Effects of Pterocaulon polystachyum DC.: (Asteraceae) on onion (Allium cepa) root-tip cells

In Brazil leaf infusions of the plant Pterocaulon polystachyum DC (Asteraceae) are used to treat digestive problems. We used plants from six P. polystachyum populations to prepare fresh aqueous leaf infusions at the concentration normally used in Brazil (2.5 g L-1) and at twice (5 g L-1) and four times (10 g L-1) this concentration. We rooted onion bulbs in a water control or one of the infusions for 24 h and used the in vivo onion (Allium cepa) root-tip cell test to investigate the potential mutagenicity of the infusions by calculating the mitotic index for the control and the experimental treatments and comparing them using the Chi-squared test (chi(2), p = 0.05). There was a highly significant decrease in the mitotic index of root-tip cells treated with infusion as compared to those exposed to water only. These results indicate that P. polystachyum infusions present cytotoxic and anti-proliferative activity and therefore have therapeutic potential.