South African medicinal plant extracts active against influenza A virus

Identification of South African Plant-Based Bioactive Compounds as Potential Inhibitors against the SARS-CoV-2 Receptor

The expected progress in SARS-CoV-2 vaccinations, as anticipated in 2020 and 2021, has fallen short, exacerbating global disparities due to a lack of universally recognized "safe and effective" vaccines. This study focuses on extracts of South African medicinal plants, Artemisia annua and Artemisia afra, to identify metabolomic bioactive compounds inhibiting the binding of the SARS-CoV-2 spike protein to ACE2 receptors. The extracts were monitored for cytotoxicity using a resazurin cell viability assay and xCELLigence real-time cell analyzer. Chemical profiling was performed using UPLC-MS/MS, orthogonal projection to latent structures (OPLS), and evaluated using principle component analysis (PCA) models. Identified bioactive compounds were subjected to in vitro SARS-CoV-2 enzyme inhibition assay using standard methods and docked into the spike (S) glycoprotein of SARS-CoV-2 using Schrodinger® suite followed by molecular dynamics simulation studies. Cell viability assays revealed non-toxic effects of extracts on HEK293T cells at lower concentrations. Chemical profiling identified 81 bioactive compounds, with compounds like 6″-O-acetylglycitin, 25-hydroxyvitamin D3-26,23-lactone, and sesaminol glucoside showing promising binding affinity. Molecular dynamics simulations suggested less stable binding, but in vitro studies demonstrated the ability of these compounds to interfere with SARS-CoV-2 spike protein's binding to the human ACE2 receptor. Sesaminol glucoside emerged as the most effective inhibitor against this interaction. This study emphasizes the importance of multiplatform metabolite profiling and chemometrics to understand plant extract composition. This finding is of immense significance in terms of unravelling metabolomics bioactive compounds inhibiting the binding of the SARS-CoV-2 spike protein to ACE2 receptors and holds promise for phytotherapeutics against SARS-CoV-2.

Computational peptide engineering approach for selection of the new C05 antibody-driven peptide with potency to blocking influenza a virus attachment; from in silico to in vivo

Antiviral drugs are currently used to prevent or treat viral infections like influenza A Virus (IAV). Nonetheless, annual genetic mutations of influenza viruses make them resistant to efficient treatment by current medications. Antiviral peptides have recently attracted researchers' attention and can potentially supplant the current medications. This study aimed to design peptides against IAV propagation. For this purpose, P2 and P3 peptides were computationally designed based on the HCDR3 region of the C05 antibody (a monoclonal antibody that neutralizes influenza HA protein and inhibits the virus attachment). The synthesized peptides were tested against the influenza A virus (A/Puerto Rico/8/34 (H1N1)) in vitro, and the most efficient peptide was selected for in vivo experiments. It was shown that the designed peptide shows much more prophylactic and therapeutic effects against the virus. These findings demonstrated that the designed peptide can control the virus infection without any cytotoxicity effect. Antiviral peptide design is acknowledged as a critical tactic to manage viral infections by preventing viral binding to the host cells.Communicated by Ramaswamy H. Sarma.

In Vitro Antiviral and Anti-Inflammatory Activities of N-Acetylglucosamine: Development of an Alternative and Safe Approach to Fight Viral Respiratory Infections

Viral respiratory tract infections (RTIs) are responsible for significant morbidity and mortality worldwide. A prominent feature of severe respiratory infections, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, is the cytokine release syndrome. Therefore, there is an urgent need to develop different approaches both against viral replication and against the consequent inflammation. N-acetylglucosamine (GlcNAc), a glucosamine (GlcN) derivative, has been developed as an immunomodulatory and anti-inflammatory inexpensive and non-toxic drug for non-communicable disease treatment and/or prevention. Recent studies have suggested that GlcN, due to its anti-inflammatory activity, could be potentially useful for the control of respiratory virus infections. Our present study aimed to evaluate in two different immortalized cell lines whether GlcNAc could inhibit or reduce both viral infectivity and the inflammatory response to viral infection. Two different viruses, frequent cause of upper and lower respiratory tract infections, were used: the H1N1 Influenza A virus (IAV) (as model of enveloped RNA virus) and the Human adenovirus type 2 (Adv) (as model of naked DNA virus). Two forms of GlcNAc have been considered, bulk GlcNAc and GlcNAc in nanoform to overcome the possible pharmacokinetic limitations of GlcNAc. Our study suggests that GlcNAc restricts IAV replication but not Adv infection, whereas nano-GlcNAc inhibits both viruses. Moreover, GlcNAc and mainly its nanoformulation were able to reduce the pro-inflammatory cytokine secretion stimulated by viral infection. The correlation between inflammatory and infection inhibition is discussed.

Medicinal plants used for the management of respiratory diseases in Zimbabwe: Review and perspectives potential management of COVID-19

Respiratory diseases have in the recent past become a health concern globally. More than 523 million cases of coronavirus disease (COVID19), a recent respiratory diseases have been reported, leaving more than 6 million deaths worldwide since the start of the pandemic. In Zimbabwe, respiratory infections have largely been managed using traditional (herbal) medicines, due to their low cost and ease of accessibility. This review highlights the plants' toxicological and pharmacological evaluation studies explored. It seeks to document plants that have been traditionally used in Zimbabwe to treat respiratory ailments within and beyond the past four decades. Extensive literature review based on published papers and abstracts retrieved from the online bibliographic databases, books, book chapters, scientific reports and theses available at Universities in Zimbabwe, were used in this study. From the study, there were at least 58 plant families comprising 160 medicinal plants widely distributed throughout the country. The Fabaceae family had the highest number of medicinal plant species, with a total of 21 species. A total of 12 respiratory ailments were reportedly treatable using the identified plants. From a total of 160 plants, colds were reportedly treatable with 56, pneumonia 53, coughs 34, chest pain and related conditions 29, asthma 25, tuberculosis and spots in lungs 22, unspecified respiratory conditions 20, influenza 13, bronchial problems 12, dyspnoea 7, sore throat and infections 5 and sinus clearing 1 plant. The study identified potential medicinal plants that can be utilised in future to manage respiratory infections.

