Current lead natural products for the chemotherapy of human immunodeficiency virus (HIV) infection

Antiviral activity of chrysin and naringenin against porcine epidemic diarrhea virus infection

Porcine epidemic diarrhea virus (PEDV) is one of the critical pathogens causing diarrhea in piglets and has caused huge economic losses to the swine industry in worldwide. However, there is currently no effective therapeutic medication available for the treatment of PEDV. Natural compounds are a hot topic for researching and screening antiviral lead compounds due to their abundant sources, varied activities, and low toxicity. In this study, a total of 6 compounds from different plant sources were selected for in vitro anti-PEDV screening, including chrysin, naringenin, soy isoflavone, glycyrrhetinic acid, oleanolic acid, and geniposide. Then two active compounds, chrysin and naringenin, were further evaluated on PEDV infected cells at different stage. And the anti-PEDV mechanism was analyzed by molecule docking and molecular dynamics. The results showed that both chrysin and naringenin showed the most significant anti-PEDV activity by increasing the cell viability and decreasing the virus copy number. Both natural compounds could inhibit viral titer, mRNA and protein levels in the prophylactic and post-viral entry stages of PEDV infection. Furthermore, chrysin and naringenin mainly interacted with viral replicase proteins such as 3CLpro and PLP-2 through hydrogen bonds and hydrophobic forces. The complexes formed by chrysin and naringenin with the two PEDV replication proteases had high stability. These results suggested that chrysin and naringenin may exert antiviral effects by interacting with the virus 3CLpro protein or PLP2 protein, thereby affecting their role in the formation of PEDV non-structural proteins or interfering with virus replication. This study lays the foundation for developing chrysin and naringenin as novel anti-PEDV therapeutic drugs.

Bibliometric analysis and visualization of research trends on HIV-1 capsid inhibitors (2000-2022)

Background: Acquired immunodeficiency syndrome (AIDS) has seriously endangered human life and health, the main pathogenic agent is human immunodeficiency virus type 1 (HIV-1). The combination antiretroviral therapy (cART) has shown serious drug resistance and side effects, and the discovery of HIV-1 capsid inhibitors is an effective way to solve the problem. Recent studies have shown significant progress in the research of HIV-1 capsid inhibitors. However, there is still a lack of comprehensive overview of bibliometric analysis in this field. This study aimed to provide the research trends and hotspots of HIV-1 capsid inhibitors. Method: Publications related to HIV-1 capsid inhibitors from 2000 to 2022 were searched on the Web of Science Core Collection (WoSCC) database and screened according to inclusion criteria. VOSviewer was conducted to evaluate the results. Results: 96 publications from 25 countries were finally included, and the number of annual publications related to HIV-1 capsid inhibitors showed an increasing trend. The United States was the most productive country with the most publication number, H-index, and total citation number, as well as the widest international cooperation. The most popular journal in this field was Journal of Virology. Drexel University was the most productive institution, and Simon Cocklin participated in the most publications. Keywords co-occurrence analysis exhibited that studying the molecular mechanism of capsid protein, discovering drug candidates, and improving antiretroviral therapy are the main and hot topics in this field. Conclusion: This is the first bibliometric study in the field of HIV-1 capsid inhibitors, which comprehensively analyzed the research trends and hotspots in this direction. This work is expected to provide the scientific community with new insights to promote the research of HIV-1 capsid inhibitors.

Biological properties and potential of compounds extracted from red seaweeds

Macroalgae have been recently used for different applications in the food, cosmetic and pharmaceutical industry since they do not compete for land and freshwater against other resources. Moreover, they have been highlighted as a potential source of bioactive compounds. Red algae (Rhodophyta) are the largest group of seaweeds, including around 6000 different species, thus it can be hypothesized that they are a potential source of bioactive compounds. Sulfated polysaccharides, mainly agar and carrageenans, are the most relevant and exploited compounds of red algae. Other potential molecules are essential fatty acids, phycobiliproteins, vitamins, minerals, and other secondary metabolites. All these compounds have been demonstrated to exert several biological activities, among which antioxidant, anti-inflammatory, antitumor, and antimicrobial properties can be highlighted. Nevertheless, these properties need to be further tested on in vivo experiments and go in-depth in the study of the mechanism of action of the specific molecules and the understanding of the structure-activity relation. At last, the extraction technologies are essential for the correct isolation of the molecules, in a cost-effective way, to facilitate the scale-up of the processes and their further application by the industry. This manuscript is aimed at describing the fundamental composition of red algae and their most studied biological properties to pave the way to the utilization of this underused resource.

Isolation, Screening, and Active Metabolites Identification of Anti-Vibrio Fungal Strains Derived From the Beibu Gulf Coral

The Beibu Gulf harbors abundant underexplored marine microbial resources, which are rich in diversified secondary metabolites. The genera Vibrio is a well-known pathogenic bacterium of aquatic animals. In this study, 22 fungal strains were isolated and identified from the Beibu Gulf coral via the serial dilution method and internal transcribed spacer (ITS) sequence analysis, which were further divided into three branches by phylogenetic tree analysis. The crude extracts of them via small-scale fermentation were selected for the screening of inhibitory activity against Vibrio alginalyticus, Vibrio coralliilyticus, Vibrio harveyi, Vibrio parahaemolyticus, Vibrio owensii, and Vibrio shilonii. The results showed that eight fungal extracts displayed anti-Vibrio activity via the filter paper disk assay. Several of them showed strong inhibitory effects. Then, two tetramic acid alkaloids, equisetin (1) and 5'-epiequisetin (2), were identified from Fusarium equiseti BBG10 by bioassay-guided isolation, both of which inhibited the growth of Vibrio spp. with the MIC values of 86-132 μg/ml. The scanning electron microscope results showed that cell membranes of Vibrio became corrugated, distorted or ruptured after treatment with 1 and 2. Taken together, this study provided eight fungal isolates with anti-Vibrio potentials, and two alkaloid-type antibiotics were found with anti-Vibrio effects from the bioactive strain F. equiseti BBG10. Our findings highlight the importance of exploring promising microbes from the Beibu Gulf for the identification of anti-Vibrio for future antibiotic development.

Equisetin is an anti-obesity candidate through targeting 11β-HSD1

Obesity is increasingly prevalent globally, searching for therapeutic agents acting on adipose tissue is of great importance. Equisetin (EQST), a meroterpenoid isolated from a marine sponge-derived fungus, has been reported to display antibacterial and antiviral activities. Here, we revealed that EQST displayed anti-obesity effects acting on adipose tissue through inhibiting adipogenesis in vitro and attenuating HFD-induced obesity in mice, doing so without affecting food intake, blood pressure or heart rate. We demonstrated that EQST inhibited the enzyme activity of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), a therapeutic target of obesity in adipose tissue. Anti-obesity properties of EQST were all offset by applying excessive 11β-HSD1's substrates and 11β-HSD1 inhibition through knockdown in vitro or 11β-HSD1 knockout in vivo. In the 11β-HSD1 bypass model constructed by adding excess 11β-HSD1 products, EQST's anti-obesity effects disappeared. Furthermore, EQST directly bond to 11β-HSD1 protein and presented remarkable better intensity on 11β-HSD1 inhibition and better efficacy on anti-obesity than known 11β-HSD1 inhibitor. Therefore, EQST can be developed into anti-obesity candidate compound, and this study may provide more clues for developing higher effective 11β-HSD1 inhibitors.

