Induction of apoptosis in human bladder cancer cells by triterpenoids isolated from Holarrhena antidysenterica through differential reactive oxygen species generation

A novel triterpenoid, holarol(1),3β-lup-20(31)-en-3,29,30-triol along with one seco-triterpenoid, dihydrocanaric acid(2) and one known pentacyclic triterpenoid, betulin(3) have been isolated from Holarrhena antidysenterica (L.)Wall. (Family: Apocynaceae). The structures of the compounds were elucidated by extensive IR, 1D, 2D NMR and mass spectrometric analysis. The optimised geometry of (1) was calculated by density-functional theory (DFT) using M06-2X hybrid functional and 6-31 G(D) basis set. The compounds showed differential cytotoxic activities in the cell lines-HeLa, EAC, Raji and T24. Seco-triterpenoid (2) showed highest sensitivity (IC₅₀: 1.710 μg/mL) against the bladder cancer cell line T24 followed by (1) (IC₅₀ 9.698 µg/mL) and (3) (IC₅₀ 11.769 µg/mL). Compound (1) showed highest reactive oxygen species (ROS) generation in T24 cell line followed by (3) and (2) resulting in induction of apoptosis through activation of caspase, cleavage of PARP and reduction of Bcl-2/Bax ratio. Thus compounds (1), (2) along with (3) could be potent anticancer agents.

Keywords: Apocynaceae; DFT; apoptosis; bladder cancer; reactive oxygen species.