Study on the molecular structure and chemical properties of the polyoxypregnane derivatives 11α-O-2-methylbutyryl-12β-O-tigloyl tenacigenin B and 11α,12β-O-ditigloyl tenacigenin B by combining experimental and theoretical methods

The title compounds, 11α-O-2-methylbutyryl-12β-O-tigloyl tenacigenin B and 11α,12β-O-ditigloyl tenacigenin B were isolated from the rhizomes and roots of Marsdenia tenacissima. The molecular geometries were optimized using DFT approach applying B3LYP/6–311G(d,p) base set and confirmed by infrared, nuclear magnetic resonance (NMR), Raman and UV–visible spectroscopic methods (experimental and theoretical). The present experimental data were found in reasonable agreement with the computational results. The vibrational features and the potential energy distribution (PED) of the title compounds were predicted. Moreover, the HOMOs and LUMOs analyses, total (TDOS) and (PDOS) partial density of states, chemical reactivity parameters, molecular electrostatic potential (MEP) and the intramolecular interactions such as topological analysis, natural bond orbital (NBO), reduced density gradient (RDG) of the optimized geometries were also performed. Nonlinear optical properties (NLO) for the title compounds were predicted. Besides, the molecular docking was investigated with the protein-PDB:3iw4 to check the mode of interactions. Therefore, these studies give important information pertaining to the true geometric configuration, stability, reactivity and bioactivity of the title compounds and show that 11αM12βTTB and 11αT12βTTB could have a great effect in the anticancer activity due to its protein active sites affinity and binding energy. The results are beneficial for the further research in order to design them as the novel drugs.