Algae biotechnology for industrial wastewater treatment, bioenergy production, and high-value bioproducts

A growing world population is causing hazardous compounds to form at an increasingly rapid rate, calling for ecological action. Wastewater management and treatment is an expensive process that requires appropriate integration technology to make it more feasible and cost-effective. Algae are of great interest as potential feedstocks for various applications, including environmental sustainability, biofuel production, and the manufacture of high-value bioproducts. Bioremediation with microalgae is a potential approach to reduce wastewater pollution. The need for effective nutrient recovery, greenhouse gas reduction, wastewater treatment, and biomass reuse has led to a wide interest in the use of microalgae for wastewater treatment. Furthermore, algae biomass can be used to produce bioenergy and high-value bioproducts. The use of microalgae as medicine (production of bioactive and medicinal compounds), biofuels, biofertilizers, and food additives has been explored by researchers around the world. Technological and economic barriers currently prevent the commercial use of algae, and optimal downstream processes are needed to reduce production costs. Therefore, the simultaneous use of microalgae for wastewater treatment and biofuel production could be an economical approach to address these issues. This article provides an overview of algae and their application in bioremediation, bioenergy production, and bioactive compound production. It also highlights the current problems and opportunities in the algae-based sector, which has recently become quite promising.

Advances in Therapeutic L-Nucleosides and L-Nucleic Acids with Unusual Handedness

Nucleic-acid-based small molecule and oligonucleotide therapies are attractive topics due to their potential for effective target of disease-related modules and specific control of disease gene expression. As the non-naturally occurring biomolecules, modified DNA/RNA nucleoside and oligonucleotide analogues composed of L-(deoxy)riboses, have been designed and applied as innovative therapeutics with superior plasma stability, weakened cytotoxicity, and inexistent immunogenicity. Although all the chiral centers in the backbone are mirror converted from the natural D-nucleic acids, L-nucleic acids are equipped with the same nucleobases (A, G, C and U or T), which are critical to maintain the programmability and form adaptable tertiary structures for target binding. The types of L-nucleic acid drugs are increasingly varied, from chemically modified nucleoside analogues that interact with pathogenic polymerases to nanoparticles containing hundreds of repeating L-nucleotides that circulate durably in vivo. This article mainly reviews three different aspects of L-nucleic acid therapies, including pharmacological L-nucleosides, Spiegelmers as specific target-binding aptamers, and L-nanostructures as effective drug-delivery devices.

Reduction of oxidative stress blunts the NLRP3 inflammatory cascade in LPS stimulated human gingival fibroblasts and oral mucosal epithelial cells

The therapeutic armamentarium for the treatment of oral mucositis is very poor. Catechin and baicalin are two natural flavonoids that have been individually reported to have a curative potential. Flavocoxid is a mixed extract containing baicalin and catechin showing antioxidant effects and anti-inflammatory activity mainly due to a dual inhibition of inducible cyclooxygenase (COX-2), 5-lipoxygenase (5-LOX) and NLRP3 pathway. The aim of this study was to evaluate the anti-inflammatory and anti-oxidant effects of flavocoxid in an "in vitro" model of oral mucositis induced by triggering an inflammatory phenotype in human gingival fibroblasts (GF) and human oral mucosal epithelial cells (EC). GF and EC were challenged with lipopolysaccharide (LPS 2 μg/ml) alone or in combination with flavocoxid (32 μg/ml). Flavocoxid increased Nrf2, prompted a marked reduction in malondialdehyde levels and reduced the expression of COX-2 and 5-LOX together with PGE₂, and LTB₄ levels. Flavocoxid caused also a great decrease in the expression of NF-κB and turned off NLRP3 inflammasome and its downstream effectors signal, as caspase-1, IL-1β and IL-18 in both GF and EC cells stimulated with LPS. These results suggest a correlation between oxidative stress and NLRP3 activation and indicate that flavocoxid suppresses the inflammatory storm that accompanies oral mucositis. This preclinical evidence deserves to be confirmed in a clinical setting.

Licorice (Glycyrrhiza glabra) Extracts-Suitable Pharmacological Interventions for COVID-19? A Review

Even though vaccination has started against COVID-19, people should continue maintaining personal and social caution as it takes months or years to get everyone vaccinated, and we are not sure how long the vaccine remains efficacious. In order to contribute to the mitigation of COVID-19 symptoms, the pharmaceutical industry aims to develop antiviral drugs to inhibit the SARS-CoV-2 replication and produce anti-inflammatory medications that will inhibit the acute respiratory distress syndrome (ARDS), which is the primary cause of mortality among the COVID-19 patients. In reference to these tasks, this article considers the properties of a medicinal plant named licorice (Glycyrrhiza glabra), whose phytochemicals have shown both antiviral and anti-inflammatory tendencies through previous studies. All the literature was selected through extensive search in various databases such as google scholar, Scopus, the Web of Science, and PubMed. In addition to the antiviral and anti-inflammatory properties, one of the licorice components has an autophagy-enhancing mechanism that studies have suggested to be necessary for COVID-19 treatment. Based on reviewing relevant professional and historical literature regarding the medicinal properties of licorice, it is suggested that it may be worthwhile to conduct in vitro and in vivo studies, including clinical trials with glycyrrhizic and glycyrrhetinic acids together with other flavonoids found in licorice, as there is the potentiality to provide natural interventions against COVID-19 symptoms.

Targeting Drug Chemo-Resistance in Cancer Using Natural Products

Cancer is one of the leading causes of death globally. The development of drug resistance is the main contributor to cancer-related mortality. Cancer cells exploit multiple mechanisms to reduce the therapeutic effects of anticancer drugs, thereby causing chemotherapy failure. Natural products are accessible, inexpensive, and less toxic sources of chemotherapeutic agents. Additionally, they have multiple mechanisms of action to inhibit various targets involved in the development of drug resistance. In this review, we have summarized the basic research and clinical applications of natural products as possible inhibitors for drug resistance in cancer. The molecular targets and the mechanisms of action of each natural product are also explained. Diverse drug resistance biomarkers were sensitive to natural products. P-glycoprotein and breast cancer resistance protein can be targeted by a large number of natural products. On the other hand, protein kinase C and topoisomerases were less sensitive to most of the studied natural products. The studies discussed in this review will provide a solid ground for scientists to explore the possible use of natural products in combination anticancer therapies to overcome drug resistance by targeting multiple drug resistance mechanisms.

