HPTLC quantification of quercetin from leaf extracts of C. occidentalis L. and its inhibitory activity against protease enzyme of P. falciparum

Most of the therapeutically relevant antimalarial medications target the parasite during the blood stage of its life cycle. As a result, new antimalarial medicines have focused on inhibiting the breakdown of host-cell hemoglobin . C. occidentalis was reported to have antimalarial activity and proved very effective in the conventional Indian medical system. This study aimed to analyze the quercetin content of four different leaf extracts of C. occidentalis using a validated HPTLC method and to evaluate the inhibitory activity of quercetin against Plasmepsin-II of P. falciparum using in silico approach. HPTLC results revealed that the CF extract of C. occidentalis had the highest quercetin content with 4.10% (w/w), followed by the ME extract with 2.37% (w/w), PE extract with 2.09% (w/w), and WT extract with 1.79% (w/w). In silico investigations of quercetin with the Plasmepsin-II enzyme of P. falciparum portrayed excellent binding affinities of (− 7.5 kcal/mol) and convenient molecular interactions with important amino acid residues of the target receptor as compared with control. Furthermore, MD simulation study confirmed the finding of molecular docking by depicting the stability of the simulated system both in water and in vacuum. Finally, the study suggested that the chloroform extract of C. occidentalis is the most suitable and efficient solvent for extracting high-quantity and quality quercetin. The findings of the molecular docking and MD simulation analysis further supported the potential inhibitory activity of quercetin against Plasmepsin-II. This research contributes to the understanding of quercetin and its potential applications in combating antimalarial drug resistance.