In vitro anti-influenza assessment of anionic compounds ascorbate, acetate and citrate

Background

Influenza A virus (IAV) infection remains a serious public health threat. Due to drug resistance and side effects of the conventional antiviral drugs, repurposing the available natural compounds with high tolerability and fewer side effects has attracted researchers’ attention. The aim of this study was to screen in vitro anti-influenza activity of three anionic compounds ascorbate, acetate, and citrate.

Methods

The non-cytotoxic concentration of the compounds was determined by MTT assay and examined for the activity against IAV in simultaneous, pre-, and post-penetration combination treatments over 1 h incubation on Madin-Darby Canine Kidney (MDCK) cell line. The virus titer and viral load were determined using hemagglutination assay (HA) and qPCR, respectively. Few pro-inflammatory and anti-inflammatory cytokines were evaluated at RNA and protein levels by qPCR and ELISA, respectively.

Results

The non-cytotoxic concentrations of the ascorbate (200 mg/ml), acetate and citrate (both 3 mg/ml) reduced the viral titer by 6.5, 4.5, and 1.5 logs in the simultaneous combination treatment. The M protein gene copy number decreased significantly in simultaneous treatment (P < 0.01). The expression of cytokines was also affected by the treatment of these compounds.

Conclusions

These anionic compounds could affect the influenza virus load, thereby reducing pro-inflammatory cytokines and increasing anti-inflammatory cytokines levels.

In Vitro Investigation of the Antioxidant and Cytotoxic Potential of Tabernaemontana ventricosa Hochst. ex A. DC. Leaf, Stem, and Latex Extracts

Tabernaemontana ventricosa (Apocynaceae) a latex-bearing plant is used in traditional medicine for its therapeutic benefits in reducing fever and hypertension and wound healing. Due to limited information on the plant’s pharmacological activities, this study aimed to investigate the antioxidant potential of the leaf, stem, and latex extracts of T. ventricosa, using the Folin-Ciocalteu (total phenolics), aluminum chloride colorimetric (total flavonoids), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) assays. The cytotoxic activity was evaluated in the human HEK293 (embryonic kidney), HeLa (cervical carcinoma), and MCF-7 (breast adenocarcinoma) cell lines using the MTT assay. The latex extracts possessed the highest total phenolic content (115.36 ± 2.89 mg GAE/g), followed by the stem hexane extracts (21.33 ± 0.42 mg GAE/g), the chloroform leaf (7.89 ± 0.87 mg GAE/g), and the chloroform stem (4.69 ± 0.21 mg GAE/g) extracts. The flavonoid content was substantially high ranging from 946.92 ± 6.29 mg QE/g in the stem hexane, 768.96 ± 5.43 mg QE/g in the latex, 693.24 ± 4.12 mg QE/g in the stem chloroform, and 662.20 ± 1.00 mg QE/g in the leaf hexane extracts. The DPPH assays showed the highest percentage of inhibition at 240 µg/mL, for the stem hexane (70.10%), stem methanol (65.24%), and stem chloroform (60.26%) extracts, with their respective IC50 values of 19.26 µg/mL (stem hexane), 6.19 µg/mL (stem methanol), and 22.56 µg/mL (stem chloroform). The FRAP assays displayed minimal inhibition ranging from 4.73% to 14.40%, except for the latex extracts which displayed moderate inhibition at 15 µg/mL (21.82%) and substantial inhibition at 240 µg/mL (98.48%). The HeLa and MCF-7 cell lines were the most sensitive to the extracts, with the hexane, chloroform, and methanol leaf and stem, and latex extracts significantly affecting the percentage cell survival. Overall, the various parts of T. ventricosa exhibited strong antioxidant activity correlating to its cytotoxicity. Further studies should focus on the isolation of specific antioxidant compounds that could be investigated for their anticancer potential.

Potential Benefits of Antiviral African Medicinal Plants in the Management of Viral Infections: Systematic Review

Background: Viruses cause various human diseases, some of which become pandemic outbreaks. This study synthesized evidence on antiviral medicinal plants in Africa which could potentially be further studied for viral infections including Coronavirus disease 2019 (COVID-19) treatment.

Methods: PUBMED, CINAHIL, Scopus, Google Scholar, and Google databases were searched through keywords; antiviral, plant, herb, and Africa were combined using “AND” and “OR”. In-vitro studies, in-vivo studies, or clinical trials on botanical medicine used for the treatment of viruses in Africa were included.

Results: Thirty-six studies were included in the evidence synthesis. Three hundred and twenty-eight plants were screened for antiviral activities of which 127 showed noteworthy activities against 25 viral species. These, were Poliovirus (42 plants), HSV (34 plants), Coxsackievirus (16 plants), Rhinovirus (14plants), Influenza (12 plants), Astrovirus (11 plants), SARS-CoV-2 (10 plants), HIV (10 plants), Echovirus (8 plants), Parvovirus (6 plants), Semiliki forest virus (5 plants), Measles virus (5 plants), Hepatitis virus (3 plants), Canine distemper virus (3 plants), Zika virus (2 plants), Vesicular stomatitis virus T2 (2 plants). Feline herpesvirus (FHV-1), Enterovirus, Dengue virus, Ebola virus, Chikungunya virus, Yellow fever virus, Respiratory syncytial virus, Rift Valley fever virus, Human cytomegalovirus each showed sensitivities to one plant.

Conclusion: The current study provided a list of African medicinal plants which demonstrated antiviral activities and could potentially be candidates for COVID-19 treatment. However, all studies were preliminary and in vitro screening. Further in vivo studies are required for plant-based management of viral diseases.

Efficacy of the commercial plant products acting against influenza-a review

Background

Influenza infection always poses a threat to human and animal health. Vaccines and antiviral drugs are recommended to deal with the situation. The drawback of these remedial agents made the scientist change their focus on an alternative therapy. The anti-influenza effects of plants have been extensively studied, and many pharmaceutical companies have prepared their products on this basis.

Main body

The present review documents the successfully launched anti-influenza commercial products. In specific, it exposes the scientifically validated and evidence-based supporting inhibitory action of influenza and its strains.