Virtual screening of plant-derived compounds against SARS-CoV-2 viral proteins using computational tools

The new SARS-CoV-2, responsible for the COVID-19 pandemic, has been threatening public health worldwide for more than a year. The aim of this work was to evaluate compounds of natural origin, mainly from medicinal plants, as potential SARS-CoV-2 inhibitors through docking studies. The viral spike (S) glycoprotein and the main protease M^pro, involved in the recognition of virus by host cells and in viral replication, respectively, were the main molecular targets in this study. Molecular docking was performed using AutoDock, which allowed us to select the plant actives with the highest affinity towards the viral targets and to identify the interaction molecular sites with the SARS-CoV2 proteins. The best energy binding values for S protein were, in kcal/mol: -19.22 for glycyrrhizin, -17.84 for gitoxin, -12.05 for dicumarol, -10.75 for diosgenin, and -8.12 for delphinidin. For M^pro were, in kcal/mol: -9.36 for spirostan, -8.75 for N-(3-acetylglycyrrhetinoyl)-2-amino-propanol, -8.41 for α-amyrin, -8.35 for oleanane, -8.11 for taraxasterol, and -8.03 for glycyrrhetinic acid. In addition, the synthetic drugs umifenovir, chloroquine, and hydroxychloroquine were used as controls for S protein, while atazanavir and nelfinavir were used for M^pro. Key hydrogen bonds and hydrophobic interactions between natural compounds and the respective viral proteins were identified, allowing us to explain the great affinity obtained in those compounds with the lowest binding energies. These results suggest that these natural compounds could potentially be useful as drugs to be experimentally evaluated against COVID-19.

Computational and network pharmacology studies of Phyllanthus emblica to tackle SARS-CoV-2

Background

Since December 2019, SARS-CoV-2 had been a significant threat globally, which has accounted for about two million deaths. Several types of research are undergoing and have reported the significant role of repurposing existing drugs and natural lead in the treatment of COVID-19. The plant Phyllanthus emblica (Synonym-Emblica officinalis) (Euphorbiaceae) is a rich source of vitamin C, and its use as an antiviral agent has been well established.

Purpose

The present study was undertaken to investigate the potency of the several components of Phyllanthus emblica against three protein targets of 2019-nCoV viz. NSP15 endoribonuclease, main protease, and receptor binding domain of prefusion spike protein using molecular docking and dynamics studies.

Methods

The docking simulation studies were carried out using Schrödinger maestro 2018-1 MM share version, while dynamics studies were conducted to understand the binding mechanism and the complexes' stability studies.

Results

Out of sixty-six tested compounds, Chlorogenic acid, Quercitrin, and Myricetin were most effective in showing the highest binding energy against selected protein targets of SARS-CoV-2. The network pharmacology analysis study confirmed these compounds' role in modulating the immune response, inflammatory cascade, and cytokine storm through different signaling pathways.

Conclusion

Current pharmacoinformatic approach shows possible role of Phyllanthus emblica in the treatment and management of COVID-19.

Identification of bioactive compounds from Glycyrrhiza glabra as possible inhibitor of SARS-CoV-2 spike glycoprotein and non-structural protein-15: a pharmacoinformatics study

At present, the world is facing a pandemic named as COVID-19, caused by SARS-CoV-2. Traditional Chinese medicine has recommended the use of liquorice (Glycyrrhiza species) in the treatment of infections caused by SARS-CoV-2. Therefore, the present investigation was carried out to identify the active molecule from the liquorice against different protein targets of COVID-19 using an in-silico approach. The molecular docking simulation study of 20 compounds along with two standard antiviral drugs (Lopinavir and Rivabirin) was carried out with the help of Autodock vina software using two protein targets from COVID-19 i.e. spike glycoprotein (PDB ID: 6VSB) and Non-structural Protein-15 (Nsp15) endoribonuclease (PDB ID: 6W01). From the observed binding energy and the binding interactions, glyasperin A showed high affinity towards Nsp15 endoribonuclease with uridine specificity, while glycyrrhizic acid was found to be best suited for the binding pocket of spike glycoprotein and also prohibited the entry of the virus into the host cell. Further, the dynamic behavior of the best-docked molecules inside the spike glycoprotein and Nsp15 endoribonuclease were explored through all-atoms molecular dynamics (MD) simulation study. Several parameters from the MD simulation have substantiated the stability of protein-ligand stability. The binding free energy of both glyasperin A and glycyrrhizic acid was calculated from the entire MD simulation trajectory through the MM-PBSA approach and found to high binding affinity towards the respective protein receptor cavity. Thus, glyasperin A and glycyrrhizic acid could be considered as the best molecule from liquorice, which could find useful against COVID-19. Communicated by Ramaswamy H. Sarma.

Evaluation of Microalgae Antiviral Activity and Their Bioactive Compounds

During the last year, science has been focusing on the research of antivirally active compounds overall after the SARS-CoV-2 pandemic, which caused a great amount of deaths and the downfall of the economy in 2020. Photosynthetic organisms such as microalgae are known to be a reservoir of bioactive secondary metabolites; this feature, coupled with the possibility of achieving very high biomass levels without excessive energetic expenses, make microalgae worthy of attention in the search for new molecules with antiviral effects. In this work, the antiviral effects of microalgae against some common human or animal viruses were considered, focusing our attention on some possible effects against SARS-CoV-2. We summed up the data from the literature on microalgae antiviral compounds, from the most common ones, such as lectins, polysaccharides and photosynthetic pigments, to the less known ones, such as unidentified proteins. We have discussed the effects of a microalgae-based genetic engineering approach against some viral diseases. We have illustrated the potential antiviral benefits of a diet enriched in microalgae.

Insights into forsythia honeysuckle (Lianhuaqingwen) capsules: A Chinese herbal medicine repurposed for COVID-19 pandemic

Background

In December 2019, a novel coronavirus, SARS-CoV-2 caused a series of acute atypical respiratory diseases worldwide. However, there is still a lack of drugs with clear curative effects, and the clinical trial research of vaccines has not been completely finished.

Purpose

LH capsules are approved TCM patent medicine that are widely used for the treatment of respiratory tract infectious diseases caused by colds and flu. On April 12, 2020, LH capsules and granules were officially repurposed by the China Food and Drug Administration (CFDA) for patients with mild COVID-19 based on their safety and efficacy demonstrated through multicentre, randomized, controlled clinical trials. We hope to conduct a comprehensive review of it through modern pharmacy methods, and try to explain its possible mechanism.

