Betulinic acid exhibits antiviral effects against dengue virus infection

Host serine protease ACOT2 assists DENV proliferation by hydrolyzing viral polyproteins

Dengue fever is a mosquito-borne tropical disease caused by the dengue virus (DENV). The replication of DENV relies on the processing of its genome-encoded polyprotein by both viral protease NS3 (NS3pro) and host proteases. However, the impact of host proteases on DENV proliferation is not well understood. In this study, we utilized fluorophosphonate-based probes (FPs) to investigate the up-regulation of host serine proteases during DENV infection in detail. Among the identified proteases, acyl-CoA thioesterase 2 (ACOT2), an enzyme that hydrolyzes acyl-CoA molecules to generate fatty acids and free CoA, exhibited cleavage activity against DENV polypeptide substrates. Enzymatic assays and virological experiments confirmed that ACOT2 contributes to DENV propagation during the replication stage by cleaving the viral polyprotein. Docking models provided insights into the binding pocket of viral polypeptides and the catalytic mechanism of ACOT2. Notably, this study is the first to demonstrate that ACOT2 functions as a serine protease to hydrolyze protein substrates. These findings offer novel insights into DENV infection, host response, as well as the potential development of innovative antiviral strategies.IMPORTANCEDENV, one of the major pathogens of Dengue fever, remains a significant public health concern in tropical and subtropical regions worldwide. How DENV efficiently hijacks the host and accesses its life cycle with delicate interaction remains to be elucidated. Here, we deconvoluted that the host protease ACOT2 assists the DENV replication and characterized the ACOT2 as a serine protease involved in the hydrolysis of the DENV polypeptide substrate. Our results not only further the understanding of the DENV life cycle but also provide a possibility for the usage of activity-based proteomics to reveal host-virus interactions.

Expanding the anti-flaviviral arsenal: Discovery of a baicalein-derived Compound with potent activity against DENV and ZIKV

With approximately 3.8 billion people at risk of infection in tropical and sub-tropical regions, Dengue ranks among the top ten threats worldwide. Despite the potential for severe disease manifestation and the economic burden it places on endemic countries, there is a lack of approved antiviral agents to effectively treat the infection. Flavonoids, including baicalein, have garnered attention for their antimicrobial properties. In this study, we took a rational and iterative approach to develop a series of baicalein derivatives with improved antiviral activity against Dengue virus (DENV). Compound 11064 emerged as a promising lead candidate, exhibiting antiviral activity against the four DENV serotypes and representative strains of Zika virus (ZIKV) in vitro, with attractive selectivity indices. Mechanistic studies revealed that Compound 11064 did not prevent DENV attachment at the cell surface, nor viral RNA synthesis and viral protein translation. Instead, the drug was found to impair the post-receptor binding entry steps (endocytosis and/or uncoating), as well as the late stage of DENV infection cycle, including virus assembly/maturation and/or exocytosis. The inability to raise DENV resistant mutants, combined with significant antiviral activity against an unrelated RNA virus (Enterovirus-A71) suggested that Compound 11064 targets the host rather than a viral protein, further supporting its broad-spectrum antiviral potential. Overall, Compound 11064 represents a promising antiviral candidate for the treatment of Dengue and Zika.

Tracing down the Updates on Dengue Virus-Molecular Biology, Antivirals, and Vaccine Strategies

BACKGROUND

Nearly half of the world is at risk of developing dengue infection. Dengue virus is the causative agent behind this public healthcare concern. Millions of dengue cases are reported every year, leading to thousands of deaths. The scientific community is working to develop effective therapeutic strategies in the form of vaccines and antiviral drugs against dengue.

METHODS

In this review, a methodological approach has been used to gather data from the past five years to include the latest developments against the dengue virus.

RESULTS

Different therapeutics and antiviral targets against the dengue virus are at different stages of development, but none have been approved by the FDA. Moreover, various vaccination strategies have also been discussed, including attenuated virus vaccines, recombinant subunit vaccines, viral vector vaccines, DNA vaccines, nanotechnology, and plant-based vaccines, which are used to develop effective vaccines for the dengue virus. Many dengue vaccines pass the initial phases of evaluation, but only two vaccines have been approved for public use. DENGVAXIA is the only FDA-approved vaccine against all four stereotypes of the dengue virus, but it is licensed for use only in individuals 6-16 years of age with laboratory-confirmed previous dengue infection and living in endemic countries. Takeda is the second vaccine approved for use in the European Union, the United Kingdom, Brazil, Argentina, Indonesia, and Thailand. It produced sustained antibody responses against all four serotypes of dengue virus, regardless of previous exposure and dosing schedule. Other dengue vaccine candidates at different stages of development are TV-003/005, TDENV PIV, V180, and some DNA vaccines.

