Two N-Phenyl-Carbamic Acid Methyl Esters from Spatholobus littoralis and their Cytotoxic Effect Against Breast Cancer Using In Vitro and In Silico Methods

Spatholobus littoralis is an herbal plant widely used in traditional medicine in Kalimantan, Indonesia. This study aimed to isolate and characterize phytoconstituents from the wood of Spatholobus littoralis, and evaluate their cytotoxic activity against breast cancer cells in vitro and in silico.  The ethanol extract was fractionated by solvent-solvent partitioning using n-hexane, chloroform, and ethyl acetate sequentially. The chloroform fraction was subjected to gravity silica gel column chromatography using various solvent system to isolate the phytoconstituents. The structures of the isolated compounds were determined using a combination of spectroscopic techniques, including ultra-violet (UV), infra-red (IR), 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and liquid chromatography-high resolution mass spectrometry (LC-HRMS). The cytotoxic activity of the isolated compounds was tested against T47D and 4T1 breast cancer cells, and their potential activity against breast cancer receptor (2IOG) was also studied in silico using molecular docking simulations. The chromatographic separation of the chloroform fraction of Spatholobus littoralis wood led to the isolation of two carbamic acid esters characterized as dimethyl (methylene bis(4,1-phenylene)) dicarbamate (1) and asperteramide A (2). Compound 1 was cytotoxic to 4T1 cancer cells with an IC50 of 84.82 µg/mL, while compound 2 was cytotoxic to T47D with an IC50 of 134.71 µg/mL. Compounds 1 and 2 showed high affinity with the 2IOG receptor with binding affinity of -6.8 and -8.1 kcal/mol, respectively.  Therefore, S. littoralis wood extract has the potential to be developed as a natural source of anticancer agents against breast cancer.