Conclusion

This review highlighted the efficacy of the commercial products which effectively combat influenza. It provides a complementary strategy to deal with the worst-case scenario of flu. Meanwhile, to face the emerging strains, brand new products are in great necessity besides prevailing and available drugs.

Ophiopogon japonicus inhibits white spot syndrome virus proliferation in vivo and enhances immune response in Chinese mitten crab Eriocheir sinensis

White spot syndrome virus (WSSV) is a fatal pathogen threatening global crustacean industry with no commercially available drugs to control. Herbal medicines have been widely used to treat a number of viral infections, which could offer a rich reserve for antiviral drug discovery. Here, we evaluated the inhibition activities of 30 herbal medicines against WSSV in Chinese mitten crab Eriocheir sinensis. A WSSV infection model in E. sinensis was firstly established in order to determine the antiviral effects of the plant extracts and to explore the potential action mechanisms. Results showed that the highest anti-WSSV activity was obtained by the treatment of Ophiopogon japonicus extract (93.03%, 100 mg/kg). O. japonicus treatment decreased viral loads in a dose-dependent manner and significantly improved the survival of WSSV-challenged crabs. O. japonicus reduced the expression of vital genes in viral life cycle in vivo, particularly for the immediate-early stage gene ie1. Further results indicated that O. japonicus could repress the JAK-STAT signaling pathway to block ie1 transcription. Moreover, O. japonicus could modulate certain immune genes such as the myosin, toll-like receptor, crustin, and prophenoloxidase in the interactions between WSSV and crabs. The up-regulated expression of pro-autophagic factors (Gabarap and Atg7) and elevated levels of antioxidant enzymes (SOD, CAT and GSH) suggested that O. japonicus may induce autophagy and attenuate WSSV-induced oxidative stress. Taken together, O. japonicus could inhibit WSSV proliferation and improve the survival of WSSV-challenged crabs. Thus, O. japonicus may have the potential to be developed as a preventive or therapeutic agent against WSSV, and its effective compounds merit further isolation and identification.

Potential antiviral effects of some native Iranian medicinal plants extracts and fractions against influenza A virus

Background

Influenza A virus (IAV) infection is a continual threat to the health of animals and humans globally. Consumption of the conventional drugs has shown several side effects and drug resistance. This study was aimed to screen some Iranian medicinal plants extracts and their fractions against influenza A virus.

Methods

Glycyrrhiza glabra (rhizome), Myrtus  commonis (leaves), Melissa officinalis (leaves), Hypericum perforatum (aerial parts), Tilia platyphyllos (flower), Salix alba (bark), and Camellia sinensis (green and fermented leaves) were extracted with 80% methanol and fractionated with chloroform and methanol, respectively. The cytotoxicity of the compounds were determined by MTT colorimetric assay on MDCK cells. The effective concentrations (EC₅₀) of the compounds were calculated from the MTT results compared to the negative control with no significant effects on cell viability. The effects of EC₅₀ of the compounds on viral surface glycoproteins and viral titer were tested by HI and HA virological assays, respectively and compared with oseltamivir and amantadine. Preliminary phytochemical analysis were done for promising anti-IAV extracts and fractions.

Results

The most effective samples against IAV titer (P ≤ 0.05) were crude extracts of G. glabra, M. officinalis and S. alba; methanol fractions of M. communis and M. officinalis; and chloroform fractions of M. communis and C. sinensis (fermented) mostly in co- and pre-penetration combined treatments. The potential extracts and fractions were rich in flavonoids, tannins, steroids and triterpenoids.

Conclusion

The outcomes confirmed a scientific basis for anti-influenza A virus capacity of the extracts and fractions from the selected plants for the first time, and correlated their effects with their phytochemical constituents. It is worth focusing on elucidating pure compounds and identifying their mechanism(s) of action.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03423-x.

Natural Compounds With Antimicrobial and Antiviral Effect and Nanocarriers Used for Their Transportation

Due to the increasing prevalence of life-threatening bacterial, fungal and viral infections and the ability of these human pathogens to develop resistance to current treatment strategies, there is a great need to find and develop new compunds to combat them. These molecules must have low toxicity, specific activity and high bioavailability. The most suitable compounds for this task are usually derived from natural sources (animal, plant or even microbial). In this review article, the latest and most promising natural compounds used to combat bacteria, filamentous fungi and viruses are presented and evaluated. These include plant extracts, essential oils, small antimicrobial peptides of animal origin, bacteriocins and various groups of plant compounds (triterpenoids; alkaloids; phenols; flavonoids) with antimicrobial and antiviral activity. Data are presented on the inhibitory activity of each natural antimicrobial substance and on the putative mechanism of action against bacterial and fungal strains. The results show that among the bioactive compounds studied, triterpenoids have significant inhibitory activity against coronaviruses, but flavonoids have also been shown to inhibit SARS-COV-2. The last chapter is devoted to nanocarriers used to improve stability, bioavailability, cellular uptake/internalization, pharmacokinetic profile and reduce toxicity of natural compunds. There are a number of nanocarriers such as liposomes, drug delivery microemulsion systems, nanocapsules, solid lipid nanoparticles, polymeric micelles, dendrimers, etc. However, some of the recent studies have focused on the incorporation of natural substances with antimicrobial/antiviral activity into polymeric nanoparticles, niosomes and silver nanoparticles (which have been shown to have intrinsic antimicrobial activity). The natural antimicrobials isolated from animals and microorganisms have been shown to have good inhibitory effect on a range of pathogens, however the plants remain the most prolific source. Even if the majority of the studies for the biological activity evaluation are in silico or in vitro, their internalization in the optimum nanocarriers represents the future of “green therapeutics” as shown by some of the recent work in the field.

