Methylenebissantin: A rare methylene-bridged bisflavonoid from Dodonaea viscosa which inhibits Plasmodium falciparum enoyl-ACP reductase

Exploring the Therapeutic Potential of Traditional Antimalarial and Antidengue Plants: A Mechanistic Perspective

Malaria, a highly perilous infectious disease, impacted approximately 230 million individuals globally in 2019. Mosquitoes, vectors of over 10% of worldwide diseases, pose a significant public health menace. The pressing need for novel antimalarial drugs arises due to the imminent threat faced by nearly 40% of the global population and the escalating resistance of parasites to current treatments. This study comprehensively addresses prevalent parasitic and viral illnesses transmitted by mosquitoes, leading to the annual symptomatic infections of 400 million individuals, placing 100 million at constant risk of contracting these diseases. Extensive investigations underscore the pivotal role of traditional plants as rich sources for pioneering pharmaceuticals. The latter half of this century witnessed the ascent of bioactive compounds within traditional medicine, laying the foundation for modern therapeutic breakthroughs. Herbal medicine, notably influential in underdeveloped or developing nations, remains an essential healthcare resource. Traditional Indian medical systems such as Ayurveda, Siddha, and Unani, with a history of successful outcomes, highlight the potential of these methodologies. Current scrutiny of Indian medicinal herbs reveals their promise as cutting-edge drug reservoirs. The propensity of plant-derived compounds to interact with biological receptors positions them as prime candidates for drug development. Yet, a comprehensive perspective is crucial. While this study underscores the promise of plant-based compounds as therapeutic agents against malaria and dengue fever, acknowledging the intricate complexities of drug development and the challenges therein are imperative. The journey from traditional remedies to contemporary medical applications is multifaceted and warrants prudent consideration. This research aspires to offer invaluable insights into the management of malaria and dengue fever. By unveiling plant-based compounds with potential antimalarial and antiviral properties, this study aims to contribute to disease control. In pursuit of this goal, a thorough understanding of the mechanistic foundations of traditional antimalarial and antidengue plants opens doors to novel therapeutic avenues.

Ketosulfonylmethylenation and sulfonylethyleneation of imidazoheterocycles with dimethylformamide as a methylene source

A hitherto unreported ketosulfonylmethylenation occurring at the C-3 position of imidazoheterocycles, with dimethylformamide as the methylene source was described. Using CoCl2·6H2O or Fe(acac)3 as efficient and inexpensive catalysts, some important biologically active methylenated compounds were prepared, with high efficacy, favorable functional group compatibilities, and a broad substrate scope.

Lead/Drug Discovery from Natural Resources

Natural products and their derivatives have been shown to be effective drug candidates against various diseases for many years. Over a long period of time, nature has produced an abundant and prosperous source pool for novel therapeutic agents with distinctive structures. Major natural-product-based drugs approved for clinical use include anti-infectives and anticancer agents. This paper will review some natural-product-related potent anticancer, anti-HIV, antibacterial and antimalarial drugs or lead compounds mainly discovered from 2016 to 2022. Structurally typical marine bioactive products are also included. Molecular modeling, machine learning, bioinformatics and other computer-assisted techniques that are very important in narrowing down bioactive core structural scaffolds and helping to design new structures to fight against key disease-associated molecular targets based on available natural products are considered and briefly reviewed.

Xanthones and benzophenones isolated from the endophytic fungus Penicillium sp. ct-28 of Corydlis tomentella and their cytotoxic activity

One new xanthone, griseophenexanthone A (1), one new benzophenone, digriseophene A (2), and 14 previously reported compounds were isolated from the culture of Penicillium sp. ct-28, an endophytic fungus of Corydlis tomentella. The structures of the isolated compounds were identified by an extensive analysis of HRESIMS, 1D and 2D NMR. MTT assay showed that six xanthones (1 and 3-7) significantly inhibited cell proliferation in four cancer cell lines, with IC₅₀ values ranging from 18.12 ± 2.42 to 85.55 ± 7.66 μM. Our results showed that slight structural changes led to obvious activity differences among these compounds. We also investigated the effects of the six xanthones on cell cycle and apoptosis in human hepatoma HepG2 cells. Compound 7 caused cell cycle arrest at G1 phase, compounds 5 and 6 caused cell cycle arrest at S phase, whereas compounds 1, 3 and 4 had no effects on cell cycle distribution. All six xanthones induced apoptosis in dose-dependent manners in HepG2 cells accompanied by degradation of PARP and activation of caspase 3. The structure-activity relationship analysis revealed that the effects of these xanthones on cell cycle and apoptosis in HepG2 cells were closely related to the substituent groups on their skeleton. Our studies provide novel insights for the structural optimization of xanthones in the development of new anticancer drugs.

