Methanolic extract of Syzygium aromaticum bud enhances the chloroquine sensitivity in Plasmodium falciparum in vitro study

Abstract Background: Malaria remains a major health issue in tropical and subtropical countries, with the development of drug resistance posing a significant challenge to disease management and control. A key problem associated with drug resistance is the decrease in drug sensitivity. Because developing new drugs takes time, improving the effectiveness of existing medications by targeting efflux pumps, which play a role in some mechanisms of drug resistance, may offer a quick solution. Building on previous research using Pseudomonas aeruginosa as an in vitro model, this study examines the methanolic extract of Syzygium aromaticum and its potential to increase chloroquine (CQ) sensitivity in Plasmodium falciparum . Materials and Methods: The study involved in vitro culturing of Plasmodium falciparum (3D7 strain), followed by initial chloroquine sensitivity testing in the presence of a methanolic extract. The potential of Syzygium aromaticum to enhance chloroquine sensitivity was evaluated using an assay standardized with verapamil. The methnolic extract was then tested for toxicity in vitro using J774 and CHO cell lines. Results: Syzygium aromatum methanolic extract (SA-ME) significantly enhanced the effect of CQ, showing 58.12 ± 1.2% parasite growth inhibition compared to CQ alone, which showed 15.8 ± 0.81% in the growing culture of P. falciparum . VRP, a known efflux pump inhibitor used as a standard in this study, inhibited parasite growth by 55.72 ± 1.21% when combined with CQ. The SA-ME demonstrated considerable growth-inhibition potential against P. falciparum when co-administered with CQ at a 1:4 ratio, indicating significant CQ enhancement. The preliminary cytotoxicity profile of this extract indicated that it is nontoxic up to the highest concentration tested (100 µg/mL) on both J774 and CHO cell lines in vitro . Conclusion: This study investigated the potential of the methanolic extract of Syzygium aromaticum to enhance CQ sensitivity against P. falciparum using a VRP efflux model. The CQ sensitivity enhancement model was developed using the known efflux pump inhibitor, VRP. The same assay was used, substituting aortic extract for VRP, to assess its potential to enhance CQ’s effectiveness. Its combination with CQ resulted in a significant increase in parasite growth inhibition. Due to its edible and low-toxicity properties, S. aromaticum is a promising source of efflux pump-inhibitor compounds that could help restore CQ’s efficacy. Further research is needed to isolate and identify the active components responsible for this effect. Therefore, this plant could be used in cases where decreased CQ sensitivity or CQ resistance is observed in P. falciparum .