Phytochemical Profiles and their Anti-inflammatory Responses Against Influenza from Traditional Chinese Medicine or Herbs

Traditional Chinese medicine (TCM) or herbs are widely used in the prevention and treatment of viral infectious diseases. However, the underlying mechanisms of TCMs remain largely obscure due to complicated material basis and multi-target therapeutics. TCMs have been reported to display anti-influenza activity associated with immunoregulatory mechanisms by enhancing host antiinfluenza immune responses. Previous studies have helped us understand the direct harm caused by the virus itself. In this review, we have tried to summarize recent progress in TCM-based anti-influenza research on the indirect harmful immune responses caused by influenza viruses. In particular, the phytochemicals from TCMs responsible for molecular mechanisms of action belonging to different classes, including phenolic compounds, flavonoids, alkaloids and polysaccharides, have been identified and demonstrated. In addition, this review focuses on the pharmacological mechanism, e.g., inflammatory responses and the interferon (IFN) signaling pathway, which can provide a theoretical basis and approaches for TCM based anti-influenza treatment.

African Herbal Medicines: Adverse Effects and Cytotoxic Potentials with Different Therapeutic Applications

The African continent is naturally endowed with various plant species with nutritional and medicinal benefits. About 80% of the people in developing countries rely on folk medicines to treat different diseases because of indigenous knowledge, availability, and cost-effectiveness. Extensive research studies have been conducted on the medicinal uses of African plants, however, the therapeutic potentials of some of these plants has remained unexploited. Over the years, several studies have revealed that some of these African floras are promising candidates for the development of novel drugs. Despite the plethora of studies on medicinal plant research in Africa, there is still little scientific data supporting the folkloric claims of these plants. Besides, safety in the use of folk medicines has been a major public health concern over the year. Therefore, it has become mandatory that relevant authority should take measures in safeguarding the populace on the use of herbal mixtures. Thus, the present review extracted relevant information from different scientific databases and highlighted some problems associated with folk medicines, adverse effects on reproductive systems, issue about safety due to the toxicity of some plants and their toxicity effects with potential therapeutic benefits are discussed.

Therapeutic Potentials of Antiviral Plants Used in Traditional African Medicine With COVID-19 in Focus: A Nigerian Perspective

The coronavirus disease 2019 (COVID-19) pandemic is caused by an infectious novel strain of coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which was earlier referred to as 2019-nCoV. The respiratory disease is the most consequential global public health crisis of the 21st century whose level of negative impact increasingly experienced globally has not been recorded since World War II. Up till now, there has been no specific globally authorized antiviral drug, vaccines, supplement or herbal remedy available for the treatment of this lethal disease except preventive measures, supportive care and non-specific treatment options adopted in different countries via divergent approaches to halt the pandemic. However, many of these interventions have been documented to show some level of success particularly the Traditional Chinese Medicine while there is paucity of well reported studies on the impact of the widely embraced Traditional African Medicines (TAM) adopted so far for the prevention, management and treatment of COVID-19. We carried out a detailed review of publicly available data, information and claims on the potentials of indigenous plants used in Sub-Saharan Africa as antiviral remedies with potentials for the prevention and management of COVID-19. In this review, we have provided a holistic report on evidence-based antiviral and promising anti-SARS-CoV-2 properties of African medicinal plants based on in silico evidence, in vitro assays and in vivo experiments alongside the available data on their mechanistic pharmacology. In addition, we have unveiled knowledge gaps, provided an update on the effort of African Scientific community toward demystifying the dreadful SARS-CoV-2 micro-enemy of man and have documented popular anti-COVID-19 herbal claims emanating from the continent for the management of COVID-19 while the risk potentials of herb-drug interaction of antiviral phytomedicines when used in combination with orthodox drugs have also been highlighted. This review exercise may lend enough credence to the potential value of African medicinal plants as possible leads in anti-COVID-19 drug discovery through research and development.

Major Bioactive Alkaloids and Biological Activities of Tabernaemontana Species (Apocynaceae)

Several species belonging to the genus Tabernaemontana have been well researched and utilized for their wide-ranging biological activities. A few of the most prominent species include Tabernaemontana divaricata, Tabernaemontana catharinensis, Tabernaemontana crassa, and Tabernaemontana elegans. These species and many others within the genus often display pharmacological importance, which is habitually related to their chemical constituents. The secondary metabolites within the genus have demonstrated huge medicinal potential for the treatment of infections, pain, injuries, and various diseases. Regardless of the indispensable reports and properties displayed by Tabernaemontana spp., there remains a wide variety of plants that are yet to be considered or examined. Thus, an additional inclusive study on species within this genus is essential. The current review aimed to extensively analyze, collate, and describe an updated report of the current literature related to the major alkaloidal components and biological activities of species within the genus Tabernaemontana.

Quercetin as a Natural Therapeutic Candidate for the Treatment of Influenza Virus

The medical burden caused by respiratory manifestations of influenza virus (IV) outbreak as an infectious respiratory disease is so great that governments in both developed and developing countries have allocated significant national budget toward the development of strategies for prevention, control, and treatment of this infection, which is seemingly common and treatable, but can be deadly. Frequent mutations in its genome structure often result in resistance to standard medications. Thus, new generations of treatments are critical to combat this ever-evolving infection. Plant materials and active compounds have been tested for many years, including, more recently, active compounds like flavonoids. Quercetin is a compound belonging to the flavonols class and has shown therapeutic effects against influenza virus. The focus of this review includes viral pathogenesis as well as the application of quercetin and its derivatives as a complementary therapy in controlling influenza and its related symptoms based on the targets. We also touch on the potential of this class of compounds for treatment of SARS-COV-2, the cause of new pandemic.

The epidemiology of seasonal influenza after the 2009 influenza pandemic in Africa: a systematic review

Background

Influenza infection is a serious public health problem that causes an estimated 3 to 5 million cases and 250,000 deaths worldwide every year. The epidemiology of influenza is well-documented in high- and middle-income countries, however minimal effort had been made to understand the epidemiology, burden and seasonality of influenza in Africa. This study aims to assess the state of knowledge of seasonal influenza epidemiology in Africa and identify potential data gaps for policy formulation following the 2009 pandemic.

Method

We reviewed articles from Africa published into four databases namely: MEDLINE (PubMed), Google Scholar, Cochrane Library and Scientific Research Publishing from 2010 to 2019.

Results

We screened titles and abstracts of 2070 studies of which 311 were selected for full content evaluation and 199 studies were considered. Selected articles varied substantially on the basis of the topics they addressed covering the field of influenza surveillance (n=80); influenza risk factors and co-morbidities (n=15); influenza burden (n=37); influenza vaccination (n=40); influenza and other respiratory pathogens (n=22) and influenza diagnosis (n=5).

