In vitro antibacterial and molecular docking analysis of anthraquinone compounds from the roots of Canarina eminii

Canarina eminii is a medicinal plant traditionally used to treat various ailments. Chemical investigation of the DCM/MeOH (1:1) roots extract of Canarina eminii afforded three anthraquinone compounds (1-3) that were previously unreported from this species. The structures of the isolated compounds 1-3 were elucidated using HR- ESI-MS, 1D and 2D NMR spectroscopic analysis, and comparison with literature data. The DCM/MeOH (1:1) extract showed a maximal inhibitory zone of 18.40 ± 0.24 mm in diameter against S. aureus, which is promising in comparison to the standard, gentamicin (20.03 ± 0.01 mm). Among isolated compounds, the largest mean inhibition zone of 13.50 ± 0.03 mm was measured for compound 2 against S. aureus, comparable to the standard drug gentamicin (20.03 ± 0.01 mm). Compounds 1-3 displayed binding affinity with minimum binding energies ranging from -8.0 to -9.2 kcal/mol, -8.2 to -8.6 kcal/mol, and - 9.2 to -9.4 kcal/mol against Pseudomonas quinolone signal A, E. coli DNAgyrase B, and S. aureus pyruvate kinase, respectively, that showed greater binding affinity compared to the standard drug gentamicin. The Insilco drug likeness of compounds 1-3 showed projected toxicity class 5, indicating that they had no effect on organic toxicity. Compounds 1 and 3 predicted immunotoxicity and mutagenicity while, compound 2 is active only in mutagenicity. Overall, the in vitro antibacterial activity of the extract and compounds, molecular docking analysis results of the isolated compounds suggest DCM/MeOH crude extract and compound 2 are promising antibacterial agents, which corroborates with the traditional uses of the roots of C. eminii.