylori strain 51. Among the isolates, 1-[O-β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl]oxy-2-phenol (7) and arbutin cinnamate (8) exhibited antibacterial activity against H. pylori strain 51, with inhibitions of 31.4% and 33.9%, respectively, at a final concentration of 100 μM. These results were comparable to that of quercetin (38.4% inhibition), which served as a positive control. Generally, these findings highlight the potential of the active compounds 7 and 8 as antibacterial agents against H. pylori.

Recent Advances in Cell-Based In Vitro Models to Recreate Human Intestinal Inflammation

Inflammatory bowel disease causes a major burden to patients and healthcare systems, raising the need to develop effective therapies. Technological advances in cell culture, allied with ethical issues, have propelled in vitro models as essential tools to study disease aetiology, its progression, and possible therapies. Several cell-based in vitro models of intestinal inflammation have been used, varying in their complexity and methodology to induce inflammation. Immortalized cell lines are extensively used due to their long-term survival, in contrast to primary cultures that are short-lived but patient-specific. Recently, organoids and organ-chips have demonstrated great potential by being physiologically more relevant. This review aims to shed light on the intricate nature of intestinal inflammation and cover recent works that report cell-based in vitro models of human intestinal inflammation, encompassing diverse approaches and outcomes.

Inter- and intraspecific diversity of Salix bark phenolic profiles - A resource for the pharmaceutical industry

Due to their content of phenolic compounds, willow bark preparations are used as an herbal remedy. The large diversity of phenolic secondary metabolites in Salix still provides a resource for the identification of bioactive compounds in particular species, including species not yet in focus from a phytopharmaceutical perspective. The present study describes the bark phenolic profile of 13 Salix species analyzed by HPLC-MS: Salix alba, Salix babylonica, Salix daphnoides, Salix fragilis, Salix hastata, Salix myrsinifolia, Salix pentandra, Salix purpurea, Salix repens (including subspecies S. repens ssp. arenaria and S. repens ssp. repens), Salix rosmarinifolia, Salix sachalinensis, Salix triandra and Salix viminalis. The analyzed profiles comprised the chemical groups of salicylates, flavonoids, procyanidins, phenolic acid derivatives, and some unclassified phenolics. Particular compounds were detected in species where they have not been previously reported. Apart from interspecific diversity, qualitative variability within species was observed as certain components were detected only in some of the analyzed genotypes. The knowledge on specific phenolic profiles of species and genotypes is the basis for the selection of suitable willow bark material with certain desired bioactive properties. Furthermore, the high inter- and intraspecific variability points out the necessity for product standardization of willow bark raw material.

Effect of Microwave and Ultrasound-Assisted Extraction on the Phytochemical and In Vitro Biological Properties of Willow (Salix alba) Bark Aqueous and Ethanolic Extracts

White willow (Salix alba) is a medicinal plant used in folk medicine. In this study, aqueous and ethanolic willow bark extracts were obtained via ultrasonic-assisted extraction (UAE) and microwave-assisted extraction (MAE), and analyzed regarding their phytochemical (total phenolics, phenolic acids, flavonoids, and tannins) content and in vitro biological properties (antibacterial and antifungal activity, acetylcholinesterase AChE inhibitory activity and anti-inflammatory effects). The highest phenolic, tannin, and flavonoid contents were found for willow bark extracts obtained via microwave-assisted extraction using ethanol as a solvent (SA-ME). The polyphenol load of all MAE and UAE extracts was higher when conventional solid-liquid extraction was applied (ρ < 0.05). The antioxidant capacities were stronger for microwave-assisted ethanolic extracts, with the lowest IC₅₀ values of 12 μg/mL for DPPH^• and a value of 16 μg/mL for ABTS•+, whereas the conventional extraction had the highest IC₅₀ values (22 μg/mL and 28 μg/mL, respectively). Willow bark extract showed antibacterial activity against Gram-positive bacteria S. aureus and P. aeruginosa. AChE inhibitory activity was dependent on the extraction method and solvent used, and the highest inhibition among samples was observed for SA-ME. Taken altogether, our findings suggest that willow (Salix alba) bark extract obtained via ethanolic microwave-assisted extraction is a phytochemical-rich resource with in vitro, anti-inflammatory, and AchE inhibitory properties and, therefore, potential multiple medicinal end-uses.

