Investigation of Stilbenoids as Potential Therapeutic Agents for Rotavirus Gastroenteritis

Induction of the Prenylated Stilbenoids Arachidin-1 and Arachidin-3 and Their Semi-Preparative Separation and Purification from Hairy Root Cultures of Peanut (Arachis hypogaea L.)

Prenylated stilbenoids such as arachidin-1 and arachidin-3 are stilbene derivatives that exhibit multiple pharmacological activities. We report an elicitation strategy using different combinations of cyclodextrin, hydrogen peroxide, methyl jasmonate and magnesium chloride to increase arachidin-1 and arachidin-3 production in peanut hairy root cultures. The treatment of hairy root cultures with cyclodextrin with hydrogen peroxide selectively enhanced arachidin-1 yield (132.6 ± 20.4 mg/L), which was 1.8-fold higher than arachidin-3. Similarly, cyclodextrin combined with methyl jasmonate selectively enhanced arachidin-3 yield (178.2 ± 6.8 mg/L), which was 5.5-fold higher than arachidin-1. Re-elicitation of the hairy root cultures further increased the levels of arachidin-1 and arachidin-3 by 24% and 42%, respectively. The ethyl acetate extract of the culture medium was consecutively fractionated by normal- and reversed-phase column chromatography, followed by semi-preparative HPLC purification on a C18 column to yield arachidin-1 with a recovery rate of 32% and arachidin-3 with a recovery rate of 39%, both at higher than 95% purity. This study provided a sustainable strategy to produce high-purity arachidin-1 and arachidin-3 using hairy root cultures of peanuts combined with column chromatography and semi-preparative HPLC.

Resveratrol and neuroprotection: an insight into prospective therapeutic approaches against Alzheimer's disease from bench to bedside

Alzheimer's disease (AD) is the most common cause of dementia and cognitive impairment; yet, there is currently no treatment. A buildup of Aβ, tau protein phosphorylation, oxidative stress, and inflammation in AD is pathogenic. The accumulation of amyloid-beta (Aβ) peptides in these neurocognitive areas is a significant characteristic of the disease. Therefore, inhibiting Aβ peptide aggregation has been proposed as the critical therapeutic approach for AD treatment. Resveratrol has been demonstrated in multiple studies to have a neuroprotective, anti-inflammatory, and antioxidant characteristic and the ability to minimize Aβ peptides aggregation and toxicity in the hippocampus of Alzheimer's patients, stimulating neurogenesis and inhibiting hippocampal degeneration. Furthermore, resveratrol's antioxidant effect promotes neuronal development by activating the silent information regulator-1 (SIRT1), which can protect against the detrimental effects of oxidative stress. Resveratrol-induced SIRT1 activation is becoming more crucial in developing novel therapeutic options for AD and other diseases that have neurodegenerative characteristics. This review highlighted a better knowledge of resveratrol's mechanism of action and its promising therapeutic efficacy in treating AD. We also highlighted the therapeutic potential of resveratrol as an AD therapeutic agent, which is effective against neurodegenerative disorders.

Antioxidant Assessment of Prenylated Stilbenoid-Rich Extracts from Elicited Hairy Root Cultures of Three Cultivars of Peanut (Arachis hypogaea)

Peanut produces prenylated stilbenoids upon biotic stress. However, the role of these compounds against oxidative stress have not been thoroughly elucidated. To this end, the antioxidant capacity of extracts enriched in prenylated stilbenoids and derivatives was studied. To produce these extracts, hairy root cultures of peanut cultivars Hull, Tifrunner, and Georgia Green were co-treated with methyl jasmonate, cyclodextrin, hydrogen peroxide, and magnesium chloride and then the stilbenoids were extracted from the culture medium. Among the three cultivars, higher levels of the stilbenoid derivatives arachidin-1 and arachidin-6 were detected in cultivar Tifrunner. Upon reaction with 2,2-diphenyl-1picrylhydrazyl, extracts from cultivar Tifrunner showed the highest antioxidant capacity with an IC₅₀ of 6.004 µg/mL. Furthermore, these extracts had significantly higher antioxidant capacity at 6.25 µg/mL and 3.125 µg/mL when compared to extracts from cultivars Hull and Georgia Green. The stilbenoid-rich extracts from peanut hairy roots show high antioxidant capacity and merit further study as potential nutraceuticals to promote human health.

