Natural products as potential lead compounds to develop new antiviral drugs over the past decade

Recent advances in the natural product analogues for the treatment of neurodegenerative diseases

Neurodegenerative diseases (NDs) represent a hallmark of numerous incapacitating and untreatable conditions, the incidence of which is escalating swiftly, exemplified by Alzheimer's disease and Parkinson's disease. There is an urgent necessity to create pharmaceuticals that exhibit high efficacy and minimal toxicity in order to address these debilitating diseases. The structural complexity and diversity of natural products confer upon them a broad spectrum of biological activities, thereby significantly contributing to the history of drug discovery. Nevertheless, natural products present challenges in drug discovery, including time-consuming separation processes, low content, low bioavailability, and other related issues. To address these challenges, numerous analogs of natural products have been synthesized. This methodology enables the rapid synthesis of analogs of natural products with the potential to serve as lead compounds for drug development, thereby paving the way for the discovery of novel pharmaceuticals. This paper provides a summary of 127 synthetic analogues featuring various natural product structures, including flavonoids, alkaloids, coumarins, phenylpropanoids, terpenoids, polyphenols, and amides. The compounds are categorized based on their efficacy in treating various diseases. Furthermore, this article delves into the structure-activity relationship (SAR) of certain analogues, offering a thorough point of reference for the systematic development of pharmaceuticals aimed at addressing neurodegenerative conditions.

Potential COX-2 inhibitors modulating NF-κB/MAPK signaling pathways: Design, synthesis and evaluation of anti-inflammatory activity of Pterostilbene-carboxylic acid derivatives with an oxime ether moiety

In this work, a series of novel Pterostilbene-oxime ether-carboxylic acid (POC) derivatives (d1-d10, e1-e10 and 1-13) were designed, synthesized, and characterized by spectroscopic techniques. In order to further determine the absolute configuration of these compounds, one of them, compound d3, was investigated by X-ray single crystal diffraction method. d3 had a triclinic crystal with P-1 space group, and its CHCH and CHN was confirmed as E configuration. A strong hydrogen bond was formed between the hydrogen atom in CHCH moiety and the nitrogen atom in CHN moiety, which was a vital factor in the formation and stability of E configuration in the CHCH and CHN. The safety and anti-inflammatory activities of compounds (d1-d10, e1-e10 and 1-13) in vitro were evaluated. At 20 μM, compounds (d1-d10, e1-e10 and 1-13 were non-toxic and exhibited weak to strong inhibitory effects on the LPS-induced NO release. Among them, five compounds (1, 2, 7, 8 and 9) showed excellent anti-inflammatory effects with IC50 (NO) values ranging from 9.87 to 19.78 μM, as well as strong COX-2 inhibitory abilities with IC50 (COX-2) values ranging from 85.44 to 140.88 nM. Moreover, there was a rough positive correlation between their anti-inflammatory properties and the COX-2 inhibitory abilities. Compounds (1, 2, 7, 8 and 9) smoothly docked with COX-2 protein (PDB ID: 5KIR) to form stable complexes with strong hydrogen bonds, with an affinity range of -8.3 to -9.9 kcal/mol. SAR indicated that the amidation of POC at R2 position was more favorable for enhancing the compound's biological actives than esterification. In addition, the 4-fluobenzyl substitution at R2 position of the oxime ether moiety can obviously enhance the activity of above amide derivates. Introducing acyl groups (CO(CH2)nCH3, n = 2, 4 and 6) into NH(CH2)3OH group to form ester chain is disadvantageous for activity enhancing, moreover, the longer the carbon chain, the poorer the activity. The strongest COX-2 inhibitor (IC50 (COX-2) = 85.44 ± 3.88 nM), compound 7, exerted as anti-inflammatory activities (IC50 (NO) = 9.87 ± 1.38 μM) by down-regulating the expression of COX-2 and iNOS, and modulating NF-κB/MAPK signaling pathways.