CONCLUSION

There is a need to put more effort into developing effective vaccines and therapeutics for dengue, as already approved vaccines and therapeutics have limitations. DENGVAXIA is approved for use in children and teenagers who are 6-16 years of age and have confirmed dengue infection, while Takeda is approved for use in certain countries, and it has withdrawn its application for FDA approval.

Systems pharmacology dissection of pharmacological mechanisms of Xiaochaihu decoction against human coronavirus

BACKGROUND

Although coronavirus disease 2019 (COVID-19) pandemic is still rage worldwide, there are still very limited treatments for human coronaviruses (HCoVs) infections. Xiaochahu decoction (XCHD), which is one of the traditional Chinese medicine (TCM) prescriptions in Qingfeipaidu decoction (QFPDD), is widely used for COVID-19 treatment in China and able to relieve the symptoms of fever, fatigue, anorexia, and sore throat. To explore the role and mechanisms of XCHD against HCoVs, we presented an integrated systems pharmacology framework in this study.

METHODS

We constructed a global herb-compound-target (H-C-T) network of XCHD against HCoVs. Multi-level systems pharmacology analyses were conducted to highlight the key XCHD-regulated proteins, and reveal multiple HCoVs relevant biological functions affected by XCHD. We further utilized network-based prediction, drug-likeness analysis, combining with literature investigations to uncover the key ani-HCoV constituents in XCHD, whose effects on anit-HCoV-229E virus were validated using cytopathic effect (CPE) assay. Finally, we proposed potential molecular mechanisms of these compounds against HCoVs via subnetwork analysis.

RESULTS

Based on the systems pharmacology framework, we identified 161 XCHD-derived compounds interacting with 37 HCoV-associated proteins. An integrated pathway analysis revealed that the mechanism of XCHD against HCoVs is related to TLR signaling pathway, RIG-I-like receptor signaling pathway, cytoplasmic DNA sensing pathway, and IL-6/STAT3 pro-inflammatory signaling pathway. Five compounds from XCHD, including betulinic acid, chrysin, isoliquiritigenin, schisandrin B, and (20R)-Ginsenoside Rh1 exerted inhibitory activity against HCoV-229E virus in Huh7 cells using in vitro CPE assay.

CONCLUSION

Our work presented a comprehensive systems pharmacology approach to identify the effective molecules and explore the molecular mechanism of XCHD against HCoVs.

Angiotensin II and dengue

Dengue is a disease caused by a flavivirus that is transmitted principally by the bite of an Aedes aegypti mosquito and represents a major public-health problem. Many studies have been carried out to identify soluble factors that are involved in the pathogenesis of this infection. Cytokines, soluble factors, and oxidative stress have been reported to be involved in the development of severe disease. Angiotensin II (Ang II) is a hormone with the ability to induce the production of cytokines and soluble factors related to the inflammatory processes and coagulation disorders observed in dengue. However, a direct involvement of Ang II in this disease has not been demonstrated. This review primarily summarizes the pathophysiology of dengue, the role of Ang II in various diseases, and reports that are highly suggestive of the involvement of this hormone in dengue.

Antiviral Activity of Catechin against Dengue Virus Infection

Dengue virus (DENV) is the cause of dengue fever, infecting 390 million people worldwide per year. It is transmitted to humans through the bites of mosquitoes and could potentially develop severe symptoms. In spite of the rising social and economic impact inflicted by the disease on the global population, a conspicuous lack of efficacious therapeutics against DENV still persists. In this study, catechin, a natural polyphenol compound, was evaluated as a DENV infection inhibitor in vitro. Through time-course studies, catechin was shown to inhibit a post-entry stage of the DENV replication cycle. Further investigation revealed its role in affecting viral protein translation. Catechin inhibited the replication of all four DENV serotypes and chikungunya virus (CHIKV). Together, these results demonstrate the ability of catechin to inhibit DENV replication, hinting at its potential to be used as a starting scaffold for further development of antivirals against DENV infection.