Methods

Using the full names of LH capsules Lianhuaqingwen, Lianhua Qingwen andSARS-COV-2, COVID-19 as the keywords of the search terms, systemically search for existing related papers in various databases such as Web of Science and PubMed. And completed the collection of clinical data in ClinicalTrials.gov and Chinese Clinical Trial Registry. Last but not least, we have sorted out the anti-inflammatory and antiviral mechanisms of LH capsules through literature and Selleck.

Results

This review systematically sorted out the active ingredients in LH capsules. Furthermore, the related pharmacological and clinical trials of LH capsule on SARS-CoV-2, IAV and IBV were discussed in detail. Moreover, the present review provides the first summary of the potential molecular mechanism of specific substances in LH capsules involved in resistance to SARS-COV-2 infection and the inhibition of cytokine storm syndrome (CSS) caused by IL-6.

Conclusion

This review summarizes the available reports and evidence that support the use of LH capsules as potential drug candidates for the prevention and treatment of COVID-19. However, TCM exerts its effects through multiple targets and multiple pathways, and LH capsules are not an exception. Therefore, the relevant mechanisms need to be further improved and experimentally verified.

Medicinal plants: Treasure for antiviral drug discovery

The pandemic of viral diseases like novel coronavirus (2019-nCoV) prompted the scientific world to examine antiviral bioactive compounds rather than nucleic acid analogous, protease inhibitors, or other toxic synthetic molecules. The emerging viral infections significantly associated with 2019-nCoV have challenged humanity's survival. Further, there is a constant emergence of new resistant viral strains that demand novel antiviral agents with fewer side effects and cell toxicity. Despite significant progress made in immunization and regenerative medicine, numerous viruses still lack prophylactic vaccines and specific antiviral treatments that are so often influenced by the generation of viral escape mutants. Of importance, medicinal herbs offer a wide variety of therapeutic antiviral chemotypes that can inhibit viral replication by preventing viral adsorption, adhering to cell receptors, inhibiting virus penetration in the host cell, and competing for pathways of activation of intracellular signals. The present review will comprehensively summarize the promising antiviral activities of medicinal plants and their bioactive molecules. Furthermore, it will elucidate their mechanism of action and possible implications in the treatment/prevention of viral diseases even when their mechanism of action is not fully understood, which could serve as the base for the future development of novel or complementary antiviral treatments.

Antiviral activity of glycyrrhizic acid conjugates with amino acid esters against Zika virus

Zika virus (ZIKV) is a new pathogenic flavivirus transmitted by mosquitoes Aedes spp. ZIKV infection is accompanied by serious neurological complications and is especially dangerous for pregnant women, in which it can lead to congenital malformations of the fetus and microcephaly in neonates. Currently, there are no licensed vaccines or specific post-infectious therapies for ZIKV infection. This report is devoted to the study of glycyrrhizic acid (GL) derivatives as ZIKV inhibitors. The inhibitory assays on the cytopathic effect (CPE) and viral infectivity of ZIKV in three different human cell lines revealed that the conjugation of GL with amino acids and their esters (methyl, ethyl) is influenced by the antiviral activity of the compounds. GL conjugates with Glu(OMe)-OMe 11, Glu(OH)-OMe 12, Asp(OMe)-OMe 13, TyrOMe 14, LeuOEt 15, and PheOEt 16 with free COOH groups in the triterpene moiety were active against ZIKV. The most active compounds 13 and 14 have IC50 values of 0.23 μM and 0.09 μM against low doses (MOI = 0.05) of ZIKV strain PRVABC59, 1.20 μM and 0.74 μM against high doses (MOI = 10) of ZIKV strain Natal RGN single-round infectious particles, respectively. The lead compound was 14 with a high selectivity index (SI < 500). Compound 13 showed a higher inhibitory effect on the early stage (entry) of ZIKV replication than compound 14, and was less potent than compound 14 at the post-entry stage, consistent with the docking models. Compounds 13 and 14 also had a strong interaction with the active site pocket of NS5 MTase. Compounds 13 and 14 are recommended for expanded antiviral studies against ZIKV infection.

Naturally Occurring Calanolides: Occurrence, Biosynthesis, and Pharmacological Properties Including Therapeutic Potential

Calanolides are tetracyclic 4-substituted dipyranocoumarins. Calanolide A, isolated from the leaves and twigs of Calophyllum lanigerum var. austrocoriaceum (Whitmore) P. F. Stevens, is the first member of this group of compounds with anti-HIV-1 activity mediated by reverse transcriptase inhibition. Calanolides are classified pharmacologically as non-nucleoside reverse transcriptase inhibitors (NNRTI). There are at least 15 naturally occurring calanolides distributed mainly within the genus Calophyllum, but some of them are also present in the genus Clausena. Besides significant anti-HIV properties, which have been exploited towards potential development of new NNRTIs for anti-HIV therapy, calanolides have also been found to possess anticancer, antimicrobial and antiparasitic potential. This review article provides a comprehensive update on all aspects of naturally occurring calanolides, including their chemistry, natural occurrence, biosynthesis, pharmacological and toxicological aspects including mechanism of action and structure activity relationships, pharmacokinetics, therapeutic potentials and available patents.

Lasso Peptides: Heterologous Production and Potential Medical Application

Lasso peptides are natural products found in bacteria. They belong to a specific family of ribosomally-synthesized and posttranslationally-modified peptides with an unusual lasso structure. Lasso peptides possess remarkable thermal and proteolytic stability and various biological activities, such as antimicrobial activity, enzyme inhibition, receptor blocking, anticancer properties and HIV antagonism. They have promising potential therapeutic effects on gastrointestinal diseases, tuberculosis, Alzheimer’s disease, cardiovascular disease, fungal infections and cancer. Lasso peptides with high stability have been shown to be good carriers for other bioactive peptides. These make them attractive candidates for pharmaceutical research. This review aimed to describe the strategies used for the heterologous production of lasso peptides. Also, it indicated their therapeutical potential and their capacity to use as an efficient scaffold for epitope grafting.

Phlorotannins as HIV Vpu inhibitors, an in silico virtual screening study of marine natural products

The importance of new effective treatment methodologies for human immunodeficiency virus (HIV) is undeniable for the medical society. Viral protein U (Vpu), one of the disparaged accessory proteins of HIV, is responsible for the dissemination of viral particles, and HIV mutants lacking Vpu protein have remarkably reduced pathogenicity. Here, we explored the marine natural products to find the leading structures which can potentially inhibit the activity of Vpu in silico. To fulfill this goal, we set up a virtual screening based on molecular docking to evaluate the binding capacity of different marine products to Vpu. For validation, we used molecular dynamics simulation and monitored the root mean square deviation value and binding interactions. The results were intriguing when we realized that the hit compounds (phlorotannins) had previously been identified as reverse transcriptase and HIV protease inhibitors. This research inaugurates a new road to combat HIV by multifaceted mode of action of these marine natural products without putting the normal cells in jeopardy (with their safe toxicological profile).

