Evaluation of tocopherol variability in wild Helianthus species: A genetic resource for sunflower breeding

Tocopherols are one of the most important bioactive compounds which improve the quality of the oil regards to their antioxidant properties. Considering that wild Helianthus species are a very important source of genes for the breeding of cultivated sunflower the aim of this research was to evaluate the variability in tocopherol content and composition within a germplasm collection. The evaluated germplasm included seven annual Helianthus species (H. annuus, H. argophyllus, H. debilis, H. neglectus, H. niveus, H. petiolaris and H. praecox). Oil samples were extracted using a hydraulic press. Tocopherol quantification was performed using high-performance liquid chromatography (HPLC) on a Nucleosil 100-5 NH2 column with fluorescence detection (λex=280 nm, λem=340 nm). The mobile phase comprised n-hexane/ethyl acetate (70/30, v/v) at a flow rate of 1 ml/min. Tocopherols were identified and confirmed based on their relative retention values and maximum absorption peaks, using 20 μl injection volumes. The obtained results of the comparative tocopherol analysis revealed significant variability among wild Helianhus species. Tocopherol content averaged 333.5 mg kg-1 seed in the all analyzed species, with an average profile of 328.56 mg kg-1 (98.5%) of alphatocopherol, which is dominant. Only in species H. annuus and H. niveus, in small concentrations (6.83 mg kg-1 and 6.65 mg kg-1 ), beta-tocopherol was identified. By applying of the Principal Components Analysis the species with the lowest tocopherol content (H. praecox 133.59 mg kg-1 and H. niveus mg 238.23 kg-1) and the species with the highest content (H. annuus 458.11 mg kg-1 and H. neglectus 459.35 mg kg-1) were clearly distinguished. The obtained results could serve as a tool to select species with high concentration of these bioactive compounds in design management strategies to obtain them in the breeding programs of cultivated sunflower.