Physicochemical properties, antioxidant activity and in vitro gastrointestinal digestion of purified proteins from black cumin seeds

• Published in: International journal of biological macromolecules 2019-04, Vol.126, p.454-465
• Main Authors: Trigui, Ines, Zarai, Zied, Chevance, Soizic, Cheikh-Rouhou, Salma, Attia, Hamadi, Ayadi, M.A.
• Format: Article
• Language: English
• Subjects: Antioxidant activity; Black cumin seeds; Chemical Sciences; Functional properties; Purified proteins; Structural properties
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2018.12.198

The main purpose of this work was to investigate some physiochemical and antioxidant properties of purified proteins of 18 kDa from black cumin seeds. The structural properties of purified proteins were characterized using Fourier Transform-Infrared spectroscopy (FT-IR) and Circular dichroism (CD) spectroscopy analysis. The Tunisian purified protein exhibited a α-helix structure and the Turkish purified protein adopted a β-sheet conformation. The thermal properties were also evaluated by differential scanning calorimetry (DSC). The Tunisian purified protein presented two endothermic peaks, the first one was at 76.71 °C and the second one was at 131.32 °C. However, only one endothermic peak was found for the Turkish purified protein at 157.63 °C. Both Tunisian and Turkish purified proteins were very stable towards heat-induced denaturation. In addition, the effect of pH, salt (NaCl and Na2SO4) and temperature on functional properties was investigated. The Tunisian black cumin seeds pure protein exhibited better antioxidant activity than that of the Turkish one at all tested concentrations (0.2 to 1 mg/mL) and temperatures (50 °C, 75 °C and 100 °C), as well as after gastrointestinal digestion simulation. •Proteins of 18 kDa were purified from black cumin seeds.•Structural properties of pure proteins were characterized by FT-IR and CD spectroscopy.•Purified proteins are stable towards heat-induced denaturation.•Purified proteins present attractive functional properties and are a promising source of natural antioxidants.•The antioxidant activity of purified proteins increased after gastrointestinal digestion simulation.