The use of medicinal plants by the general population is an old and still widespread practice, which makes studies of their genotoxicity essential. Psidium guajava L. and Achillea millefolium L. are examples of plants commonly used in popular medicine. P. guajava L. is indicated for diarrhea and also as an antiseptic, while A. millefolium L. is indicated as an analgesic, antispasmodic, digestive, diuretic, antiseptic, astringent, emollient, wound healer and hemorrhoid medication. The aim of this study was to determine the effects of the infusions of these two plant species on chromosomes and the cell cycle. Leaves from the plants were used to prepare infusions, in the same manner as teas, but at two different concentrations. Allium cepa L. root-tip cells (P. guajava L. -2.62 and 26.2 mg/mL, and A. millefolium L. -3.5 and 35.0 mg/mL) and Wistar rat bone marrow cells (P. guajava L. -2.62 and 26.2 mg/100g body weight, and A. millefolium L. -3.5 and 35.0 mg/100g body weight) were used as in vivo plant and animal test systems, respectively. Human peripheral blood lymphocytes (P. guajava L. -0.262 and 2.62 µg/mL culture medium, and A. millefolium L. -0.35 and 3.5 µg/mL culture medium) were used as in vitro test system. The P. guajava L. infusion at the higher concentration caused a statistically significant inhibition of cellular division in the onion root-tip cells, not observed in onion root-tip cells treated with A. millefolium L. No statistically significant alterations were found, as compared to untreated controls, in either the cell cycle or the number of chromosome alterations, after treatments with either plant, in rat cells or in cultured human lymphocytes. These results regarding the cytotoxicity and mutagenicity of these plants provide valuable information about the safety of using them as therapeutic agents.

Meiotic and mitotic chromosomes of Isocopris inhiata and Diabroctis mimas were studied by standard staining procedures, C-banding, silver nitrate staining and FISH using Apis mellifera 28S rDNA as probe. Isocopris inhiata presented a 2n = 18 (8II+ Xy p ) karyotype, composed of meta-submetacentric chromosomes with gradual reduction in size. The karyotype of D. mimas was 2n = 20 (9II+ Xy p ), composed of meta-submetacentric (pairs 1, 2, 3, 4 and 7) and acrocentric (pairs 5, 6, 8 and 9) chromosomes, with gradual reduction in size. Analysis of constitutive heterochromatin revealed similar C-banding patterns for both species, showing pericentromeric and telomeric bands and diphasic chromosomes. In addition, the X chromosomes of these species were found to be almost completely heterochromatic. The presence of chromocenters was checked in one or more phases of prophase I of these species. All heterochromatin reacted positively for the silver stain. By FISH analysis we were able to locate the rDNA in medium-size autosome pairs in both species and in the X chromosome of D. mimas.

Medicinal plants are widely used to treat various diseases, and in Brazil the plants Maytenus ilicifolia Mart. and Bauhinia candicans Benth are commonly used in popular medicine. However, there are a large number of compounds in plants which can produce alterations in genetic material, and this study was conducted to investigate any possible mutagenic and cytotoxic effects that M. ilicifolia and B. candicans infusions may have on the cell cycle and chromosomes. Infusions were prepared with in natura leaves to give two concentrations of infusions, one at the concentration normally used by the population in general and the other at 10 times this value (i.e. 3.5 and 35 mg/mL for M. ilicifolia and 0.465 and 4.65 mg/mL for B. candicans). Onion (Allium cepa L.) root-tip cells (RTC) and Wistar rat bone-marrow cells (BMC) were used as test systems in in vivo assays. The M. ilicifolia infusions at both concentrations, and the B. candicans infusion at the lower concentration, had no statistically significant depressive mitotic effect on RTC. A statistically significant depressive mitotic effect on RTC was found with the more concentrated (4.65 mg/mL) B. candicans infusion as compared with a negative control. In BMC, infusions of B. candicans and M. ilicifolia produced no statistically significant increase in the number of chromosome alterations or rates of cell division as compared to controls. The significance of these findings are discussed in the light of the use of these plants as therapeutic agents.

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