Isolation, structure elucidation and in vitro anticancer activity of phytochemical constituents of Goniothalamus wynaadensis Bedd. and identification of Alpha -Tubulin as a putative molecular target by in Silico study

Abstract

The phytochemical analysis of ethyl acetate and methanol extract of Goniothalamus wynaadensis Bedd. leaves led to an isolation of eight (1-8) known molecules, among them seven (2-8) isolated for the first time from this species, which includes (+)-goniothalamin oxide (2), goniodiol-7-monoacetate (3), goniodiol-8-monoacetate (4), goniodiol (5), (+)-8-epi-9-deoxygoniopypyrone (6) etc. The phytochemical modification by acetylation of 3 and 4 gave goniodiol diacetate (9) with absolute configuration (6R, 7R, 8R) confirmed by single crystal X-ray diffraction. Compounds 3-9 were cytotoxic against breast, ovarian, prostate and colon cancer cell lines with IC sub(50)less than 10 micrometre. Cell cycle analysis and Annexin-V assay on MDA-MB-231 cell using goniodiol-7-monoacetate (3) exhibited apoptotic response as well as necrotic response and showed cell proliferation arrest at G2/M phase. An in silico target identification for these molecules was carried out with an Alpha-tubulin protein target by covalent docking. To gain an in-depth understanding and identify the stability of these protein-ligand complexes on thermodynamic energy levels, further assessment of the isolated molecules binding to the Cys-316 of Alpha-tubulin was performed based on reaction energetic analysis via DFT studies which hinted the isolated molecules may be Alpha-tubulin inhibitors similar to Pironetin. Molecular dynamics reiterated the observations.