Methylene-bridged dimeric natural products involving one-carbon unit in biosynthesis

This review summarizes the methylene-bridged dimeric natural products involving one-carbon unit in biosynthesis, including their structures, biological activities, synthetic methods, and formation mechanisms.

Natural biflavonoids as potential therapeutic agents against microbial diseases

Microbes broadly constitute several organisms like viruses, protozoa, bacteria, and fungi present in our biosphere. Fast-paced environmental changes have influenced contact of human populations with newly identified microbes resulting in diseases that can spread quickly. These microbes can cause infections like HIV, SARS-CoV2, malaria, nosocomial Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), or Candida infection for which there are no available vaccines/drugs or are less efficient to prevent or treat these infections. In the pursuit to find potential safe agents for therapy of microbial infections, natural biflavonoids like amentoflavone, tetrahydroamentoflavone, ginkgetin, bilobetin, morelloflavone, agathisflavone, hinokiflavone, Garcinia biflavones 1 (GB1), Garcinia biflavones 2 (GB2), robustaflavone, strychnobiflavone, ochnaflavone, dulcisbiflavonoid C, tetramethoxy-6,6″-bigenkwanin and other derivatives isolated from several species of plants can provide effective starting points and become a source of future drugs. These biflavonoids show activity against influenza, severe acute respiratory syndrome (SARS), dengue, HIV-AIDS, coxsackieviral, hepatitis, HSV, Epstein-Barr virus (EBV), protozoal (Leishmaniasis, Malaria) infections, bacterial and fungal infections. Some of the biflavonoids can provide antiviral and protozoal activity by inhibition of neuraminidase, chymotrypsin-like protease, DV-NS5 RNA dependant RNA polymerase, reverse transcriptase (RT), fatty acid synthase, DNA polymerase, UL54 gene expression, Epstein-Barr virus early antigen activation, recombinant cysteine protease type 2.8 (r-CPB2.8), Plasmodium falciparum enoyl-acyl carrier protein (ACP) reductase or cause depolarization of parasitic mitochondrial membranes. They may also provide anti-inflammatory therapeutic activity against the infection-induced cytokine storm. Considering the varied bioactivity of these biflavonoids against these organisms, their structure-activity relationships are derived and wherever possible compared with monoflavones. Overall, this review aims to highlight these natural biflavonoids and briefly discuss their sources, reported mechanism of action, pharmacological uses, and comment on resistance mechanism, flavopiridol repurposing and the bioavailability aspects to provide a starting point for anti-microbial research in this area.

Enzymatic dimerization in the biosynthetic pathway of microbial natural products

Covering: up to August 2020The dramatic increase in the identification of dimeric natural products generated by microorganisms and plants has played a significant role in drug discovery. The biosynthetic pathways of these products feature inherent dimerization reactions, which are valuable for biosynthetic applications and chemical transformations. The extraordinary mechanisms of the dimerization of secondary metabolites should advance our understanding of the uncommon chemical rules for natural product biosynthesis, which will, in turn, accelerate the discovery of dimeric reactions and molecules in nature and provide promising strategies for the total synthesis of natural products through dimerization. This review focuses on the enzymes involved in the dimerization in the biosynthetic pathway of microbial natural products, with an emphasis on cytochrome P450s, laccases, and intermolecular [4 + 2] cyclases, along with other atypical enzymes. The identification, characterization, and catalytic landscapes of these enzymes are also introduced.

Phytochemical Profile of Capsicum annuum L. cv Senise, Incorporation into Liposomes, and Evaluation of Cellular Antioxidant Activity

Overproduction of oxidants in the human body is responsible for oxidative stress, which is associated with several diseases. High intake of vegetables and fruits can reduce the risk of chronic diseases, as they are sources of bioactive compounds capable of contrasting the free radical effects involved in cancer, obesity, diabetes, and neurodegenerative and cardiovascular diseases. Capsicum annuum L. cv Senise is a sweet pepper that is grown in the Basilicata region (Italy). It is an important source of polyphenols, carotenoids, and capsinoids and can play a key role in human health. In this study, an ethanol extract was obtained from C. annuum dried peppers and the analysis of the phytochemical composition was performed by LC-ESI/LTQ Orbitrap/MS. The extract was incorporated into liposomes, which showed small size (~80 nm), good homogeneity, negative surface charge, and good stability in storage. The biological activity of the extract was evaluated in the human hepatoma (HepG2) cell line, used as model cells. The extract showed no cytotoxic activity and reduced the intracellular reactive oxygen species (ROS) level in stressed cells. The antioxidant activity was further improved when the extract was loaded into liposomes. Moreover, the extract promoted the expression of endogenous antioxidants, such as catalase, superoxide dismutase, and glutathione peroxidase through the Nrf-2 pathway evaluated by RT-PCR.

