Antimalarial properties and molecular docking analysis of compounds from Dioscorea bulbifera L. as new antimalarial agent candidates

An overview on pharmacological significance, phytochemical potential, traditional importance and conservation strategies of Dioscorea deltoidea: A high valued endangered medicinal plant

Dioscorea deltoidea Wall. ex Griseb. is an endangered species of the Dioscoreaceae family. It is the most commonly consumed wild species as a vegetable due to its high protein, vital amino acid, vitamin, and mineral content. There are approximately 613 species in the genus Dioscorea Plum. ex L., which is found in temperate and tropical climates. Dioscorea deltoidea, a plant species widespread across tropical and sub-tropical regions, called by different names in different languages. In English, it is commonly referred to as "Wild yam" or "Elephant foot". The Sanskrit name for this plant is "Varahikand," while in Hindi, it is known as "Gun" or "Singly-mingly." The Urdu language refers to it as "Qanis," and in Nepali, it is called "Tarul," "Bhyakur," or "Ghunar." Dioscorea deltoidea has been used to cure a wide range of human ailments for centuries. This plant has nutritional and therapeutic uses and also contains high amounts of steroidal saponins, allantoin, polyphenols, and most notably, polysaccharides and diosgenin. These bioactive chemicals have shown potential in providing protection against a wide spectrum of inflammatory conditions, including enteritis (inflammation of the intestines), arthritis (joint inflammation), dermatitis (skin inflammation), acute pancreatitis (inflammation of the pancreas), and neuro inflammation (inflammation in the nervous system). Furthermore, the valuable bioactive chemicals found in D. deltoidea have been associated with a range of beneficial biological activities, such as antibacterial, antioxidant, anti-inflammatory, immunomodulatory, hepatoprotective, and cytotoxic properties. Sapogenin steroidal chemicals are highly valued in the fields of medicine, manufacturing, and commerce. It has both expectorant and sedative properties. It is employed in the treatment of cardiovascular diseases, encompassing various ailments related to the heart and blood vessels, skin disease, cancer, immune deficiencies, and autoimmune diseases. Additionally, it finds application in managing disorders of the central nervous system and dysfunctional changes in the female reproductive system. Furthermore, it is valued for its role in treating bone and joint diseases. Metabolic disorders are also among the ailments for which D. deltoidea is employed. It has traditionally been used as a vermifuge, fish poison, and to kill lice. Diosgenin, a steroidal compound found in D. deltoidea, plays a crucial role as a precursor in the chemical synthesis of various hormones. Due to the presence of valuable bioactive molecule, like corticosterone and sigmasterol, D. deltoidea is cultivated specifically for the extraction of these beneficial phytochemicals. The current study aims to assess D. deltoidea's medicinal properties, ethnobotanical usage, phytochemicals, pharmacological properties, threats, and conservation techniques.

Exploring the efficacy of ethnomedicinal plants of Himalayan region against the malaria parasite

ETHNOPHARMACOLOGICAL RELEVANCE

Plasmodium falciparum multi-drug resistant (MDR) strains are a great challenge to global health care. This predicament implies the urgent need to discover novel antimalarial drugs candidate from alternative natural sources. The Himalaya constitute a rich repository of medicinal plants which have been used traditionally in the folklore medicine since ages and having no scientific evidence for their activity. Crambe kotschyana Boiss. and Eremurus himalaicus Baker are used for their antipyretic and hepatoprotective properties in Kinnaur district of Himachal Pradesh, India.

AIM OF THE STUDY

This study would investigate the antiplasmodial efficacy of C. kotschyana and E. himalaicus extracts, their fractions and active components using in vitro, in vivo and in silico approaches to provide a scientific insight into their activity.

METHODS

The methanol extracts of C. kotschyana (CKME) and E. himalaicus (EHME) were prepared by maceration followed by fractionation using ethyl acetate. The isolation of flavonoid glycosides isorhamnetin-3, 7-di-O-glucoside from C. kotschyana and luteolin-6-C-glucoside (isoorientin) from E. himalaicus was carried out by antiplasmodial activity-guided isolation. In vitro antimalarial activity was assessed by WHO method while in vitro cytotoxicity was ascertained employing the MTT assay. Molecular docking and molecular dynamics simulation were performed using the Glide module of Schrödinger Software and Gromacs-2022 software package respectively. In vivo curative activity was assessed by Ryley and Peters method.