Development of an Inflammation-Triggered In Vitro "Leaky Gut" Model Using Caco-2/HT29-MTX-E12 Combined with Macrophage-like THP-1 Cells or Primary Human-Derived Macrophages

The "leaky gut" syndrome describes a damaged (leaky) intestinal mucosa and is considered a serious contributor to numerous chronic diseases. Chronic inflammatory bowel diseases (IBD) are particularly associated with the "leaky gut" syndrome, but also allergies, autoimmune diseases or neurological disorders. We developed a complex in vitro inflammation-triggered triple-culture model using 21-day-differentiated human intestinal Caco-2 epithelial cells and HT29-MTX-E12 mucus-producing goblet cells (90:10 ratio) in close contact with differentiated human macrophage-like THP-1 cells or primary monocyte-derived macrophages from human peripheral blood. Upon an inflammatory stimulus, the characteristics of a "leaky gut" became evident: a significant loss of intestinal cell integrity in terms of decreased transepithelial/transendothelial electrical resistance (TEER), as well as a loss of tight junction proteins. The cell permeability for FITC-dextran 4 kDa was then increased, and key pro-inflammatory cytokines, including TNF-alpha and IL-6, were substantially released. Whereas in the M1 macrophage-like THP-1 co-culture model, we could not detect the release of IL-23, which plays a crucial regulatory role in IBD, this cytokine was clearly detected when using primary human M1 macrophages instead. In conclusion, we provide an advanced human in vitro model that could be useful for screening and evaluating therapeutic drugs for IBD treatment, including potential IL-23 inhibitors.

Phytoestrogen β-Sitosterol Exhibits Potent In Vitro Antiviral Activity against Influenza A Viruses

Influenza is a contagious infection in humans that is caused frequently by low pathogenic seasonal influenza viruses and occasionally by pathogenic avian influenza viruses (AIV) of H5, H7, and H9 subtypes. Recently, the clinical sector in poultry and humans has been confronted with many challenges, including the limited number of antiviral drugs and the rapid evolution of drug-resistant variants. Herein, the anti-influenza activities of various plant-derived phytochemicals were investigated against highly pathogenic avian influenza A/H5N1 virus (HPAIV H5N1) and seasonal low pathogenic human influenza A/H1N1 virus (LPHIV H1N1). Out of the 22 tested phytochemicals, the steroid compounds β-sitosterol and β-sitosterol-O-glucoside have very potent activity against the predefined influenza A viruses (IAV). Both steroids could induce such activity by affecting multiple stages during IAV replication cycles, including viral adsorption and replication with a major and significant impact on the virus directly in a cell-free status "viricidal effect". On a molecular level, several molecular docking studies suggested that β-sitosterol and β-sitosterol-O-glucoside exhibited viricidal effects through blocking active binding sites of the hemagglutinin surface protein, as well as showing inhibitory effects against replication through the binding with influenza neuraminidase activity and blocking the active sites of the M2 proton channel activity. The phytoestrogen β-sitosterol has structural similarity with the active form of the female sex hormone estradiol, and this similarity is likely one of the molecular determinants that enables the phytoestrogen β-sitosterol and its derivative to control IAV infection in vitro. This promising anti-influenza activity of β-sitosterol and its O-glycoside derivative, according to both in vitro and cheminformatics studies, recommend both phytochemicals for further studies going through preclinical and clinical phases as efficient anti-influenza drug candidates.