Conclusion

Significant progress has been made since the last pandemic in understanding the influenza epidemiology in Africa. However, efforts still remain for most countries to have sufficient data to allow countries to prioritize strategies for influenza prevention and control.

The traditional use of southern African medicinal plants in the treatment of viral respiratory diseases: A review of the ethnobotany and scientific evaluations

ETHNOPHARMACOLOGICAL RELEVANCE

Viral respiratory infections are amongst the most common infections globally, with most of the world's population contracting at least one infection annually. Numerous plant species are used in traditional southern African healing systems to treat these diseases and to alleviate the symptoms. Despite this, the therapeutic potential of these plants against viral respiratory diseases remains poorly explored.

AIM OF THE STUDY

The aim of this study was to document the southern African plant species used in traditional medicine to treat viral respiratory infections. We also examined the extent of scientific evaluations of southern African plant species against the respiratory-infective viruses, with the aim of stimulating interest in this area and focusing on future studies.

MATERIALS AND METHODS

We undertook an extensive review of ethnobotanical books, reviews and primary scientific studies to identify southern African plants which are used in traditional southern African medicine to treat viral respiratory diseases. This information was used to identify gaps in the current research that require further study.

RESULTS

Two hundred and fifty-seven southern African plant species were identified as traditional therapies for viral respiratory diseases. Surprisingly, only one of those species (as well as twenty-one other species not recorded for these purposes) has been evaluated for the ability to block respiratory virus production. Furthermore, most of these studies screened against a single viral strain and none of those studies examined the mechanism of action of the plant preparations.

CONCLUSIONS

Despite well documented records of the use of southern African plants to treat respiratory viral diseases, the field is poorly explored. Nearly all of the plant species used in traditional healing systems to treat these diseases are yet to be tested. Substantial further work is required to verify the efficacy of these traditional medicines.

A review on traditionally used South African medicinal plants, their secondary metabolites and their potential development into anticancer agents

ETHNOPHARMACOLOGICAL RELEVANCE

Approximately 70% of anticancer drugs were developed or derived from natural products or plants. Southern Africa boasts an enormous floral diversity with approximately 22,755 plant species with an estimated 3000 used as traditional medicines. In South Africa more than 27 million individuals rely on traditional medicine for healthcare. The use of South African plants for the treatment of cancer is poorly documented, however there is potential to develop anticancer agents from these plants. Limited ethnobotanical studies report the use of plants for cancer treatment in traditional medicine. Plants growing in tropical or subtropical regions, such as in South Africa, produce important secondary metabolites as a protective mechanism, which could be used to target various factors that play a key role in carcinogenesis.

AIMS

The aim was to collate information from primary ethnobotanical studies on South African plants traditionally used for the treatment of cancer. Evaluation of literature focused on traditionally used plants that have been tested for their in vitro activity against cancer cells. Secondary metabolites, previously identified within these plant species, were also included for discussion regarding their activity against cancer. The toxicity was evaluated to ascertain the therapeutic potential in further studies. Additionally, the aim was to highlight where a lack of reports were found regarding plant species with potential activity and to substantiate the need for further testing.

MATERIALS AND METHODS

A review of ethnobotanical surveys conducted in South Africa for plants used in the treatment of cancer was performed. Databases such as Science Direct, PubMed and Google Scholar, university repositories of master's dissertations and PhD theses, patents and books were used. Plant species showing significant to moderate activity were discussed regarding their toxicity. Compounds identified within these species were discussed for their activity against cancer cells and toxicity. Traditionally used plants which have not been scientifically validated for their activity against cancer were excluded.

RESULTS

Twenty plants were documented in ethnobotanical surveys as cancer treatments. Numerous scientific reports on the potential in vitro activity against cancer of these plants and the identification of secondary metabolites were found. Many of the secondary metabolites have not been tested for their activity against cancer cells or mode of action and should be considered for future studies. Lead candidates, such as the sutherlandiosides, sutherlandins, hypoxoside and pittoviridoside, were identified and should be further assessed. Toxicity studies should be included when testing plant extracts and/or secondary metabolites for their potential against cancer cells to give an indication of whether further analysis should be conducted.

CONCLUSION

There is a need to document plants used traditionally in South Africa for the treatment of cancer and to assess their safety and efficacy. Traditionally used plants have shown promising activity highlighting the importance of ethnobotanical studies and traditional knowledge. There are many opportunities to further assess these plants and secondary metabolites for their activity against cancer and their toxic effects. Pharmacokinetic studies are also not well documented within these plant extracts and should be included in studies when a lead candidate is identified.

Identification of potential SARS-CoV-2 inhibitors from South African medicinal plant extracts using molecular modelling approaches

The coronavirus is a group of viruses found in animals as well as humans and have been detected since the 1960s. However, a newly identified form, SARS-CoV-2, has triggered a recent pandemic of respiratory disease now called COVID-19. There is currently no specific antiviral drug for the treatment of this pandemic, with most treatment strategies focused on symptomatic management and supportive therapy. As such, several drug discovery efforts are ongoing for potent treatment agents, with medicinal plants gradually gaining prominence. Approximately 80% of the South African population use traditional medicines to meet their primary health care needs. The current study aimed to identify potential COVID-19 therapeutic agents from a list of 29 bioactive compounds isolated from commonly used South African medicinal plants using molecular docking and molecular dynamics. Molecular docking identified arabic acid from Acacia senegal and L-canavanine found in Sutherlandia frutescens as a potential inhibitor of SARS-CoV-2 3C-like main protease. Similarly, hypoxoside isolated from Hypoxis hemerocallidea and uzarin from Xysmalobium undulatum, were identified as a potential inhibitor of SARS-CoV-2 receptor binding domain and SARS-CoV-2 RNA-dependent polymerase. These four bioactive compounds exhibited favourable binding orientations characterized by strong molecular interactions within respective inhibitors binding pockets of the target enzymes. Molecular dynamics simulations revealed that the binding of the identified inhibitors are characterized by structural perturbations which favour the inhibitory potency of these bioactive compounds. Additionally, in silico pharmacokinetic assessment of the compounds demonstrated favourable anti-SARS-CoV-2 properties. Although not conclusive, further experimental exploration of these compounds could serve as a starting point for the discovery of novel SARS-CoV-2 therapeutic.

