Novel halogenated arylvinyl-1,2,4 trioxanes as potent antiplasmodial as well as anticancer agents: Synthesis, bioevaluation, structure-activity relationship and in-silico studies

Abstract

Herein, we have synthesized a series of lipophilic, halogenated-arylvinyl-1,2,4-trioxanes 8a-g (28 compounds) and assessed for their in vitro anti-plasmodial activity in Plasmodium falciparum culture using SYBRgreen-I fluorescence assay against chloroquine-resistant Pf INDO and artemisinin-resistant Pf Cam 3.1^R539T (MRA-1240) strains. Alongside, the cell cytotoxic potential of 8a-g has also been determined against the HEK293 cell line in vitro. Out of twenty-eight halogenated-arylvinyl-1,2,4-trioxanes; ten analogues (8a₂, 8a₄, 8b₂, 8b₄, 8d₄, 8e₁, 8e₂, 8e_4,8f₂, and 8g₄) have shown potent in vitro antiplasmodial activity with IC₅₀ < 27 nM (IC₅₀ range = 4.48-26.58 nM). Also, the selectivity index (SI) for these ten analogues were found in the range of 72.00-3972.50 which indicates their selective potential towards Plasmodium cells. Results of the cell cycle stage specificity with two of the most potent compounds 8a₄ {(IC₅₀ = 4.48 nM; SI = 3972.50) more potent than chloroquine (IC₅₀ = 546 nM; SI = 36.64) and artesunate (IC₅₀ = 6.6 nM; SI = 4333.33)} and 8e₂ (IC₅₀ = 9.69 nM; SI = 1348) against Pf INDO indicated all three stages to be the target of the action of 8e₂ while only rings and trophozoites appeared to be targeted by 8a₄. Ring stage survival assay against artemisinin-resistant Pf Cam 3.1^R539T indicated that 8a₄ may be well suited to replace artemisinin from current ACTs which are experiencing in vivo delayed parasite clearance. With intraperitoneal (i.p.) and oral (p.o.) route at the dose of 50 mg/kg/day × 4 days; 8a₄ has also shown 100% suppression of parasitemia in P. berghei ANKA infected Balb C mice. Further, the in vitro anticancer activity of 8a-g performed against human lung (A549) and liver (HepG2) cancer cell lines as also against immortalized normal lung (BEAS-2B) and liver (LO2) cell lines has revealed that most of the derivatives are endowed also with promising anticancer activity (IC₅₀ = 0.69-15 μM; SI = 1.02-20.61) in comparison with standard drugs such as chloroquine (IC₅₀ = 100 μM; SI = 0.03), artemisinin (IC₅₀ = 100 μM), and artesunic acid (IC₅₀ = 9.85 μM; SI = 0.76), respectively. All the derivatives have shown moderate anticancer activity against liver (HepG2) cancer cell lines. Arylvinyl-1,2,4-trioxanes 8f₂ (IC₅₀ = 0.69 μM; SI = 16.66), the most active compound of the series, has shown ∼145 fold more cytotoxic potential with higher selectivity in comparison to reference drugs chloroquine (IC₅₀ = 100 μM; SI = 0.03) and artemisinin (IC₅₀ = 100 μM), respectively against the lung (A549) cancer cell line. Finally, the in-silico docking studies of the potent halogenated 1,2,4-trioxanes along with reference drug molecules against epidermal growth factor receptor (EGFR; PDB ID: 1M17) have demonstrated the strong virtual interaction.

Keywords: Anticancer; Antimalarial; Structure-activity relationship; Synthetic route; Trioxane.