Potencial antiproliferativo e genotóxico de extratos aquosos de Stevia rebaudiana bertoni pelo teste Allium cepa L sob diferentes aplicações de glifosato

Abstract

Some plant species of the Asteraceae family, due to the secondary compounds produced, have high medicinal and economic value. Stevia rebaudiana Bertoni (Bertoni), a species of this family, has natural sweeteners extracted from its leaves, mainly rebaudioside and stevioside, which have a sweetening power about 300 to 450 times greater than sucrose. These substances are important, because they are not caloric and can be part of the diet of people with sugar restriction. In addition, it has antibacterial, antiseptic, anti-inflammatory, hypotensive, diuretic, cardiotonic, and contraceptive properties. The cultivation of S. rebaudiana is highly sensitive to competition with unwanted plants, requiring the use of herbicides for control, and among these is the use of glyphosate, which is known to be mutagenic. This research aimed to analyze the genotoxic and antiproliferative potential of aqueous extracts from fresh and dried leaves of S. rebaudiana treated with different applications of glyphosate. The genotoxicity analysis was performed using the Allium cepa in vivo bioassay, which allows the investigation of chromosomal alterations and mitotic index. The plant material used for the in vivo test was grown in a protected environment, and divided into five groups (control, plants that received only water, and plants treated with glyphosate diluted in distilled water at concentrations of 0,25 mL L-1; 0.5 mL L-1; 1 mL L-1, and 2 mL L-1) and collected 3 days after the application. The aqueous extracts were prepared from fresh and dried leaves of S. rebaudiana at concentrations of 1.5 g L-1 and 3 g L-1 with distilled water and glyphosate 31.25 mL L-1 (1.5%) representing the negative and positive controls, respectively. Chi-square test (χ2) was used for statistical analysis of mitotic indices and Scott & Knott test was used for changes, both with 5% level of error probability. As the concentration increased, the aqueous extracts of stevia that received only water showed lower mitotic index than the negative control (water), except 1.5 g L-1 of fresh leaves. The extracts treated with glyphosate dilutions, also had decreased cell proliferation, except 3 g L-1 that received 0.5 mL L-1. All extracts showed chromosomal aberrations, but not all differed significantly from water. The extracts of 1.5 g L-1 and 3 g L-1 of fresh leaves and 1.5 g L-1 of dried stevia leaves, which received only water, showed genotoxic potential. Thus, it is concluded that the extracts of 3 g L-1 of fresh leaves and 1.5 g L-1 and 3 g L-1 of dried stevia leaves that received only water have antiproliferative potential, as do the extracts that received glyphosate (except 3 g L-1 that received 0.5 mL L-1). Of the treatments that received the dilutions, the extracts of 1.5 g L-1 of fresh leaves that received 1 mL L-1 and 2 mL L-1, 3 g L-1 of fresh leaves that received all dilutions, and the extracts of 1.5 g L-1 of dried leaves that received 0.25 mL L-1, 1 mL L-1, and 2 mL L-1 are genotoxic.