RESULTS

The methanol extracts of both the plants illustrated the best antiplasmodial activity followed by the ethyl acetate fractions. Iso-orientin (IC50 6.49 μg/ml) and Isorhamnetin-3,7-di-O-glucoside (IC50 9.22 μg/ml) illustrated considerable in vitro activity even against P. falciparum resistant strain. Extracts/fractions as well as the isolated compounds were found to be non-toxic with CC50 > 640 μg/ml. Molecular docking studies were performed with these 2 O-glucosides against four malaria targets to understand the binding pose of these molecules and the results suggested that these molecules have selectivity for lactate dehydrogenase enzyme. CKME and EHME exhibited curative activity in vivo along with increase in Mean Survival Time of mice.

CONCLUSION

The research delineated the scientific evidence that both the therapeutic herbs possessed antimalarial activity and notably, bioactive compounds responsible to exhibit the antimalarial activity have been isolated, identified and characterized. Further studies are underway to assess the antiplasmodial efficacy of isolated compounds alone and in combination with standard antimalarials.

Structure-based virtual screening against multiple Plasmodium falciparum kinases reveals antimalarial compounds

The continuous emergence of resistance against most frontline antimalarial drugs has led to countless deaths in malaria-endemic countries, counting 619,000 deaths in 2021, with mutation in drug targets being the sole cause. As mutation is correlated frequently with fitness cost, the likelihood of mutation emergence in multiple targets at a time is extremely low. Hence, multitargeting compounds may seem promising to address drug resistance issues with additional benefits like increased efficacy, improved safety profile, and the requirement of fewer pills compared to traditional single and combinational drugs. In this study, we attempted to use the High Throughput Virtual Screening approach to predict multitarget inhibitors against six chemically validated Plasmodium falciparum (Pf) kinases (PfPKG, PfMAP2, PfCDPK4, PfTMK, PfPK5, PfPI4K), resulting in 21 multitargeting hits. The molecular dynamic simulation of the top six complexes (Myricetin-MAP2, Quercetin-CDPK4, Myricetin-TMK, Quercetin-PKG, Salidroside-PK5, and Salidroside-PI4K) showed stable interactions. Moreover, hierarchical clustering reveals the structural divergence of the compounds from the existing antimalarials, indicating less chance of cross-resistance. Additionally, the top three hits were validated through parasite growth inhibition assays, with quercetin and myricetin exhibiting an IC50 value of 1.84 and 3.93 µM, respectively.

In Silico Studies of Four Compounds of Cecropia obtusifolia against Malaria Parasite

Malaria is a disease that affects many people in the world. In Mexico, malaria remains an active disease in certain regions, particularly in the states of Chiapas and Chihuahua. While antimalarial effects have been attributed to some species of Cecropia in various countries, no such studies have been conducted in Mexico. Therefore, the objective of this study was to evaluate the in silico antimalarial activity of some active compounds identified according to the literature in the species of Cecropia obtusifolia, belonging to the Cecropiaceae family, such as ursolic acid, α-amyrin, chrysin, and isoorientin. These compounds were evaluated with specific molecular docking and molecular dynamics (MD) studies using three different malarial targets with the PDB codes 1CET, 2BL9, and 4ZL4 as well as the prediction of their pharmacokinetic (Pk) properties. Docking analysis revealed the following best binding energies (kcal/mol): isoorientin-1CET (-9.1), isoorientin-2BL9 (-8.8), and chrysin-4ZL4 (-9.6). MD simulation validated the stability of the complexes. Pharmacokinetics analysis suggested that the compounds would generally perform well if administered. Therefore, these results suggest that these compounds may be used as potential drugs for the treatment of malaria.

In Silico Screening and Molecular Dynamics Simulation of Potential Anti-Malarial Agents from Zingiberaceae as Potential Plasmodium falciparum Lactate Dehydrogenase (PfLDH) Enzyme Inhibitors

Malaria continues to be a major public health issue in a number of countries, particularly in tropical regions-the emergence of drug-resistant Plasmodium falciparum encourages new drug discovery research. The key to Plasmodium falciparum survival is energy production up to 100 times greater than other parasites, primarily via the PfLDH. This study targets PfLDH with natural bioactive compounds from the Zingiberaceae family through molecular docking and molecular dynamic studies. Sulcanal, quercetin, shogosulfonic acid C, galanal A and naringenin are the Top 5 compounds with a lower binding energy value than chloroquine, which was used as a control in this study. By binding to NADH and substrate binding site residues, the majority of them are expected to inhibit pyruvate conversion to lactate and NAD+ regeneration. When compared to sulcanal and control drugs, the molecular dynamics (MD) simulation study indicated that quercetin may be the most stable molecule when interacting with PfLDH.

