Costunolide, a naturally occurring sesquiterpene lactone, was investigated experimentally and theoretically to determine the structural, electronic, spectroscopic, and chemical reactivity properties. As deduced from a single crystal X-ray diffraction (XRD) analysis, the absolute configurations of the two chiral centres were assigned as (6R,7S). Vibrational frequencies (IR, UV and NMR), electronic properties (HOMO and LUMO), and the molecular structure of costunolide were investigated by DFT calculations using Gaussian 09 molecular package at the B3LYP/6-311++G(d,p) level of theory. NMR chemical shifts were calculated from the magnetic shielding tensors obtained through the gauge-independent atomic orbital (GIAO) method, while the UV-vis spectrum was simulated by time dependent-DFT (TD-DFT) calculations. All calculations showed correlations to experimental data. The 6-311+G(2d,p) basis set was additionally used for better correlation in NMR studies. The first order hyperpolarizability value indicated that costunolide has nonlinear optical (NLO) properties. Costunolide stability arising from hyperconjugative interactions and charge delocalisation was analysed using natural bond orbital (NBO). Thermodynamic parameters also correlated in the temperature range 100–700 K. The molecular docking results showed that costunolide binds strongly to the Onchocerca volvulus main protease with a relative binding affinity of –5.94 kcal mol^–1 and an inhibition constant of 44.61 µM.

Costunolide 是一种天然存在的倍半萜内酯，通过实验和理论研究来确定其结构、电子、光谱和化学反应特性。从单晶 X 射线衍射 (XRD) 分析推断，两个手性中心的绝对构型指定为 (6 R ,7 S). 使用 Gaussian 09 分子包在 B3LYP/6-311++G(d,p) 水平上通过 DFT 计算研究了木香烃内酯的振动频率（IR、UV 和 NMR）、电子特性（HOMO 和 LUMO）和分子结构的理论。NMR 化学位移是根据通过与规范无关的原子轨道 (GIAO) 方法获得的磁屏蔽张量计算的，而紫外-可见光谱是通过时间相关的 DFT (TD-DFT) 计算模拟的。所有计算都显示了与实验数据的相关性。6-311+G(2d,p) 基组还用于 NMR 研究中更好的相关性。一阶超极化率值表明木香烃内酯具有非线性光学 (NLO) 特性。使用自然键轨道 (NBO) 分析了由超共轭相互作用和电荷离域引起的 Costunolide 稳定性。热力学参数也在 100–700 K 的温度范围内相关。分子对接结果表明，木香烃内酯与盘尾丝虫主要蛋白酶，相对结合亲和力为 –5.94 kcal mol ^–1，抑制常数为 44.61 µM。