Screening of neuraminidase inhibitors from traditional Chinese medicine by transverse diffusion mediated capillary microanalysis

Antiviral alkaloid principles of the plant family Amaryllidaceae

BACKGROUND

Viral-borne diseases are amongst the oldest diseases known to mankind. They are responsible for some of the most ravaging effects wrought on human health and well-being. The use of plants against these ailments is entrenched in both traditional and secular medicine around the globe. Their natural abundance and chemical diversity have also boosted their appeal in drug discovery.

AIM

The plant family Amaryllidaceae is distinguished for its alkaloid principles, some of which are of considerable interest in the clinical arena. This account is the outcome of a literature review undertaken to establish the applicability of these substances as antiviral agents.

METHODS

The survey utilized the search engines Google Scholar, PubMed, SciFinder, Scopus and Web of Science engaging the word 'antiviral' in conjunction with 'Amaryllidaceae' and 'Amaryllidaceae alkaloid'. The search returned over five hundred hits, of which around eighty were of relevance to the theme of the text.

RESULTS

Over eighty isoquinoline alkaloids have been screened against nearly fifty pathogens from fourteen viral families, the majority of which were RNA viruses. Potent activities were reported in some instances, such as that of trans-dihydronarciclasine against Yellow fever virus (IC₅₀ 0.003 μg/ml), with minimal effects being manifested on host cells. There were also promising results obtained from in vivo studies, in most cases without lethal effects on test subjects. Structure-activity relationship studies afforded useful insight to the antiviral pharmacophore, with the phenanthridone alkaloid nucleus shown to be the most enabling. Although the mechanistic basis to these activities pertained mostly to inhibition of DNA, RNA and protein synthesis, evidence was also forthcoming about the inhibitory action of some of the alkaloids against viral neuraminidase, protease and reverse transcriptase. In silico methods of analysis have offered further perspectives of how some of the alkaloids interact at the active sites of their targets.

CONCLUSION

The Amaryllidaceae offers a viable platform for plant-based antiviral drug discovery. Its cause is strengthened not only by its wide proliferation and exploitation of its members in alternative forms of medicine, but also by its rich chemical diversity which has already spawned useful antiviral drug leads.

Recent advances on discovery of enzyme inhibitors from natural products using bioactivity screening

The essence of enzymes is to keep the homeostasis and balance of human by catalyzing metabolic responses and modulating cell. Suppression of enzyme slows the progress of some diseases, making it a therapeutic target. Therefore, it is important to develop enzyme inhibitors by proper bioactivity screening strategies for the future treatment of some major diseases. In this review, we summarized the recent (2015-2020) applications of several screening strategies (electrophoretically mediated microanalysis, enzyme immobilization, affinity chromatography, and affinity ultrafiltration) in finding enzyme inhibitors from certain species of bioactive natural compounds of plant origin (flavonoids, alkaloids, phenolic acids, saponins, anthraquinones, coumarins). At the same time, the advantages and disadvantages of each strategy were also discussed, and the future possible development direction in enzyme inhibitor screening has prospected. To sum up, it is expected to help readers select suitable screening strategies for enzyme inhibitors and provide useful information for the study of the biological of specific kinds of natural products. This article is protected by copyright. All rights reserved.

Screening of lactate dehydrogenase inhibitor from bioactive compounds in natural products by electrophoretically mediated microanalysis

Lactate dehydrogenase (LDH) is a key enzyme in the glycolysis, which has been reported that the expression of LDH is elevated in a variety of cancer types and can promote tumor invasion and metastasis. Therefore, LDH has come to be an emerging therapeutic target for cancer. In this work, we described a new strategy for rapid screening of LDH inhibitors from natural products by integrating electrophoretically mediated microanalysis (EMMA), transverse diffusion of laminar flow profiles (TDLFP) and rapid pressure direction switching. LDH activity could be assayed by the quantification of the peak area of the produced β-Nicotinamide adenine dinucleotide hydrate (NAD⁺) and the inhibitory effect on LDH was reflected by the reduction of NAD⁺ peak area. Parameters affecting CE separation and enzymatic reaction were evaluated, including the pH of background electrolyte, incubation time, methanol percentage and enzyme concentration. The Michaelis-Menten constant (K_m) determined on-line by EMMA method were 226.9 μM and 31.8 μM for substrates sodium pyruvate and NADH, respectively and the half-maximal inhibitory concentration (IC₅₀) for the known positive inhibitor gossypol was determined to be 9.269 μM, which was comparable with the previous literature. Then the inhibitory activity of 12 bioactive compounds from natural products on LDH was investigated by employing the developed method. Three compounds including quercetin, luteolin, ursolic acid had potential inhibitory effect on LDH. Molecular docking study was implemented and well supported the experimental results. This study provides a potential tool for the preliminary screening of LDH inhibitors from bioactive compounds in natural products by capillary electrophoresis.