Antiplasmodial natural products: an update

Background

Malaria remains a significant public health challenge in regions of the world where it is endemic. An unprecedented decline in malaria incidences was recorded during the last decade due to the availability of effective control interventions, such as the deployment of artemisinin-based combination therapy and insecticide-treated nets. However, according to the World Health Organization, malaria is staging a comeback, in part due to the development of drug resistance. Therefore, there is an urgent need to discover new anti-malarial drugs. This article reviews the literature on natural products with antiplasmodial activity that was reported between 2010 and 2017.

Methods

Relevant literature was sourced by searching the major scientific databases, including Web of Science, ScienceDirect, Scopus, SciFinder, Pubmed, and Google Scholar, using appropriate keyword combinations.

Results and Discussion

A total of 1524 compounds from 397 relevant references, assayed against at least one strain of Plasmodium, were reported in the period under review. Out of these, 39% were described as new natural products, and 29% of the compounds had IC₅₀ ≤ 3.0 µM against at least one strain of Plasmodium. Several of these compounds have the potential to be developed into viable anti-malarial drugs. Also, some of these compounds could play a role in malaria eradication by targeting gametocytes. However, the research into natural products with potential for blocking the transmission of malaria is still in its infancy stage and needs to be vigorously pursued.

Computational Evaluation and Anti-inflammatory and Analgesic Activities of Nebrodenside A Isolated From Dodonaea viscosa

Nebrodenside A was isolated from the plant Dodonaea viscosa and its chemical structure was elucidated by spectroscopic methods. Molecular docking simulation predicted its strong ability to be tested as a potential anti-inflammatory compound. Carrageen-induced paw model and formalin test were utilized for the assessment of anti-inflammatory and analgesic potential. Nebrodenside A was found to be significantly active in reducing inflammation, when compared with diclofenac as a standard drug. Similarly, the compound also possesses substantial analgesic activity in the formalin-induced writhing test. Thus, nebrodenside A revealed a robust potential to be developed as a possible leading medicinal agent for better management of pain and inflammation.

Hepatoprotective activity of viscosine is mediated by attenuation of hepatic macrophages and iNOS expression in CCl4-intoxicated rats

This study investigated the molecular mechanism(s) of the protective effects of a C-alkylated flavonoid, viscosine on an animal model of CCl₄-induced hepatotoxicity. Viscosine at 20, 50 and 100 mg kg^-1 was orally administered in a dose dependent manner per day for 3 days before the CCl₄ (1 : 1 v/v in olive oil, 1 ml kg^-1) treatment and 2 days after the treatment. Hepatoprotection was assessed in terms of reduction in serum enzyme activities (ALT, AST, and ALP) that occur after CCl₄ injury, and by histopathology and immunohistochemistry. The rise in serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) in CCl₄-intoxicated rats was markedly suppressed by viscosine in a concentration dependent manner. The decrease in the activity of hepatic antioxidant enzyme, SOD, was significantly prevented by viscosine, likewise gradually the levels of MDA and GSH were also normalized compared to silymarin. Viscosine also reduced the CCl₄-induced damaged area from 2% to 0% as assessed by histopathology and prevented the mixed inflammatory infiltrate. Viscosine attenuated the inflammation in the liver around the injured central vein region by downregulating the CCl₄ induced activation of hepatic CD68+ macrophages, thereby reducing their number as well. The expression of inducible nitric oxide synthase (iNOS) was more potentially suppressed by viscosine compared to the FDA approved positive control silymarin. The results of this study indicate that viscosine could be effective in protecting the liver from acute CCl₄-induced injury. The hepatoprotective mechanisms of viscosine may be related to the free radical scavenging and attenuation of oxidative stress, as well as to the inhibition of inflammatory response in the liver. Here, we are proposing a novel mechanism of action of viscosine and suggesting that it may be a safe and better in vivo antioxidant.