Design, Synthesis and Biological Activities Evaluation of Novel Pterostilbene-urea Derivatives as Potential Anti- inflammatory Agents

1. The toxicity of derivatives was removed by the reasonable modification of bioactive skeleton. 2. As potential COX-2 inhibitor with IC50 values ranging from 39.42 to 179.84 nM/L, compounds (Q4-Q10, Q20) exhibited superior anti-inflammatory activity at low micromolar concentrations. 3. Q7 (IC50 (COX-2)=61.05 nM/L), Q10 (IC50 (COX-2)=54.68 nM/L) and Q20 (IC50 (COX-2)=39.42 nM/L) showed stronger COX-2 inhibitory abilities than Celecoxib (IC50 (COX-2)=67.89 nM/L). 4. The strongest anti-inflammatory agent, Q20 (IC50 NO= 9.96 μM/L, IC50 (COX-2)=39.42 nM/L) effectively inhibited the secretion of IL-1β and TNF-α, exhibited the IC50 values of 12.30 and 9.07 μM/L respectively. 5. Q20 exerted as anti-inflammatory actives via targeting COX-2, down-regulating iNOS and TLR4 protein, and inhibiting the activation of NLRP3 inflammasome and NF-κB signal pathway.

Aplospojaveedins A-C, unusual sulfur-containing alkaloids produced by the endophytic fungus Aplosporella javeedii using OSMAC strategy

Three sulfur-containing alkaloids aplospojaveedins A-C (1-3) with a hitherto undescribed carbon skeleton comprising octahy-dronaphthalene, α, β-unsaturated lactam and glycine-cysteine moieties were isolated from Aplosporella javeedii. Their structures were elucidated by 1D and 2D NMR spectroscopy, HR-MS, X-ray diffraction analysis, DFT-NMR and TDDFT-ECD calculations. A plausible biosynthetic pathway and putative targets are described. The blind docking suggested that 1-3 may have functional effects on several putative targets such as the GPCR cannabinoid receptor 2 or the integrin α5β1 complex.

Development of new dehydrocostuslactone derivatives for treatment of atopic dermatitis via inhibition of the NF-κB signaling pathway

Atopic dermatitis (AD), a recurrent inflammatory systemic skin disease, is difficult to cure. In the present study, several ethylenediamine-derived dehydrocostuslactone (DHCL) derivatives were prepared to assess their in vitro and in vivo anti-inflammatory activities. The results indicated that DHCL derivatives inhibited NO generation with low cytotoxicity. In particular, compound 5d exhibited the best anti-inflammatory activity. Subsequent experiments revealed that 5d not only inhibited the LPS-induced inflammatory response in RAW264.7 cells via the MAPK-NF-κB signaling pathway inhibition but also significantly decreased Th2-type cytokine levels and inhibited the NF-κB signaling pathway activation in mice with MC903-induced AD. Therefore, DHCL derivatives may be considered as new agents for the treatment of AD.

Current View on Major Natural Compounds Endowed with Antibacterial and Antiviral Effects

Nowadays, infectious diseases of bacterial and viral origins represent a serious medical problem worldwide. In fact, the development of antibiotic resistance is responsible for the emergence of bacterial strains that are refractory even to new classes of antibiotics. Furthermore, the recent COVID-19 pandemic suggests that new viruses can emerge and spread all over the world. The increase in infectious diseases depends on multiple factors, including malnutrition, massive migration of population from developing to industrialized areas, and alteration of the human microbiota. Alternative treatments to conventional antibiotics and antiviral drugs have intensively been explored. In this regard, plants and marine organisms represent an immense source of products, such as polyphenols, alkaloids, lanthipeptides, and terpenoids, which possess antibacterial and antiviral activities. Their main mechanisms of action involve modifications of bacterial cell membranes, with the formation of pores, the release of cellular content, and the inhibition of bacterial adherence to host cells, as well as of the efflux pump. Natural antivirals can interfere with viral replication and spreading, protecting the host with the enhanced production of interferon. Of note, these antivirals are not free of side effects, and their administration to humans needs more research in terms of safety. Preclinical research with natural antibacterial and antiviral compounds confirms their effects against bacteria and viruses, but there are still only a few clinical trials. Therefore, their full exploitation and more intensive clinical studies represent the next steps to be pursued in this area of medicine.

