Anti-infective potential of caffeic acid and epicatechin 3-gallate isolated from methanol extract of Euphorbia hirta (L.) against Pseudomonas aeruginosa

Phytochemicals of Euphorbia hirta L. and Their Inhibitory Potential Against SARS-CoV-2 Main Protease

Euphorbia hirta L. is a medicinal plant widely used in the Philippines and across tropical Asia against various diseases, including respiratory disorders. In this study, the phytochemical components of E. hirta were investigated in silico for their potential to inhibit the severe acute respiratory syndrome-coronavirus-2 main protease (SARS-CoV-2 Mpro), a coronavirus disease 2019 (COVID-19) drug target that plays a critical role in the infection process of SARS-CoV-2. Phytochemical mining in tandem with virtual screening (PM-VS) was the strategy implemented in this study, which allows efficient preliminary in silico assessment of the COVID-19 therapeutic potential of the reported phytochemicals from the plant. The main rationale for considering E. hirta in the investigation was its reported efficacy against respiratory disorders. It is very promising to investigate the phytochemicals of E. hirta for their potential efficacy against diseases, such as COVID-19, that also target the respiratory system. A total of 298 E. hirta phytochemicals were comprehensively collected from the scientific literature. One hundred seventy of these phytochemicals were computed through molecular docking and were shown to have comparable or better binding properties (promising inhibitors) toward SARS-CoV-2 Mpro than known in vitro inhibitors. In connection to our previous work considering different medicinal plants, antiviral compounds were also rediscovered from the phytochemical composition of E. hirta. This finding provides additional basis for the potential of the plant (or its phytochemicals) as a COVID-19 therapeutic directly targeting drug targets such as SARS-CoV-2 Mpro and/or addressing respiratory-system-related symptoms. The study also highlights the utility of PM-VS, which can be efficiently implemented in the preliminary steps of drug discovery and development.

Role of inflammation and oxidative stress in tissue damage associated with cystic fibrosis: CAPE as a future therapeutic strategy

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, responsible for the synthesis of the CFTR protein, a chloride channel. The gene has approximately 2000 known mutations and all of them affect in some degree the protein function, which makes the pathophysiological manifestations to be multisystemic, mainly affecting the respiratory, gastrointestinal, endocrine, and reproductive tracts. Currently, the treatment of the disease is restricted to controlling symptoms and, more recently, a group of drugs that act directly on the defective protein, known as CFTR modulators, was developed. However, their high cost and difficult access mean that their use is still very restricted. It is important to search for safe and low-cost alternative therapies for CF and, in this context, natural compounds and, mainly, caffeic acid phenethyl ester (CAPE) appear as promising strategies to assist in the treatment of the disease. CAPE is a compound derived from propolis extracts that has antioxidant and anti-inflammatory activities, covering important aspects of the pathophysiology of CF, which points to the possible benefit of its use in the disease treatment. To date, no studies have effectively tested CAPE for CF and, therefore, we intend with this review to elucidate the role of inflammation and oxidative stress for tissue damage seen in CF, associating them with CAPE actions and its pharmacologically active derivatives. In this way, we offer a theoretical basis for conducting preclinical and clinical studies relating the use of this molecule to CF.

Phytochemical composition analysis and evaluation of in vitro medicinal properties and cytotoxicity of five wild weeds: A comparative study

Background: Medicinal plants are a source of phytochemicals and they are used for the treatment of several oxidative stress-related or other diseases for their effectiveness, low toxicity and easy availability. Five traditionally used and less characterized herbaceous weeds of West Bengal, India, namely, Heliotropium indicum, Tridax procumbens, Cleome rutidosperma, Commelina benghalensis and Euphorbia hirta, were investigated for the current research study. Methods: Aqueous and 70% ethanolic extracts of the leaves were analyzed for estimation of essential phytochemicals and to evaluate their in vitro antioxidant status, medicinal properties and cytotoxic effects. To the best of our knowledge, several assays and comparative evaluations using these herbs are reported for the first time. For quantitative study, UV-vis spectrophotometry and high-performance liquid chromatography with diode array detector HPLC-DAD techniques were used. Antibacterial properties were investigated using the Kirby-Bauer disc diffusion method. For in vitro anti-lithiatic study, a titration method was used. The cell viability assay was done using peripheral blood mononuclear cells. Results: The aqueous extract exhibits higher content of polyphenols, flavonoids, tannins and inhibition percentage values for free radical scavenging assays, whereas the 70% ethanolic extract exhibits higher content of alkaloids and cardiac glycosides. HPLC-DAD analysis of 70% ethanolic extracts led us to identify 10 predominant phenolic constituents. Euphorbia hirta extracts showed minimum cytotoxicity (cell death ~2.5% and 4% in water and 70% ethanolic extract, respectively ), whereas Cleome rutidosperma and Tridax procumbens' 70% ethanolic extracts showed higher cell death (~13% and 28%, respectively), compared with the control (cell death ~10-12%). Conclusions: The study concluded that of all the medicinal weeds selected for the current study, Euphorbia hirta possesses the highest amount of bioactive compounds and hence exhibits the highest in vitro antioxidant activity and promising in vitro medicinal properties.