Phytochemicals from Dodonaea viscosa and their antioxidant and anticholinesterase activities with structure-activity relationships

Context Dodonaea viscosa (L.) Jacq (Sapindaceae) has been used in traditional medicine as antimalarial, antidiabetic and antibacterial agent, but further investigations are needed. Objective This study determines the antioxidant and anticholinesterase activities of six compounds (1-6) and two crystals (1A and 3A) isolated from D. viscosa, and discusses their structure-activity relationships. Materials and methods Antioxidant activity was evaluated using six complementary tests, i.e., β-carotene-linoleic acid; DPPH(•), ABTS(•+), superoxide scavenging, CUPRAC and metal chelating assays. Anticholinesterase activity was performed using the Elman method. Results Clerodane diterpenoids (1 and 2) and phenolics (3-6) - together with three crystals (1A, 3A and 7A) - were isolated from the aerial parts of D. viscosa. Compound 3A exhibited good antioxidant activity in DPPH (IC50: 27.44 ± 1.06 μM), superoxide (28.18 ± 1.35% inhibition at 100 μM) and CUPRAC (A0.5: 35.89 ± 0.09 μM) assays. Compound 5 (IC50: 11.02 ± 0.02 μM) indicated best activity in ABTS assay, and 6 (IC50: 14.30 ± 0.18 μM) in β-carotene-linoleic acid assay. Compounds 1 and 3 were also obtained in the crystal (1A and 3A) form. Both crystals showed antioxidant activity. Furthermore, crystal 3A was more active than 3 in all activity tests. Phenol 6 possessed moderate anticholinesterase activity against acetylcholinesterase and butyrylcholinesterase enzymes (IC50 values: 158.14 ± 1.65 and 111.60 ± 1.28 μM, respectively). Discussion and conclusion This is the first report on antioxidant and anticholinesterase activities of compounds 1, 2, 5, 6, 1A and 3A, and characterisation of 7A using XRD. Furthermore, the structure-activity relationships are also discussed in detail for the first time.

A Multilayer Network Approach for Guiding Drug Repositioning in Neglected Diseases

Drug development for neglected diseases has been historically hampered due to lack of market incentives. The advent of public domain resources containing chemical information from high throughput screenings is changing the landscape of drug discovery for these diseases. In this work we took advantage of data from extensively studied organisms like human, mouse, E. coli and yeast, among others, to develop a novel integrative network model to prioritize and identify candidate drug targets in neglected pathogen proteomes, and bioactive drug-like molecules. We modeled genomic (proteins) and chemical (bioactive compounds) data as a multilayer weighted network graph that takes advantage of bioactivity data across 221 species, chemical similarities between 1.7 10⁵ compounds and several functional relations among 1.67 10⁵ proteins. These relations comprised orthology, sharing of protein domains, and shared participation in defined biochemical pathways. We showcase the application of this network graph to the problem of prioritization of new candidate targets, based on the information available in the graph for known compound-target associations. We validated this strategy by performing a cross validation procedure for known mouse and Trypanosoma cruzi targets and showed that our approach outperforms classic alignment-based approaches. Moreover, our model provides additional flexibility as two different network definitions could be considered, finding in both cases qualitatively different but sensible candidate targets. We also showcase the application of the network to suggest targets for orphan compounds that are active against Plasmodium falciparum in high-throughput screens. In this case our approach provided a reduced prioritization list of target proteins for the query molecules and showed the ability to propose new testable hypotheses for each compound. Moreover, we found that some predictions highlighted by our network model were supported by independent experimental validations as found post-facto in the literature.

Neglected tropical diseases are human infectious diseases that are often associated with poverty. Historically, lack of interest from the pharmaceutical industry resulted in the lack of good drugs to combat the majority of the pathogens that cause these diseases. Recently, the availability of open chemical information has increased with the advent of public domain chemical resources and the release of data from high throughput screening assays. Our aim in this work was to make use of data from extensively studied organisms like human, mouse, E. coli and yeast, among others, to prioritize and identify candidate drug targets in neglected pathogen proteomes, and drug-like bioactive molecules to foster drug development against neglected diseases. Our approach to the problem relied on applying bioinformatics and computational biology strategies to model large datasets spanning complete proteomes and extensive chemical information from publicly available sources. As a result, we were able to prioritize drug targets and identify potential targets for orphan bioactive drugs.

Synthesis of symmetrical methylene-bridged imidazoheterocycles using DMSO as methylene source under metal-free conditions

Methylene-bridged imidazo-heterocycles were synthesized by a H₃PO₄-promoted bridging methylenation of imidazopyridines or similar heterocycles, in which DMSO was used as the carbon source.

A structure guided drug-discovery approach towards identification of Plasmodium inhibitors

This article provides a comprehensive review of inhibitors from natural, semisynthetic or synthetic sources against key targets ofPlasmodium falciparum.

