Ellagitannin-rich bioactive extracts of Tuberaria lignosa: insights into the radiation-induced effects in the recovery of high added-value compounds.

Ellagitannins are polyphenols responsible for a number of bioactivities and health-promoting effects. These industrially important molecules can be affected by post-harvest treatments and recovery processes, but little is known about the irradiation-induced effects on their integrity, bioactivity and extractability. Herein, the impact of gamma radiation on the production of ellagitannin-rich extracts was investigated using Tuberaria lignosa as a case study. These effects were compared with those induced in flavonoids and organic acids. The extracts were particularly rich in hydrophilic antioxidants (measured by in vitro assays). The recovery of different phytochemicals was favoured by longer extraction times. Ellagitannins (mainly punicalagin derivatives) were extracted better from samples irradiated at 5 kGy and were not significantly affected by the 10 kGy dose. However, the total contents of flavonoids and organic acids were decreased by the consequent increase in irradiation dose. Therefore, this study supports the use of gamma radiation for processing T. lignosa, aiming to obtain ellagitannin-rich bioactive extracts.

Diel variations in carbon isotopic composition and concentration of organic acids and their impact on plant dark respiration in different species.

Leaf respiration in the dark and its C isotopic composition (δ(13) CR ) contain information about internal metabolic processes and respiratory substrates. δ(13) CR is known to be less negative compared to potential respiratory substrates, in particular shortly after darkening during light enhanced dark respiration (LEDR). This phenomenon might be driven by respiration of accumulated (13) C-enriched organic acids, however, studies simultaneously measuring δ(13) CR during LEDR and potential respiratory substrates are rare. We determined δ(13) CR and respiration rates (R) during LEDR, as well as δ(13) C and concentrations of potential respiratory substrates using compound-specific isotope analyses. The measurements were conducted throughout the diel cycle in several plant species under different environmental conditions. δ(13) CR and R patterns during LEDR were strongly species-specific and showed an initial peak, which was followed by a progressive decrease in both values. The species-specific differences in δ(13) CR and R during LEDR may be partially explained by the isotopic composition of organic acids (e.g., oxalate, isocitrate, quinate, shikimate, malate), which were (13) C-enriched compared to other respiratory substrates (e.g., sugars and amino acids). However, the diel variations in both δ(13) C and concentrations of the organic acids were generally low. Thus, additional factors such as the heterogeneous isotope distribution in organic acids and the relative contribution of the organic acids to respiration are required to explain the strong (13) C enrichment in leaf dark-respired CO2 .