Antioxidant and Antidiabetic Activities of Flavonoid Derivatives from the Outer Skins of Allium cepa L.

Ngoc Khanh Vu, Chung Sub Kim, Manh Tuan Ha, Quynh Mai Thi Ngo, Se Eun Park, Haeun Kwon, Dongho Lee, Jae Sue Choi, Jeong Ah Kim, Byung Sun Min

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


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 (5, 6), cepadials A-D (7-9 and 14), and cepabiflas A-C (10-12)] and six known compounds (1-4, 13, 15) were obtained from the outer skins of Allium cepa L. Among them, compounds 5, 6, and 9 might 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 10-12 possessed considerable antioxidant activities with IC50 values of 4.25-8.88 and 7.12-8.14 μM against DPPH and ABTSâ +, respectively. Compounds 13-15 showed substantial inhibitory activities against both α-glucosidase and protein tyrosine phosphatase 1B (PTP1B), with IC50 values of 0.89-6.80 and 1.13-6.82 μM, respectively. On the basis of molecular docking studies, 13 and 15 were predicted to have high binding capacity and strong affinity toward the active site of PTP1B.

Original languageEnglish
Pages (from-to)8797-8811
Number of pages15
JournalJournal of agricultural and food chemistry
Issue number33
Publication statusPublished - 2020 Aug 19


  • Allium cepa skins
  • PTP1B
  • antioxidant
  • kinetic
  • molecular docking
  • α-glucosidase

ASJC Scopus subject areas

  • Chemistry(all)
  • Agricultural and Biological Sciences(all)


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