Nutritional, phytochemical, antioxidant, α-glucosidase and α-amylase inhibitory properties of Moringa oleifera seeds

Abstract The aim of this study was to analyze nutritional characteristics of Moringa oleifera seed and evaluate phytochemical compounds, as well as antioxidant and enzyme inhibitory activities, of such seeds. Results demonstrated that seed protein possessed 23.77% of indispensable amino acids, but lysine was the first limiting amino acid. Seed oil contained 78.44% of unsaturated fatty acids, with oleic acid (C18:1) greater than 70%. And seeds were rich in mineral elements, especially being a good source of Ca in the human diet. In addition, total saponins (146.92–169.82 mg GEs/g), total phenolics (37.07–40.75 mg GAEs/g), total flavonoids (6.85–8.43 mg REs/g), and condensed tannins contents (2.74–5.28 mg CEs/g) were identified in different extracts of Moringa oleifera seed. Seed extracts exhibited good antioxidant activities as assessed by different in vitro assays, including 2,2-azino-bis-3-ethylbenzothiazloine-6-sulfonic acid (ABTS), 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, and ferric reducing antioxidant power assays. The α-glucosidase and α-amylase inhibitory activity were also investigated. Furthermore, ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was utilized to characterize the bioactive components in seed extracts. Thirty-three compounds were identified, mainly consisting of glucosides, phenolics (and derivatives), and flavonoids (and derivatives).