Melatonin may decrease risk for and aid treatment of COVID-19 and other RNA viral infections

A recent retrospective study has provided evidence that COVID-19 infection may be notably less common in those using supplemental melatonin. It is suggested that this phenomenon may reflect the fact that, via induction of silent information regulator 1 (Sirt1), melatonin can upregulate K63 polyubiquitination of the mitochondrial antiviral-signalling protein, thereby boosting virally mediated induction of type 1 interferons. Moreover, Sirt1 may enhance the antiviral efficacy of type 1 interferons by preventing hyperacetylation of high mobility group box 1 (HMGB1), enabling its retention in the nucleus, where it promotes transcription of interferon-inducible genes. This nuclear retention of HMGB1 may also be a mediator of the anti-inflammatory effect of melatonin therapy in COVID-19-complementing melatonin's suppression of nuclear factor kappa B activity and upregulation of nuclear factor erythroid 2-related factor 2. If these speculations are correct, a nutraceutical regimen including vitamin D, zinc and melatonin supplementation may have general utility for the prevention and treatment of RNA virus infections, such as COVID-19 and influenza.

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.

Production and antimicrobial activity of trans-resveratrol, trans-arachidin-1 and trans-arachidin-3 from elicited peanut hairy root cultures in shake flasks compared with bioreactors

Obtaining large-scale hairy root cultures is a major challenge to increasing root biomass and secondary metabolite production. Enhanced production of stilbene compounds such as trans-resveratrol, trans-arachidin-1 and trans-arachidin-3 was achieved using an elicitor treatment procedure. Two different hairy root inoculum densities were investigated and compared between shake flask and bioreactor cultures. The lowest growth index was observed using a 20 g/L inoculum size in the bioreactor, which differed significantly from bioreactor of 5 g/L. Increasing the hairy root inoculum size from 5 g/L to 20 g/L in both the shake flask and bioreactor significantly improve antioxidant activity, phenolic content and stilbene compound levels. The highest ABTS and FRAP antioxidant activity, and levels of total phenolic compounds, trans-arachidin-1 and trans-arachidin-3 in the crude extract were demonstrated in shake flask cultures with a 20 g/L inoculum after elicitation for 72 h. The minimum inhibitory concentrations (MICs) of the crude extract to inhibit growth of foodborne microbes, S. aureus, S. typhimurium and E. coli, were 187.5, 250 and 500 μg/mL, respectively. This was due to the ability of the crude extract to disrupt the cell membrane, as observed by scanning electron microscopy (SEM) showing ruptured pores on the S. aureus and S. typhimurium cell surfaces. Moreover, the E. coli cell division process could be inhibited by the crude extract, which promoted an increase in cell size. A DNA nicking assay indicated that a 50 μg/mL concentration of the crude extract caused plasmid DNA damage that might be due to a genotoxic effect of the pro-oxidant activity of the crude extract.

Production of Prenylated Stilbenoids in Hairy Root Cultures of Peanut (Arachis hypogaea) and its Wild Relatives A. ipaensis and A. duranensis via an Optimized Elicitation Procedure

Prenylated stilbenoids are phenolic compounds produced in a small number of plants such as peanut (Arachis hypogaea) to counteract biotic and abiotic stresses. In addition to their role in plant defense, they exhibit biological activities with potential application in human health. Whereas non-prenylated stilbenoids such as resveratrol are commercially available, the availability of prenylated stilbenoids is limited. To this end, hairy root cultures of peanut were developed as an elicitor-controlled bioproduction platform for prenylated stilbenoids. An orthogonal array design approach led to the elucidation of an optimized elicitation procedure consisting of co-treatment of the hairy root cultures with 18 g/L methyl-β-cyclodextrin, 125 µM methyl jasmonate, 3 mM hydrogen peroxide (H₂O₂) and medium supplementation with additional 1 mM magnesium chloride. After 168-h of elicitor treatment, the combined yield of the prenylated stilbenoids arachidin-1, arachidin-2, arachidin-3 and arachidin-5 reached approximately 750 mg/L (equivalent to 107 mg/g DW). Moreover, hairy root cultures from the wild Arachis species A. duranensis and A. ipaensis were developed and shown to produce prenylated stilbenoids upon elicitor treatment. These wild Arachis hairy root lines may provide a platform to elucidate the biosynthetic origin of prenylated stilbenoids in peanut.