Metabolites rapid-annotation in mice by comprehensive method of virtual polygons and Kendric mass loss filtering: A case study of Dendrobium nobile Lindl

With significant advancements in high-resolution mass spectrometry, there has been a substantial increase in the amount of chemical component data acquired from natural products. Therefore, the rapid and efficient extraction of valuable mass spectral information from large volumes of high-resolution mass spectrometry data holds crucial significance. This study illustrates a targeted annotation of the metabolic products of alkaloid and sesquiterpene components from Dendrobium nobile (D. nobile) aqueous extract in mice serum through the integration of an in-houses database, R programming, a virtual metabolic product library, polygonal mass defect filtering, and Kendrick mass defect strategies. The research process involved initially establishing a library of alkaloids and sesquiterpenes components and simulating 71 potential metabolic reactions within the organism using R programming, thus creating a virtual metabolic product database. Subsequently, employing the virtual metabolic product library allowed for polygonal mass defect filtering, rapidly screening 1705 potential metabolites of alkaloids and 3044 potential metabolites of sesquiterpenes in the serum. Furthermore, based on the chemical composition database of D. nobile and online mass spectrometry databases, 95 compounds, including alkaloids, sesquiterpenes, and endogenous components, were characterized. Finally, utilizing Kendrick mass defect analysis in conjunction with known alkaloids and sesquiterpenes targeted screening of 209 demethylation, methylation, and oxidation products in phase I metabolism, and 146 glucuronidation and glutathione conjugation products in phase II metabolism. This study provides valuable insights for the rapid and accurate annotation of chemical components and their metabolites in vivo within natural products.

Ursonic acid from medicinal herbs inhibits PRRSV replication through activation of the innate immune response by targeting the phosphatase PTPN1

Porcine reproductive and respiratory syndrome (PRRS), caused by the PRRS virus (PRRSV), has caused substantial economic losses to the global swine industry due to the lack of effective commercial vaccines and drugs. There is an urgent need to develop alternative strategies for PRRS prevention and control, such as antiviral drugs. In this study, we identified ursonic acid (UNA), a natural pentacyclic triterpenoid from medicinal herbs, as a novel drug with anti-PRRSV activity in vitro. Mechanistically, a time-of-addition assay revealed that UNA inhibited PRRSV replication when it was added before, at the same time as, and after PRRSV infection was induced. Compound target prediction and molecular docking analysis suggested that UNA interacts with the active pocket of PTPN1, which was further confirmed by a target protein interference assay and phosphatase activity assay. Furthermore, UNA inhibited PRRSV replication by targeting PTPN1, which inhibited IFN-β production. In addition, UNA displayed antiviral activity against porcine epidemic diarrhoea virus (PEDV) and Seneca virus A (SVA) replication in vitro. These findings will be helpful for developing novel prophylactic and therapeutic agents against PRRS and other swine virus infections.

Puerarin-A Promising Flavonoid: Biosynthesis, Extraction Methods, Analytical Techniques, and Biological Effects

Flavonoids, a variety of plant secondary metabolites, are known for their diverse biological activities. Isoflavones are a subgroup of flavonoids that have gained attention for their potential health benefits. Puerarin is one of the bioactive isoflavones found in the Kudzu root and Pueraria genus, which is widely used in alternative Chinese medicine, and has been found to be effective in treating chronic conditions like cardiovascular diseases, liver diseases, gastric diseases, respiratory diseases, diabetes, Alzheimer's disease, and cancer. Puerarin has been extensively researched and used in both scientific and clinical studies over the past few years. The purpose of this review is to provide an up-to-date exploration of puerarin biosynthesis, the most common extraction methods, analytical techniques, and biological effects, which have the potential to provide a new perspective for medical and pharmaceutical research and development.

