It is important to understand the nature and mechanism of interaction of drugs with serum albumins as such interactions govern their pharmacokinetics and pharmacodynamics. Plumbagin is a natural phytocompound, mainly present in the bark of Plumbaginaceae family plants and it has numerous therapeutic potentials. In this study, the interaction of plumbagin with human serum albumin (HSA) was deciphered using an array of biophysical and computational tools. The UV–vis spectroscopy established the formation of plumbagin-HSA complex with binding constant as 2.32 × 10⁴ M⁻¹. Fluorescence spectroscopy revealed that there was static mode of quenching of HSA’s fluorescence by plumbagin. The binding constant obtained by fluorescence spectroscopy was of the similar order as in case of UV–vis spectroscopy. The negative value of ΔH° (−3.67) indicated an endothermic nature of the reaction and negative value of ΔG° (−6.40 to −6.58) confirmed that complexation of plumbagin to HSA was spontaneous. There was nearly one binding site in HSA for plumbagin. Titration of plumbagin to HSA in presence of site-specific markers showed that plumbagin interacted at sub-domain IIA of HSA, commonly known as Sudlow’s site I. Moreover, the binding resulted in changes in microenvironment of tryptophan while of tyrosine residues remained approximately unchanged. This interaction also resulted in decrease of α-helical content of the studied serum protein. FRET calculations revealed that distance between plumbagin and HSA’s fluorophore (Trp214) was 2.27 nm. Finally, molecular docking studies substantiated the in vitro finding. Plumbagin formed hydrogen bond with Lys199 and Arg257 of HSA. Additionally, Arg222, His242, and Ala261 interacted via van der Waals forces and Leu238, Leu260, Ile264, Ile290, and Ala291 of HSA interacted with plumbagin through hydrophobic forces.

重要的是要了解药物与血清白蛋白相互作用的性质和机理，因为这种相互作用决定了它们的药代动力学和药效学。Plumbagin是一种天然的植物化合物，主要存在于Plumbaginaceae家族植物的树皮中，具有许多治疗潜力。在这项研究中，使用了一系列生物物理和计算工具对李白素与人血清白蛋白（HSA）的相互作用进行了解释。紫外-可见光谱法确定了结合常数为2.32×10 ⁴  M ^-1的plumbagin-HSA复合物的形成。。荧光光谱表明，存在通过铅皮蛋白淬灭HSA的荧光的静态模式。荧光光谱法获得的结合常数与紫外可见光谱法相似。ΔH°（-3.67）的负值表示反应的吸热特性，而ΔG°（-6.40至-6.58）的负值确认李白蛋白与HSA的络合是自发的。HSA中几乎有一个与李白蛋白结合的位点。在存在位点特异性标记物的情况下，将铅蛋白滴定至HSA表明，铅蛋白在HSA的亚结构域IIA（通常称为Sudlow位点I）处相互作用。此外，结合导致色氨酸微环境发生变化，而酪氨酸残基保持大致不变。这种相互作用还导致所研究的血清蛋白的α-螺旋含量降低。FRET计算表明，铅瓜皮蛋白与HSA的荧光团（Trp214）之间的距离为2.27 nm。最后，分子对接研究证实了体外发现。Plumbagin与HSA的Lys199和Arg257形成氢键。另外，Arg222，His242和Ala261通过范德华力相互作用，HSA的Leu238，Leu260，Ile264，Ile290和Ala291通过疏水力与李白蛋白相互作用。