Evaluation of Antimalarial Activity of Ethanolic Extract of Annona muricata L.: An in vivo and an in silico Approach

In Nigeria, Annona muricata L. has been used to treat a variety of ailments. The mechanism of the antimalarial activity of ethanolic leaf extract of Annona muricata (EEAML) was investigated using both an in vivo and an in silico approach. The experimental mice were divided into five groups: A-F. The mice in groups B-F were inoculated with Plasmodium berghei NK-65 and treated accordingly. Groups A and B are the negative and positive controls (infected and untreated), respectively. Group C received 10 mg/kg chloroquine (standard drug), whereas groups D-F received 100, 200, and 300 mg/kg body weight of the extract orally respectively. The mice were euthanized eight days after infection, and their liver and blood were collected and used in biochemical tests. Molecular docking was performed using the extract's HPLC compounds and Plasmodium falciparum proteins. In the suppressive, prophylactic, and curative tests, there was a significant decrease (p < 0.05) in parasitemia levels in groups treated with the extract compared to the positive control and standard drug. When compared to the positive control, there was a significant (p < 0.05) reduction in liver MDA, total cholesterol, and total triglyceride levels. The binding energies of luteolin and apigenin-pfprotein complexes were significantly (p < 0.05) higher compared to their respective references. The anti-plasmodial activity of the extract may result from its hypolipidemic effect, which deprives the parasite of essential lipid molecules needed for parasite growth, as well as from the inhibitory effects of apigenin and luteolin on specific proteins required for the Plasmodium metabolic pathway.

Multitargeted Molecular Docking and Dynamic Simulation Studies of Bioactive Compounds from Rosmarinus officinalis against Alzheimer’s Disease

Alzheimer’s disease (AD) has been associated with the hallmark features of cholinergic dysfunction, amyloid beta (Aβ) aggregation and impaired synaptic transmission, which makes the associated proteins, such as β-site amyloid precursor protein cleaving enzyme 1 (BACE I), acetylcholine esterase (AChE) and synapsin I, II and III, major targets for therapeutic intervention. The present study investigated the therapeutic potential of three major phytochemicals of Rosmarinus officinalis, ursolic acid (UA), rosmarinic acid (RA) and carnosic acid (CA), based on their binding affinity with AD-associated proteins. Detailed docking studies were conducted using AutoDock vina followed by molecular dynamic (MD) simulations using Amber 20. The docking analysis of the selected molecules showed the binding energies of their interaction with the target proteins, while MD simulations comprising root mean square deviation (RMSD), root mean square fluctuation (RMSF) and molecular mechanics/generalized born surface area (MM/GBSA) binding free energy calculations were carried out to check the stability of bound complexes. The drug likeness and the pharmacokinetic properties of the selected molecules were also checked through the Lipinski filter and ADMETSAR analysis. All these bioactive compounds demonstrated strong binding affinity with AChE, BACE1 and synapsin I, II and III. The results showed UA and RA to be potential inhibitors of AChE and BACE1, exhibiting binding energies comparable to those of donepezil, used as a positive control. The drug likeness and pharmacokinetic properties of these compounds also demonstrated drug-like characteristics, indicating the need for further in vitro and in vivo investigations to ascertain their therapeutic potential for AD.

Antimalarial potential of compounds isolated from Mammea siamensis T. Anders. flowers: in vitro and molecular docking studies

Background:

The emergence of antimalarial drug resistance encourages the search for new antimalarial agents. Mammea siamensis belongs to the Calophyllaceae family, which is a medicinal plant that is used in traditional Thai preparations. The hexane and dichloromethane extracts of this plant were found to have potent antimalarial activity. Therefore, this study aimed to isolate active compounds from M. siamensis flowers and evaluate their antimalarial potential and their interactions with Plasmodium falciparum lactate dehydrogenase (PfLDH).

Methods:

The compounds from M. siamensis flowers were isolated by chromatographic techniques and evaluated for their antimalarial activity against chloroquine (CQ)-resistant P. falciparum (K1) strains using a parasite lactate dehydrogenase (pLDH) assay. Interactions between the isolated compounds and the PfLDH enzyme were investigated using a molecular docking method.