Naturally Occurring Norsteroids and Their Design and Pharmaceutical Application

The main focus of this review is to introduce readers to the fascinating class of lipid molecules known as norsteroids, exploring their distribution across various biotopes and their biological activities. The review provides an in-depth analysis of various modified steroids, including A, B, C, and D-norsteroids, each characterized by distinct structural alterations. These modifications, which range from the removal of specific methyl groups to changes in the steroid core, result in unique molecular architectures that significantly impact their biological activity and therapeutic potential. The discussion on A, B, C, and D-norsteroids sheds light on their unique configurations and how these structural modifications influence their pharmacological properties. The review also presents examples from natural sources that produce a diverse array of steroids with distinct structures, including the aforementioned A, B, C, and D-nor variants. These compounds are sourced from marine organisms like sponges, soft corals, and starfish, as well as terrestrial entities such as plants, fungi, and bacteria. The exploration of these steroids encompasses their biosynthesis, ecological significance, and potential medical applications, highlighting a crucial area of interest in pharmacology and natural product chemistry. The review emphasizes the importance of researching these steroids for drug development, particularly in addressing diseases where conventional medications are inadequate or for conditions lacking sufficient therapeutic options. Examples of norsteroid synthesis are provided to illustrate the practical applications of this research.

Chemical and Pharmacological Prospection of the Ascidian Cystodytes dellechiajei

Marine invertebrates are a traditional source of natural products with relevant biological properties. Tunicates are soft-bodied, solitary or colonial, sessile organisms that provide compounds unique in their structure and activity. The aim of this work was to investigate the chemical composition of the ascidian Cystodytes dellechiajei, selected on the basis of a positive result in biological screening for ligands of relevant receptors of the innate immune system, including TLR2, TLR4, dectin-1b, and TREM2. Bioassay-guided screening of this tunicate extract yielded two known pyridoacridine alkaloids, shermilamine B (1) and N-deacetylshermilamine B (2), and a family of methyl-branched cerebrosides (3). Compounds 2 and 3 showed selective binding to TREM2 in a dose-dependent manner. N-deacetylshermilamine B (2), together with its acetylated analogue, shermilamine B (1), was also strongly cytotoxic against multiple myeloma cell lines. TREM2 is involved in immunomodulatory processes and neurodegenerative diseases. N-deacetylshermilamine B (2) is the first example of a polycyclic alkaloid to show an affinity for this receptor.

Current Advances in Japanese Encephalitis Virus Drug Development

Japanese encephalitis virus (JEV) belongs to the Flaviviridae family and is a representative mosquito-borne flavivirus responsible for acute encephalitis and meningitis in humans. Despite the availability of vaccines, JEV remains a major public health threat with the potential to spread globally. According to the World Health Organization (WHO), there are an estimated 69,000 cases of JE each year, and this figure is probably an underestimate. The majority of JE victims are children in endemic areas, and almost half of the surviving patients have motor or cognitive sequelae. Thus, the absence of a clinically approved drug for the treatment of JE defines an urgent medical need. Recently, several promising and potential drug candidates were reported through drug repurposing studies, high-throughput drug library screening, and de novo design. This review focuses on the historical aspects of JEV, the biology of JEV replication, targets for therapeutic strategies, a target product profile, and drug development initiatives.

Modulation of the replication of positive-sense RNA viruses by the natural plant metabolite xanthohumol and its derivatives

The COVID-19 pandemic has highlighted the importance of identifying new potent antiviral agents. Nutrients as well as plant-derived substances are promising candidates because they are usually well tolerated by the human body and readily available in nature, and consequently mostly cheap to produce. A variety of antiviral effects have recently been described for the hop chalcone xanthohumol (XN), and to a lesser extent for its derivatives, making these hop compounds particularly attractive for further investigation. Noteworthy, mounting evidence indicated that XN can suppress a wide range of viruses belonging to several virus families, all of which share a common reproductive cycle. As a result, the purpose of this review is to summarize the most recent research on the antiviral properties of XN and its derivatives, with a particular emphasis on the positive-sense RNA viruses human hepatitis C virus (HCV), porcine reproductive and respiratory syndrome virus (PRRSV), and severe acute respiratory syndrome corona virus (SARS-CoV-2).