Bioprospecting phytochemicals of Rosmarinus officinalis L. for targeting SARS-CoV-2 main protease (Mpro): a computational study

CONTEXT

The persistent spread of highly contagious COVID-19 disease is one of the deadliest occurrences in the history of mankind. Despite the distribution of numerous efficacious vaccines and their extensive usage, the perpetual effectiveness of immunization is being catechized. Therefore, discovering an alternative therapy to control and prevent COVID-19 infections has become a top priority. The main protease (M^pro) plays a key role in viral replication, making it an intriguing pharmacological target for SARS-CoV-2.

METHODS

In this context, virtual screening of thirteen bioactive polyphenols and terpenoids of Rosmarinus officinalis L. was performed using several computational modules including molecular docking, ADMET, drug-likeness characteristics, and molecular dynamic simulation to predict the potential inhibitors against SARS-CoV-2 M^pro (PDB: 6LU7). The results suggest that apigenin, betulinic acid, luteolin, carnosol, and rosmarinic acid may emerge as potential inhibitors of SARS-CoV-2 with acceptable drug-likeness, pharmacokinetics, ADMET characteristics, and binding interactions comparable with remdesivir and favipiravir. These findings imply that some of the active components of Rosmarinus officinalis L. can serve as an effective antiviral source for the development of therapeutics for SARS-CoV-2 infection.

Phytochemicals as Invaluable Sources of Potent Antimicrobial Agents to Combat Antibiotic Resistance

Plants have been used for therapeutic purposes against various human ailments for several centuries. Plant-derived natural compounds have been implemented in clinics against microbial diseases. Unfortunately, the emergence of antimicrobial resistance has significantly reduced the efficacy of existing standard antimicrobials. The World Health Organization (WHO) has declared antimicrobial resistance as one of the top 10 global public health threats facing humanity. Therefore, it is the need of the hour to discover new antimicrobial agents against drug-resistant pathogens. In the present article, we have discussed the importance of plant metabolites in the context of their medicinal applications and elaborated on their mechanism of antimicrobial action against human pathogens. The WHO has categorized some drug-resistant bacteria and fungi as critical and high priority based on the need to develope new drugs, and we have considered the plant metabolites that target these bacteria and fungi. We have also emphasized the role of phytochemicals that target deadly viruses such as COVID-19, Ebola, and dengue. Additionally, we have also elaborated on the synergetic effect of plant-derived compounds with standard antimicrobials against clinically important microbes. Overall, this article provides an overview of the importance of considering phytogenous compounds in the development of antimicrobial compounds as therapeutic agents against drug-resistant microbes.

Synthesis of New Amidoethanesulfonamides of Betulonic Acid

New potentially biologically active amidoethanesulfonamides of betulonic acid were synthesized by the acid chloride method via conjugation of betulonic acid with 2-aminoethanesulfonamides as the free bases.

Grape Seed Proanthocyanidins Inhibit Replication of the Dengue Virus by Targeting NF-kB and MAPK-Mediated Cyclooxygenase-2 Expression

Dengue virus (DENV) infection is a serious global health issue as it causes severe dengue hemorrhagic fever and dengue shock syndrome. Since no approved therapies are available to treat DENV infection, it is necessary to develop new agents or supplements that can do this. In this study, grape seed proanthocyanidins extract (GSPE), which is widely consumed as a dietary supplement, dose-dependently suppressed the replication of four DENV serotypes. The inhibitory mechanism demonstrated that GSPE downregulated DENV-induced aberrant cyclooxygenase-2 (COX-2) expression, revealing that the inhibitory effect of the GSPE on DENV replication involved targeting DENV-induced COX-2 expression. Mechanistic studies on signaling regulation have demonstrated that GSPE significantly reduced COX-2 expression by inactivating NF-κB and ERK/P38 MAPK signaling activities. Administrating GSPE to DENV-infected suckling mice reduced virus replication, mortality, and monocyte infiltration of the brain. In addition, GSPE substantially reduced the expression of DENV-induced inflammatory cytokines associated with severe dengue disease, including tumor necrosis factor-α, nitric oxide synthase, interleukin (IL)-1, IL-6, and IL-8, suggesting that GSPE has potential as a dietary supplement to attenuate DENV infection and severe dengue.

