Polyphenols and Fibre: Key Players with Antioxidant Activity in Two Extracts from Pomegranate (Punica granatum)

The pomegranate fruit offers numerous health benefits to humans due to its rich composition of various chemical components, including polyphenols, fibre, flavonoids, minerals, vitamins, organic acids, alkaloids, and amino acids, among others. The antioxidant properties of pomegranate are well known, and this study aims to compare these activities in two extracts obtained from the fruit (“Whole Fruit Extract”, WFE and “Internal Membranes Extract”, IME). Various experiments were conducted using both extracts: (1) quantification of polyphenols and flavonoids using the Folin–Ciocalteu colorimetric assay and the aluminium chloride assay, respectively; (2) the measurement of the antioxidant activity was carried out by Reducing Power, Chelating Activity of Ferrous Ions (Fe2+), Radical Absorbance Capacity of Oxygen, Free Radical Scavenging Activity DPPH, and antioxidant effect in vitro; (3) quantitative and quantitative evaluation of the fibre was performed. IME has demonstrated a significantly greater antioxidant effect than WFE, despite possessing a smaller amount of both polyphenols and flavonoids (polyphenols: 68 mg GAE/g for WFE; 47 mg GAE/g for IME; flavonoids: 51mg QE/g for WFE; 35 mg QE/g for IME). For this reason, we evaluated the fibre composition in both extracts. The higher amount of glucans, xylans, and pectin in IME suggested that these fibrous components may be responsible for the greater antioxidant effect detected compared to WFE.