Affinity ultrafiltration and UPLC-HR-Orbitrap-MS based screening of thrombin-targeted small molecules with anticoagulation activity from Poecilobdella manillensis

Development of a virus-based affinity ultrafiltration method for screening virus-surface-protein-targeted compounds from complex matrixes: Herbal medicines as a case study

Herbal medicines (HMs) are one of the main sources for the development of lead antiviral compounds. However, due to the complex composition of HMs, the screening of active compounds within these is inefficient and requires a significant time investment. We report a novel and efficient virus-based screening method for antiviral active compounds in HMs. This method involves the centrifugal ultrafiltration of viruses, known as the virus-based affinity ultrafiltration method (VAUM). This method is suitable to identify virus specific active compounds from complex matrices such as HMs. The effectiveness of the VAUM was evaluated using influenza A virus (IAV) H1N1. Using this method, four compounds that bind to the surface protein of H1N1 were identified from dried fruits of Terminalia chebula (TC). Through competitive inhibition assays, the influenza surface protein, neuraminidase (NA), was identified as the target protein of these four TC-derived compounds. Three compounds were identified by high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS), and their anti-H1N1 activities were verified by examining the cytopathic effect (CPE) and by performing a virus yield reduction assay. Further mechanistic studies demonstrated that these three compounds directly bind to NA and inhibit its activity. In summary, we describe here a VAUM that we designed, one that can be used to accurately screen antiviral active compounds in HMs and also help improve the efficiency of screening antiviral drugs found in natural products.

Potential antioxidative components from Syringa oblata Lindl stems revealed by affinity ultrafiltration with multiple drug targets

Traditional Chinese medicine is the main source of natural products due to its remarkable clinical efficacy. Syringa oblata Lindl (S. oblata) was widely used because of its extensive biological activities. However, to explore the antioxidant components of S. oblata against tyrosinase, the experiments of antioxidation in vitro were employed. At the same time, the determination of TPC was also use to assess the antioxidant ability of CE, MC, EA and WA fractions and the liver protective activity of the EA fraction was evaluated by mice in vivo. Next, UF-LC-MS technology was performed to screen and identify the efficient tyrosinase inhibitors in S. oblata. The results showed that alashinol (G), dihydrocubebin, syripinin E and secoisolariciresinol were characterized as potential tyrosinase ligands and their RBA values were 2.35, 1.97, 1.91 and 1.61, respectively. Moreover, these four ligands can effectively dock with tyrosinase molecules, with binding energies (BEs) ranging from 0.74 to -0.73 kcal/mol. In addition, tyrosinase inhibition experiment was employed to evaluate the tyrosinase inhibition activities of four potential ligands, the result showed that compound 12 (alashinol G, IC50 = 0.91 ± 0.20 mM) showed the strongest activity to tyrosinase, followed by secoisolariciresinol (IC50 = 0.99 ± 0.07 mM), dihydrocubebin (IC50 = 1.04 ± 0.30 mM) and syripinin E (IC50 = 1.28 ± 0.23 mM), respectively. The results demonstrate that S. oblata might have excellent antioxidant activity, and UF-LC-MS technique is a effective means to filter out tyrosinase inhibitors from natural products.

Identification and Characterization of RK22, a Novel Antimicrobial Peptide from Hirudinaria manillensis against Methicillin Resistant Staphylococcus aureus

Staphylococcus aureus (S. aureus) infections are a leading cause of morbidity and mortality, which are compounded by drug resistance. By manipulating the coagulation system, S. aureus gains a significant advantage over host defense mechanisms, with hypercoagulation induced by S. aureus potentially aggravating infectious diseases. Recently, we and other researchers identified that a higher level of LL-37, one endogenous antimicrobial peptide with a significant killing effect on S. aureus infection, resulted in thrombosis formation through the induction of platelet activation and potentiation of the coagulation factor enzymatic activity. In the current study, we identified a novel antimicrobial peptide (RK22) from the salivary gland transcriptome of Hirudinaria manillensis (H. manillensis) through bioinformatic analysis, and then synthesized it, which exhibited good antimicrobial activity against S. aureus, including a clinically resistant strain with a minimal inhibitory concentration (MIC) of 6.25 μg/mL. The RK22 peptide rapidly killed S. aureus by inhibiting biofilm formation and promoting biofilm eradication, with good plasma stability, negligible cytotoxicity, minimal hemolytic activity, and no significant promotion of the coagulation system. Notably, administration of RK22 significantly inhibited S. aureus infection and the clinically resistant strain in vivo. Thus, these findings highlight the potential of RK22 as an ideal treatment candidate against S. aureus infection.