Traditional Herbal Medicine for the Prevention and Treatment of Cold and Flu in the Autumn of 2020, Overlapped With COVID-19

Many herbs and plants included in several traditional systems have promising bioactive compounds for modern drug therapy. The second round of COVID-19 cases will be accompanied by the spread of seasonal influenza in the fall. The combination of the influenza season and the second wave of COVID-19 may lead to more confusion and put more pressure on public health systems. A literature survey was accomplished using multiple databases including PubMed, Science Direct, ISI web of knowledge, and Google Scholar. The most important antiviral herbs for cold and flu are Thymus vulgaris, honeysuckle flowers, Andrographis, yarrow, peppermint leaf and oil, and Calendula. The most important expectorant herbs for flu and cold are tulsi, snake root, licorice root, clove, slippery elm root, marshmallow osha root, and sage leaf. Immunostimulant herbs for these 2 diseases are Echinacea root, Eucalyptus, garlic, ginseng, marshmallow, slippery elm, Isatisroot, Usnea lichen, myrrh resin, and ginger root. In this mini-review, we mention the key role of some of the most important herbal plants and prescriptions against influenza and cold on the basis of traditional Asian medicine.

The Secretory Apparatus of Tabernaemontana ventricosa Hochst. ex A.DC. (Apocynaceae): Laticifer Identification, Characterization and Distribution

Due to the inconsistencies in the interpretation of laticifers within the Apocynaceae, the current study aimed to distinguish, for the first time, the type and distribution of the laticifers in the embryos, seedlings and adult plants of Tabernaemontana ventricosa (Forest Toad tree). The characterization and distribution of laticifers were determined using light and electron microscopy. The findings revealed the presence of articulated anastomosing laticifers. The laticifers were found to have originated from ground meristematic and procambium cells and were randomly distributed in all ground and vascular tissue, displaying complex branching conformations. The presence of chemical constituents within the laticifers and latex determined by histochemical analysis revealed the presence of alkaloids, phenolics, neutral lipids, terpenoids, mucilage, pectin, resin acids, carboxylated polysaccharides, lipophilic, and hydrophilic substances and proteins. These secondary metabolites perform an indispensable role in preventing herbivory, hindering and deterring micro-organisms and may possibly have medicinal importance. The outcomes of the present study outlined the first micromorphology, anatomy, ultrastructural and chemical analysis of the laticifers of T. ventricosa. In addition, this investigation similarly established the probable functions of latex and laticifers.

In vitro screening antiviral activity of Thai medicinal plants against porcine reproductive and respiratory syndrome virus

BACKGROUND

Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV) results in economic losses in the swine industry globally. Several studies have investigated the use of plant extracts in the prevention and control of PRRS outbreaks. Thai medicinal plants may be useful for treating PRRSV infection in pigs. Therefore, we investigated the in vitro anti-PRRSV and antioxidant properties of seven Thai medicinal plants: Caesalpinia sappan Linn., Garcinia mangostana Linn., Houttuynia cordata, Perilla frutescens, Clinacanthus nutans, Phyllanthus emblica, and Tiliacora triandra.

RESULTS

Using antiviral screening, we observed that T. triandra extract strongly inhibited PRRSV infectivity in MARC-145 cells [virus titer 3.5 median tissue culture infective dose (TCID₅₀)/ml (log10)] at 24 h post-infection, whereas C. sappan extract strongly inhibited PRRSV replication [virus titer 2.5 TCID₅₀/ml (log10)] at 72 h post-infection. C. sappan extract had the highest total phenolic content [220.52 mM gallic acid equivalent/g] and lowest half-maximal inhibitory concentration [1.17 mg/ml in 2,2-diphenyl-1-picrylhydrazyl and 2.58 mg/ml in 2,2-azino-bis (3-ethylbenzothiazo-line-6-sulfonic acid) diammonium salt].

CONCLUSION

T. triandra extract could inhibit PRRSV infectivity, whereas C. sappan extract was the most effective in inhibiting PRRSV replication in MARC-145 cells. This study elucidates the antiviral activities of Thai medicinal plant extracts in vivo. The results promise that Thai medicinal plant extracts, particularly T. triandra and C. sappan extracts, can be developed into pharmaceutical drugs for the prevention of PRRS in pigs.

The genus Tragopogon (Asteraceae): A review of its traditional uses, phytochemistry, and pharmacological properties

ETHNOPHARMACOLOGICAL RELEVANCE

Species of Tragopogon are used in traditional medicine, and consumed as vegetables across the world. In terms of the medicinal uses of Tragopogon, different species have found use in traditional medicine, including uses for wound-healing, treatment of gastrointestinal and hepatic complaints, cancer, kidney and liver dysfunction, inflamed skin and certain cutaneous diseases, as well as constipation, fatigue and anoxia.

AIM OF THE STUDY

The aim of this review is to highlight and critically summarize those species of the genus that have been studied as a source of interesting lead compounds, and their traditional uses and bioactivities.

MATERIALS AND METHODS

A comprehensive and systematic review of literature on traditional uses, phytochemicals and pharmacological properties of the genus Tragopogon was carried out. Information was retrieved from secondary databases such as Scopus, Chemical Abstracts Services (Scifinder), Pubmed, Google Scholar and ScienceDirect, in addition to primary sources including books, PhD and MSc dissertations, and official websites. Species names were validated using "The Plant List" (www.theplantlist.org).