Biochemistry, Safety, Pharmacological Activities, and Clinical Applications of Turmeric: A Mechanistic Review

Turmeric (Curcuma longa L.) is a popular natural drug, traditionally used for the treatment of a wide range of diseases. Its root, as its most popular part used for medicinal purposes, contains different types of phytochemicals and minerals. This review summarizes what is currently known on biochemistry, safety, pharmacological activities (mechanistically), and clinical applications of turmeric. In short, curcumin is considered as the fundamental constituent in ground turmeric rhizome. Turmeric possesses several biological activities including anti-inflammatory, antioxidant, anticancer, antimutagenic, antimicrobial, antiobesity, hypolipidemic, cardioprotective, and neuroprotective effects. These reported pharmacologic activities make turmeric an important option for further clinical research. Also, there is a discussion on its safety and toxicity.

Abdel-Daim M, Prasad Devkota H. Traditional Uses, Bioactive Chemical Constituents, and Pharmacological and Toxicological Activities of Glycyrrhiza glabra L. (Fabaceae)

Traditional herbal remedies have been attracting attention as prospective alternative resources of therapy for diverse diseases across many nations. In recent decades, medicinal plants have been gaining wider acceptance due to the perception that these plants, as natural products, have fewer side effects and improved efficacy compared to their synthetic counterparts. Glycyrrhiza glabra L. (Licorice) is a small perennial herb that has been traditionally used to treat many diseases, such as respiratory disorders, hyperdipsia, epilepsy, fever, sexual debility, paralysis, stomach ulcers, rheumatism, skin diseases, hemorrhagic diseases, and jaundice. Moreover, chemical analysis of the G. glabra extracts revealed the presence of several organic acids, liquirtin, rhamnoliquirilin, liquiritigenin, prenyllicoflavone A, glucoliquiritin apioside, 1-metho-xyphaseolin, shinpterocarpin, shinflavanone, licopyranocoumarin, glisoflavone, licoarylcoumarin, glycyrrhizin, isoangustone A, semilicoisoflavone B, licoriphenone, and 1-methoxyficifolinol, kanzonol R and several volatile components. Pharmacological activities of G. glabra have been evaluated against various microorganisms and parasites, including pathogenic bacteria, viruses, and Plasmodium falciparum, and completely eradicated P. yoelii parasites. Additionally, it shows antioxidant, antifungal, anticarcinogenic, anti-inflammatory, and cytotoxic activities. The current review examined the phytochemical composition, pharmacological activities, pharmacokinetics, and toxic activities of G. glabra extracts as well as its phytoconstituents.

Variability of Hypericins and Hyperforin in Hypericum Species from the Sicilian Flora

Within Sicilian flora, the genus Hypericum (Guttiferae) includes 10 native species, the most popular of which is H. perforatum. Hypericum's most investigated active compounds belong to naphtodianthrones (hypericin, pseudohypericin) and phloroglucinols (hyperforin, adhyperforin), and the commercial value of the drug is graded according to its total hypericin content. Ethnobotanical sources attribute the therapeutic properties recognized for H. perforatum, also to other Hypericum species. However, their smaller distribution inside the territory suggests that an industrial use of such species, when collected from the wild, would result in an unacceptable depletion of their natural stands. This study investigated about the potential pharmacological properties of 48 accessions from six native species of Hypericum, including H. perforatum and five 'minor' species, also comparing, when possible, wild and cultivated sources. The variability in the content of active metabolites was remarkably high, and the differences within the species were often comparable to the differences among species. No difference was enlightened between wild and cultivated plants. A carefully planned cultivation of Hypericum seems the best option to achieve high and steady biomass yields, but there is a need for phytochemical studies, aimed to identify for multiplication the genotypes with the highest content of the active metabolites.

Antiviral and virucidal activities of Lucilia cuprina maggots' excretion/secretion (Diptera: Calliphoridae): first work

Maggots of Lucilia sericata and L. cuprina are a backbone of the maggot debridement therapy. Further, the excretion/secretion (E/S) of these maggots has antibacterial and antifungal activities, nevertheless the antiviral activity of E/S for these maggots still out the focus. This study aimed to evaluate the E/S of L. cuprina maggots against the Rift Valley Fever (RVF) and Coxsackie B4 (CB4) viruses for first time. After collection of the E/S, its cytotoxicity on Vero cells was evaluated and the safe concentration was determined which used to investigate the antiviral and virucidal effect of E/S on the selected viruses. The E/S decreased the titers of the tested viruses compared with that of untreated viruses. The outcome data refer to that the E/S of L. cuprina consider as a promising antiviral and virucidal agent.

Characterization of Nine Compounds Isolated from the Acid Hydrolysate of Lonicera fulvotomentosa Hsu et S. C. Cheng and Evaluation of Their In Vitro Activity towards HIV Protease

In this study, we isolated nine compounds from the acid hydrolysate of the flower buds of Lonicera fulvotomentosa Hsu et S. C. Cheng and characterized their chemical structures using ¹H-NMR, ¹³C-NMR, and electron ionization mass spectroscopy (EI-MS). These compounds were identified as β-sitosterol (1), 5,5′-dibutoxy-2,2′-bifuran (2), nonacosane-10-ol (3), ethyl (3β)-3,23-dihydroxyolean-12-en-28-oate (4), oleanolic acid (5), ethyl caffeate (6), caffeic acid (7), isovanillin (8), and hederagenin (9), with 4 as a new triterpene compound. Inhibitory activity against human immunodeficiency virus (HIV) protease was also evaluated for the compounds, and only ethyl caffeate, caffeic acid, and isovanillin (6, 7, and 8) exhibited inhibitory effects, with IC₅₀ values of 1.0 μM, 1.5 μM, and 3.5 μM, respectively. Molecular docking with energy minimization and subsequent molecular dynamic (MD) simulation showed that ethyl caffeate and caffeic acid bound to the active site of HIV protease, while isovanillin drifted out from the active site and dissociated into bulk water during MD simulations, and most of the binding residues of HIV protease have been previously identified for HIV protease inhibitors. These results suggest that caffeic acid derivatives may possess inhibitory activities towards HIV protease other than previously reported inhibitory activities against HIV integrase, and thus ethyl caffeate and caffeic acid could be used as lead compounds in developing potential HIV protease inhibitors, and possibly even dual-function inhibitors against HIV.

