RESEARCH ARTICLE
Antimalarial Activity of Globimetula oreophila Compounds: In Silico Docking Investigations on Plasmodium falciparum Protease
Academic Editor: Sanchaita Rajkhowa
Sciences of Phytochemistry|Vol. 4, Issue 2, pp. 76-84 (2025)
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Received
Mar 15, 2025Revised
Jul 17, 2025Accepted
Aug 15, 2025Published
Sep 3, 2025
Abstract
Introduction
The pathogen that causes malaria in humans and other mammalian species belongs to the genus Plasmodium (1). Most tropical and subtropical regions, including Asia, America, and Sub-Saharan Africa, including Nigeria, are affected by this disease. Although the Plasmodium genus contains four species known to cause the disease (Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae), Plasmodium falciparum is the most dangerous and pathogenic (2-7). It affects a variety of hosts and is the cause of the severe form of malaria. The Plasmodium is carried by the infected Anopheles mosquito, which also serves as a vector (7, 8). An infected person may experience fever, neurological symptoms, opisthotonous episodes, seizures, or possibly go into a coma or pass away. In 2022, there were approximately 249 million cases of malaria and 608,000 deaths globally, with sub-Saharan Africa bearing the brunt, accounting for about 94% of these cases and fatalities (1, 7). The 2023 World Malaria Report explores the relationship between climate change and malaria. Variations in temperature, humidity, and precipitation can affect the behavior and survival of Anopheles mosquitoes, which are responsible for spreading malaria. Additionally, extreme weather conditions, such as heatwaves and floods, may directly influence malaria transmission rates and overall disease impact (9). The development of effective malaria control strategies is significantly hindered by the resistance of malaria parasites to many commonly used antimalarial drugs. Currently, the treatment options for chloroquine-resistant Plasmodium falciparum infections are limited to artemisinins and artemisinin combination therapies (ACTs). However, decreased sensitivity to ACTs has been observed in some parts of Asia (1, 7). One of the significant challenges in creating new antimalarial candidate drugs is identifying lead compounds with optimal pharmacokinetic properties, including absorption, distribution, metabolism, excretion, and toxicity (ADMET) (10).
Natural product databases offer a practical source for virtual screening against therapeutic targets (), including parasitic protozoal illnesses (-). Natural products have been used as significant leads for drug development: (a) Several natural products are effective drugs despite not falling under the "rule-of-five" (); (b) despite this, they occupy different regions of biologically relevant chemical space (), including abundant oxygen-containing functionalities (rarely nitrogen) and high degrees of chirality and complexity (), (c) they have been evolved to be optimized for activity, including active transport (), and (d) they can be used as lead structures for semisynthetic modification to increase activity, selectivity, or bioavailability (). belongs to the Loranthaceae family of parasitic plants, comprising over 75 genera and more than 900 species. It is a member of the hemiparasitic mistletoe family, which is primarily found in tropical Africa, which includes the Central Africa sub-region, Nigeria, Gabon, Congo, and Cameroun () Mistletoe uses modified roots to cling to a host plant on a wide range of dicotyledonous trees. Traditional medicine often uses the species to cure a variety of ailments, such as fever, headaches, stomachaches, and diarrhea (, ). The plant has previously been subjected to qualitative and quantitative phytochemical screening, which revealed the presence of a variety of secondary metabolites, including alkaloids, flavonoids, carbohydrates, triterpenes, tannins, glycosides, and saponins (, ), which have been reported to possess antimalarial activity (, ). Additionally, according to Dauda . (), the plant's crude ethanol extract provides a rich source of necessary trace metals in the right amounts, including Zinc (Zn), Cobalt (Co), Copper (Cu), Nickel (Ni), Iron (Fe), and Cadmium (Cd), which supports the plant's therapeutic usefulness in ethnomedicine. According to reports, the genus is generally rich in secondary metabolites, and flavonols serve as a marker of the genus's taxonomy (). There have been prior reports on the antiplasmodial properties of ethanol leaf extract, as well as hexane, chloroform, ethyl acetate, and butanol fractions (, ). Previously, we conducted phytochemical investigation studies on the plant and reported the isolation of prenylated quercetin from the ethyl acetate fraction (). The analysis of the prenylated quercetin against seven enzymes was also investigated for their antimalarial activity (). Bio-assay-guided isolation of the hexane, ethyl acetate, and butanol fractions was also carried out to ascertain their antimalarial properties (). These procedures led to the isolation of five compounds: stigmasterol, quercetin, quercetrin, prenylated dihydrostilbene, and 4′-methoxy-isoliquiritigenin, two of which are novel to this plant's genus and these were characterize and elucidated using spectroscopic techniques such as UV, IR, 1D and 2D NMR, (, ). Previously studies, the isolated compounds of Globimetula oreophila showed exceptional binding affinities towards plasmepsin I and II, two main enzymes involved in hemoglobin catabolism throughout intra-erythrocytic development of Plasmodium falciparum. These tests identified that molecules such as quercetin and stigmasterol bind strongly with catalytic sites of plasmepsins, suggesting their potential as inhibitors of the proteases (). Moreover, drug-likeness and toxicity profiling using tools indicated that the isolated compounds of Globimetula oreophila possess excellent oral bioavailability and minimal toxicity levels (). These findings support their potential to serve as lead compounds for the development of novel antimalarial agents (). While oreophila compounds show activity against plasmepsin I and II (), their efficacy against other P. falciparum enzymes (e.g., falcipains, SERA5, PfDHFR-TS, and PfCDPK2) remains unexplored, despite these targets’ role in hemoglobin catabolism and parasite egress. This integrated approach aims to identify new inhibitors that would disrupt more than one stage of the parasite's life cycle. Inhibition of multiple enzymes that have multiple functions in multiple stages of the life cycle is a strategic approach to drug resistance. Inhibition of the essential enzymes which function across multiples stages of the parasite’s life cycle-offer a strategic approach to combat drug resistance: falcipains-2/3: critical for hemoglobin degradation, SERA5: mediates merozoite egress; underexplored in drug design, PfDHFR-TS/PfCDPK2: key to nucleotide synthesis and calcium-dependent signaling. In summary, the current research builds upon our previous research, which demonstrated the inhibitory activity of compounds against plasmepsin I and II. We hypothesized that flavonoids (e.g., DG1, DG2, and DG5), prenylated stilbene (DG3), and terpenoid (DG4) from G. oreophila will exhibit strong, multi-target inhibition against cysteine proteases (falcipain-2/3), SERA5, PfDHFR-TS/PfCDPK2 due to structural features (e.g., hydroxylation, prenylation, methoxylation) that align with conserved active sites across these enzymes. This study extends our prior work on plasmepsins () to identify novel, multi-target inhibitors that can disrupt critical metabolic processes, thereby providing a multifaceted antimalarial strategy. In the current study, we report the analysis of secondary metabolites (stigmasterol, quercetin, quercetrin, prenylated dihydrostilbene, and 4′-methoxy-isoliquiritigenin) against enzymes in its life cycle.
