PURPOSE: The present investigation was undertaken to characterize the interaction between 6-shogaol and the main in vivo transporter, human serum albumin (HSA).

METHODS: Various binding characteristics of 6-shogaol-HSA interaction were studied using fluorescence spectroscopy. Thermal stability of 6-shogaol-HSA system was determined by circular dichroism (CD) and differential scanning calorimetric (DSC) techniques. Identification of the 6-shogaol binding site on HSA was made by competitive drug displacement and molecular docking experiments.

RESULTS: Fluorescence quench titration results revealed the association constant, Ka of 6-shogaol-HSA interaction as 6.29 ± 0.33 × 10(4) M(-1) at 25 ºC. Values of the enthalpy change (-11.76 kJ mol(-1)) and the entropy change (52.52 J mol(-1) K(-1)), obtained for the binding reaction suggested involvement of hydrophobic and van der Waals forces along with hydrogen bonds in the complex formation. Higher thermal stability of HSA was noticed in the presence of 6-shogaol, as revealed by DSC and thermal denaturation profiles. Competitive ligand displacement experiments along with molecular docking results suggested the binding preference of 6-shogaol for Sudlow's site I of HSA.

METHODOLOGY/PRINCIPAL FINDINGS: The hexane extract of C. cassia demonstrated high anti-proliferative activity against MCF-7 and MDA-MB-231 cells (IC50, 34 ± 3.52 and 32.42 ± 0.37 μg/ml, respectively). Oxidative stress due to disruption of antioxidant enzyme (SOD, GPx and CAT) activity is suggested as the probable cause for apoptosis initiation. Though the main apoptosis pathway in both cell lines was found to be through caspase-8 activation, caspase-9 was also activated in MDA-MB-231 cells but suppressed in MCF-7 cells. Gene expression studies revealed that AKT1, the caspase-9 suppressor, was up-regulated in MCF-7 cells while down-regulated in MDA-MB-231 cells. Although, AKT1 protein expression in both cell lines was down-regulated, a steady increase in MCF-7 cells was observed after a sharp decrease of suppression of AKT1. Trans-cinnamaldehyde and coumarin were isolated and identified and found to be mainly responsible for the observed anti-proliferative activity of CE (Cinnamomum cassia).

METHODS: The cytotoxic activity of the hexane and ethyl acetate extracts of Curcuma mangga rhizomes against human colorectal adenocarcinoma cell lines (HT29) was determined by using the SRB assay.

RESULTS: The ethyl acetate extract showed a higher cytotoxic effect compared to the hexane extract. Morphological changes of the HT29 cells such as cell shrinkage, membrane blebbling and formation of apoptotic bodies while changes in nuclear morphology like chromatin condensation and nuclear fragmentation were observed. Further evidence of apoptosis in HT29 cells was further supported by the externalization of phosphatidylserine which indicate early sign of apoptosis.

OBJECTIVE: The purpose of the study was to identify an active principle of R. angustifolia and to investigate its effect on the HT29 cell death.

MATERIALS AND METHODS: The methanol and fractionated extracts (hexane, chloroform, ethyl acetate, and water) of R. angustifolia Pers. were initially investigated for their cytotoxic activity against two human carcinoma cell lines (MCF7 and HT29) and a normal human colon fibroblast cell line (CCD-18Co) using sulforhodamine B cytotoxicity assay. Eight compounds including rutamarin were isolated from the active chloroform extract and evaluated for their cytotoxic activity against HT29 human colon carcinoma cell line and CCD-18Co noncancer cells. Further studies on the induction of apoptosis such as morphological examinations, biochemical analyses, cell cycle analysis, and caspase activation assay were conducted in rutamarin-treated HT29 cells.

RESULTS: Rutamarin exhibited remarkable cytotoxic activity against HT29 cells (IC50 value of 5.6 μM) but was not toxic to CCD-18Co cells. The morphological and biochemical hallmarks of apoptosis including activation of caspases 3, 8, and 9 were observed in rutamarin-treated HT29 cells. These may be associated with cell cycle arrest at the G0/G1 and G2/M checkpoints, which was also observed in HT29 cells.

CONCLUSIONS: The present study describes rutamarin-induced apoptosis in the HT29 cell line for the first time and suggests that rutamarin has the potential to be developed as an anticancer agent.