Discovery of the potential neuraminidase inhibitors from Polygonum cuspidatum by ultrafiltration combined with mass spectrometry guided by molecular docking

Neuraminidase is an important target in the treatment of the influenza A virus. Screening natural neuraminidase inhibitors from medicinal plants is crucial for drug research. This study proposed a rapid strategy for identifying neuraminidase inhibitors from different crude extracts (Polygonum cuspidatum, Cortex Fraxini, and Herba Siegesbeckiae) using ultrafiltration combined with mass spectrometry guided by molecular docking. Firstly, the main component library of the three herbs was established, followed by molecular docking between the components and neuraminidase. Only the crude extracts with numbers of potential neuraminidase inhibitors identified by molecular docking were selected for ultrafiltration. This guided approach reduced experimental blindness and improved efficiency. The results of molecular docking indicated that the compounds in Polygonum cuspidatum demonstrated good binding affinity with neuraminidase. Subsequently, ultrafiltration-mass spectrometry was employed to screen for neuraminidase inhibitors in Polygonum cuspidatum. A total of five compounds were fished out, and they were identified as trans-polydatin, cis-polydatin, emodin-1-O-β-D-glucoside, emodin-8-O-β-D-glucoside, and emodin. The enzyme inhibitory assay showed that they all had neuraminidase inhibitory effects. In addition, the key residues of the interaction between neuraminidase and fished compounds were predicted. In all, this study could provide a strategy for the rapid screening of the potential enzyme inhibitors from medicinal herbs.

Study on endogenous inhibitors against PD-L1: cAMP as a potential candidate

The discovery of new anti-cancer drugs targeting the PD-1/PD-L1 pathway has been a research hotspot in recent years. In this study, biological affinity ultrafiltration (BAU), UPLC-HRMS, molecular dynamic (MD) simulations and molecular docking methods were applied to search for endogenous active compounds that can inhibit the binding of PD-L1 to PD-1. We screened dozens of potential cancer related endogenous compounds. Surprisingly, cyclic adenosine monophosphate (cAMP) was found to have a direct inhibitory effect on the PD-1/PD-L1 binding with an in vitro IC₅₀ value of about 36.4 ± 9.3 μM determined by homogeneous time-resolved fluorescence (HTRF) assay. cAMP could recover the proliferation of Jurkat T cells co-cultured with DU-145 cells and may suppress PD-L1 expression of DU-145 cells. cAMP was demonstrated to bind and induce PD-L1 dimerization by FRET assay, and also predicted by MD simulations and molecular docking. The finding of cAMP as a potential inhibitor directly targeting the PD-1/PD-L1 interaction could advance our understanding of the activity of endogenous compounds regulating PD-L1.

Affinity ultrafiltration and UPLC-HR-Orbitrap-MS based screening of neuraminidase inhibitors from Angelica pubescens

Traditional Chinese medicine is a rich source of natural products and has a long history of use because of its remarkable clinical efficacy. In the present study, the chemical constitutes of Angelica pubescens were studied by ultra high performance liquid chromatography and high-resolution Orbitrap mass spectrometry (UPLC-HR-Orbitrap-MS). A total of 78 compounds were identified and the main composition were coumarins and phenolic acids. Then, the neuraminidase was incubated with extract of Angelica pubescens to screen the neuraminidase inhibitors by affinity ultrafiltration methods. As a result, 13 small molecules were discovered to interact with neuraminidase for the first time. In vitro neuraminidase inhibitory activity of the screened compounds and extract of Angelica pubescens was tested, and isochlorogenic acid C, isochlorogenic acid B, osthole, chlorogenic acid, xanthotoxin, phellopterin and imperatorin were proved to have this activity. In addition, molecular docking analysis was conducted to predict the potential docking position. This study may provide a reference for the medical substance basis in Angelica and the clinical usage of this drug.