AIM AND OBJECTIVES: In this study, we aim at investigating the mechanism of apoptosis by N-(4-chlorophenyl)-2-(4- (3,4,5-trimethoxybenzyloxy)benzoyl)-hydrazinecarbothioamide, a triazole precursor, henceforth termed compound P7a, in breast cancer cell line, MCF-7. We first screen a series of analogues containing (3,4,5-trimethoxybenzyloxy) phenyl moiety in breast cancer cell lines (MCF-7 and MDA-MB-231) to select the most cytotoxic compound and demonstrate a dose- and time-dependent cytotoxicity. Then, we unravel the mechanism of apoptosis of P7a in MCF-7 as well as its ability to cause cell cycle arrest.

METHODS: Synthesis was performed as previously described by Kareem and co-workers. Cytotoxicity of analogues containing (3,4,5-trimethoxybenzyloxy)phenyl moiety against MCF-7 and MDA-MB-231 cell lines was evaluated using the MTS assay. Flow cytometric analyses was done using Annexin V/PI staining, JC-1 staining and ROS assay. The activity of caspases using a chemoluminescence assay and western blot analysis was conducted to study the apoptotic pathway induced by the compound in MCF-7 cells. Lastly, cell cycle analysis was conducted using flow cytometry.

RESULTS: Upon 48 hours of treatment, compound P7a inhibited the proliferation of human breast cancer cells with IC50 values of 178.92 ± 12.51μM and 33.75 ± 1.20μM for MDA-MB-231 and MCF-7, respectively. Additionally, compound P7a showed selectivity towards the cancer cell line, MCF-7 compared to the normal breast cell line, hTERT-HME1, an advantage against current anticancer drugs (tamoxifen and vinblastine). Flow cytometric analyses using different assays indicated that compound P7a significantly increased the proportion of apoptotic cells, increased mitochondria membrane permeabilisation and caused generation of ROS in MCF-7. In addition, cell cycle analysis showed that cell proliferation was arrested at the G1 phase in the MCF-7 cell line. Furthermore, upon treatment, the MCF-7 cell line showed increased activity of caspase-3/7, and caspase-9. Lastly, the western blot analysis showed the up-regulation of pro-apoptotic proteins along with up-regulation of caspase-7 and caspase-9, indicating that an intrinsic pathway of apoptosis was induced.

OBJECTIVE: It is of great interest to identify the oxidation products of sesamol that may be beneficial to humans. This study was undertaken to identify the oxidation products of sesamol and investigate their antioxidant and cytotoxic activities.

MATERIALS AND METHODS: Using the ferricyanide oxidation approach, four oxidation products of sesamol (2, 3, 20 & 21) have been identified. Structural elucidation of these compounds was established on the basis of their detailed NMR spectroscopic analysis, mass spectrometry and x-ray crystallography. Additionally, a formation mechanism of compound 20 was proposed based on high-resolution mass spectrometry-fragmentation method. The antioxidant activities of these compounds were determined by the DPPH, FRAP, and ABTS assays. The in vitro antiproliferative activity of these compounds was evaluated against a panel of human cancer cell lines as well as non-cancerous cells.

RESULTS: Two oxidation products of sesamol were found to contain an unusual methylenedioxy ring-opening skeleton, as evidenced by spectroscopic and x-ray crystallographic data. Among all compounds, 20 displayed impressive antiproliferative activities against a panel of human cancer cell lines yet remained non-toxic to noncancerous cells. The antioxidant activities of compound 20 are significantly weaker than sesamol as determined by the DPPH, FRAP, and ABTS assays.

RESULTS: Metabolite profile analysis of the yeast culture extracts by GC-MS showed the production of several sesquiterpene alcohols (C15H26O), including cadinols and germacrene D-4-ol as major products. Other detected sesquiterpenes include selina-6-en-4-ol, β-elemene, β-cubebene, and cedrene. Two purified major compounds namely (+)-torreyol and α-cadinol synthesised by GME3638 and GME3634 respectively, are stereoisomers and their chemical structures were confirmed by 1H and 13C NMR. Phylogenetic analysis revealed that GME3638 and GME3634 are a pair of orthologues, and are grouped together with terpene synthases that synthesise cadinenes and related sesquiterpenes. (+)-Torreyol and α-cadinol were tested against a panel of human cancer cell lines and the latter was found to exhibit selective potent cytotoxicity in breast adenocarcinoma cells (MCF7) with IC50 value of 3.5 ± 0.58 μg/ml while α-cadinol is less active (IC50 = 18.0 ± 3.27 μg/ml).