(R)-13aα-Densiindolizidine, A New Phenanthroindolizidine Alkaloid From Cryptocarya densiflora Blume (Lauraceae) and Molecular Docking Against SARS-CoV-2

Cryptocarya densiflora Blume (Lauraceae) is an evergreen tree widely distributed throughout the hills and mountain forests up to 1500 m in Malaysia and Indonesia. The plant has been reported to contain phenanthroindolizidine-type of alkaloids. In the present work, a new phenanthroindolizidine alkaloid named (R)-13aα-densiindolizidine, was isolated from the dichloromethane (DCM) extract of the leaves. The structure of the alkaloid was established based on 1D and 2D nuclear magnetic resonance (NMR) and liquid chromatography mass spectrometry-ion trap-time of flight (LCMS-IT-TOF) analysis. (R)-13aα-densiindolizidine displayed binding interactions with crucial amino acid residues in the active sites of severe acute respiratory syndrome coronavirus 2 Mpro (SARS-CoV-2 Mpro) and RNA-dependent protease (RdRp) in silico, whilst fulfilling the absorption, distribution, metabolism, excretion, and toxicity (ADMET) criteria and Lipinsky's rule, thus revealing its potential as a lead compound.