Cheminformatics-Based Study Identifies Potential Ebola VP40 Inhibitors

The Ebola virus (EBOV) is still highly infectious and causes severe hemorrhagic fevers in primates. However, there are no regulatorily approved drugs against the Ebola virus disease (EVD). The highly virulent and lethal nature of EVD highlights the need to develop therapeutic agents. Viral protein 40 kDa (VP40), the most abundantly expressed protein during infection, coordinates the assembly, budding, and release of viral particles into the host cell. It also regulates viral transcription and RNA replication. This study sought to identify small molecules that could potentially inhibit the VP40 protein by targeting the N-terminal domain using an in silico approach. The statistical quality of AutoDock Vina’s capacity to discriminate between inhibitors and decoys was determined, and an area under the curve of the receiver operating characteristic (AUC-ROC) curve of 0.791 was obtained. A total of 29,519 natural-product-derived compounds from Chinese and African sources as well as 2738 approved drugs were successfully screened against VP40. Using a threshold of −8 kcal/mol, a total of 7, 11, 163, and 30 compounds from the AfroDb, Northern African Natural Products Database (NANPDB), traditional Chinese medicine (TCM), and approved drugs libraries, respectively, were obtained after molecular docking. A biological activity prediction of the lead compounds suggested their potential antiviral properties. In addition, random-forest- and support-vector-machine-based algorithms predicted the compounds to be anti-Ebola with IC50 values in the micromolar range (less than 25 μM). A total of 42 natural-product-derived compounds were identified as potential EBOV inhibitors with desirable ADMET profiles, comprising 1, 2, and 39 compounds from NANPDB (2-hydroxyseneganolide), AfroDb (ZINC000034518176 and ZINC000095485942), and TCM, respectively. A total of 23 approved drugs, including doramectin, glecaprevir, velpatasvir, ledipasvir, avermectin B1, nafarelin acetate, danoprevir, eltrombopag, lanatoside C, and glycyrrhizin, among others, were also predicted to have potential anti-EBOV activity and can be further explored so that they may be repurposed for EVD treatment. Molecular dynamics simulations coupled with molecular mechanics Poisson–Boltzmann surface area calculations corroborated the stability and good binding affinities of the complexes (−46.97 to −118.9 kJ/mol). The potential lead compounds may have the potential to be developed as anti-EBOV drugs after experimental testing.

Elsholtzia: A genus with antibacterial, antiviral, and anti-inflammatory advantages

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Elsholtzia (family Labiaceae) is an important source of folk traditional Chinese medicine, mainly used to relieve the symptoms of cold, fever, pneumonia and so on. However, currently available data on its traditional and pharmacological advantages have not been comprehensively reviewed.

AIM OF THE REVIEW

This review provides up-to-date and comprehensive information on the ethnopharmacological, phytochemical, pharmacological properties and toxicity of Elsholtzia, highlights the antibacterial, antiviral, and anti-inflammatory advantages of the genus, and explores its therapeutic potential.

MATERIALS AND METHODS

Use Google Scholar, Scifinder, PubMed, Springer, Elsevier, Wiley, Web of Science and other online database search to collect the research literatures on application, chemistry and biological activity of Elsholtzia published before December 2021. Their scientific names have been verified using The Plant List and World Flora Online websites.

RESULTS

A total of 42 species of Elsholtzia are widely distributed all over the world, especially in Yunnan Province (China). Since Elsholtzia genus is commonly used in the folk to treat respiratory infectious diseases such as cold and fever, growing numbers of studies have confirmed their antiviral, antibacterial and anti-inflammatory activities. So far, about 221 non-volatile compounds and 1008 volatile compounds have been identified from Elsholtzia plants, mainly containing flavonoids and terpenoids showing convincing antibacterial, antiviral and anti-inflammatory activities. Further research found that their antibacterial and antiviral spectrums are broad, and volatile oils are considered to be the main antibacterial components. Their anti-inflammatory mechanism is mainly through the inhibition of NF-κB and MAPKs signaling pathways. Toxicological studies have not established its toxicity.

CONCLUSIONS

By summarizing the latest information on genus Elsholtzia, their traditional uses, material basis and mechanisms of action in antiviral, antibacterial and anti-inflammatory aspects were described, providing new insights for the genus and its importance as a potential natural resource of antiviral and anti-inflammatory drugs, giving evidence and new ideas for the development of herbal medicines.