Natural Plant Products: A Less Focused Aspect for the COVID-19 Viral Outbreak

The sudden emergence of COVID-19 caused by a novel coronavirus (nCoV) led the entire world to search for relevant solutions to fight the pandemic. Although continuous trials are being conducted to develop precise vaccines and therapeutic antibodies, a potential remedy is yet to be developed. Plants have largely contributed to the treatment of several human diseases and different phytoconstituents have been previously described to impede the replication of numerous viruses. Despite the previous positive reports of plant-based medications, no successful clinical trials of phyto-anti-COVID drugs could be conducted to date. In this article, we discuss varying perspectives on why phyto-anti-viral drug clinical trials were not successful in the case of COVID-19. The issue has been discussed in light of the usage of plant-based therapeutics in previous coronavirus outbreaks. Through this article, we aim to identify the disadvantages in this research area and suggest some measures to ensure that phytoconstituents can efficiently contribute to future random viral outbreaks. It is emphasized that if used strategically phyto-inhibitors with pre-established clinical data for other diseases can save the time required for long clinical trials. The scientific community should competently tap into phytoconstituents and take their research up to the final stage of clinical trials so that potential phyto-anti-COVID drugs can be developed.

Therapeutics and Immunoprophylaxis Against Noroviruses and Rotaviruses: The Past, Present, and Future

Background:

Noroviruses and rotaviruses are important viral etiologies of severe gastroenteritis. Noroviruses are the primary cause of nonbacterial diarrheal outbreaks in humans, whilst rotaviruses are a major cause of childhood diarrhea. Although both enteric pathogens substantially impact human health and economies, there are no approved drugs against noroviruses and rotaviruses so far. On the other hand, whilst the currently licensed rotavirus vaccines have been successfully implemented in over 100 countries, the most advanced norovirus vaccine has recently completed phase-I and II trials.

Methods:

We performed a structured search of bibliographic databases for peer-reviewed research litera-ture on advances in the fields of norovirus and rotavirus therapeutics and immunoprophylaxis.

Results:

Technological advances coupled with a proper understanding of viral morphology and replication over the past decade has facilitated pioneering research on therapeutics and immunoprophylaxis against noroviruses and rotaviruses, with promising outcomes in human clinical trials of some of the drugs and vaccines. This review focuses on the various developments in the fields of norovirus and rotavirus thera-peutics and immunoprophylaxis, such as potential antiviral drug molecules, passive immunotherapies (oral human immunoglobulins, egg yolk and bovine colostral antibodies, llama-derived nanobodies, and anti-bodies expressed in probiotics, plants, rice grains and insect larvae), immune system modulators, probiot-ics, phytochemicals and other biological substances such as bovine milk proteins, therapeutic nanoparti-cles, hydrogels and viscogens, conventional viral vaccines (live and inactivated whole virus vaccines), and genetically engineered viral vaccines (reassortant viral particles, virus-like particles (VLPs) and other sub-unit recombinant vaccines including multi-valent viral vaccines, edible plant vaccines, and encapsulated viral particles).

Conclusions:

This review provides important insights into the various approaches to therapeutics and im-munoprophylaxis against noroviruses and rotaviruses..

Stilbenoid prenyltransferases define key steps in the diversification of peanut phytoalexins

Defense responses of peanut (Arachis hypogaea) to biotic and abiotic stresses include the synthesis of prenylated stilbenoids. Members of this compound class show several protective activities in human disease studies, and the list of potential therapeutic targets continues to expand. Despite their medical and biological importance, the biosynthetic pathways of prenylated stilbenoids remain to be elucidated, and the genes encoding stilbenoid-specific prenyltransferases have yet to be identified in any plant species. In this study, we combined targeted transcriptomic and metabolomic analyses to discover prenyltransferase genes in elicitor-treated peanut hairy root cultures. Transcripts encoding five enzymes were identified, and two of these were functionally characterized in a transient expression system consisting of Agrobacterium-infiltrated leaves of Nicotiana benthamiana We observed that one of these prenyltransferases, AhR4DT-1, catalyzes a key reaction in the biosynthesis of prenylated stilbenoids, in which resveratrol is prenylated at its C-4 position to form arachidin-2, whereas another, AhR3'DT-1, added the prenyl group to C-3' of resveratrol. Each of these prenyltransferases was highly specific for stilbenoid substrates, and we confirmed their subcellular location in the plastid by fluorescence microscopy. Structural analysis of the prenylated stilbenoids suggested that these two prenyltransferase activities represent the first committed steps in the biosynthesis of a large number of prenylated stilbenoids and their derivatives in peanut. In summary, we have identified five candidate prenyltransferases in peanut and confirmed that two of them are stilbenoid-specific, advancing our understanding of this specialized enzyme family and shedding critical light onto the biosynthesis of bioactive stilbenoids.

