4-Nerolidylcatechol analogues as promising anticancer agents.

4-Nerolidylcatechol (1) is an isolated compound from Pothomorphe umbellata L. (Piperaceae) with promising antitumor cells properties. However it presents lability under light and room temperatures. Many efforts have been directed towards discovering anticancer agents endowed with cytotoxic activities. Here, we evaluated cytotoxic effects of 4-NRC analogues (LQFMs 2-6) and the cell death pathways induced by these compounds in multidrug-resistant K562 cells. Compounds (2-6) exhibited cytotoxic activities in a concentration-dependent manner against leukaemic cells, specially the compounds (3) and (5). Additionally, compounds (1), (3) and (5) promoted marked alterations on the cell morphology, including nuclear changes as demonstrated by Hoescht 33342 staining. Moreover, these compounds promoted apoptosis induction in K562 cells by phosphatidylserine exposure, increase of sub-G1 cells and modulation of the caspases-3/7, -8 and -9 activation. In addition, the pancaspase inhibitor z-VAD-fmk partially reduced the apoptosis induced by the compounds (1) and (5)-induced, suggesting caspase-dependent and caspase-independent cell death pathways. Compounds (1) and (5) also modified the cell cycle progression by G0/G1 and S arrest, respectively. Furthermore, compounds (1), (3) and (5) promoted mitochondrial dysfunction associated to accumulation of cytosolic cytochrome c and modulated the NF-ĸB activation. In addition, unlike their analogues, 4-NRC (1) also promoted a significant cyclin D1 inhibition. Together, these data suggest that the mechanism of cell death of 4-NRC and its analogues (3) and (5) occurs by apoptosis through mitochondrial mechanisms. Considering that LQFMs are biocompatible synthetic analogues produced by molecular simplification of (1) without the chiral centre, which is associated with the instability found in compound (1), we suggest that these compounds are promising candidates for further pre-clinical studies.