Accumulation of Flavonols over Hydroxycinnamic Acids Favors Oxidative Damage Protection under Abiotic Stress

Efficient detoxification of reactive oxygen species (ROS) is thought to play a key role in enhancing the tolerance of plants to abiotic stresses. Although multiple pathways, enzymes, and antioxidants are present in plants, their exact roles during different stress responses remain unclear. Here, we report on the characterization of the different antioxidant mechanisms of tomato plants subjected to heat stress, salinity stress, or a combination of both stresses. All the treatments applied induced an increase of oxidative stress, with the salinity treatment being the most aggressive, resulting in plants with the lowest biomass, and the highest levels of H2O2 accumulation, lipid peroxidation, and protein oxidation. However, the results obtained from the transcript expression study and enzymatic activities related to the ascorbate-glutathione pathway did not fully explain the differences in the oxidative damage observed between salinity and the combination of salinity and heat. An exhaustive metabolomics study revealed the differential accumulation of phenolic compounds depending on the type of abiotic stress applied. An analysis at gene and enzyme levels of the phenylpropanoid metabolism concluded that under conditions where flavonols accumulated to a greater degree as compared to hydroxycinnamic acids, the oxidative damage was lower, highlighting the importance of flavonols as powerful antioxidants, and their role in abiotic stress tolerance.This work was supported by the Ministry of Economy and Competitiveness from Spain (GrantNo. AGL2015-66033-R), and Seneca Foundation from Region of Murcia, Spain (Grant no.15288/ PI/10).Peer reviewedPeer Reviewe

Phenolic Profiling and Antioxidant Capacity of Eugenia uniflora L. (Pitanga) Samples Collected in Different Uruguayan Locations

The use of nutrient-rich foods to enhance the wellness, health and lifestyle habits of consumers is globally encouraged. Native fruits are of great interest as they are grown and consumed locally and take part of the ethnobotanic knowledge of the population. Pitanga is an example of a native fruit from Uruguay, consumed as a jelly or an alcoholic beverage. Pitanga has a red-violet pigmentation, which is a common trait for foods that are a good source of antioxidants. Hence, fruits from different Uruguayan regions were analyzed via miniaturized sample preparation method, HPLC-DAD-ESI/MSn and RP-HPLC-DAD techniques to identify and quantify phenolic compounds, respectively. The antioxidant capacity was evaluated via DPPH and ORAC (Oxygen Radical Absorbance Capacity) assays. A multivariate linear regression was applied to correlate the observed antioxidant capacity with the phenolic content. Furthermore, Principal Components Analysis was performed to highlight characteristics between the various samples studied. The main results indicated differences between northern and southern Uruguayan samples. Delphinidin-3-hexoside was present in southern samples (mean of 293.16 µmol/100 g dry weight (DW)) and absent in the sample collected in the north (sample 3). All the samples contain high levels of cyanidin-3-hexoside, but a noticeable difference was found between the northern sample (150.45 µmol/100 g DW) and the southern sample (1121.98 µmol/100 g DW). The antioxidant capacity (mean ORAC of 56370 µmol Trolox®/100 g DW) were high in all the samples compared to the Food and Drug Administration (FDA) database of similar berry-fruits. The results of this study highlight the nutraceutical value of a native fruit that has not been exploited until now.The authors gratefully acknowledge the CYTED program for the support of the international collaboration through the Thematic Network AGL 112RT0460 CORNUCOPIA

Banana Passion Fruit (Passiflora mollissima (Kunth) L.H. Bailey): Microencapsulation, Phytochemical Composition and Antioxidant Capacity

Passiflora mollissima (Kunth) L.H. Bailey is an exotic fruit native to South America, known as taxo in Ecuador. This paper characterizes its flavonoid and carotenoid composition and antioxidant capacity and evaluates the effect of the spray-drying process on its phytochemical composition and antioxidant capacity. A total of 18 flavonoid compounds, nine proanthocyanidins and nine flavan-3-ol monomers, were identified and quantified. Glycosides of (epi)-afzelechin stood out as the most abundant flavonoid. Three carotenoids were identified, with β-carotene having the highest concentration. The DPPH· and ORAC assay methods indicated a high antioxidant capacity. Furthermore, the bioactive content showed a positive and direct correlation with antioxidant capacity. On the other hand, the spray-drying process produced a stable phytochemical composition and antioxidant activity of taxo. These results demonstrate the potential applicability of microencapsulated taxo as a functional ingredient in the food industry.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).: Quality technical work from Ana Benítez González (Universidad de Sevilla) is acknowledged. María Torres reviewed the English edition of this study. The authors would like to thank the Spanish Ministry of Economy and Competitiveness (MINECO) and CSIC-VITRI with the Project I-COOP+2014 (Ref. COOPB20125) for funding this project. This study was financed by PIS 12-21 and PIMI 14-14 sponsored by Escuela Politécnica Nacional. Part of this work was carried out in international research collaboration within the CYTED Program (Refs. 112RT0460-CORNUCOPIA and 112RT0445-IBERCAROT, Thematic Networks). AGR also thanks the Ecuadorian Secretary of Higher Education, Science, Technology and Innovation for the Prometeo Postdoctoral Grant