Peanut arachidin-1 enhances Nrf2-mediated protective mechanisms against TNF-α-induced ICAM-1 expression and NF-κB activation in endothelial cells

Arachidin-1 [trans-4-(3-methyl-1-butenyl)-3,5,3',4'-tetrahydroxystilbene] is a polyphenol produced by peanut kernels during germination. The aim of the present study was to investigate the mechanism underlying the anti-inflammatory effect of arachidin-1 in endothelial cells (ECs). The results of cell adhesion and western blotting assays demonstrated that arachidin-1 attenuated tumor necrosis factor (TNF)-α-induced monocyte/EC adhesion and intercellular adhesion molecule-1 (ICAM-1) expression. Arachidin-1 was demonstrated to exert its inhibitory effects by the attenuation of TNF-α-induced nuclear factor-κB (NF-κB) nuclear translocation and inhibitor of κB-α (IκBα) degradation. Furthermore, arachidin-1 upregulated nuclear factor-E2-related factor-2 (Nrf-2), a known mediator of phase II enzyme expression, and increased the transcriptional activity of antioxidant response element. Transfection of ECs with Nrf-2 siRNA blocked the inhibitory effect of arachidin-1 on ICAM-1 expression, NF-κB nuclear translocation and IκBα degradation. In addition, arachidin-1 induced the expression of the phase II enzymes thioredoxin-1, thioredoxin reductase-1, heme oxygenase-1, glutamyl-cysteine synthetase and glutathione S-transferase. Following arachidin-1 pretreatment, the H2O2-induced generation of reactive oxygen species was reduced. Therefore, the present results indicate that arachidin-1 suppresses TNF-α-induced inflammation in ECs through the upregulation of Nrf-2-related phase II enzyme expression.

Medicinal plants and natural molecules with in vitro and in vivo activity against rotavirus: A systematic review

BACKGROUND

Rotaviruses can cause life-threatening health disorders, such as severe dehydrating gastroenteritis and diarrhea in children. Vaccination is the main preventive strategy to reduce rotavirus diarrhea and the severity of episodes, but vaccines are not fully effective and new episodes may occur, even in vaccinated children. The WHO recommends oral rehydration therapy and zinc supplementation for rotavirus-induced diarrhea management. There is little preclinical evidence to support the use of phytotherapeutics in the management of rotaviral infections.

PURPOSE

We aim to review the use of medicinal plants and natural molecules in the management of rotavirus infections in experimental studies.

METHODS

Articles, published in the English language between 1991 and 2016, were retrieved from PubMed, Scopus and Web of Science using relevant keywords. The scientific literature mainly focusing on plant natural products with therapeutic efficacies against experimental models of rotavirus, were identified and tabulated. In addition, an assessment of the reliability of animal experiments was determined under ``Risk of Bias'' criteria.

CHAPTERS

After an initial search and a revision of the inclusion criteria, 41 reports satisfied the objectives of the study. 36 articles were found concerning the anti-rotaviral potential in rotavirus infected cell lines. Among the active secondary metabolites screened for rotavirus inhibition, the polyphenols of flavonoid structure had acquired the highest number of studies in our survey, compared to phenolic acids, stilbenoids, tannins, pectins, terpenoids and flavonoid glycosides. Also, many phytochemicals reduced the efficacy of viral capsid proteins foremost to their elimination and improved the tendency of host-cell inhibiting virus absorption or by prevention of viral replication. Furthermore, five in vivo studies reported that herbs, as well its components, reduced the duration and severity of diarrhea in mice and piglets. The anti-rotavirus efficacy were highlighted based on improvements in reduction on liquid stool, fecal virus shedding, small intestinal histology, levels of inflammation related cytokines and signaling receptors. However, the quality of the experiments in animal studies contained certain types of bias in terms of how they were conducted and reported.

CONCLUSION

We identified and summarized studies on medicinal plants and natural molecules having anti-rotavirus activity in order to further future developments of cures for rotavirus gastroenteritis.

Rotavirus replication and the role of cellular lipid droplets: New therapeutic targets?

Rotaviruses (RVs) are a major cause of acute gastroenteritis in infants and young children worldwide. These viruses infect the villous epithelium of the small intestine. Part of their replication occurs in cytoplasmic inclusion bodies termed viroplasms. Viroplasms and the lipid droplets (LDs) of cellular organelles are known to interact both physically and functionally. Compounds interfering with the homoeostasis of LDs significantly decrease the production of infectious RV progeny. There is considerable scope for more detailed exploration of such compounds as potential antiviral agents for a disease for which at present no specific therapy exists.