Plants extracts from Cameroon pharmacopeia strongly inhibit the Chikungunya virus infection by targeting entry and replication steps

ETHNOPHARMACOLOGICAL RELEVANCE

Cameroon is one of the sub-Saharan African countries affected by Chikungunya virus (CHIKV). With the absence of approved treatment, this disease represents globally a major public health concern. Several plants are traditionally used in Cameroon for the treatment of virus induced fever and arthralgia. But to date there is no study that validate the efficacy of these plants for the treatment of Chikungunya virus infection.

AIM OF THE STUDY

This study aims to explore the inhition effect, mechanism of action of plant extracts against Chikungunya virus.

MATERIAL AND METHODS

An ethnobotanical survey conducted in some regions of Cameroon, led to the identification of nine medicinal plants used in traditional medicine for the healing of fever-related diseases and arthritis. Crude hydro-ethanolic extracts of each plant were prepared by maceration and their effects against CHIKV infection were investigated. CHIKV S27 strain was used to infection in Vero cell line. The antiviral activities were determined by plaque assay and/or RT-PCR targeting E1 envelope gene of CHIKV. Dose-response studies of the active plants were also determined by flow cytometry and Western blot.

RESULTS

Four extracts, Entada africana Guill et Pers. (E4), Entandrophragma cylindricum Sprague (EI), Khaya grandifoliola C. D.C. Sapindales (E2) and Macaranga hurifolia Beille (E6) showed antiviral activity with the half-maximal inhibitory concentration of 8.29; 8.14; 12.81 and 26.89 μg/mL respectively. All extracts were nontoxic up to the concentration of 100 μg/μL. Entandrophragma cylindricum Sprague (EI), Khaya grandifoliola C. D.C. Sapindales (E2), and Entada africana Guill et Pers. (E4) showed strong inhibition on the entry step of viral infection. At the same time, only Entandrophragma cylindricum Sprague (EI) inhibited the viral titer significantly in replication and intercellular assembly steps. Four plant extracts namely Entandrophragma cylindricum Sprague (EI), Macaranga hurifolia Beille (E6), Phragmentera capitata (Sprengel) Balle (E12), and Detarium microcarpum (E13) were effective against egression step.

CONCLUSIONS

Together, the results of this study showed anti-chikungunya activities of Entandrophragma cylindricum Sprague (EI) and Macaranga hurifolia Beille (E6), with therapeutics perspectives and can be promising sources of the development of anti-CHIKV molecule in future.

Recent Advances in Antiviral Activities of Triterpenoids

Triterpenoids, important secondary plant metabolites made up of six isoprene units, are found widely in higher plants and are studied for their structural variety and wide range of bioactivities, including antiviral, antioxidant, anticancer, and anti-inflammatory properties. Numerous studies have demonstrated that different triterpenoids have the potential to behave as potential antiviral agents. The antiviral activities of triterpenoids and their derivatives are summarized in this review, with examples of oleanane, ursane, lupane, dammarane, lanostane, and cycloartane triterpenoids. We concentrated on the tetracyclic and pentacyclic triterpenoids in particular. Furthermore, the particular viral types and possible methods, such as anti-human immunodeficiency virus (HIV), anti-influenza virus, and anti-hepatitis virus, are presented in this article. This review gives an overview and a discussion of triterpenoids as potential antiviral agents.

Contemporary exploitation of natural products for arthropod-borne pathogen transmission-blocking interventions

An integrated approach to innovatively counter the transmission of various arthropod-borne diseases to humans would benefit from strategies that sustainably limit onward passage of infective life cycle stages of pathogens and parasites to the insect vectors and vice versa. Aiming to accelerate the impetus towards a disease-free world amid the challenges posed by climate change, discovery, mindful exploitation and integration of active natural products in design of pathogen transmission-blocking interventions is of high priority. Herein, we provide a review of natural compounds endowed with blockade potential against transmissible forms of human pathogens reported in the last 2 decades from 2000 to 2021. Finally, we propose various translational strategies that can exploit these pathogen transmission-blocking natural products into design of novel and sustainable disease control interventions. In summary, tapping these compounds will potentially aid in integrated combat mission to reduce disease transmission trends.

