Possible modulating actions of plant extracts on the chromosome breaking activity of MMC and Ara-C in human lymphocytes in vitro.

Plants popularly used as medicine have been seen as promising natural agents by the pharmaceutical industry. In the present study the action of Psidium guajava L. (Pg) and Achillea millefolium L. (Am) infusions on chromosomal aberration formation in human lymphocyte system in vitro was assessed, associating them with the alkylating agent mitomycin C (MMC) and the DNA repair inhibitor cytosine-beta-arabin-furanoside (Ara-C). The cells were cultivated for 72 h and treated continuously with Pg and the Am infusions at dosages of 2.62 x 10(-4) g and 3.5 x 10(-4) g/ml culture medium, respectively. Treatments with MMC (0.30 microg/ml) or Ara-C (5 x 10(-7) microg/ml) were administered after 48 h of cell culture. Each samples (five individual) were exposed to nine treatments (control with PBS; Pg; Am; MMC; MMC+Pg; MMC+Am; Ara-C; Ara-C+Pg; and Ara-C+Am) and 100 cells were analyzed per cell culture. The used doses of each infusion did not cause clastogenic effects significantly different to the negative control (control=1%; Pg=2.2%; Am=1.8%). Nevertheless, the aberrant cell frequency after MMC treatment was significantly increased by the Am infusion (MMC=32.4%; MMC+Pg=36.2%; MMC+Am=44%), especially when the chromatid break types number was scored (MMC=151; MMC+Pg=173; MMC+Am=249). Regarding DNA repair inhibition by Ara-C, the Pg infusion caused a significant reduction in aberrant cell frequency (Ara-C=15.8%; Ara-C+Pg=11%; Ara-C+Am=14.4%), only when the chromatid break types number was scored (Ara-C=63; Ara-C+Pg=40; Ara-C+Am=58). These results indicate that the plant infusions per se do not have clastogenic activity, but can influence the clastogenic action of MMC and Ara-C on DNA break induction, in vitro.