Increased Production of Inflammatory Cytokines after Inoculation with Recombinant Zoster Vaccine in Mice

Increasing numbers of patients with zoster were reported recently, and recombinant zoster vaccine (Shingrix^®) was licensed using the AS01_B adjuvant system. Although it induces highly effective protection, a high incidence of local adverse events (regional pain, erythema, and swelling) has been reported with systemic reactions of fever, fatigue, and headache. To investigate the mechanism of local adverse events, cytokine profiles were investigated in mice injected with 0.1 mL of Shingrix^®. Muscle tissue and serum samples were obtained on days 0, 1, 3, 5, and 7, and at 2 and 4 weeks after the first dose. The second dose was given 4 weeks after the first dose and samples were obtained on days 1, 3, 5, 7, and 14. IL-6 and G-CSF were detected in muscle tissues on day 1 of the first injection, decreased on day 3 and afterward, and enhanced production was demonstrated on day 1 of the second dose. In sera, the elevated levels of IL-6 were detected on day 1 of the first dose, and IL-10 was detected on day 1 with increased levels on day 3 of the first dose. IL-4 was detected in muscle tissue on day 1 of the second dose and IL-5 on day 1 of both the first and second doses. IFN-γ production was not enhanced in muscle tissue but increased in serum samples on day 1 of the first dose. These results in the mouse model indicate that the induction of inflammatory cytokines is related to the cause of adverse events in humans.

SARS-CoV-2 Omicron variant escapes neutralizing antibodies and T cell responses more efficiently than other variants in mild COVID-19 convalescents

Coronavirus disease 2019 (COVID-19) convalescents living in regions with low vaccination rates rely on post-infection immunity for protection against re-infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluate humoral and T cell immunity against five variants of concern (VOCs) in mild-COVID-19 convalescents at 12 months after infection with ancestral virus. In this cohort, ancestral, receptor-binding domain (RBD)-specific antibody and circulating memory B cell levels are conserved in most individuals, and yet serum neutralization against live B.1.1.529 (Omicron) is completely abrogated and significantly reduced for other VOCs. Likewise, ancestral SARS-CoV-2-specific memory T cell frequencies are maintained in >50% of convalescents, but the cytokine response in these cells to mutated spike epitopes corresponding to B.1.1.529 and B.1.351 (Beta) VOCs were impaired. These results indicate that increased antigen variability in VOCs impairs humoral and spike-specific T cell immunity post-infection, strongly suggesting that COVID-19 convalescents are vulnerable and at risk of re-infection with VOCs, thus stressing the importance of vaccination programs.

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Most mild COVID-19 convalescents maintain immunity at 12 months after disease onset

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B.1.1.529 escapes antibodies in convalescents infected with ancestral SARS-CoV-2

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SARS-CoV-2 VOCs can partially avoid recognition by antigen-specific T cells

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Antigenic drift in SARS-CoV-2 VOCs significantly challenges convalescent immunity

Molecular Docking and Dynamics Investigations for Identifying Potential Inhibitors of the 3-Chymotrypsin-like Protease of SARS-CoV-2: Repurposing of Approved Pyrimidonic Pharmaceuticals for COVID-19 Treatment

This study demonstrates the inhibitory effect of 42 pyrimidonic pharmaceuticals (PPs) on the 3-chymotrypsin-like protease of SARS-CoV-2 (3CL^pro) through molecular docking, molecular dynamics simulations, and free binding energies by means of molecular mechanics-Poisson Boltzmann surface area (MM-PBSA) and molecular mechanics-generalized Born surface area (MM-GBSA). Of these tested PPs, 11 drugs approved by the US Food and Drug Administration showed an excellent binding affinity to the catalytic residues of 3CL^pro of His41 and Cys145: uracil mustard, cytarabine, floxuridine, trifluridine, stavudine, lamivudine, zalcitabine, telbivudine, tipiracil, citicoline, and uridine triacetate. Their percentage of residues involved in binding at the active sites ranged from 56 to 100, and their binding affinities were in the range from -4.6 ± 0.14 to -7.0 ± 0.19 kcal/mol. The molecular dynamics as determined by a 200 ns simulation run of solvated docked complexes confirmed the stability of PP conformations that bound to the catalytic dyad and the active sites of 3CL^pro. The free energy of binding also demonstrates the stability of the PP-3CL^pro complexes. Citicoline and uridine triacetate showed free binding energies of -25.53 and -7.07 kcal/mol, respectively. Therefore, I recommend that they be repurposed for the fight against COVID-19, following proper experimental and clinical validation.