Current Trends on Seaweeds: Looking at Chemical Composition, Phytopharmacology, and Cosmetic Applications

Seaweeds have received huge interest in recent years given their promising potentialities. Their antioxidant, anti-inflammatory, antitumor, hypolipemic, and anticoagulant effects are among the most renowned and studied bioactivities so far, and these effects have been increasingly associated with their content and richness in both primary and secondary metabolites. Although primary metabolites have a pivotal importance such as their content in polysaccharides (fucoidans, agars, carragenans, ulvans, alginates, and laminarin), recent data have shown that the content in some secondary metabolites largely determines the effective bioactive potential of seaweeds. Among these secondary metabolites, phenolic compounds feature prominently. The present review provides the most remarkable insights into seaweed research, specifically addressing its chemical composition, phytopharmacology, and cosmetic applications.

Glycyrrhizic acid derivatives as Dengue virus inhibitors

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It is the first report to display structure-anti-DENV activity relationships of Glycyrrhizic acid (GL) derivatives.

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GL conjugates with isoleucine 13 and 11-aminoundecanoic acid 17 have been identified as potent DENV2 inhibitors.

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GL derivatives 13 and 17 showed lower IC50 values (1.2–1.3 μM) against DENV2 infectivity in Vero E6 cells than GL (IC50 8.1 μM).

Dengue virus (DENV) is one of the most geographically distributed pathogenic flaviviruses transmitted by mosquitoes Aedes sps. In this study, the structure-antiviral activity relationships of Glycyrrhizic acid (GL) derivatives was evaluated by the inhibitory assays on the cytopathic effect (CPE) and viral infectivity of DENV type 2 (DENV2) in Vero E6 cells. GL (96% purity) had a low cytotoxicity to Vero E6 cells, inhibited DENV2-induced CPE, and reduced the DENV-2 infectivity with the IC50 of 8.1 μM. Conjugation of GL with amino acids or their methyl esters and the introduction of aromatic acylhydrazide residues into the carbohydrate part strongly influenced on the antiviral activity. Among compounds tested GL conjugates with isoleucine 13 and 11-aminoundecanoic acid 17 were found as potent anti-DENV2 inhibitors (IC50 1.2–1.3 μM). Therefore, modification of GL is a perspective way in the search of new antivirals against DENV2 infection.

Triterpenoid gene expression and phytochemical content in Iranian licorice under salinity stress

Licorice is a well-known medicinal plant, containing various secondary metabolites of triterpenoid and phenolic families. The aim of this study is to evaluate the effect of salinity stress on the expression of key genes involved in the biosynthetic pathway of triterpenoids such as glycyrrhizin, betulinic acid, soyasaponins, and phytosterols in licorice root, as well as providing a phonemic platform to characterize antioxidant properties, glycyrrhizin, and total phenolic content. This study also includes measuring the gene expression level and glycyrrhizin content in leaves and roots of control plants. The studied genes included squalene synthase (SQS1 and SQS2), β-amyrin synthase (bAS), lupeol synthase (LUS), cycloartenol synthase (CAS), β-amyrin 11-oxidase (CYP88D6), and β-amyrin 24-hydroxylase (CYP93E6). Our results revealed that all of the mentioned genes were upregulated following the stress condition with different transcription rates. The highest increase (12-fold) was observed for the expression of the LUS gene, which is related to the betulinic acid pathway. Also, the highest content of glycyrrhizin was observed at 72 h post-treatment, which was consistent with the upregulated transcription levels of the glycyrrhizin pathway genes especially SQS1 and CYP88D6 at the same time. Correlation and stepwise regression analysis proved the key role of SQS1 gene in the biosynthetic pathway of glycyrrhizin. Antioxidant activity and phenolic content also were increased following stress condition. A comparison between the expression levels of SQS1 and other genes involved in the production of glycyrrhizin, phytosterols, and soyasaponins revealed a similar transcription trend, which shows the gene expression in the roots was significantly higher than the leaves. In contrast, SQS2 and LUS genes displayed a higher expression in leaf tissues. The genes related to betulinic acid biosynthetic pathway exhibited an expression rate different from other triterpenoid pathway genes, which could be observed in the leaves and roots of control plants and the roots of salt-treated plants. Furthermore, results showed that these two SQS genes have different expression rates due to different plant tissues (roots and leaves) and stress conditions. Importantly, in contrast to previous reports, we detected the glycyrrhizin in leaf tissues. This result may indicate the presence of a different genetic background in native Iranian licorice germplasm.

Diarylheptanoids as nutraceutical: A review

Phenolic compounds are naturally occurring compounds present ubiquitously in plants. They have potential health benefits and substantiate evidence for their nutraceutical applications. Diarylheptanoids are part of the broad class of plant phenolics with structurally divergent compounds. They have been used in traditional medicines and homemade remedies to treat various ailments, as organoleptic additives in foods, and also for aesthetic purposes. With their potential therapeutic and organoleptic characteristics, diarylhepatanoids can be rightly termed as nutraceuticals. This review summarizes the wide range of pharmacological activities of diarylhepatanoids and nutraceutical formulations, with relevance to human health.

Metabolic Engineering of Glycyrrhizin Pathway by Over-Expression of Beta-amyrin 11-Oxidase in Transgenic Roots of Glycyrrhiza glabra

Glycyrrhiza glabra is one of the most important and well-known medicinal plants which produces various triterpene saponins such as glycyrrhizin. Beta-amyrin 11-oxidase (CYP88D6) plays a key role in engineering pathway of glycyrrhizin production and converts an intermediated beta-amyrin compound to glycyrrhizin. In this study, pBI121^GUS-9:CYP88D6 construct was transferred to G. glabra using Agrobacterium rhizogene ATCC 15834. The quantitation of transgene was measured in putative transgenic hairy roots using qRT-PCR. The amount of glycyrrhizin production was measured by HPLC in transgenic hairy root lines. Gene expression analysis demonstrated that CYP88D6 was over-expressed only in one of transgenic hairy root lines and was reduced in two others. Beta-amyrin 24-hydroxylase (CYP93E6) was significantly expressed in one of the control hairy root lines. The amount of glycyrrhizin metabolite in over-expressed line was more than or similar to that of control hairy root lines. According to the obtained results, it would be recommended that multi-genes of glycyrrhizin biosynthetic pathway be transferred simultaneously to the hairy root in order to increase glycyrrhizin content.

Medicinal Plants Used in the Treatment of Human Immunodeficiency Virus

Since the beginning of the epidemic, human immunodeficiency virus (HIV) has infected around 70 million people worldwide, most of whom reside is sub-Saharan Africa. There have been very promising developments in the treatment of HIV with anti-retroviral drug cocktails. However, drug resistance to anti-HIV drugs is emerging, and many people infected with HIV have adverse reactions or do not have ready access to currently available HIV chemotherapies. Thus, there is a need to discover new anti-HIV agents to supplement our current arsenal of anti-HIV drugs and to provide therapeutic options for populations with limited resources or access to currently efficacious chemotherapies. Plant-derived natural products continue to serve as a reservoir for the discovery of new medicines, including anti-HIV agents. This review presents a survey of plants that have shown anti-HIV activity, both in vitro and in vivo.

