Aegle marmelos (Rutaceae) and Syzygium aromaticum (Myrtaceae), have a rich use in Indian traditional medicine with broad-spectrum cures for a range of illnesses. Although crude extract of these plants was found to exhibit antimalarial potential, we employed bioassay-guided fractionation to isolate and purify the compounds responsible for the effect. For this purpose, in vitro assays using SYBR Green-I-based fluorescence tests and in silico molecular docking studies were employed. The methanolic extracts of A. marmelos leaves and S. aromaticum flower buds, alongside their fractions (hexane, chloroform, ethyl acetate, and methanol), were appraised against Plasmodium falciparum 3D7 strain. Further, cytotoxicity was assessed in HeLa cell lines by MTT assay. Comprehensive spectroscopic analyses, including NMR and IR, were carried out for bioactive compound structural characterization. On fractionation, purification, and characterization, four compounds were isolated from A. marmelos leaves and S. aromaticum flower buds, and they exhibited significant antimalarial activity. Lupeol, isolated from A. marmelos, exhibited the most significant effect with 94.0% inhibition and an IC50 of 8.73 µg/mL. β-Sitosterol and 1,3-dimethylpyrimidine-2,4(1H,3H)-dione, also isolated from A. marmelos, showed moderate activity. Eugenol, isolated from S. aromaticum, displayed moderate antimalarial activity with an IC50 of 19.30 µg/mL. The cytotoxicity investigation indicated a TC50 value over 100 µg/mL for lupeol, whereas other drugs exhibited mild toxicity. Docking studies revealed binding affinities of -9.5 and -9.4 kcal/mol for lupeol and β-sitosterol, respectively, toward ribosome inhibitor protein, current candidate drug target of P. falciparum 3D7. Lead compounds were also advantageous with drug-likeness and safety profiles. These results scientifically substantiate the conventional utilization of A. marmelos and S. aromaticum as potential sources of antimalarial compounds.
Naveenkumar et al. (Sun,) studied this question.