Evaluation of DNA Binding and Topoisomerase I Inhibitory Activities of 16’‐Decarbomethoxydihydrovoacamine from Tabernaemontana corymbosa

Abstract

An iboga‐vobasine bisindole alkaloid, 16′‐decarbomethoxydihydrovoacamine (1) isolated from the stem bark extract of Tabernaemontana corymbosa exhibited strong cytotoxicity against colorectal cancer cell lines in our preliminary study. As an initial step to elucidate its anti‐proliferative mechanism, the DNA binding and topoisomerase I (topo1) inhibitory activities of the bisindole 1 were investigated. The results of the in vitro DNA binding studies and molecular docking calculations collectively suggested that 1 binds to the DNA minor groove via hydrophobic interactions with a binding constant (Kb) of 7.40×105 M−1. Treatment of Escherichia coli topo1 with 1 did not inhibit the enzyme from relaxing the supercoiled plasmid DNA pBR322, indicating that the cytotoxicity of 1 in colorectal cancer cells is independent of topo1. The bisindole is predicted to possess substantial bioavailability without major toxicity. Moreover, the cytotoxicity of 1 is selective towards the colorectal cancer cells as evaluated using the MTT assay.

The Bisindole Alkaloids Angustilongines M and A from Alstonia penangiana Induce Mitochondrial Apoptosis and G0/G1 Cell Cycle Arrest in HT-29 Cells through Promotion of Tubulin Polymerization

“…The MTT method was employed to test the ability of angustilongine M ( 1 ) and angustilongine A ( 2 ) to inhibit cancer cell growth in conventional 2D monolayer cultures, as outlined previously . An adaptation of this method was used to evaluate the antiproliferative activity of the test compounds against HT-29 spheroids in 3D format, as previously described .…”

“…Tubulin protein structure was obtained from the Protein Data Bank (PDB entry 1JFF). Molecular docking calculation was performed as previously described, using the AutoDock 4.2 software package, and the graphical interface AutoDockTools 1.5.6 (ADT) was used to prepare the system . The graphical depiction of the docked model was accomplished by UCSF Chimera and Discovery Studio 3.1 (Accelrys, USA).…”

“…The physiochemical properties of angustilongine M ( 1 ) and angustilongine A ( 2 ) were computed using the MedChem Designer v.3 program and ORISIS Data Warrior as previously described …”

Antiproliferative and Microtubule-stabilizing Activities of Two Iboga-vobasine Bisindoles Alkaloids from Tabernaemontana corymbosa in Colorectal Adenocarcinoma HT-29 Cells

“…The expression pattern of these genes is therefore consistent with the microarray results (Table 2). The physiochemical properties of bisindole 1 were calculated based upon molecular structure and compared with those of bisindole 2 [11]. As shown in Table 1S (Supporting Information), bisindole 1 with the lower Log P and MLog P values is relatively less lipophilic and more polar than bisindole 2, presumable owing to the presence of the 19,20double bond in the vobasinyl unit.…”

“…The assay was carried out as outlined previously with some modifications [11]. For the conventional 2D monolayer cultures, 2 × 10 3 cells per well were seeded into 96-well microplates, incubated overnight, and then treated with 200 µL of various concentrations of bisindoles 1 and 2 for 48 h, with 5-FU as a positive control.…”