RESULTS

The taxa of the genus Tragopogon are known for their local and traditional uses as medicine for treatment of various diseases, and have been consumed as vegetables and snacks for generations in Eurasia, the Mediterranean, Caucasus, Europe and North America. From the approximately 110 species of Tragopogon, only twelve species have been scientifically evaluated for their bioactivity and/or phytochemical composition. Tragopogon species are a rich source of phytochemical constituents and among those that have been identified are 19 flavonoids, 35 terpenoids, seven bibenzyl derivatives, five benzylphtalides, six stilbenes, nine dihydroisocoumarin derivatives, nine phenylmethane derivatives, three hydroxyphenylacetic acid derivatives, four phenylpropane derivatives, four esters of phenylpropanoic acids, a coumarin derivative, and a spermine derivative. Various extracts of the taxa, in addition to the isolated compounds, demonstrated pharmacological properties such as antitumor, antimicrobial, anti-inflammatory and enzyme inhibitory activities, in addition to hepatoprotective, antihyperlipidaemic and wound-healing properties.

CONCLUSION

This review highlights the traditional uses, phytochemistry and pharmacological properties of the few studied taxa of the genus Tragopogon. Some of the reviewed papers were not of an appropriate methodological standard. For instance, phytochemical profiles were not determined, and the fundamental requirements of the pharmacological properties were not defined such as including appropriate positive and negative controls, and calculating the MIC values. Furthermore, these studies did not provide an in depth evaluation of bioactivity of the extracts and the isolated compounds or in vivo experiments which could indicate therapeutic relevance. From a phytopharmacological point of view, this review recommends more high quality evidence-based research on Tragopogon species for further development of plant-derived remedies and compounds.

Experimental validation and computational modeling of anti-influenza effects of quercetin-3-O-α-L-rhamnopyranoside from indigenous south African medicinal plant Rapanea melanophloeos

BACKGROUND

Influenza A virus (IAV) is still a major health threat. The clinical manifestations of this infection are related to immune dysregulation, which causes morbidity and mortality. The usage of traditional medication with immunomodulatory properties against influenza infection has been increased recently. Our previous study showed antiviral activity of quercetin-3-O-α-L-rhamnopyranoside (Q3R) isolated from Rapanea melanophloeos (RM) (L.) Mez (family Myrsinaceae) against H1N1 (A/PR/8/34) infection. This study aimed to confirm the wider range of immunomodulatory effect of Q3R on selective pro- and anti-inflammatory cytokines against IAV in vitro, to evaluate the effect of Q3R on apoptosis pathway in combination with H1N1, also to assess the physical interaction of Q3R with virus glycoproteins and RhoA protein using computational docking.

METHODS

MDCK cells were exposed to Q3R and 100CCID50/100 μl of H1N1 in combined treatments (co-, pre- and post-penetration treatments). The treatments were tested for the cytokines evaluation at RNA and protein levels by qPCR and ELISA, respectively. In another set of treatment, apoptosis was examined by detecting RhoA GTPase protein and caspase-3 activity. Molecular docking was used as a tool for evaluation of the potential anti-influenza activity of Q3R.

RESULTS

The expressions of cytokines in both genome and protein levels were significantly affected by Q3R treatment. It was shown that Q3R was much more effective against influenza when it was applied in co-penetration treatment. Q3R in combination with H1N1 increased caspase-3 activity while decreasing RhoA activation. The molecular docking results showed strong binding ability of Q3R with M2 transmembrane, Neuraminidase of 2009 pandemic H1N1, N1 and H1 of PR/8/1934 and Human RhoA proteins, with docking energy of - 10.81, - 10.47, - 9.52, - 9.24 and - 8.78 Kcal/mol, respectively.

CONCLUSIONS

Quercetin-3-O-α-L-rhamnopyranoside from RM was significantly effective against influenza infection by immunomodulatory properties, affecting the apoptosis pathway and binding ability to viral receptors M2 transmembrane and Neuraminidase of 2009 pandemic H1N1 and human RhoA cellular protein. Further research will focus on detecting the detailed specific mechanism of Q3R in virus-host interactions.

Investigation of Brassica juncea, Forsythia suspensa, and Inula britannica: phytochemical properties, antiviral effects, and safety

BACKGROUND

General antiviral agents such as oseltamivir are associated with certain adverse effects and the emergence of resistance. This study investigated the phytochemical properties, antiviral activities, and safety of three herbs used in traditional Korean medicine.

METHODS

Extracts of three medicinal herbs (Brassica juncea, Forsythia suspensa, and Inula britannica) were prepared using ethanol or water. The total phenolic, flavonoid, and saponin content, condensed tannin content, and reducing sugar content of the herb extracts were determined via phytochemical screening. Tandem mass analysis was performed using an ultra-performance liquid chromatography (UPLC)-electrospray ionization (ESI)-Q/Orbitrap instrument. Virus titrations were determined via tissue culture infective dose (TCID50) and cytotoxicity assays. Hemolysis and hepatotoxicity were measured to determine safety.

RESULTS

Among the three medicinal herbs, F. suspensa showed the highest concentration of phenolic compounds, flavonoids, and saponins. The number of phytochemical compounds detected via tandem mass analysis of B. juncea, F. suspensa, and I. britannica was 5 (including sinigrin, m/z [M-H] = 358.02), 14 (including forsythoside A, m/z [M-H] = 623.19), and 18 (including chlorogenic acid, m/z [M-H] = 353.20), respectively. The antiviral effects of the B. juncea extracts (ethanol and water) and I. britannica extract (ethanol) were further investigated. The ethanol extract of B. juncea showed a 3 Log TCID50/25 μL virus titration reduction and the water extract showed a selectivity index of 13.668 against infected influenza H1N1 virus A/NWS/33. The B. juncea extracts did not show hemolysis activities and hepatotoxicity (< 20%). The ethanol extract of I. britannica showed the most effective virus titration decrease, whereas its hemolytic and hepatotoxicity values were the most significantly different compared to the control. Despite the high concentration of phytochemicals detected in F. suspensa, the extract showed approximately 1 Log TCID50/25 μL at the highest concentration.

CONCLUSION

B. juncea may show antiviral effects against H1N1 in a host. In addition, B. juncea may also show decreased disadvantages compared to other antiviral agents.

