基于密度泛函理论研究白花丹素分子的光谱与激发态性质

Study on the Spectral and Excited-State Properties of Plumbagin Based on Density Functional Theory

摘要: 白花丹素，即5-羟基-2-甲基-1,4-萘醌，具有抗菌、抗真菌、抗动脉粥样硬化和抗肿瘤等作用，是传统民间药材白花丹(拉丁学名：Plumbago zeylanica L.)中含量最丰富的核心生物活性成分。本文基于密度泛函理论，得到了白花丹素稳定的分子结构，理论计算得到的红外光谱与实验的红外峰数据具有较好的一致性。运用简正振动分析方法，获得各振动模式的势能分布，对摩尔吸收系数大于300 L·mol⁻¹·cm⁻¹的9个振动模式做出了归属指认。采用含时密度泛函理论，计算得到紫外-可见光吸收光谱图，在100~450 nm范围内存在5个明显吸收峰，并揭示出其源于7个主要电子跃迁。通过对跃迁相关的10个分子轨道进行可视化分析，结合分子轨道的波函数等值面图，阐明了这些激发态的电子结构特征。该工作可为阐释白花丹素的光谱学行为及其潜在药理作用机制提供理论依据。

Abstract: Plumbagin, 5-hydroxy-2-methyl-1,4-naphthoquinone, possesses antibacterial, antifungal, anti-atherosclerotic, and antitumor activities, and is the most abundant core bioactive component in the traditional folk medicinal herb Plumbago zeylanica L.. Based on density functional theory, this paper obtained the stable molecular structure of plumbagin, and the theoretically calculated infrared spectrum showed good consistency with the experimental infrared peak data. Using normal mode analysis, the potential energy distribution of each vibrational mode was obtained, and nine vibrational modes with molar absorptivity greater than 300 L·mol⁻¹·cm⁻¹ were assigned and identified. By employing time-dependent density functional theory, the ultraviolet-visible absorption spectrum was calculated, revealing five distinct absorption peaks in the range of 100~450 nm, which originated from seven main electronic transitions. Through visual analysis of the 10 molecular orbitals related to the transitions, combined with the isosurface of the molecular orbital wave functions, the electronic structural characteristics of these excited states were elucidated. This work provides a theoretical basis for elucidating the spectroscopic behavior and potential pharmacological mechanisms of plumbagin.