Results:

The isolation produced the following thirteen compounds: two terpenoids, lupeol (1) and a mixture of β-sitosterol and stigmasterol (5); two mammea coumarins, mammea A/AA cyclo D (6) and mammea A/AA cyclo F (7); and nine xanthones, 4,5-dihydroxy-3-methoxyxanthone (2), 4-hydroxyxanthone (3), 1,7-dihydroxyxanthone (4), 1,6-dihydroxyxanthone (8), 1-hydroxy-5,6,7-trimethoxyxanthone (9), 3,4,5-trihydroxyxanthone (10), 5-hydroxy-1-methoxyxanthone (11), 2-hydroxyxanthone (12), and 1,5-dihydroxy-6-methoxyxanthone (13). Compound 9 exhibited the most potent antimalarial activity with an IC₅₀ value of 9.57 µM, followed by 10, 1, 2 and 13 with IC₅₀ values of 15.48, 18.78, 20.96 and 22.27 µM, respectively. The molecular docking results indicated that 9, which exhibited the most potent activity, also had the best binding affinity to the PfLDH enzyme in terms of its low binding energy (-7.35 kcal/mol) and formed interactions with ARG109, ASN140, and ARG171.

Conclusion:

These findings revealed that isolated compounds from M. siamensis flowers exhibited antimalarial activity. The result suggests that 1-hydroxy-5,6,7-trimethoxyxanthone is a possible lead structure as a potent inhibitor of the PfLDH enzyme.

In Vitro and In Silico Potential Inhibitory Effects of New Biflavonoids from Ochna rhizomatosa on HIV-1 Integrase and Plasmodium falciparum

The aim of this study was to identify bioactive secondary metabolites from Ochna rhizomatosa with potential inhibitory effects against HIV and Plasmodium falciparum. A phytochemical study of O. rhizomatosa root barks resulted in the identification of three new biflavonoids (1–3), along with four known ones (4–7). Compound 7 (Gerontoisoflavone A) was a single flavonoid present in the rootbark of the plant and was used as a reference. Compound 1 (IC₅₀ = 0.047 µM) was the only one with a noteworthy inhibitory effect against HIV-1 integrase in vitro. Chicoric acid (IC₅₀ = 0.006 µM), a pure competitive inhibitor of HIV-1 integrase, was used as control. Compound 2 exhibited the highest antiplasmodial activity (IC₅₀ = 4.60 µM) against the chloroquine-sensitive strain of Plasmodium falciparum NF54. Computational molecular docking revealed that compounds 1 and 2 had the highest binding score (−121.8 and −131.88 Kcal/mol, respectively) in comparison to chicoric acid and Dolutegravir (−116 and −100 Kcal/mol, respectively), towards integrase receptor (PDB:3LPT). As far as Plasmodium-6 cysteine s48/45 domain inhibition is concerned, compounds 1 and 2 showed the highest binding scores in comparison to chloroquine, urging the analysis of these compounds in vivo for disease treatment. These results confirm the potential inhibitory effect of compounds 1 and 2 for HIV and malaria treatment. Therefore, our future investigation to find inhibitors of these receptors in vivo could be an effective strategy for developing new drugs.

Bioactivity of Natural Polyphenols as Antiparasitic Agents and their Biochemical Targets

BACKGROUND

Leishmaniasis and trypanosomiasis are diseases that affect public health worldwide due to their high incidence, morbidity, and mortality. Available treatments are costly, prolonged, and toxic, not to mention the problem of parasite resistance. The development of alternative treatments is justified and polyphenols show promising activity.

OBJECTIVE

The main aim of this mini-review was to analyze the most promising phenolic compounds with reported antileishmanial and antitrypanosomal activity as well as their mechanisms of action.

RESULTS

We found that the mode of action of these natural compounds mainly lignans, neolignans, and flavonoids depends on the organism they act on and includes, macrophage activation, induction of morphological changes such as chromatin condensation, DNA fragmentation, accumulation of acidocalcisomes, and glycosomes, Golgi damage and mitochondrial dysfunction as well as negative regulation of mitochondrial enzymes and other essential enzymes for parasite survival such as arginase. This gives a wide scope for future research towards the rational development of anti-kinetoplastid drugs.

CONCLUSION

Although the specific molecular targets, bioavailability, route of administration, and dosages of some of these natural compounds need to be determined, polyphenols and their combinations represent a very promising and safe strategy to be considered for use against Leishmania spp and Trypanosoma spp. In addition, these compounds may provide a scaffold for developing new, more potent, and more selective antiprotozoal agents.