Ameliorative effect of betulinic acid against zearalenone exposure triggers testicular dysfunction and oxidative stress in mice via p38/ERK MAPK inhibition and Nrf2-mediated antioxidant defense activation

Zearalenone (ZEA) is a nonsteroidal estrogenic mycotoxin, which mainly contaminates grains and has estrogen-like effects on the reproductive system. Betulinic acid (BA), a natural lupane-type pentacyclic triterpene, has anti-oxidative and anti-inflammatory properties. This study aimed to investigate whether BA alleviates ZEA-induced testicular damage and explore the possible mechanism. Here, BA ameliorated testicular damage by mitigating the disordered arrangement of seminiferous tubules, the exfoliation of lumen cells, and the increase of cell apoptosis caused by ZEA. Meanwhile, BA alleviated ZEA-triggered testicular damage by restoring hormone levels and sperm motility, and reconstructing the blood-testis-barrier. Moreover, BA alleviated ZEA-exposed testicular oxidative stress by activating Nrf2 pathway. Furthermore, BA moderated ZEA-evoked testicular inflammation by inhibiting p38/ERK MAPK pathway. Overall, our results revealed that BA has a therapeutic protective effect on ZEA-induced testicular injury and oxidative stress via p38/ERK MAPK inhibition and Nrf2-mediated antioxidant defense activation, which provides a viable alternative to alleviate ZEA-induced male reproductive toxicology.

In Vitro Antiviral Activity of Potential Medicinal Plant Extracts Against Dengue and Chikungunya Viruses

Dengue and chikungunya are two important mosquito-borne infections which are known to occur extensively in tropical and subtropical areas. Presently, there is no treatment for these viral diseases. In vitro antiviral screening of 25 extracts prepared from the plants of Vitex negundo, Plumeria alba, Ancistrocladus heyneanus, Bacopa monnieri, Anacardium occidentale, Cucurbita maxima, Simarouba glauca, and Embelia ribes using different solvents and four purified compounds (anacardic acid, chloroquinone, glaucarubinone, and methyl gallate) were carried out for their anti-dengue virus (DENV) and anti-chikungunya virus (CHIKV) activities. Maximum nontoxic concentrations of the chloroform, methanol, ethyl acetate, petroleum ether, dichloromethane, and hydroalcoholic extracts of eight plants were used. The antiviral activity was assessed by focus-forming unit assay, quantitative real-time RT-PCR, and immunofluorescence assays. Extracts from Plumeria alba, Ancistrocladus heyneanus, Bacopa monnieri, and Cucurbita maxima showed both anti-DENV and CHIKV activity while extract from Vitex negundo showed only anti-DENV activity. Among the purified compounds, anacardic acid, chloroquinone and methyl gallate showed anti-dengue activity while only methyl gallate had anti-chikungunya activity. The present study had identified the plant extracts with anti-dengue and anti-chikungunya activities, and these extracts can be further characterized for finding effective phytopharmaceutical drugs against dengue and chikungunya.

Anti-Zika Virus Activity of Plant Extracts Containing Polyphenols and Triterpenes on Vero CCL-81 and Human Neuroblastoma SH-SY5Y Cells

Zika virus (ZIKV) infection is a global threat associated to neurological disorders in adults and microcephaly in children born to infected mothers. No vaccine or drug is available against ZIKV. We herein report the anti-ZIKV activity of 36 plant extracts containing polyphenols and/or triterpenes. ZIKV-infected Vero CCL-81 cells were treated with samples at non-cytotoxic concentrations, determined by MTT and LDH assays. One third of the extracts elicited concentration-dependent anti-ZIKV effect, with viral loads reduction from 0.4 to 3.8 log units. The 12 active extracts were tested on ZIKV-infected SH-SY5Y cells and significant reductions of viral loads (in log units) were induced by Maytenus ilicifolia (4.5 log), Terminalia phaeocarpa (3.7 log), Maytenus rigida (1.7 log) and Echinodorus grandiflorus (1.7 log) extracts. Median cytotoxic concentration (CC₅₀ ) of these extracts in Vero cells were higher than in SH-SY5Y lineage. M. ilicifolia (IC₅₀ =16.8±10.3 μg/mL, SI=3.4) and T. phaeocarpa (IC₅₀ =22.0±6.8 μg/mL, SI=4.8) were the most active extracts. UPLC-ESI-MS/MS analysis of M. ilicifolia extract led to the identification of 7 triterpenes, of which lupeol and a mixture of friedelin/friedelinol showed no activity against ZIKV. The composition of T. phaeocarpa extract comprises phenolic acids, ellagitannins and flavonoids, as recently reported by us. In conclusion, the anti-ZIKV activity of 12 plant extracts is here described for the first time and polyphenols and triterpenes were identified as the probable bioactive constituents of T. phaeocarpa and M. ilicifolia, respectively.