Lignans from Euphorbia hirta L

Five new lignans, euphorhirtins A-D (1-4), 5-methoxyvirgatusin (5), three artefacts, 7S-ethoxyisolintetralin (6), 7R-ethoxyisolintetralin (7), and 7R-ethoxy-3-methoxyisolintetralin (8), together with 13 known ones (9-21) were isolated from the medicinal plant Euphorbia hirta L. The structures of the compounds were elucidated by means of extensive spectroscopic analysis, including 1D and 2D NMR and HR-ESI-MS experiments. The absolute configurations of compound 1 was determined by ECD calculation. The isolates were evaluated for their inhibitory effects against the proliferation of the cancer cell lines (Hep G2, A549, and DU145) and compounds 14 and 18 showed inhibitory activity against the Hep G2 cells with IC₅₀ values 7.2 ± 0.17 and 8.5 ± 0.36 μM.

Natural products against acute respiratory infections: Strategies and lessons learned

ETHNOPHARMACOLOGICAL RELEVANCE

A wide variety of traditional herbal remedies have been used throughout history for the treatment of symptoms related to acute respiratory infections (ARIs).

AIM OF THE REVIEW

The present work provides a timely overview of natural products affecting the most common pathogens involved in ARIs, in particular influenza viruses and rhinoviruses as well as bacteria involved in co-infections, their molecular targets, their role in drug discovery, and the current portfolio of available naturally derived anti-ARI drugs.

MATERIALS AND METHODS

Literature of the last ten years was evaluated for natural products active against influenza viruses and rhinoviruses. The collected bioactive agents were further investigated for reported activities against ARI-relevant bacteria, and analysed for the chemical space they cover in relation to currently known natural products and approved drugs.

RESULTS

An overview of (i) natural compounds active in target-based and/or phenotypic assays relevant to ARIs, (ii) extracts, and (iii) in vivo data are provided, offering not only a starting point for further in-depth phytochemical and antimicrobial studies, but also revealing insights into the most relevant anti-ARI scaffolds and compound classes. Investigations of the chemical space of bioactive natural products based on principal component analysis show that many of these compounds are drug-like. However, some bioactive natural products are substantially larger and have more polar groups than most approved drugs. A workflow with various strategies for the discovery of novel antiviral agents is suggested, thereby evaluating the merit of in silico techniques, the use of complementary assays, and the relevance of ethnopharmacological knowledge on the exploration of the therapeutic potential of natural products.

CONCLUSIONS

The longstanding ethnopharmacological tradition of natural remedies against ARIs highlights their therapeutic impact and remains a highly valuable selection criterion for natural materials to be investigated in the search for novel anti-ARI acting concepts. We observe a tendency towards assaying for broad-spectrum antivirals and antibacterials mainly discovered in interdisciplinary academic settings, and ascertain a clear demand for more translational studies to strengthen efforts for the development of effective and safe therapeutic agents for patients suffering from ARIs.