Drug-Drug Interaction Potential, Cytotoxicity, and Reactive Oxygen Species Production of Salix Cortex Extracts Using Human Hepatocyte-Like HepaRG Cells

Herbal preparations of willow bark (Salix cortex) are available in many countries as non-prescription medicines for pain and inflammation, and also as dietary supplements. Currently only little information on toxicity and drug interaction potential of the extracts is available. This study now evaluated the effects of two Salix cortex extracts on human hepatocyte-like HepaRG cells, in view of clinically relevant CYP450 enzyme activity modulation, cytotoxicity and production of reactive oxygen species (ROS). Drug metabolism via the CYP450 enzyme system is considered an important parameter for the occurrence of drug-drug interactions, which can lead to toxicity, decreased pharmacological activity, and adverse drug reactions. We evaluated two different bark extracts standardized to 10 mg/ml phenolic content. Herein, extract S6 (S. pentandra, containing 8.15 mg/ml total salicylates and 0.08 mg/ml salicin) and extract B (industrial reference, containing 5.35 mg/ml total salicylates and 2.26 mg/ml salicin) were tested. Both Salix cortex extracts showed no relevant reduction in cell viability or increase in ROS production in hepatocyte-like HepaRG cells. However, they reduced CYP1A2 and CYP3A4 enzyme activity after 48 h at ≥25 μg/ml, this was statistically significant only for S6. CYP2C19 activity inhibition (0.5 h) was also observed at ≥25 μg/ml, mRNA expression inhibition by 48 h treatment with S6 at 25 μg/ml. In conclusion, at higher concentrations, the tested Salix cortex extracts showed a drug interaction potential, but with different potency. Given the high prevalence of polypharmacy, particularly in the elderly with chronic pain, further systematic studies of Salix species of medical interest should be conducted in the future to more accurately determine the risk of potential drug interactions.

Identification of Salicylates in Willow Bark (Salix Cortex) for Targeting Peripheral Inflammation

Salix cortex-containing medicine is used against pain conditions, fever, headaches, and inflammation, which are partly mediated via arachidonic acid-derived prostaglandins (PGs). We used an activity-guided fractionation strategy, followed by structure elucidation experiments using LC-MS/MS, CD-spectroscopy, and 1D/2D NMR techniques, to identify the compounds relevant for the inhibition of PGE2 release from activated human peripheral blood mononuclear cells. Subsequent compound purification by means of preparative and semipreparative HPLC revealed 2'-O-acetylsalicortin (1), 3'-O-acetylsalicortin (2), 2'-O-acetylsalicin (3), 2',6'-O-diacetylsalicortin (4), lasiandrin (5), tremulacin (6), and cinnamrutinose A (7). In contrast to 3 and 7, compounds 1, 2, 4, 5, and 6 showed inhibitory activity against PGE2 release with different potencies. Polyphenols were not relevant for the bioactivity of the Salix extract but salicylates, which degrade to, e.g., catechol, salicylic acid, salicin, and/or 1-hydroxy-6-oxo-2-cycohexenecarboxylate. Inflammation presents an important therapeutic target for pharmacological interventions; thus, the identification of relevant key drugs in Salix could provide new prospects for the improvement and standardization of existing clinical medicine.