Structural basis of multi-target interactions of Henna Dye Lawsone: an experimental and theoretical evaluation

Lawsone (2-hydroxy-1,4-naphthoquinone), also known as hennotannic acid, is a red-orange dye present in the leaves of the henna plant (<i>Lawsonia inermis</i>) having lots of biological activities. In this paper, we have investigated the structural basis of binding affinities of Lawsone towards two different targets namely, calf thymus DNA (CT-DNA) and protein bovine serum albumin (BSA) using experimental and computational approaches. This phytochemical binds to the minor groove of DNA and Sudlow site II, Domain III of BSA. The binding constants obtained from spectroscopic studies for Lawsone with DNA and BSA have been determined as 1.79 × 10³ M⁻¹ and 2.18 × 10³ M⁻¹, respectively with corresponding Gibbs free energies of −4.46 kcal/mol and −4.58 kcal/mol. Conformational changes in the secondary structures of the receptors upon binding with Lawsone is observed. Isothermal titration calorimetry (ITC) experiments reveal that binding is favoured mainly due to negative enthalpy changes (−18.2 kcal/mol for DNA and −98.77 kcal/mol for BSA). Molecular docking and dynamics simulations elucidate intermolecular contacts between Lawsone and the receptors, providing insight into the energetic profile of the complexes and revealing Lawsone’s reorientation within the binding sites. Both experimental and computational findings highlight the significance of hydrogen bonding and hydrophobic interactions in the binding process, offering valuable insights into Lawsone’s molecular interactions with biomolecules and its potential therapeutic applications.

散沫花素（2-羟基-1,4-萘醌），又名海娜鞣酸，是一种存在于散沫花（Lawsonia inermis）叶片中的红橙色染料，具备多种生物活性。本研究采用实验与计算相结合的方法，探究了散沫花素与两种不同靶标——小牛胸腺DNA（CT-DNA）以及牛血清白蛋白（BSA）结合亲和力的结构基础。该植物化学成分可结合于DNA的小沟以及牛血清白蛋白的苏洛位点II（Sudlow site II）结构域III。光谱学研究测得散沫花素与DNA、BSA的结合常数分别为1.79 × 10³ M⁻¹和2.18 × 10³ M⁻¹，对应的吉布斯自由能分别为-4.46 kcal/mol和-4.58 kcal/mol。研究观察到，受体的二级结构在与散沫花素结合后发生了构象变化。等温滴定量热法（Isothermal titration calorimetry, ITC）实验结果显示，结合过程的主要驱动力为焓变负值（与DNA结合时为-18.2 kcal/mol，与BSA结合时为-98.77 kcal/mol）。分子对接与分子动力学模拟阐明了散沫花素与受体之间的分子间相互作用模式，揭示了复合物的能量分布特征，并解析了散沫花素在结合位点内的重定向过程。实验与计算结果均证实，氢键与疏水相互作用在结合过程中发挥关键作用，为解析散沫花素与生物大分子的分子互作机制及其潜在治疗应用提供了重要理论依据。