Impacto do boro na produtividade de grãos, teor e qualidade do óleo e potencial biológico de extratos de folha e capítulo de girassol.

Abstract

The use of sunflower on food industry is valuable, due to its high grain productivity and oil quality. Some inherent properties of sunflower have been generating special interest on chemical research because of special metabolites with biological potential. Nevertheless, a limiting factor to be considered for sunflower characteristics is the nutrient availability. Regarding essential micronutrients for desirable productivity and oil quality, it is noticed that sunflower’s culture has high sensibility to excessive input of Boron element (B). This element acts on physiological and morphological processes and, therefore, it affects chemical and agronomic aspects. This work aims to evaluate sunflower’s grain productivity, content and quality of the seed oil. Moreover, the biological potential of sunflower’s tissue extracts grown under differential boron supply. During field experiments, three sunflower’s genotypes (Helio251, BRS323 and BRS324) were supplied with different doses of B: 0, 2.5, 5 and 8 kg ha-1. The B sensibility was evaluated using the amount of grains, content and quality of the seed oil, and B content in grains. The biological potential was determined using the highest B-sensitive genotype (Helio251). Aqueous (0.1 and 0.5%) and ethanolic (0.025 and 0.050%) extracts were produced using leaf and capitulum tissues, which were collected during R5 field stage. Afterwards, “in vitro” and “in vivo”assays led us to estimate antioxidant capacity and activity, respectively. Furthermore, aqueous extracts of leaf and capitulum (2.5, 5 and 10%) were evaluated in relation to its allelophatic potential on seed germination of Digitaria insularis. As a result, genotypes showed distinct response for B fertilization on field experiment. This micronutrient influenced grain productivity of the Helio251 and BRS323, and oil content in all genotypes. However, B was not recognized on major unsatured fatty acid profiles and grain protein. Despite of that, it was observed genotypical differences in oil quality, either on fatty acid parameters or on crude protein content. In vitro evaluation of hydroalcoholic and aqueous extracts of leaves and capitulum using ABTS and FRAP confirmed phenolic content, absence of flavonoids and antioxidant capacity. Also, the Saccharomyces cerevisiae biological model shown antioxidant activity in aqueous and ethanolic extracts using “in vivo” assays. In the other hand, some better values for antioxidant activity were found using ethanol as extraction solvent. In HPLC-PDA analysis, it was confirmed chlorogenic antioxidant compounds. As a result, this work led us to evidence multiple functions of B, and its biological potential in sunflower leaves and capitulum extracts. It was noticed that B element influences sunflower crop production either negatively or positively, depending on the applied dose and genotype. In summary, the amount of antioxidant components may change with variations of B supply. Moreover, sunflower has special metabolites with allelopathic and antioxidant contents that have potential to be useful for both chemical and agricultural industries.