Evaluation of the in vitro bioaccessibility of phenolic compounds of black cumin (BARI‐1cumin) methanolic extract

Abstract

Abstract This study aims to evaluate the phenolic contents, chemical composition, mineral amount as well as antioxidant activity of methanolic extracts from dried black cumin (Nigella sativa L; family: Ranunculaceae) seed powder. We also performed an in vitro gastrointestinal digestion process to understand the effect on phenolic components and their antioxidant activity after gastrointestinal digestion. Black cumin showed high amounts of total phenolic and flavonoid contents, such as dihydroxybenzoic acid and ferulic acid, through high‐performance liquid chromatography analysis. Six mineral elements (Ca, Cu, Fe, K, Se, and Zn) were determined by using coupled plasma mass spectrometry, while 25 fatty acids (13 saturated, 7 unsaturated, and 5 unsaturated omega fatty acids) were also identified by gas chromatography, with linoleic acid the most present. In addition, black cumin extract presented high antioxidant capacity measured by DPPH, FRAP, and TEAC. Additionally, dried black cumin powder was evaluated after gastrointestinal digestion: phenolic compounds (1.81‐fold), flavonoids (1.03‐fold), and antioxidant capacity (up to 2.1‐fold) increased in gastric fraction compared to the undigested methanolic extract. Moreover, a higher amount (p < 0.05) of total phenolic content and flavonoids, as well as higher total antioxidant capacity, were found in the gastric and elimination fraction than in the bioaccessible fraction. Our results demonstrated that there were a significant decrease in the quantity of phenolic compounds (68%) and flavonoids (95.53%) after gastrointestinal digestion in the bioaccessible fraction as well as a reduced the antioxidant activity (10.79%–94.84%), suggesting that phenolic compounds are responsible for antioxidant activity.

Keywords

• antioxidants
• black cumin
• fatty acid profile
• gastrointestinal digestion
• mineral content
• polyphenols