Iminosugar C-Nitromethyl Glycoside: Stereoselective Synthesis of Isoxazoline and Isoxazole-Fused Bicyclic Iminosugars

A simple and efficient method for the stereoselective synthesis of isoxazoline/isoxazole-fused iminosugar derivatives has been developed using intramolecular nitrile oxide cycloaddition (INOC) as a key step. Iminosugar C-nitromethyl glycosides, derived from simple carbohydrates, served as excellent nitrile oxide precursors in 1,3-dipolar cycloaddition reactions. N-Alkenyl iminosugar C-nitromethyl glycosides afforded novel isoxazoline-fused indolizidine-, pyrrolizidine-, and quinolizidine-based iminosugars in excellent yields with a high degree of stereoselectivity, whereas N-alkynyl iminosugar C-nitromethyl glycosides furnished the corresponding isoxazole containing tricyclic iminosugars in very good yields.

Glycyrrhiza glabra: Chemistry and Pharmacological Activity

Nature is an attractive source of new therapeutic candidate compounds as a tremendous chemical diversity is found in millions of species of plants, animals, marine organisms, and microorganisms as potential medicinal agents. This chapter of research is an effort to highlight the phytochemical/chemical constituents of an ancient medicinal plant G. glabra and their pharmacological importance. G. glabra is an old age medicinal plant that belongs to Leguminosae/Fabaceae/Papilionaceae family and commonly known as mulaithi in north India. The chemical composition of G. glabra is glycyrrhizin, glycyrrhetic acid, isoliquiritin, isoflavones, etc., and their derivatives have been reported for several pharmacological activities like, expectorant, antidemulcent, antiulcer, anticancer, anti-inflammatory, antidiabetic, etc. These phytochemicals hold strong promise for designing new herbal drugs, and derivatives of these compounds are being generated to evaluate their pharmacological purposes for future drug use. Natural products have been a prime source for the treatment of many forms of ailments, many of which are consumed daily with the diet. They provide significant protection against various diseases and disorders.

Synthesis and biological evaluation of N-arylated-lactam-type iminosugars as potential immunosuppressive agents

Since the immunosuppressive agents currently used in clinics have significant side effects, it is very important to search for new effective and safe immunosuppressants. Iminosugars as a new class of immunosuppressants are less explored. In this report, 24 new N-arylated iminosugar derivatives, including d-talo and d-galacto epimers, were designed and synthesized, and their immunosuppressive effects were evaluated by MTT assay. The experimental data demonstrated that compound 20 showed the strongest inhibition effect (IC₅₀ = 6.94 μM). Further studies revealed that the inhibitory effects on splenocyte proliferation may come from the suppression of both IFN-γ and IL-4 cytokines. The preliminary structure-activity relationship (SAR) analysis suggested that N-arylated d-galacto-type iminosugars showed better inhibitory activities than d-talo-type analogues. The SAR analysis also showed that the inhibition effect of iminosugars can be improved by decreasing the polarity or increasing the hydrophobicity. These results may be beneficial to the discovery of new iminosugar derivatives as immunosuppressive agents.

Medicinal plants: a repository of antiviral metabolites

The global disease burden caused by viral infection has persuaded scientists to develop novel and more effective antiviral drugs. Synthetic antiviral drugs contain substances other than viruses, which have the ability to offer defensive or therapeutic effects in favor of virus-infected host. Medicinal plants, on the other hand, have proven to be potent sources of antiviral agents with some major advantages over conventional drug therapy due to their broad therapeutic potency and limited side effects. Medicinal plants synthesize and preserve a variety of biochemical products possessing potential therapeutic index, aiding elimination/inhibition of viruses. This mini-review provides an insight into medicinal plants and their metabolites explaining their potential role as major alternatives in the treatment of viral infections.

Bioactive Pentacyclic Triterpene Ester Derivatives from Alnus viridis ssp. viridis Bark

Seven derivatives of pentacyclic triterpene acids (1-7) were isolated from the bark of Alnus viridis ssp. viridis using a combination of column chromatography and semipreparative HPLC. Compounds 1-3, 6, and 7 were determined to be new after spectroscopic data interpretation and were assigned as 27-hydroxyalphitolic acid derivatives (1-3), a 27-hydroxybetulinic acid derivative (6), and a 3-epi-maslinic acid derivative (7), respectively. Pentacyclic triterpenoids with a C-27 hydroxymethyl group have been found in species of the genus Alnus for the first time. These compounds were subjected to cytotoxicity testing against a number of cancer cell lines. Also, selected pentacyclic triterpenoids were selected as potential inhibitors of topoisomerases I and IIα for an in silico investigation.

The Molecular Basis of Toxins' Interactions with Intracellular Signaling via Discrete Portals

An understanding of the molecular mechanisms by which microbial, plant or animal-secreted toxins exert their action provides the most important element for assessment of human health risks and opens new insights into therapies addressing a plethora of pathologies, ranging from neurological disorders to cancer, using toxinomimetic agents. Recently, molecular and cellular biology dissecting tools have provided a wealth of information on the action of these diverse toxins, yet, an integrated framework to explain their selective toxicity is still lacking. In this review, specific examples of different toxins are emphasized to illustrate the fundamental mechanisms of toxicity at different biochemical, molecular and cellular- levels with particular consideration for the nervous system. The target of primary action has been highlighted and operationally classified into 13 sub-categories. Selected examples of toxins were assigned to each target category, denominated as portal, and the modulation of the different portal’s signaling was featured. The first portal encompasses the plasma membrane lipid domains, which give rise to pores when challenged for example with pardaxin, a fish toxin, or is subject to degradation when enzymes of lipid metabolism such as phospholipases A₂ (PLA₂) or phospholipase C (PLC) act upon it. Several major portals consist of ion channels, pumps, transporters and ligand gated ionotropic receptors which many toxins act on, disturbing the intracellular ion homeostasis. Another group of portals consists of G-protein-coupled and tyrosine kinase receptors that, upon interaction with discrete toxins, alter second messengers towards pathological levels. Lastly, subcellular organelles such as mitochondria, nucleus, protein- and RNA-synthesis machineries, cytoskeletal networks and exocytic vesicles are also portals targeted and deregulated by other diverse group of toxins. A fundamental concept can be drawn from these seemingly different toxins with respect to the site of action and the secondary messengers and signaling cascades they trigger in the host. While the interaction with the initial portal is largely determined by the chemical nature of the toxin, once inside the cell, several ubiquitous second messengers and protein kinases/ phosphatases pathways are impaired, to attain toxicity. Therefore, toxins represent one of the most promising natural molecules for developing novel therapeutics that selectively target the major cellular portals involved in human physiology and diseases.