Declarations
Acknowledgment
We are thankful to all staff members of the Department of Pharmaceutical and Medicinal Chemistry, Ahmadu Bello University Zaria, Kaduna, Nigeria.
Conflict of Interest
The authors declare no conflicting interest.
Data Availability
All data generated or analyzed during this study are included in this published article and its supplementary information files.
Funding Information
The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.
Supplemental Material
The following supporting information can be downloaded at: https://etflin.com/file/document/20250315092247666709040.docx. Table S1: Consensus log P values of compound DG1, Table S2: Grid box parameter for the enzymes, Table S3: The crystal structures of enzyme complexes and re-docked ligands super-imposed on the crystal structures for validation, Table S4: Molecular interactions of the amino acid residues of compounds from Azadirachta indica with Falcipain-2 (6SSZ), Table S5: Molecular interactions of the amino acid residues of compounds from Azadirachta indica with Falcipain-3 (3BPM), Table S6: Molecular interactions of the amino acid residues of compounds from Azadirachta indica with Plasmepsin I (3SQ1), Table S7: Molecular interactions of the amino acid residues of compounds from Azadirachta indica with Plasmepsin II (1LF3), Table S9: Molecular interactions of the amino acid residues of compounds from Azadirachta indica with Calcium Dependent Protein Kinase 2 (4MVF), Table S10: Molecular interactions of the amino acid residues of compounds from Azadirachta indica with crystal structures of Plasmodium falciparum vital enzyme DHFR-TS, Figure S1: binding affinities of ligands (DG1-DG5) against Plasmodium falciparum enzymes, Figure S2: 3D molecular pose and 2D interactions of DG2 on the binding cavity of Falcipain-2, Figure S3: 3D molecular pose and 2D interactions of DG3 on the binding cavity of Falcipain-2, Figure S4: 3D molecular pose and 2D interactions of DG4 on the binding cavity of Falcipain-2, Figure S5: 3D molecular pose and 2D interactions of DG5 on the binding cavity of Falcipain-2, Figure S6: 3D molecular pose and 2D interactions of DG2 on the binding cavity of Falcipain-3, Figure S7: 3D molecular pose and 2D interactions of DG3 on the binding cavity of Falcipain-3, Figure S8: 3D molecular pose and 2D interactions of DG4 on the binding cavity of Falcipain-3, Figure 9: 3D molecular pose and 2D interactions of DG1 on the binding cavity of Plasmepsin-I, Figure S10: 3D molecular pose and 2D interactions of DG2 on the binding cavity of Plasmepsin-I, Figure S11: 3D molecular pose and 2D interactions of DG3 on the binding cavity of Plasmepsin-I, Figure S12: 3D molecular pose and 2D interactions of DG5 on the binding cavity of Plasmepsin-I, Figure S13: 3D molecular pose and 2D interactions of DG1 on the binding cavity of Plasmepsin-II, Figure S14: 3D molecular pose and 2D interactions of DG2 on the binding cavity of Plasmepsin-II, Figure S15: 3D molecular pose and 2D interactions of DG3 on the binding cavity of Plasmepsin-II, Figure S16: 3D molecular pose and 2D interactions of DG5 on the binding cavity of Plasmepsin-II, Figure S17: 3D molecular pose and 2D interactions of DG2 on the binding cavity of SERA5, Figure S18: 3D molecular pose and 2D interactions of DG3 on the binding cavity of SERA5, Figure S19: 3D molecular pose and 2D interactions of DG4 on the binding cavity of SERA5, Figure S20: 3D molecular pose and 2D interactions of DG5 on the binding cavity of SERA5, Figure S21: 3D molecular pose and 2D interactions of DG2 on the binding cavity of PfCDPK2, Figure S22: 3D molecular pose and 2D interactions of DG3 on the binding cavity of PfCDPK2, Figure S23: 3D molecular pose and 2D interactions of DG4 on the binding cavity of PfCDPK2, Figure S24: 3D molecular pose and 2D interactions of DG5 on the binding cavity of PfCDPK2, Figure S25: 3D molecular pose and 2D interactions of DG1 on the binding cavity of PfDHFR, Figure S26: 3D molecular pose and 2D interactions of DG2 on the binding cavity of PfDHFR, FigureS27: 3D molecular pose and 2D interactions of DG3 on the binding cavity of PfDHFR, Figure S28: 3D molecular pose and 2D interactions of DG5 on the binding cavity of PfDHFR.