Screening carbonic anhydrase IX inhibitors in traditional Chinese medicine based on electrophoretically mediated microanalysis

An electrophoretically mediated microanalysis (EMMA) method for the screening of carbonic anhydrase IX inhibitors in traditional Chinese medicine (TCM) was developed. This method combines transverse diffusion of laminar flow profiles (TDLFP) and rapid polarity switching technology to achieve rapid mixing of different reactants. Different electromigration rates of different substances make it possible that incubation, separation and detection are carried out continuously in a same fused-silica capillary. In this experiment, p-nitrophenyl acetate (pNPA) was used as the substrate for the enzyme reaction, which solved the problem that capillary electrophoresis could not detect carbonate, carbon dioxide, etc., the conventional substrates of carbonic anhydrase IX. After optimizing the enzyme reaction and separation conditions, the separation of substrate and product can be finished by baseline within 4 min. The Michaelis constant of carbonic anhydrase IX was measured to be 1.2 mM. A known inhibitor acetazolamide was used to evaluate the feasibility of this method for screening carbonic anhydrase IX inhibitors, and the half-maximal inhibitory concentration (IC₅₀) was calculated to be 1.26 μM. Finally, 4 natural compounds of 15 traditional Chinese medicine standards were discovered to exhibit enzyme inhibitory activity, including polydatin, matrine, dauricine and cepharanthine, proving that the EMMA method is an effective means for screening carbonic anhydrase IX inhibitors. The results were supported by molecular docking study.

Development of a new nano arginase HPLC capillary column for the fast screening of arginase inhibitors and evaluation of their binding affinity

A simple and rapid Nano LC method has been developed for the screening of arginase inhibitors. The method is based on the immobilization of biotinylated arginase on a neutravidin functionalized nano HPLC capillary column. The arginase immobilization step performed by frontal analysis is very fast and only takes a few minutes. The miniaturized capillary column of 170 nL (length 5 cm, internal diameter 75 μm) significantly decreased the required amount of used enzyme (25 pmol). This was of significance importance when working with less available or expensive purified enzyme. Non-selective adsorption of the organic monolith matrix was reduced (<6%) and the arginase efficient yield was high (92%). The resultant affinity capillary columns showed excellent repeatability and long lifetime. The arginase reaction product was achieved within 60 s and the immobilized arginase retained 97% of the initial activity beyond 90 days. This novel approach can thus be used for the fast evaluation of recognition assay induced bya series of inhibitor molecules (caffeic acid phenylamide, chlorogenic acid, piceatannol, nor-NOHA acetate) and plant extracts.

Identification and Screening of Natural Neuraminidase Inhibitors from Reduning Injection via One-Step High-Performance Liquid Chromatography-Fraction Collector and UHPLC/Q-TOF-MS

Neuraminidase plays an essential role in the spread of influenza viruses via cleaving sialic acids from the host cell receptors and virions. Neuraminidase has been regarded as an essential target for prevention and treatment of influenza infection. The one-step high-performance liquid chromatography-fraction collector (HPLC-FC) was selected to prepare fractions from Reduning (RDN) injection, while ultra-high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UHPLC/Q-TOF-MS) was used to identify fractions depending on their retention time and molecular ion. As a result, 75 fractions were prepared and 28 fractions out of them exhibited NA inhibitory effects with the dose-effect relationship. Exploring it further, six components including neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, isochlorogenic acid B, isochlorogenic acid A, and isochlorogenic acid C were the main components that accounted for almost 80% of inhibitory activity of RDN injection. Accordingly, these results demonstrated that this strategy could not only rapidly identify but also accurately screen active components from traditional Chinese medicine.

Recent advances in screening of enzymes inhibitors based on capillary electrophoresis

Capillary electrophoresis with many advantages plays an important role in pharmaceutical analysis and drug screening. This review gives an overview on the recent advances in the developments and applications of capillary electrophoresis in the field of enzyme inhibitor screening. The period covers 2013 to 2017. Both the pre-capillary enzyme assays and in-capillary enzyme assays which include electrophoretically mediated microanalysis (EMMA) and immobilized enzyme microreactor (IMER) are summarized in this article.

Screening of tyrosinase inhibitors by capillary electrophoresis with immobilized enzyme microreactor and molecular docking

A new method for screening tyrosinase inhibitors from traditional Chinese medicines (TCMs) was successfully developed by capillary electrophoresis with reliable online immobilized enzyme microreactor (IMER). In addition, molecular docking study has been used for supporting inhibition interaction between enzyme and inhibitors. The IMER of tyrosinase was constructed at the outlet of the capillary by using glutaraldehyde as cross-linker. The parameters including enzyme reaction, separation of the substrate and product, and the performance of immobilized tyrosinase were investigated systematically. Because of using short-end injection procedure, the product and substrate were effectively separated within 2 min. The immobilized tyrosinase could remain 80% active for 30 days at 4°C. The Michaelis-Menten constant of tyrosinase was determined as 1.78 mM. Kojic acid, a known tyrosinase inhibitor, was used as a model compound for the validation of the inhibitors screening method. The half-maximal inhibitory concentration of kojic acid was 5.55 μM. The method was successfully applied for screening tyrosinase inhibitors from 15 compounds of TCM. Four compounds including quercetin, kaempferol, bavachinin, and bakuchiol were found having inhibitory potentials. The results obtained in this work were supported by molecular docking study.