Quantitative ethnobotanical survey of medicinal flora thriving in Malakand Pass Hills, Khyber Pakhtunkhwa, Pakistan

STUDY OBJECTIVE

Ethnobotanical knowledge is proving to be invaluable for drug discovery in the wake of effective prospecting from biodiversity. On the other hand, the escalating human pressure is threatening the endogenous flora. Situated at the foothill of the Himalayas, Pakistan boasts of rich floristic distribution. However, many lush yet imperiled regions of this country has never been explored. It inspired us to evaluate and document the taxonomic composition, significance of medicinal plants and associated traditional knowledge in the District of Malakand, Khyber Pakhtunkhwa Province.

MATERIALS AND METHODS

Vegetation growing in Malakand pass hills, Pakistan was studied and data were collected using an open-ended questionnaire, in addition to interviewing the local elderly, knowledgeable persons, and herbal practitioners. Relative Frequency Citation (RFC) and Use Value (UV) of the medicinal plants were calculated and their correlation was determined by Pearson correlation coefficient.

RESULTS

This study encompasses 92 plant species belonging to 56 families thriving in the study area. The information gathered includes ethnobotanical inventory and their pharmacological uses. Quantitative analysis throws light on the consistence of RFC and UV. Asteraceae and Lamiaceae were the most abundant families represented by 6 species each. Shoots were the most used parts (23.6%) and wound healing (7.91%) was the most common therapeutic use.

CONCLUSION

The result obtained from the study implies that local inhabitants rely on these plants for their medicinal requirements. Also, the statistics reveal that, the vegetation can be assessed for potential drug leads. However, urban expansion is threatening the existence of indigenous flora and old generation with ancient herbal wisdom is perishing. So, it appears imperative to preserve the traditional knowledge. This survey is expected to contribute to the discovery of novel bioactive constituents, stimulate conservation efforts of the perturbed flora and promote sustainable exploitation of the medicinal bounty.

Two structurally distinct chalcone dimers from Helichrysum zivojinii and their activities in cancer cell lines

Dimers tomoroside A (1) and tomoroside B (2) of the co-occuring known chalcone monomer (3), along with the seven known flavonoid glucosides (4-10), were isolated from the aerial parts of Helichrysum zivojinii Černjavski & Soška. The structures of the isolated compounds were elucidated by spectroscopic techniques. Compound 1 inhibited topo IIα and hif-1α expression and stimulated doxorubicin anticancer effect, while 2 increased the expression of hif-1α, probably acting as antioxidant and redox status modulator. Notably, 2 synergized with Tipifarnib showing potential to improve the action of this new chemotherapeutic involved in the modulation of mitogene activated protein (MAP) kinase signaling pathway.

Hautriwaic acid as one of the hepatoprotective constituent of Dodonaea viscosa

It is widely known that hepatitis and its complications such as cirrhosis or hepatocellular carcinoma are one of the major health problems of the world especially since no specific treatment is available. In the present study we investigated the hepatoprotective potential of the methanolic extract of the whole plant of Dodonaea viscosa and its ethyl acetate, aqueous, butanol and n-hexane fractions against carbon tetrachloride (CCl₄) induced hepatoxicity in rats. Hepatoprotection was assessed in terms of reduction in serum enzymes (ALT, AST, and ALP) that occur after CCl₄ injury, and by histopathology and immunohistochemistry. The methanolic extract reduced the serum enzyme level (ALT, AST, and ALP) down to control levels despite CCl₄ treatment. It also reduced the CCl₄-induced damaged area to 0% as assessed by histopathology. The CD68+ macrophages were also reduced in number around the central vein area by the methanolic extract. These hepatoprotective effects were better than the positive control silymarin. Similar hepatoprotective activities were found with the ethyl acetate, and aqueous fractions of the methanolic extract. The butanol and n-hexane fractions showed elevated levels of ALT, AST and ALP as compared to the positive control silymarin. Histopathology showed ∼30% damage to the liver cells with the butanol and n-hexane fractions which still showed some protective activity compared to the CCl₄ treated control. HPLC fingerprinting suggested that hautriwaic acid present in the methanolic extract and its ethyl acetate, and aqueous fractions may be responsible for this hepatoprotective activity of Dodonaea viscosa which was confirmed by in vivo experiments.

Isoprenylated flavonoids and clerodane diterpenoids from Dodonaea viscosa

Phytochemical investigation of the aerial parts of Dodonaea viscosa led to the isolation of six new compounds including four isoprenylated flavonoids, dodovisones A-D (1–4), and two clerodane diterpenoids, dodovislactones A and B (5 and 6). Their structures were established by extensive spectroscopic analysis.