Anti-viral triterpenes: a review

Triterpenes are naturally occurring derivatives biosynthesized following the isoprene rule of Ruzicka. The triterpenes have been reported to possess a wide range of therapeutic applications including anti-viral properties. In this review, the recent studies (2010-2020) concerning the anti-viral activities of triterpenes have been summarized. The structure activity relationship studies have been described as well as brief biosynthesis of these triterpenes is discussed.

Facial Synthesis and Bioevaluation of Well-Defined OEGylated Betulinic Acid-Cyclodextrin Conjugates for Inhibition of Influenza Infection

Betulinic acid (BA) and its derivatives exhibit a variety of biological activities, especially their anti-HIV-1 activity, but generally have only modest inhibitory potency against influenza virus. The entry of influenza virus into host cells can be competitively inhibited by multivalent derivatives targeting hemagglutinin. In this study, a series of hexa-, hepta- and octavalent BA derivatives based on α-, β- and γ-cyclodextrin scaffolds, respectively, with varying lengths of flexible oligo(ethylene glycol) linkers was designed and synthesized using a microwave-assisted copper-catalyzed 1,3-dipolar cycloaddition reaction. The generated BA-cyclodextrin conjugates were tested for their in vitro activity against influenza A/WSN/33 (H1N1) virus and cytotoxicity. Among the tested compounds, 58, 80 and 82 showed slight cytotoxicity to Madin-Darby canine kidney cells with viabilities ranging from 64 to 68% at a high concentration of 100 μM. Four conjugates 51 and 69–71 showed significant inhibitory effects on influenza infection with half maximal inhibitory concentration values of 5.20, 9.82, 7.48 and 7.59 μM, respectively. The structure-activity relationships of multivalent BA-cyclodextrin conjugates were discussed, highlighting that multivalent BA derivatives may be potential antiviral agents against influenza infection.

The Role of Cyclodextrins in the Design and Development of Triterpene-Based Therapeutic Agents

Triterpenic compounds stand as a widely investigated class of natural compounds due to their remarkable therapeutic potential. However, their use is currently being hampered by their low solubility and, subsequently, bioavailability. In order to overcome this drawback and increase the therapeutic use of triterpenes, cyclodextrins have been introduced as water solubility enhancers; cyclodextrins are starch derivatives that possess hydrophobic internal cavities that can incorporate lipophilic molecules and exterior surfaces that can be subjected to various derivatizations in order to improve their biological behavior. This review aims to summarize the most recent achievements in terms of triterpene:cyclodextrin inclusion complexes and bioconjugates, emphasizing their practical applications including the development of new isolation and bioproduction protocols, the elucidation of their underlying mechanism of action, the optimization of triterpenes’ therapeutic effects and the development of new topical formulations.

Microbial transformation and inhibitory effect assessment of uvaol derivates against LPS and HMGB1 induced NO production in RAW264.7 macrophages

For the discovery of new pentacyclic triterpenes as a potential anti-inflammatory agent, microbial transformation of uvaol by Penicilium griseofulvum CICC 40293 and Streptomyces griseus ATCC 13273 was investigated. Stereoselective hydroxylation and epoxidation reactions were observed in the biotransformation. Moreover, six new metabolites were isolated and structurally elucidated by HR-ESI-MS and NMR spectrum. All the compounds were evaluated upon the inhibitory effects of nitric oxide (NO) release in RAW 264.7 cells induced by lipopolysaccharide (LPS) and high-mobility group box 1 (HMGB1). Among them, compound 3 (13, 28-epoxy-3β, 7β, 21β-trihydroxy-urs-11-ene) with the unique epoxy structure and compound 5 (3β, 21β, 24, 28-tetrahydroxy-urs-12-en-30-oic acid), exhibited a considerable inhibitory effect on both models while compound 2 (urs-12-ene-3β, 7β, 21β, 28-tetraol) showed a significant bias in the LPS-induced inflammatory response with IC₅₀ value of 2.22 μM. Therefore, this study could provide some insights on the discovery of the pentacyclic triterpene leads for the treatment of either DAMPs or PAMPs triggered inflammation.

