UPLC-HRMS/MS Guided Isolation and NMR Investigation of Major Flavonoids from Enarthrocarpus strangulatus Boissier (Brassicaceae) with In Vitro Enzymes Inhibitory Potential

Various members of the family Brassicaceae are economically important and traditionally used to treat many disorders. Among the family members, Enarthrocarpus strangulatus Boissier is a common Egyptian species that was rarely studied. Consequently, the current study aims to characterize its phytochemical composition and assess its potential bioactivity comprehensively. A metabolomics approach integrating UPLC-HRMS/MS-based molecular networking enabled the dereplication of 91 metabolites, including primary (i. e. organic acids, amino acids, fatty acids, and phospholipids) and secondary metabolites (i. e. glucosinolates, phenolic acids, and flavonoids). Among the 91 annotated features, 13 major metabolites were fully characterized following their isolation and purification. Exclusive of only three flavonoids, all the detected metabolites are described for the first time within this species. Furthermore, the crude extract and four major isolated flavonoids were subjected to in vitro biological screening, including antioxidant, radical scavenging, anti-diabetic, anti-Alzheimer's, and anti-inflammatory activities. It was noticed that nobiletin (61) exhibited the highest antioxidant and anti-Alzheimer's activities. At the same time, isorhamnetin 3-O-glucose (51) showed the highest anti-diabetic activity compared to the other isolated flavonoids and the total extract itself. Regarding the anti-inflammatory activity, no obvious differences were detected numerically among all studied flavonoids.