Antioxidant and Antidiabetic Activities of Flavonoid Derivatives from the Outer Skins ofL.
J Agric Food Chem. 2020 Aug 19 ;68(33):8797-8811. Epub 2020 Aug 5. PMID: 32603104
Ngoc Khanh Vu
The onion, known as the bulb onion or common onion, is not only a key ingredient in many tasty and healthy vegetarian meals but also many traditional medicines. Nine new flavonoids [cepaflavas A, B (,), cepadials A-D (-and), and cepabiflas A-C (-)] and six known compounds (-,,) were obtained from the outer skins ofL. Among them, compounds,, andmight be artificial products formed during extraction and isolation. New compounds were structurally elucidated using various spectroscopy/spectrometry techniques, including NMR and HRMS, and computational methods. Their absolute configurations were determined using time-dependent density functional theory calculations, combined with ECD spectroscopy, optical rotation calculation, and statistical procedures (CP3 and DP4 analysis). The free radical scavenging assays revealed that the new compounds-possessed considerable antioxidant activities with ICvalues of 4.25-8.88 and 7.12-8.14μM against DPPH and ABTS, respectively. Compounds-showed substantial inhibitory activities against bothα-glucosidase and protein tyrosine phosphatase 1B (PTP1B), with ICvalues of 0.89-6.80 and 1.13-6.82μM, respectively. On the basis of molecular docking studies,andwere predicted to have high binding capacity and strong affinity toward the active site of PTP1B.