Combination of Epicatechin 3-Gallate from Euphorbia hirta and Cefepime Promotes Potential Synergistic Eradication Action against Resistant Clinical Isolate of Pseudomonas aeruginosa

Pseudomonas aeruginosa is naturally resistant to many classes of antipseudomonal antibiotics due to the species ability to easily acquire resistance. Plant-based antibacterial agent in combination with the existing antibiotic proposes an alternative treatment regimen for the eradication of resistant bacterial infections. The antibacterial effects of the isolated epicatechin 3-gallate compound from Euphorbia hirta in combination with cefepime were investigated in vitro against resistant P. aeruginosa. The fractional inhibitory concentration index of the combination was determined using checkerboard broth microdilution method. Epicatechin 3-gallate combined with cefepime had produced synergistic effect against P. aeruginosa (with average FIC index of 0.24). The MIC of epicatechin 3-gallate was effectively reduced to MIC/4, MIC/8, MIC/16, and MIC/32 in the presence of cefepime. Time-kill study of epicatechin 3-gallate combined with cefepime exhibited remarkable bactericidal activity where the eradication of P. aeruginosa occurred within 4 h of treatment. Scanning electron micrographs revealed apparent cell membrane damage and leakage of cytoplasmic contents from P. aeruginosa cells which eventually led to the cell lysis after the combination treatment of epicatechin 3-gallate and cefepime. The potential of epicatechin 3-gallate to act synergistically with cefepime against clinically resistant P. aeruginosa strain possibly will maximize the successful outcomes when choosing empirical antibiotic treatment in hospitals or health care institutions.

Mechanism of Action of Isolated Caffeic Acid and Epicatechin 3-gallate from Euphorbia hirta against Pseudomonas aeruginosa

BACKGROUND

The escalating dominance of resistant Pseudomonas aeruginosa strains as infectious pathogen had urged the researchers to look for alternative and complementary drugs.

OBJECTIVE

The objective of this study is to address the biological targets and probable mechanisms of action underlying the potent antibacterial effect of the isolated compounds from Euphorbia hirta (L.) against P. aeruginosa.

MATERIALS AND METHODS

The action mechanisms of caffeic acid (CA) and epicatechin 3-gallate (ECG) on P. aeruginosa cells were investigated by several bacterial physiological manifestations involving outer membrane permeabilization, intracellular potassium ion efflux, and nucleotide leakage.

RESULTS

The findings revealed that ECG and CA targeted both cell wall and cytoplasmic membrane of P. aeruginosa. The cellular membrane destruction and ensuing membrane permeability perturbation of P. aeruginosa had led to the ascending access of hydrophobic antibiotics, release of potassium ions, and leakages of nucleotides.

CONCLUSION

The overall study concludes that ECG and CA isolated from E. hirta possess remarkable anti-infective potentials which can be exploited as drug template for the development of new antibacterial agent against resistant P. aeruginosa pathogen.

SUMMARY

Epicatechin 3-gallate (ECG) and caffeic acid (CA) exhibited remarkable bactericidal abilities by increasing the outer membrane and plasma membrane permeability of Pseudomonas aeruginosa pathogenECG and CA had facilitated the entry of hydrophobic antibiotics into P. aeruginosa by disintegrating the lipopolysaccharides layer of the outer membraneECG-induced potassium efflux with efficiency close to that obtained with cefepime suggesting mode of action through membrane disruptionBoth ECG and CA had caused consistent leakage of intracellular nucleotide content with the increase in time. Abbreviations used: ECG: Epicatechin 3-gallate; CA: Caffeic acid; E. hirta: Euphoria hirta.

Dissecting Xuesaitong's mechanisms on preventing stroke based on the microarray and connectivity map

Elucidating action mechanisms of Chinese medicines has remained a challenging task due to the chemical and biological complexity that needs to be resolved. In this study we applied a gene expression data and connectivity map (CMAP) based approach to study action mechanisms of a Chinese medicine Xuesaitong injection (XST) on preventing cerebral ischemia-reperfusion injury. XST is a standardized patent Chinese medicine of Panax notoginseng roots and it has long been used for the effective prevention and treatment of stroke in China. However, more research is needed to understand the mechanisms underlying its effects against ischemic stroke. We first evaluated the effect of XST against ischemic stroke in an ischemia-reperfusion rat animal model and dissected its mechanisms based on gene expression data of injured brain. The results showed that treatment with XST significantly attenuated infarct area and histological damage. Based upon pathway analysis and the CMAP query of microarray data, anti-inflammatory response and anti-platelet coagulation were found as the major mechanisms of XST against stroke, which were further validated in vitro and with pharmacological assays of serum. We demonstrated the feasibility of applying the combination of the microarray with the CMAP in identifying mechanisms of Chinese medicine.