Plasmodium falciparum is the most lethal malaria parasite. The present study investigates the interaction capabilities of select plant derivatives, iso-mukaadial acetate (IMA) and ursolic acid acetate (UAA), against P. falciparum Hsp70-1 (PfHsp70-1) using in vitro approaches. PfHsp70-1 facilitates protein folding in the parasite and is deemed a prospective antimalarial drug target. Recombinant PfHsp70-1 protein was expressed in E. coli BL21 cells and homogeneously purified by affinity chromatography. The interaction between the compounds and PfHsp70-1 was evaluated using malate dehydrogenase (MDH), and luciferase aggregation assay, ATPase activity assay, and Fourier transform infrared (FTIR). PfHsp70-1 prevented the heat-induced aggregation of MDH and luciferase. However, the PfHsp70-1 chaperone role was inhibited by IMA or UAA, leading to both MDH and luciferase’s thermal aggregation. The basal ATPase activity of PfHsp70-1 (0.121 nmol/min/mg) was closer to UAA (0.131 nmol/min/mg) (p = 0.0675) at 5 mM compound concentration, suggesting that UAA has no effect on PfHsp70-1 ATPase activity. However, ATPase activity inhibition was similar between IMA (0.068 nmol/min/mg) (p < 0.0001) and polymyxin B (0.083 nmol/min/mg) (p < 0.0001). The lesser the Pi values, the lesser ATP hydrolysis observed due to compound binding to the ATPase domain. FTIR spectra analysis of IMA and UAA resulted in PfHsp70-1 structural alteration for β-sheets shifting the amide I band from 1637 cm⁻¹ to 1639 cm⁻¹, and for α-helix from 1650 cm⁻¹ to 1652 cm⁻¹, therefore depicting secondary structural changes with an increase in secondary structure percentage suggesting that these compounds interact with PfHsp70-1.

恶性疟原虫是最致命的疟原虫。本研究使用体外方法研究了选择的植物衍生物、iso-mukaadial 醋酸酯 (IMA) 和熊果酸醋酸酯 (UAA) 对恶性疟原虫Hsp70-1 (PfHsp70-1) 的相互作用能力。PfHsp70-1 促进寄生虫中的蛋白质折叠，被认为是一种潜在的抗疟药物靶点。重组 PfHsp70-1 蛋白在大肠杆菌中表达BL21 细胞并通过亲和层析进行均匀纯化。使用苹果酸脱氢酶 (MDH)、荧光素酶聚集测定、ATP 酶活性测定和傅里叶变换红外 (FTIR) 评估化合物与 PfHsp70-1 之间的相互作用。PfHsp70-1 阻止热诱导的 MDH 和荧光素酶聚集。然而，IMA 或 UAA 抑制了 PfHsp70-1 伴侣的作用，导致 MDH 和荧光素酶的热聚集。在 5 mM 化合物浓度下， PfHsp70-1 (0.121 nmol/min/mg) 的基础 ATPase 活性更接近于 UAA (0.131 nmol/min/mg) ( p = 0.0675)，表明 UAA 对 PfHsp70-1 ATPase 没有影响活动。然而，IMA (0.068 nmol/min/mg) 之间的 ATPase 活性抑制相似 ( p< 0.0001) 和多粘菌素 B (0.083 nmol/min/mg) ( p < 0.0001)。P i值越小，由于化合物与 ATP 酶结构域的结合，观察到的 ATP 水解越少。IMA 和 UAA 的 FTIR 光谱分析导致 PfHsp70-1 结构改变，β-折叠将酰胺 I 带从 1637 cm ^-1移动到 1639 cm ^-1，对于 α-螺旋从 1650 cm ^-1移动到 1652 cm ^-1，因此描述了二级结构百分比增加的二级结构变化，表明这些化合物与 PfHsp70-1 相互作用。