Antibacterial activity and mode of action of acetone crude leaf extracts of under-investigated Syzygium and Eugenia (Myrtaceae) species on multidrug resistant porcine diarrhoeagenic Escherichia coli

BACKGROUND

Diarrhoea, a global economically important disease burden affecting swine and, especially piglets, is commonly caused by infection with entero-toxigenic E. coli (ETEC). Adherence of ETEC to porcine intestinal epithelial cells following infection, is necessary for its pathogenesis. While antimicrobials are commonly given as therapy or as feed additives for prophylaxis against microbial infections, the concern over increased levels of antimicrobial resistance necessitate the search for safe and effective alternatives in livestock feed. Attention is shifting to natural products including plants as suitable alternatives to antimicrobials. The activity of acetone crude leaf extracts of nine under-explored South African endemic plants from the Myrtaceae family with good antimicrobial activity were tested against pathogenic E. coli of porcine origin using a microplate serial dilution method. Bioautography, also with p-iodonitrotetrazolium violet as growth indicator was used to view the number of bioactive compounds in each extract. In vitro toxicity of extracts was determined against Caco-2 cells using the 3-(4,5-dimethythiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay. The antimicrobial susceptibility of E. coli isolates was tested on a panel of antimicrobials using the Kirby-Bauer agar diffusion method while the anti-adherence mechanism was evaluated using a Caco-2 cell enterocyte anti-adhesion model.

RESULTS

The MIC of the extracts ranged from 0.07-0.14 mg/mL with S. legatii having the best mean MIC (0.05 mg/mL). Bioautography revealed at least two active bands in each plant extract. The 50% lethal concentration (LC₅₀) values ranged between 0.03-0.66 mg/mL. Eugenia zeyheri least cytotoxic (LC₅₀ = 0.66 mg/ml) while E. natalitia had the highest cytotoxicity (LC₅₀ = 0.03 mg/mL). All the bacteria were completely resistant to doxycycline and colistin sulphate and many of the plant extracts significantly reduced adhesion of E. coli to Caco-2 cells.

CONCLUSIONS

The extracts of the plants had good antibacterial activity as well as a protective role on intestinal epithelial cells against enterotoxigenic E. coli bacterial adhesion. This supports the potential use of these species in limiting infection causes by E. coli. Some of these plants or extracts may be useful as phytogenic feed additives but it has to be investigated by animal feed trials.

Acute adrenal failure: a potentially fatal consequence of an adulterated herbal remedy

Herbal remedies adulterated with glucocorticoids can cause Cushing's syndrome. We report a severe presentation of a 'herbal remedy' adulterated with glucocorticoids; causing a potentially fatal adrenal crisis precipitated by acute illness. Investigations were consistent with adrenal suppression and confirmed, after tablet analysis, to be due to a 'herbal remedy' containing synthetic betamethasone/dexamethasone. This case highlights the need for clinical vigilance and patient education about the potential risks associated with the use of unlicensed treatments and the role of tablet analysis in routine biochemistry.

Immunomodulatory properties of quercetin-3-O-α-L-rhamnopyranoside from Rapanea melanophloeos against influenza a virus

BACKGROUND

Influenza infection is a major public health threat. The role of influenza A virus-induced inflammatory response in severe cases of this disease is widely recognized. Drug resistance and side effects of chemical treatments have been observed, resulting in increased interest in alternative use of herbal medications for prophylaxis against this infection. The South African medicinal plant, Rapanea melanophloeos (RM) (L.) Mez of the family Myrsinaceae was selected owing to its traditional use for the treatment of several diseases such as respiratory ailments and also previous preliminary studies of anti-influenza activity of its methanolic extract. The aim of this study was to investigate the immunomodulatory properties of a glycoside flavone isolated from RM against influenza A virus.

METHODS

The non-cytotoxic concentration of the quercetin-3-O-α-L-rhamnopyranoside (Q3R) was determined by MTT assay and tested for activity against influenza A virus (IAV) in simultaneous, pre-penetration and post-penetration combination treatments over 1 h incubation on MDCK cells. The virus titer and viral load targeting NP and M2 viral genes were determined using HA and qPCR, respectively. TNF-α and IL-27 as pro- and anti-inflammatory cytokines were measured at RNA and protein levels by qPCR and ELISA, respectively.

RESULTS

Quercetin-3-O-α-L-rhamnopyranoside at 150 μg/ml decreased the viral titer by 6 logs (p < 0.01) in the simultaneous procedure. The NP and M2 genes copy numbers as viral target genes, calculated based on the Ct values and standard formula, significantly decreased in simultaneous treatment (p < 0.01). The expression of cytokines was also considerably affected by the compound treatment.

CONCLUSIONS

This is the first report of quercetin-3-O-α-L-rhamnopyranoside from RM and its immunomodulatory properties against influenza A virus. Further research will focus on detecting the specific mechanism of virus-host interactions.

Bioprospecting of South African Plants as a Unique Resource for Bioactive Endophytic Microbes

South Africa has a long history and strong belief in traditional herbal medicines. Using ethnobotanical knowledge as a lead, a large number of South African medicinal plants have been discovered to possess a wide spectrum of pharmacological properties. In this review, bioprospecting of endophytes is highlighted by following the advantages of the ethnomedicinal approach together with identifying unique medicinal plants where biological activity may be due to endophytes. This review focuses on the current status of South African medicinal plants to motivate the research community to harness the benefits of ethnobotanical knowledge to investigate the presence of endophytic microbes from the most potent South African medicinal plants. The potential chemical diversity and subsequent putative medicinal value of endophytes is deserving of further research. A timely and comprehensive review of literature on recently isolated endophytes and their metabolites was conducted. Worldwide literature from the last 2 years demonstrating the importance of ethnobotanical knowledge as a useful approach to discover endophytic microbes was documented. Information was obtained from scientific databases such as Pubmed, Scopus, Scirus, Google Scholar, Dictionary of Natural Products, Chemical Abstracts Services, official websites, and scientific databases on ethnomedicines. Primary sources such as books, reports, dissertations, and thesises were accessed where available. Recently published information on isolated endophytes with promising bioactivity and their bioactive natural products worldwide (2015-2017) was summarized. The potential value of South African medicinal plants as sources of endophytes is discussed. The insights provided through this study indicate that medicinal plants in South Africa are highly under-investigated sources of potentially useful endophytic microbes. New approaches may be used by medicinal plant scientists for further exploration of natural products from endophytic fungi and bacteria in southern Africa.