Novel C-3 and C-20 derived analogs of betulinic acid as potent cytotoxic agents: design, synthesis, in vitro and in silico studies

Abstract

In this report, novel derivatives of betulinic acid were designed and synthesized by targeting the C-3-OH group and C-20 olefinic bond in an endeavour to develop potent antitumor agents. These analogs were screened for their anticancer activity against six different human cancer cell lines including breast cancer MCF-7, lung cancer A549, colon cancer HCT-116, leukemia MOLT-4, prostate carcinoma cell PC-3 and pancreatic cancer cell Miapaca-2 by MTT assay. Many derivatives displayed better cytotoxicity than the parent compound BA. More significantly compounds 9b, 9e, 10 and 11a were found to have more promising activity than BA. Compound 11a was the most potent analog with IC₅₀ values of 7.15 (MCF-7), 8.0 (A549), 3.13 (HCT-116), 13.88 (MOLT-4), 8.0 (PC-3) and 6.96 (MiaPaCa-2) μM. In addition to experimental investigations, in silico aspects were evaluated for the parent compound, BA and 11a derivative based on its potential bioactive behaviour. The representative compounds were optimized structurally using density functional theory (DFT). GaussView 6.1 graphical interface associated GAUSSIAN 09 (Revision C.01) software package was used for the calculations under 6-311g(d,p)/B3LYP formalism using under a SMD model (water as solvent) for the parent compound BA and 11a to explain the respective bioactive behaviour. This was followed by molecular docking studies suggesting that compound 11a binds efficiently with all the three proteins with the docking score of −7.2 kcal mol⁻¹ in the case of matrix metalloproteinase-2 (PDB ID: 1HOV) and poly[ADP-ribose] polymerase-1 (PDB ID: 1UK0) and −6.7 kcal mol⁻¹ in the case of TRAF2 (PDB ID: 2X7F). Further, molecular dynamics studies between 11a and the three proteins were carried out using Desmond Maestro v11.3 to study protein–ligand interactions and protein stability.