Identification of antimalarial phytoconstituents from Tinospora sinensis (Lour.) Merr. Stem by in vitro whole cell assay and multiple targets directed in silico screening against Plasmodium falciparum.

ETHNOPHARMACOLOGICAL RELEVANCE: Tinospora sinensis (Lour.) Merr., from the family Menispermaceae, is widely used in Indian folk and Ayurvedic medicine. Indigenous tribes such as the Tea-tribe and Chorei-tribe of Assam use its bark and stem as a herbal remedy to treat malaria and it is also traditionally employed for conditions such as dyspepsia, inflammation, fever, ulcers, jaundice, diabetes and various urinary, skin, and liver diseases.

AIM OF THE STUDY: This study aims to identify and characterize antimalarial phytoconstituents from the active extract of T. sinensis stem by in vitro screening against both the Chloroquine-sensitive (Pf3D7) as well as Chloroquine-resistant (PfRKL-9) strains of Plasmodium falciparum, along with exploring potential targets and mechanisms using molecular docking and dynamics simulation studies.

MATERIALS AND METHODS: T. sinensis stems were collected from Assam, India, and authenticated by the Botanical Survey of India. The plant materials were initially extracted with non-polar to polar solvents and screened for in vitro antimalarial potency against Pf3D7 and PfRKL-9. Then, the methanol extract was selected for bioassay-guided isolation of phytoconstituent(s). The isolated phytoconstituent(s) were screened for antimalarial potential and active compounds were further evaluated for cytotoxicity using the HEK-293 cell line. Structural characterization of the active compounds involved the use of UV-VIS, IR, NMR and HRMS analyses. Molecular docking and dynamics simulation studies were performed on selected targets from P. falciparum to predict binding affinities and mechanisms of action.

RESULTS: From the methanol extract of T. sinensis stem, five phytoconstituents were isolated, including isoquinoline alkaloids Berberine (NG1) and Palmatine (NG2) showed the best antimalarial activity (IC50 < 1 μg/ml) against both Pf3D7 and PfRKL-9. Cytotoxicity assays confirmed their safety and selectivity. Molecular docking and dynamic simulation studies revealed that Berberine and Palmatine formed stable complexes with P. falciparum lysyl-tRNA synthetase and P. falciparum aminopeptidase N, respectively, indicating their potential as antimalarial leads.

CONCLUSION: This study identifies two potent antimalarial phytoconstituents in the stem of T. sinensis, validating its traditional use and demonstrating its safety and efficacy for potential global application in malaria treatment.