No abstract

The pimarane-type diterpene, pimaradienoic acid (PA), is known for its diverse biological properties such as antimicrobial, anti-inflammatory and trypanocidal. A preliminary study was undertaken to investigate in vitro the free radical-scavenging potential of PA. In addition, the genotoxic potential of PA and its ability to modulate genotoxicity induced by doxorubicin (DXR) and methyl methanesulfonate (MMS) were studied in Chinese hamster lung fibroblasts (V79 cells) and in male Swiss mice using the comet and micronucleus assays. The DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay showed that PA exerted no antioxidant activity when compared to quercetin. The colony-forming assay using V79 cells showed that PA was cytotoxic at concentrations >5.0μg/mL. Therefore, concentrations of 0.625, 1.25, 2.5, and 5.0μg/mL were used for evaluation of the genotoxic and antigenotoxic potential of PA in V79 cells. For genotoxic and antigenotoxic assessment in Swiss mice, three PA doses were tested (20, 40, and 80mg/kg body weight) based on the solubility limit of the diterpene in dimethylsulfoxide and water. The in vitro results demonstrated that PA induced DNA damage at concentrations of 2.5 and 5.0μg/mL in the comet assay. However, no genotoxic effect was observed in the micronucleus test using V79 cells. In the in vivo evaluation of genotoxicity, a significant increase in the frequency of DNA damage was observed in hepatocytes of animals treated with the highest PA dose (80mg/kg) when compared to the control group, but this difference was not seen in the micronucleus test. Furthermore, PA significantly reduced the frequency of DXR- and MMS-induced micronuclei and extent of DNA damage in in vitro and in vivo test systems.

In general, the effects of Cadmium (Cd) on crop quality are evaluated solely by Cd accumulation in the edible plant parts; thus, the potential effects on several nutritional features are not often taken into account. This study evaluated Cd effects on the enzymatic activities of lysine (Lys) metabolism, storage protein and amino acid profile in maize. Stress parameters were also assessed. In vegetative organs, Cd was accumulated in the following decreasing order: roots > stems > leaves. Cadmium accumulation in grains decreased at grain maturity (from 0.25 to 0.07 µg g-1 DW). In leaves, neither hydrogen peroxide content nor superoxide dismutase, catalase, ascorbate peroxide and guaiacol peroxidase activities did not change in Cd-treated plants compared to control plants. Lipid peroxidation was not detected in immature grains and leaves of plants under Cd exposure, indicating that Cd accumulation mainly in the roots is a mechanism to avoid oxidative stress in aboveground parts of the plant. However, Lys metabolism in immature grains was modified, showing increases in the specific activities of aspartate kinase (AK) and dihydrodipicolinate synthase (DHDPS) after Cd exposure. AK sensitivity to Lys feedback inhibition increased, but decreased in DHDPS in Cd-treated plants, suggesting differential regulation for these enzymes. In mature grains, the Lys content did not change, while the proline content increased by 54 % in Cd-treated plants. This is the first report on Cd effects on amino acid profile, storage protein contents and enzymes from Lys metabolism in grains of a cereal plant species.

This work aimed to quantify the concentration of soluble amino acids, nitrogen (N) and Cd in the developing seeds of maize plants that were grown in Cd-contaminated soil from seed sowing to the reproductive stages. The specific activities and feedback inhibition properties of lysine (Lys) metabolic enzymes were also determined in developing seeds. The potential maize yield was depressed by Cd exposure. Cadmium concentration in plant organs followed the decreasing order: roots [ stems = leaves [ developing seeds (37.04, 1.95, 1.46 and 0.22 mg kg -1 Cd, respectively). The relatively low Cd concentration in the remained developing seeds was a result from root-and earmediated reductions of the Cd translocation in plants. Plants under Cd exposure presented developing seeds with an increased N concentration (up to 7%) when compared to control plants. Furthermore, the level of soluble amino acids (particularly histidine, glycine, tyrosine, methionine, isoleucine and valine) was increased in the developing seeds of Cd-treated plants.In addition, changes in the feedback properties of dihydrodipicolinate synthase (DHDPS), an enzyme from lysine metabolism, were observed in developing seeds. In conclusion, the current study showed that maternal plant exposure to Cd can alter the concentration of soluble amino acids and the behavior of Lys metabolic enzymes in developing seeds. This study provided not only new information about the influence of the long-term Cd exposure on plants, but also data about protective plant strategies against Cd toxicity.