Characterization and antioxidant properties of alcoholic extracts from gamma irradiated κ-carrageenan

• Alcoholic extracts from irradiated κ-carrageenan (solid and 1% w/v) were obtained.
• Extracts consisted of low molecular weight oligomers with Mw from 2300 to 5000 Da.
• Structural analysis showed C=O and C=C functional groups in the extracts.
• Fraction with Mw<2000 Da exhibited higher antioxidant potential.

Different extracts from unirradiated and gamma irradiated κ-carrageenan (solid and 1% w/v aqueous solution) were obtained with isopropyl alcohol (IPA) at concentrations of 40%, 60% and 80% v/v at room temperature. Physical and chemical properties of the different IPA extracts were analyzed by GPC, UV, and FT-IR. The extracts consisted of low molecular weight fragments with an average molecular weight (Mw) ranging from 2300 Da to 5000 Da. UV analyses of extracts from irradiated carrageenan showed varying maximum absorptions in the range of 265–280 nm. FT-IR spectra of all extracts from irradiated carrageenan showed all the important functional groups of carrageenan in the fingerprint region (4000–600 cm−1) and additional carbonyl C=O and C=C double bond peaks. Antioxidant properties of the different extracts were investigated using reducing power assay. The reducing power of extracts from the irradiated solution follows the order of 80%>60%>40% while no trend was observed for all extracts from irradiated solid κ-carrageenan.