Bioactive small-molecule constituents of Lao plants

Laos has a rich plant diversity, and medicinal plants are used extensively in Lao traditional medicine for the treatment of a variety of human diseases. However, only a relatively small number of these plants have been investigated for their major components with potential antitumor, anti-infective, and other types of bioactivities. These species include Asparagus cochinchinensis, Diospyros quaesita, Gongronema napalense, Marsypopetalum modestum, Nauclea orientalis, Rourea minor, Stemona pierrei, and Stemona tuberosa. Thus far, the bioactive compounds isolated from these Lao plants include alkaloids, glycerol esters, phenolic compounds such as lignans and stilbenoids, steroids, and triterpenoids. Of these, the norlignan, nyasol (1b), the triterpenes, pyracrenic acid [3β-O-trans-caffeoylbetulinic acid (3)] and betulinic acid (3b), and the dimeric thiopyridine, dipyrithione (5), were found to show both cancer cell cytotoxicity and anti-infective activity. The present review focuses on examples of promising lead compounds isolated from Lao plants, with their possible development as potential therapeutic agents being discussed. It is hoped that this contribution will provide useful information on higher plants growing in Laos to help stimulate future discoveries of potential agents for the treatment of cancer, infections, and other diseases.

Modulating Neurological Complications of Emerging Infectious Diseases: Mechanistic Approaches to Candidate Phytochemicals

Growing studies are revealing the critical manifestations of influenza, dengue virus (DENV) infection, Zika virus (ZIKV) disease, and Ebola virus disease (EVD) as emerging infectious diseases. However, their corresponding mechanisms of major complications headed for neuronal dysfunction are not entirely understood. From the mechanistic point of view, inflammatory/oxidative mediators are activated during emerging infectious diseases towards less cell migration, neurogenesis impairment, and neuronal death. Accordingly, the virus life cycle and associated enzymes, as well as host receptors, cytokine storm, and multiple signaling mediators, are the leading players of emerging infectious diseases. Consequently, chemokines, interleukins, interferons, carbohydrate molecules, toll-like receptors (TLRs), and tyrosine kinases are leading orchestrates of peripheral and central complications which are in near interconnections. Some of the resulting neuronal manifestations have attracted much attention, including inflammatory polyneuropathy, encephalopathy, meningitis, myelitis, stroke, Guillain-Barré syndrome (GBS), radiculomyelitis, meningoencephalitis, memory loss, headaches, cranial nerve abnormalities, tremor, and seizure. The complex pathophysiological mechanism behind the aforementioned complications urges the need for finding multi-target agents with higher efficacy and lower side effects. In recent decades, the natural kingdom has been highlighted as promising neuroprotective natural products in modulating several dysregulated signaling pathways/mediators. The present study provides neuronal manifestations of some emerging infectious diseases and underlying pathophysiological mechanisms. Besides, a mechanistic-based strategy is developed to introduce candidate natural products as promising multi-target agents in combating major dysregulated pathways towards neuroprotection in influenza, DENV infection, ZIKV disease, and EVD.

Betulinic acid exerts antigenotoxic and anticarcinogenic activities via inhibition of COX-2 and PCNA in rodents

Phytochemicals have been suggested as an effective strategy for cancer prevention. Within this context, triterpene betulinic acid (BA) exhibits several biological properties but its chemopreventive effect has not been fully demonstrated. The present study investigated the antigenotoxic potential of BA against doxorubicin (DXR)-induced genotoxicity using the mouse peripheral blood micronucleus assay, as well as its anticarcinogenic activity against 1,2dimethylhydrazine (DMH)-induced colorectal lesions in rats. Micronuclei (MN) assay and aberrant crypt foci assay were used to assess the antigenotoxic and the anticarcinogenic potential, respectively. The molecular mechanisms underlying the anticarcinogenic activity of BA were evaluated by assessing anti-inflammatory (COX-2) and antiproliferative (PCNA) pathways. The results demonstrated that BA at the dose of 0.5 mg/kg bodyweight exerted antigenotoxic effects against DXR, with a reduction of 70.2% in the frequencies of chromosomal damage. Animals treated with BA showed a 64% reduction in the number of preneoplastic lesions when compared to those treated with the carcinogen alone. The levels of COX-2 and PCNA expression in the colon were significantly lower in animals treated with BA and DMH compared to those treated with the carcinogen alone. The chemopreventive effect of BA is related, at least in part, to its antiproliferative and anti-inflammatory activity, indicating a promising potential of this triterpene in anticancer therapies, especially for colorectal cancer.