Anti-HSV-2 activity of Terminalia chebula Retz extract and its constituents, chebulagic and chebulinic acids

Background

Development of new and effective therapeutics for sexually transmitted herpes simplex virus-2 (HSV-2) infection is important from public health perspective. With an aim to identify natural products from medicinal plants, in the present study, the potential of Terminalia chebula Retz was investigated for its activity against HSV-2.

Methods

Fruits of Terminalia chebula Retz were used to prepare 50% ethanolic extract. In addition, chebulagic acid and chebulinic acid both purified from T. chebula were also used. The extract as well as purified compounds were first used to determine their in vitro cytotoxicity on Vero cells by MTT assay. T. chebula extract, chebulagic acid, chebulinic acid along with acyclovir were subsequently assessed for direct anti-viral activity, and their ability to inhibit attachment and penetration of HSV-2 to the Vero cells. In addition, their anti-HSV-2 activity was also determined by in vitro post-infection plaque reduction assay.

Results

Cytotoxicity assay using Vero cells revealed CC₅₀ = 409.71 ± 47.70 μg/ml for the extract whereas chebulagic acid and chebulinic acid showed more than 95% cell viability up to 200 μg/ml. The extract from T. chebula (IC₅₀ = 0.01 ± 0.0002 μg/ml), chebulagic (IC₅₀ = 1.41 ± 0.51 μg/ml) and chebulinic acids (IC₅₀ = 0.06 ± 0.002 μg/ml) showed dose dependent potent in vitro direct anti-viral activity against HSV-2. These also effectively prevented the attachment as well as penetration of the HSV-2 to Vero cells. In comparison, acyclovir showed poor direct anti-viral activity and failed to significantly (p > 0.05) prevent the attachment as well as penetration of HSV-2 to Vero cells when tested upto 50 μg/ml. However, in post-infection plaque reduction assay, T. chebula extract, chebulagic and chebulinic acids showed IC₅₀ values of 50.06 ± 6.12, 31.84 ± 2.64, and 8.69 ± 2.09 μg/ml, respectively, which were much lower than acyclovir (71.80 ± 19.95 ng/ml).

Conclusions

The results presented herein suggest that T. chebula extract, chebulagic and chebulinic acids have higher direct antiviral activity against HSV-2 and efficacy to inhibit virus attachment and penetration to the host cells as compared to acyclovir. However, acyclovir is more potent to inhibit post-infection virus replication. Hence, T. chebula may be a useful candidate for developing alternative therapy for prevention of sexually transmitted HSV-2 infection.

Graphical abstract

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Electrochemical Alcohol Oxidation Mediated by TEMPO-like Nitroxyl Radicals

The electrocatalytic oxidation of alcohols mediated by TEMPO-like nitroxyl radicals is an economically and industrially viable method that will shortly find commercial application in the synthesis of valued substances including active pharmaceutical ingredients (APIs), valued natural product derivatives, fine chemicals, and valued nanomaterials.

Pharmacological Activities and Phytochemical Constituents

Glycyrrhiza glabra is one of the most popular medicinal plants and it has been used in traditional herbal remedy since ancient times (Blumenthal et al. in Herbal medicine: expanded commission E monographs. Integrative Medicine Communications, Newton, 2000; Parvaiz et al. in Global J Pharmocol 8(1):8–13, 2014; Altay et al. in J Plant Res 129(6):1021–1032, 2016). Many experimental, pharmacological and clinical studies show that liquorice has antimicrobial, antibacterial, antiviral, antifungal, antihepatotoxic, antioxidant, antiulcer, anti-hemorrhoid antihyperglycemic, antidiuretic, antinephritic, anticarcinogenic, antimutagenic, anticytotoxic, anti-inflammatory, and blood stopper activity.

Clinical efficacy of melittin in the treatment of cats infected with the feline immunodeficiency virus

OBJECTIVE

The bee venom melittin shows an antiviral efficacy against the human immunodeficiency virus in cell culture. It was shown to be non-toxic for cats. Aim of this pilot study was to investigate the clinical efficacy and side-effects of melittin in cats naturally infected with feline immunodeficiency virus (FIV).

MATERIAL AND METHODS

The study was performed as a prospective, placebo-controlled double-blinded trial. Twenty cats were included, of which 10 cats each were treated with either melittin (500 µg/kg body weight) or phosphate-buffered saline (placebo) subcutaneously twice per week. During the treatment period of 6 weeks, the cats' general health status, determined by the Karnofsky's score, and the severity of clinical signs (conjunctivitis and stomatitis) using a clinical scoring system were evaluated. Haematology, biochemistry profiles, lymphocyte subpopulations, CD4/CD8 ratio, and pterines (biopterine, 7-xanthopterine) as surrogate parameters were also compared.

RESULTS

The general health status and the clinical scores for conjunctivitis and stomatitis improved in cats treated with melittin. A statistically significant improvement however could only be detected for conjunctivitis in cats treated with melittin compared to cats treated with placebo which was likely due to different scores between both groups at the beginning. No influence on the lymphocyte subpopulations, CD4/CD8 ratio, and pterine concentrations was observed. No side effects occurred in this study.

CONCLUSION AND CLINICAL RELEVANCE

In the protocol used in the present study, no significant efficacy of melittin could be detected. However, efficacy of melittin, especially if applied in a higher dosage as in the present study or for a longer period, could be evaluated in further studies. Synergistic effects if used in combination with classic antiretroviral drugs could be an interesting future approach.

Melittin-Induced Lipid Extraction Modulated by the Methylation Level of Phosphatidylcholine Headgroups

Protein- and peptide-induced lipid extraction from membranes is a critical process for many biological events, including reverse cholesterol transport and sperm capacitation. In this work, we examine whether such processes could display specificity for some lipid species. Melittin, the main component of dry bee venom, was used as a model amphipathic α-helical peptide. We specifically determined the modulation of melittin-induced lipid extraction from membranes by the change of the methylation level of phospholipid headgroups. Phosphatidylcholine (PC) bilayers were demethylated either by substitution with phosphatidylethanolamine (PE) or chemically by using mono- and dimethylated PE. It is shown that demethylation reduces the association of melittin with membranes, likely because of the resulting tighter chain packing of the phospholipids, which reduces the capacity of the membranes to accommodate inserted melittin. This reduced binding of the peptide is accompanied by an inhibition of the lipid extraction caused by melittin. We demonstrate that melittin selectively extracts PC from PC/PE membranes. This selectivity is proposed to be a consequence of a PE depletion in the surroundings of bound melittin to minimize disruption of the interphospholipid interactions. The resulting PC-enriched vicinity of melittin would be responsible for the observed formation of PC-enriched lipid/peptide particles resulting from the lipid efflux. These findings reveal that modulating the methylation level of phospholipid headgroups is a simple way to control the specificity of lipid extraction from membranes by peptides/proteins and thereby modulate the lipid composition of the membranes.