Isolation, Solid-state Structure Determination, In Silico and In Vitro Anticancer Evaluation of an Indole Amino Acid Alkaloid L-Abrine

Background: Abrus precatorius Linn. (Kunch in Bengali) is widely spread in tropical and sub-tropical regions. It is a typical plant species which is well-known simultaneously as folk medicine and for its toxicity. Objective: Phytoceutical investigation of the white variety seeds of Abrus precatorius Linn. Methods: Traditional extraction, separation, isolation, and purification processes were followed. The structure was elucidated by various spectral analyses and the solid-state structure of this indolealkaloid was determined by X-ray crystallographic analysis. Docking interactions of L-abrine had been studied against ten major proteins, responsible for various types of cancers. In silico studies were done by Schrödinger Maestro, AutoDock4, PyMOL and AutoDock Vina. The protein structures were downloaded from Protein Data Bank. Sulforhodamine B (SRB) colorimetric assay was used for in vitro anticancer evaluation against four human cancer cell lines. Results: An indole-containing unusual amino acid alkaloid had been isolated from the white variety seeds of Abrus precatorius Linn. In silico docking studies demonstrated significant antiproliferative activity against four human cancer cell lines. Conclusion: The solid-state zwitterion structure of the indole-containing alkaloid (α-methylamino- β-indolepropionic acid, L-abrine) has been confirmed for the first time by X-ray crystallography. Highly promising in silico and in vitro results indicate that L-abrine may find its space in future anticancer drug discovery research.